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Recycled Tyre Rubber Modified Bitumens for road asphalt mixtures_ A literature review

Review

Recycled Tyre Rubber Modi?ed Bitumens for road asphalt mixtures:A literature review

Davide Lo Presti ?

Nottingham Transportation Engineering Centre,University of Nottingham,Nottingham,UK

h i g h l i g h t s

Introducing the Recycled Tyre Rubber (RTR)material as environmental problem as well as engineering resource. Introducing the wet process technology.

Describing in details the existing products associated to the wet process high viscosity technology. Describing in details the wet process No Agitation technology.

Comparing the described technologies and providing justi?cations and suggestions toward a widespread use of RTR-MBs.

a r t i c l e i n f o Article history:

Received 24June 2013

Received in revised form 3September 2013Accepted 6September 2013

Available online 29September 2013Keywords:

Recycled Tyre Rubber Asphalt Rubber Bitumen Rubber Crumb Rubber Terminal blend

a b s t r a c t

Nowadays,only a small percentage of waste tyres are being land-?lled.The Recycled Tyre Rubber is being used in new tyres,in tyre-derived fuel,in civil engineering applications and products,in moulded rubber products,in agricultural uses,recreational and sports applications and in rubber modi?ed asphalt appli-cations.The bene?ts of using rubber modi?ed asphalts are being more widely experienced and recog-nized,and the incorporation of tyres into asphalt is likely to increase.The technology with much different evidence of success demonstrated by roads built in the last 40years is the rubberised asphalt mixture obtained through the so-called ‘‘wet process’’which involves the utilisation of the Recycled Tyre Rubber Modi?ed Bitumens (RTR-MBs).Since 1960s,asphalt mixtures produced with RTR-MBs have been used in different parts of the world as solutions for different quality problems and,despite some down-sides,in the majority of the cases they have demonstrated to enhance performance of road’s pavement.This study reports the results of a literature review upon the existing technologies and speci?cations related to the production,handling and storage of RTR-MBs and on their current applications within road asphalt mixtures.Furthermore,considering that RTR-MBs technologies are still struggling to be fully adopted worldwide,mainly because of poor information,lack of training of personnel and stakeholders and rare support of local policies,the present work aims to be an up-to-date reference to clarify bene?ts and issues associated to this family of technologies and to ?nally provide suggestions for their wide-spread use.

Contents 1.

Tyre rubber:environmental problem or engineering resource? (864)

1.1.Recycled Tyre Rubber as engineering material ........................................................................8651.

2.From ELTs to Crumb Rubber Modifier ...............................................................................

8651.2.1.Ambient grinding ........................................................................................8661.2.2.Cryogenic grinding .......................................................................................8661.2.3.Other processes .........................................................................................

866

Abbreviations:CRM,Crumb Rubber Modi?er;ELTs,end of life tyres;RTR-MB,Recycled Tyre Rubber Modi?ed Bitumen;RTR,Recycled Tyre Rubber.

This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial-No Derivative Works License,which permits non-commercial use,distribution,and reproduction in any medium,provided the original author and source are credited.?Tel.:+447587140422.

E-mail address:davide.lopresti@https://www.doczj.com/doc/cf16968269.html,

864 D.Lo Presti/Construction and Building Materials49(2013)863–881

1.3.History of RTR in road asphalt mixtures (867)

2.Recycled Tyre Rubber Modified Bitumens(RTR-MBs) (868)

2.1.Geography of RTR-MBs in road asphalt mixtures (868)

2.2.Overview of the bitumen–RTR interaction process (868)

2.3.Terminology associated with RTR-MBs (869)

2.3.1.McDonald process (869)

2.3.2.Continuous blending-reaction systems (869)

2.3.3.Field blends (869)

2.3.4.Terminal blends (870)

2.3.5.Caltrans terminology (870)

3.Wet process-high viscosity (870)

3.1.Asphalt-Rubber binder(USA) (871)

3.1.1.CRM requirements (871)

3.1.2.Base binder requirements (871)

3.1.3.Asphalt-Rubber plant production (871)

3.1.4.Asphalt-Rubber storage (872)

3.2.Bitumen Rubber binder(RSA) (872)

3.2.1.Rubber requirements (872)

3.2.2.Base bitumen requirements (872)

3.2.3.Bitumen Rubber production (872)

3.2.4.Bitumen Rubber storage (873)

3.3.Crumb Rubber Modified binder(AUS&NZ) (873)

3.3.1.CRM requirements (874)

3.3.2.Base bitumen requirements (874)

3.3.3.Crumb Rubber Modified binder production (874)

3.3.4.Crumb Rubber Modified binder storage (875)

3.4.Wet process-high viscosity:benefits,issues and limitation (875)

3.4.1.Benefits (875)

3.4.2.Limitations (875)

3.4.3.Environmental Issues (877)

4.Wet process-No-Agitation (877)

4.1.Production (878)

4.2.Storage stability (878)

4.3.Properties(Like a PMB) (878)

4.4.Applications (878)

5.Discussion and conclusion (879)

5.1.Conclusions (880)

References (880)

1.Tyre rubber:environmental problem or

resource?

The increasing number of vehicles on the

and developing nations generates millions of

About1.4billion tyres are sold worldwide

quently as many eventually fall into the

(ELTs)(Fig.1).Moreover,the amount of ELTs

pan are about to increase because of the

of vehicles and increasing traf?c worldwide.

the largest and most problematic sources of

volume produced and their durability.The US

tection Agency reports that290million scrap

in2003(EPA,2007).Of the290million,45

tyres were used to make automotive and

Europe every year,355million tyres are

representing the24%of world production[1].

has millions of used tyres that have been

stockpiled.The inadequate disposal of tyres

pose a potential threat to human health(?re

or other pests such as mosquitoes)and

ronmental risks.Most countries,in Europe and

lied on land?lling to dispose of used tyres

and their potential for reuse has led to many

a ban on this practice.The current estimate for

piles throughout the EU stands at5.5million

the2009annual used tyres arising)and the Fig.1.Evolution of ELTs recovery rates in major tyre markets,adapted from[2]

producing in Europe,was set up under the strategic guidance of the European Tyre and Rubber Manufacturers Association (ETRMA).This Group was dedicated to the management of end of life tyres (ELTs).Also thanks to this group,since 1996,the collection rate has increased steadily while there has been a continuous decline in the land ?lling of used tyres (Table 1).In 2009the European Un-ion was faced with the challenge of managing,in an environmen-tally sound manner,more than 3.2million tonnes of used tyres of which 95%were recovered.This con?rms Europe as one of the most active areas in the world in the recovery of ELTs.

Country arise and recovery rates demonstrate that ELTs man-agement in Europe is allowing the progressive elimination of land ?lling and raises the availability of Recycled Tyre Rubber (RTR)to be recycled for other purposes.In fact,the same make waste tyres such a problem also make re-used waste materials,as RTR is very lised in other products.These efforts should further develop the use of ELTs in rubberised struction,which has high growth potential in relatively underutilised [2].

1.1.Recycled Tyre Rubber as engineering The tyre is a complex and high-tech safety a century of manufacturing innovation,From the material point of view the tyre is components materials:(i)elastomeric (iii)steel.The fabric and steel form the tyre with the rubber forming the ‘‘?esh’’of side wall,apexes,liner and shoulder wedge process is necessary to transform natural to ensure performance,durability and safety.In is sticky in nature and can easily deform when brittle when cooled down (Table 2).In this to make products with a good level of inelastic deformation of not-vulcanised the chemical nature as rubber is made of These polymer chains can move other,and this will result in a change of shape.By the process of vulcanisation cross-links are formed between the polymer chains,so the chains cannot move independently anymore.As a result,when stress is applied the vulcanised rubber will deform,but upon release of the stress the rubber article will go back to its original https://www.doczj.com/doc/cf16968269.html,pounding is ?nally used to improve the physical prop-erties of rubber by incorporating the ingredients and ancillary sub-stances necessary for vulcanisation,but also to adjust the hardness and modulus of the vulcanised product to meet the end require-ment.Different substances can be added according to the different tyre mixtures;these include mineral oil and reinforcing ?llers as carbon black and silica [4].In general,truck TR contains larger per-centages of natural rubber compared to that from car tyres [5].Ta-ble 3summarises the general tyre composition of tyres used in cars and trucks in the EU [2].

From the structural point of view,the main components of a tyre are the tread,the body,side walls and the beads (Fig.2).The tread is the raised pattern in contact with the road.The body

supports the tread and gives the tyre its speci?c shape.Beads are metal-wire bundles covered with rubber,which holds the tyre on the wheel.The inherent characteristics of the tyre are the same worldwide.They include:the resistance to mould,mildew,heat and humidity,retardation of bacterial development,resistance to sunlight,ultraviolet rays,some oils,many solvents,acids and other chemicals.Other physical characteristics include their non-biode-gradability,non-toxicity,weight,shape and elasticity.However,many of the characteristics,which are bene?cial during their on-road life as consumer products,are disadvantageous in their post-consumer life and can create problems for collection,storage and/or disposal [6].

1.2.From ELTs to Crumb Rubber Modi?er

The tyre life cycle traditionally comprises ?ve main stages,which includes extraction,production,consumption,collection of

Table 1

ELTS management trends in the EU,adapted from [1].

1994(%)

1996(%)1998(%)2000(%)2002(%)2004(%)2006(%)2008(%)2008(%)Re-use/export 118111101199810Reconstruction 10121111111211108Material recovery 61118192528343840Energy recovery 112020212731313738Land?ll (disposal)

Table 2

Effect of temperature on natural rubber,adapted from [2].à10°C Brittle and opaque

20°C Soft,resilient and translucent 50°C

Plastic and sticky

120°C à160°C Vulcanised when agents e.g.,sulphur are added 180°C Break down as in the masticator 200°C

Decomposes

Table 3

Comparison of passenger car and truck tyres in the EV,adapted from [3].Fig.2.Tyre structure,adapted from [7].

D.Lo Presti /Construction and Building Materials 49(2013)863–881865

used tyres and waste management.A simpli?ed version of the tyre cycle is illustrated in Fig.3.After the collection of ELTs,the next stage includes land?lling and recovery.Worldwide there has been a continuous decline in land?lling used tyres,while the recovery routes include different options such as:‘‘energy recovery’’where ELTs having a calori?c value equivalent to that of good quality coal are used as an alternative to fossil fuels,or ‘‘chemical processing’’such as pyrolysis,thermolysis and gasi?cation,(the economic via-bility of these options has yet to be proved)and ?nally ‘‘granulate recovery’’.The latter involves tyre shredding and chipping pro-cesses which is carried out by using large machinery that cuts up tyres into small pieces of different sizes.At this stage,after the re-moval of the steel and fabric components,the material RTR can be used for a variety of civil engineering projects:rubberised asphalt pavements,?ooring for playgrounds and sports stadiums,as shock absorbing mats,paving blocks,roo?ng materials,etc.

The size of the tyre shreds may range from as large as 460mm to as small as 25mm,with most particles within the 100mm to 200mm range,while the tyre chips range from 76mm down to approximately 13mm.By further reducing

the size of shreds and chips,it is possible to produce Ground and Crumb Rubber,also known as size-reduced rubber,which are suitable to be re-used in the asphalt industry.Crumb Rubber Modi?er (CRM)is the com-mon name used to identify the RTR particles used to modify bitu-men.It is important to recognize that today CRM is typically highly controlled material.The process is no up a stockpile of ELTs and adding the handling and shredding process is carefully tored to produce a clean and highly During the process,the tyre’s reinforcing wire The steel is removed by magnets and the ration.The resulting rubber particles are very clean.Automated bagging systems weights and eliminate cross contamination There are several technologies to reduce 1.2.1.Ambient grinding

This is a method of processing where processed at or above ordinary room cessing is typically required to provide particles with relatively large surface areas to with the paving bitumen.This is a mechanical by means of rotating blades and knives,in the separation of the ?bers,amongst which steel ?bers.Once separated from the grinding is able to produce rubber crumbs from 5to 0.5mm.Ambient grinding is the most commonly used and probably the most cost effective method of processing end of life tyres.A schematic representation of ambient grinding is shown in Fig.4.

1.2.2.Cryogenic grinding

As shown in Fig.5,this process uses liquid nitrogen to freeze the RTR (typically between à87to à198°C)until it becomes brittle,and then uses a hammer mill to shatter the frozen rubber into smooth particles with relatively lower surface area (Fig.6)than those obtained by ambient grinding (Figs.7and 5).Oliver [10]showed that several characteristics of the rubber granulate deter-mine the elastic properties of the Crumb Rubber and those con-ferred on the ?nal mix:they enhance with the decrease of speci?c gravity and particle size,and increase with the higher sur-face porosity of the granules.In fact,in wet process,rubber parti-cles with a smooth surface,showed reduced reaction with the bitumen and worst the elastic properties of the mixture,if com-pared with those obtained by using granules with bigger porous surfaces and less speci?c weight.As a result,the use of CRM from cryogenic process in bituminous mixtures is discouraged [11].A comparison between the properties of cryogenic and ambient ground rubber is summarised in Table 4.

1.2.3.Other processes

In addition to conventional ambient grinding techniques and the cryogenic process,there other less common proprietary pro-cesses currently in use to reduce RTR in crumbs or ?ne powder to be used as CRM:

Wet -grinding is a patented grinding process in which tiny rub-ber particles are further size reduced by grinding into a liquid medium,usually water.Grinding is performed between two closely spaced grinding wheels.The obtained ?ne mesh RTR is mainly used as bitumen modi?er [12].

Hydro jet size reduction .This is a technique of processing RTR into ?ner particles with the help of pressurised water.Water jets at very high operating pressure (around 55.000psi)rotate Fig.3.Life cycle of end of life tyres,adapted from [8].

Fig.4.Schematic representation of ambient grinding,adapted from [3].

Materials 49(2013)863–881

1.3.History of RTR in road asphalt mixtures

The accumulation of ELTs and premature pavement failures are both interconnected and dependant of each other due to enormous increase in traf?c density and axle loading respectively.The use in asphalt pavements started170years ago,with an experi-ment involving natural rubber with bitumen in the1840s attempting to capture the?exible nature of rubber in a longer paving surface.In1960s scrap tyres were processed and

secondary material in the pavement industry.One application introduced by two Swedish companies which produced a

asphalt mixture with the addition of a small quantity ground rubber from discarded tyres as a substitute for a part mineral aggregate in the mixture,in order to obtain asphalt mixture with improved resistance to studded tyres as well as snow chains,via a process known as‘‘dry process’’[14].In same period Charles McDonalds,a materials engineer of the Phoenix in Arizona(USA),was the?rst to?nd that after thor-oughly mixing crumbs of RTR with bitumen(CRM)and allowing react for a period of45min to an hour,this material captured bene?cial engineering characteristics of both base ingredients. called it Asphalt Rubber and the technology is well known as process’’(Fig.9).By1975,Crumb Rubber was successfully incorporated into asphalt mixtures and in1988a de?nition rubberised bitumen was included in the American Society for Test-and Materials(ASTM)D8and later speci?ed in ASTM D6114-Nowadays,these rubberised bitumen materials,obtained through the wet process,have spread worldwide as solutions for different quality problems(asphalt binders,pavements,stress absorbing lays and inlayers,roo?ng materials,etc.)with much dif-ferent evidence of success demonstrated by roads built in the last 30years.

Fig.5.Schematic representation of cryogenic grinding,adapted from[3].

Fig.6.Ambient rubber crumbs.SEM analysis at200um and400x magni?cation, adapted from[12].

Cryogenic rubber crumbs.SEM analysis at200um and400x magni?cation, adapted from[12].

Hydrojet rubber crumbs.SEM analysis at200um and400x magni?cation, adapted from[12].

2.Recycled Tyre Rubber Modi?ed Bitumens (RTR-MBs)2.1.Geography of RTR-MBs in road asphalt mixtures

Since the invention of McDonald,the wet process technology has been used and modi?ed more widely in four states in the US:Arizona,California,Texas,and Florida.More recently wet pro-cess has been used also in South Carolina,Nevada and New Mexico.The preference for using this particular modi?er was due to the fact that not only does the utilisation of ELTs solve environmental problems but it also offers other bene?ts such as increased skid

?exibility and crack resistance,and reduced Australia started introducing bitumen–rubber for seals from the early 1980s and mid South Africa,both wet and dry processes been used successfully although the dry pro-asphalt [17].Two states in Australia (New Victoria)adopted the wet process for limited asphalt,mainly as a crack resisting layer,has been predominantly for sprayed seal In Europe wet rubberised asphalt has been successfully used in road pavements application since 1981in Belgium,as well as in France,Austria,Netherlands,Poland and Germany [19],more re-cently also in Greece [20]and UK [21],but the countries with a higher numbers of applications are Portugal [22],Spain [23],Italy [24],Czech Republic [25]and Sweden [26].

Nowadays the rubberised asphalt technology is being adopted in many other parts of the world:As reported by Widyatmoko and Elliot [18],Taiwan was reported to have adopted the Arizona DOT gap-graded and open-graded rubberised asphalt mixtures for ?exible pavement rehabilitation;furthermore,rubberised as-phalt has been trialled in Beijing and nance work as part of the preparation China and it has also been used in EcoPark On the basis of ?rst positive experiences [28]are strongly investing in the application road pavements.

2.2.Overview of the bitumen –RTR interaction The term ‘‘wet process’’refers to a whole which varies a lot with regards with Fig.9.Scheme of rubberised asphalt production through the ‘‘wet process’’.

Fig.10.Bitumen-RTR interaction phenomenon at elevated temperatures:change of properties over time.Adapted from [31].

conditions.The nature of the mechanism by which the interaction between bitumen and CRM takes place has not been fully charac-terised.Traditionally it is reported that bitumen–rubber interac-tion is not chemical in nature[13],but other studies claim that the increase in binder viscosity cannot be accounted for only by existence of the rubber swelling particles[29].

The reaction itself is made up of two simultaneous processes (Fig.10):partial digestion of the rubber into the bitumen on one hand and,on the other,adsorption of the aromatic oils available in this latter within the polymeric chains that are the main compo-nents of the rubber,both natural and synthetic,contained in the RTR.The absorption of aromatic oils from the bitumen into the rubber’s polymer chains causes the rubber to swell and soften[30].

Rubber particles are swollen by the absorption of the bitumen oily phase at high temperatures(160–220°C)into the polymer chains,which are the key components of the RTR-MB to form a gel-like material.Therefore,during the reaction there is a contem-poraneous reduction in the oily fraction and an increase of rubber particle sizes with a consequent reduction of the inter-particle dis-tance.This implies the formation of gel structures that produce a viscosity increase up to a factor of10[13].

Rubber reacts in a time–temperature dependent manner.If the temperature is too high or the time is too long,the swelling will continue to the point where,due to long exposure to the high tem-peratures,swelling is replaced by depolymerisation/devulcanisa-tion which causes dispersion of the rubber into the bitumen. Depolymerisation starts releasing rubber components back to the liquid phase causing a decrease in the complex modulus(G?), which is related to the material stiffness,while the the phase angle (d),related to the elastic properties,continue to modify(Fig.10a and b).If temperature is high or time is long enough,depolymer-isation will continue causing more destruction of the binder net-working and so d modi?cation is lost[32].The interaction between bitumen and rubber materials is material-speci?c and de-pends on a number of basic factors,including:

Processing variables:temperature,time and device(applied shear stress).

Base binder properties:bitumen source and eventual use of oil time of reaction[33].Moreover,RTR-MBs must be properly de-signed and,where necessary,produced to comply with speci?ca-tions and provide a quality product suitable for the expected climate and traf?c conditions.Depending on the adopted process-ing system,on the chosen processing conditions and on the se-lected materials,the wet process leads to different technologies as explained in the next sections.

2.3.Terminology associated with RTR-MBs

On the grounds of research done around the globe,rubberised bitumen is used as a general term to identify a group of concepts that incorporate RTR into bituminous binders for paving applica-tions.These terms refer to the uses of RTR,in form of CRM as mod-ifying agent in bitumen,that are different in their mix composition, method of production or preparation and in their physical and structural properties.The method of modifying bitumen with CRM produced from scrap tyres and other components as required before incorporating the binder into the bitumen paving materials, is referred to as the‘wet process’.Wet process is obtainable through two different processing systems.

2.3.1.McDonald process

This terminology is related to the system of producing RTR-MB with the original wet process proposed by Charles McDonald in the 1960s.The McDonald blend is a Bitumen Rubber blend produced in a blending tank by blending Crumb Rubber and bitumen.This modi?ed binder is then passed to a holding tank,provided with au-gers to ensure circulation,to allow the reaction of the blend for a suf?cient period(generally45–60min).The reacted binder is then used for mix production(Fig.11).

2.3.2.Continuous blending-reaction systems

This system is similar to the McDonald process of blending,the difference is that CRM and bitumen are continuously blended dur-ing the mix production or prepared by hand and then stored in storage tanks for later use.Therefore,it consists of a unique unit with agitators,in which the reaction occurs during the blending [13].

Fig.11.Schematic diagram of McDonald’s wet process.

D.Lo Presti/Construction and Building Materials49(2013)863–881869

the job-site or rarely transported to the ?eld within equipped with special augers,For this reason,these blends well-known as Field blends.

Wet process-high viscosity binders typically require at CRM to achieve the threshold viscosity.However,for speci?cations [36]the viscosity requirements are meet also than 15%of RTR content.A number of RTR-MBs and mix i?cations have been developed based on this original idea and them is related to a speci?c technology.This section will each of these technologies listed in Table 5by providing by step framework to operate an appropriate plan production storage of these materials.At last,this paragraph will provide overview of the bene?ts and limitations related to the wet cess-high viscosity.

Fig.12.Example of mobile Mixing unit for Asphalt-Rubber,adapted from [34]Fig.13.Example of mobile reaction tank for Asphalt-Rubber,adapted from [34]Fig.14.Terminal blend binder system,adapted from [35].

speci?cations for rubberised asphalt mixtures.Technologies Speci?cations

Country Asphalt-Rubber binder

ASTM D6114/D6114M,[4]Caltrans’Asphalt-Rubber user guide,[5]

USA Bitumen Rubber binder

SABITA Manual 19,[6]AsAc Technical Guideline,[7]RSA Crumb Rubber binder

Austroads,[8]

AUS NZ

3.1.Asphalt-Rubber binder(USA)

According to the ASTM D6114[37],

of asphalt cement,CRM and certain additives in component is at least15%by weight of the total blend acted in the hot asphalt cement suf?ciently to cause rubber particles’’.

3.1.1.CRM requirements

According to ASTM D6114,in order to produce

the rubber should have the following characteristics: Less than0.75%moisture and free?owing.

Speci?c gravity of1.15±0.05.

No visible nonferrous metal particles.

No more than0.01%ferrous metal particles by Fibre content shall not exceed0.5%by weight binder applications).

Recommends all rubber particles pass the No.8(2.36mm) sieve.

(Note that Rubber gradation may affect the physical prop-erties and performance of Bitumen Rubber hot mix).

Caltrans(2006)speci?es that CRM to be used as modi?er must include25±2%by mass of high natural rubber and75±2%of CRM from scrap tyre.Both types of rubber must meet speci?c chemical and physical requirements including gradation and limits on fabric and wire contaminants.The RTR consists primarily of2mm to 600l n sized particles(No.10to No.30sieve sizes).The high nat-ural rubber CRM is somewhat?ner,mostly1.18mm to300urn sieve sizes(Table6).

3.1.2.Base binder requirements

ASTM D6114speci?es three different types of Asphalt-Rubber. Each of them is associated to a suitable bitumen to be used as base of modi?cation

Type-I binders typically include stiffer base bitumen and are generally recommended for hot climates,such as:AC-

20,AR-8000and PG64-16.

Type-Il binders typically include base bitumen softer than Type-I and are generally recommended for moderate cli-

mates,such as:AC-10,AR-4000and PG58-22.

Type-Ill binders typically include the softest grade base bitumen and are generally recommended for cold climates,

such as:AC-5,AR-2000and PG52-28.

where AC(asphalt cement)and AR(Aged Residue)are referred to the American grading systems based on viscosity.For example, an AC20asphalt has a viscosity of2000poise(+20%)at60°C, whilst an AR4000bitumen has a viscosity of4000poise(+25%) at60°C after aging.A rough comparison between penetration and viscosity(AC and AR)bitumen grades is shown in Fig.15.3.1.3.Asphalt-Rubber plant production

By de?nition,Asphalt-Rubber is prepared using the‘‘wet pro-cess-high viscosity’’system.Physical property requirements are listed in ASTM D6114,‘‘Standard Speci?cation for Asphalt-Rubber binder’’(Table8).The Asphalt-Rubber is produced at elevated tem-peratures(P350F,177°C)in low shear(Shatanawi,2010)to pro-mote the physical interaction of the asphalt binder and rubber constituents,and to keep the rubber particles suspended in the blend.Various petroleum distillates or extender oil may be added, at a rate of2.5–6%by mass of the bitumen binder,to reduce viscos-ity,facilitate spray applications,and promote workability.Field production of high viscosity Asphalt-Rubber binders is a relatively straightforward process and it is still based on the McDonald pro-cess(Fig.11).Equipment for feeding and blending may differ among Asphalt-Rubber types and manufacturers,but the processes are similar.The component materials are metered into high shear blending units to incorporate the correct proportions of extender oil and CRM into the paving grade asphalt.The blending units thor-oughly mix the CRM into the hot asphalt cement and extender oil, and the blend is pumped into a heated tank where the Asphalt-Rubber interaction proceeds.

RTR is usually supplied in1ton(0.91tonne)super sacks that are fed into a weigh hopper for proportioning.Augers are needed to agitate the Asphalt-Rubber inside the tanks to keep the CRM particles well dispersed,otherwise the particles tend either to set-tle to the bottom or?oat near the surface.Agitation can be veri?ed by periodic observation through the top hatch or the port where the auger control is inserted.The Asphalt-Rubber binder must be interacted with agitation for a minimum of45min at temperatures from190to218°C to achieve the desired interaction between bitumen and rubber.In order to maintain the reaction temperature within the speci?ed range,the bitumen must be hot,204–224°C before the design proportions of scrap tyre CRM and high natural rubber CRM are added.This is because the CRM is added at ambi-ent temperature(not heated)and reduces the temperature of the blend.The component materials are metered into blending units to incorporate the correct proportions of CRM into the bitumen, and are thoroughly mixed.The Asphalt-Rubber producer is allowed to add the extender oil while adding the rubber,although in some cases the base binder may be supplied with the extender included. If the Asphalt-Rubber producer adds the extender oil,use of a sec-ond meter is recommended to best control the proportioning.The meter for the extender oil should be linked to that for the bitumen. An Asphalt-Rubber binder interacted at lower temperatures will never achieve the same physical properties as the laboratory de-sign,although it may achieve the minimum speci?cation values for use.Hand held rotational viscometers are used to monitor the

Table6

Typical gradation of the RTR to be used in the Asphalt-Rubber binder,adapted from [38].

Sieve#Nominal size(mm)%Passing

10 2.36100

16 1.1875–100

30600l m25–100

50300l m0–45

100150l m0–10

30075l https://www.doczj.com/doc/cf16968269.html,parison of Penetration and Viscosity bitumen grades.

D.Lo Presti/

viscosity of the Asphalt-Rubber interaction over time for quality control and assurance.Before any Asphalt-Rubber binder can be used,compliance with the minimum viscosity requirement must be veri?ed using an approved rotational viscometer (e.g.Brook-?eld).As long as the viscosity is in compliance and the interaction has proceeded for at least 45min,the Asphalt-Rubber may be used [36].

Caltrans (2006)recognises that before starting the plant pro-duction,an appropriate Asphalt-Rubber binder design must be developed (Table 7).It also speci?es that at least 2weeks prior to start of construction the Contractor must supply to the Engineer,for approval,an Asphalt-Rubber binder formulation (design or ‘‘recipe’’)that includes results of speci?ed physical property tests,along with samples of all of the component materials.Samples of the prepared Asphalt-Rubber binder must also be submitted to the Engineer at least 2weeks before it is scheduled for use on the project.

3.1.

4.Asphalt-Rubber storage

Caltrans requires heating to be discontinued if Asphalt-Rubber material is not used within 4h after the 45-min reaction period.The rate of cooling in an insulated tank varies,but reheating is re-quired if the temperature drops below 190°C.A reheat cycle is de-?ned as any time an Asphalt-Rubber binder cools below and is reheated to 190–218°C.Caltrans allows two reheat cycles,but the Asphalt-Rubber binder must continue to meet all require-ments,including the minimum viscosity.

Sometimes the binder must be held overnight.The bitumen and rubber will continue to interact at least as long as the Asphalt-Rub-ber remains liquid.The rubber breaks down (is digested)over time,which reduces viscosity.Up to 10%more CRM by binder mass can be added to restore the viscosity to speci?ed levels.The resulting Asphalt-Rubber blend must be interacted at 190–218°C for 45min and must meet the minimum viscosity requirement before it can be used.

3.2.Bitumen Rubber binder (RSA)

Bitumen Rubber binder is a terminology used for the rubberised bitumen obtained by the wet process in South Africa.Bitumen Rubber binders combine rubber crumbs (Table 9)with bitumen

at high temperatures to achieve a complex two phase product,named non-homogeneous binder.In the Technical Guideline of the South African Asphalt Acadamey [38],is also reported that properties of the modi?ed binder used in hot mix asphalt will in?uence the engineering properties of the resultant mix,therefore the substitution of a conventional bitumen with a modi?ed binder can result in higher air voids due to reduced workability of the higher viscosity modi?ed binders.For this reason,it is important that split samples of the modi?ed binder are sent to all the partic-ipating laboratories (e.g.:supplier,site and control laboratories)and tested before commencement of a project to ensure that the results are within the reproducible limits as prescribed by the test methods.

3.2.1.Rubber requirements

In South Africa,the Committee of Land Transport Of?cials (COL-TO)’s speci?cation requires the reclaimed rubber to have not less than 30%natural rubber by mass of hydrocarbon content [39],whilst the SABITA Manual [40]and the Technical Guideline of the South African Asphalt Acadamey [38]specify 60–75%natural rubber by mass of hydrocarbon content,with all rubber particles passing the 1.18mm sieve.The CRM is produced by a mechanical size reduction process.CRM produced by cryogenic-mechanical techniques are not permitted in South Africa.The CRM must be pulverised,free of fabric,steel cords and other contaminants.3.2.2.Base bitumen requirements

The binder used in the production of the bitumen–rubber must be SABITA B12or B8road-grade bitumen (60/70or 80/100pene-tration-grade bitumen respectively)or a blend of these grades to provide a product with a particular viscosity and other prescribed properties.

3.2.3.Bitumen Rubber production

The binder is manufactured from blending penetration grade bitumen (72–82%by mass),plus extender oil (0–4%)plus rubber crumbs (18–24%)in a patented high shear mixer with a speed of

Table 7

Caltrans speci?cation for rubberised bitumen [36].Test parameter

Speci?cation limits Apparent viscosity,Haake,190°C:cp

1500–4000Cone penetration at 25°C (ASTM D217):dmm 25–70Softening point (ASTM D36):°C

52–74

Resilience at 25°C (ASTM D3407):%

Minimum 18

Table 8

Speci?cation for Asphalt-Rubber [37].Binder speci?cation

ASTM D6114(2009)Type I

Type II Type III Apparent viscosity 177.5°C (ASTM D 2196):cp 1500–50001500–50001500–5000Penetration at 25°C (ASTM D5):dmm 25–7525–7550–100Penetration at 4°C (ASTM D5):dmm Min 10Min 15Min 25Softening point (ASTM D36):°C

Min 57.2Min 54.4Min 51.7Resilience at 25°C (ASTM D5329):%Min 25Min 20Min 10Flash point (ASTM D93):°C

Min 232.2Min 232.2Min 232.2After TFOT (ASTM D1754),residual penetration at 4°C (ASTM D5):%Min 75Min 75Min 75Climatic region

Hot Moderate Cold Average minimum monthly temperature:°C Min à1Min à9Min à9Average maximum monthly temperature:°C

Min 43

Max 43

Max 27

Table 9

Rubber crumbs requirements for bitumen–rubber,adapted from [38].

Property

Requirement

Test method Sieve analysis (%mass)MB-14

Passing screen (mm)1.1801000.60040–700.075

0–5Poly-isoprene content (%m/m total hydrocarbon)25min Thermo gravimetric Analysis Fibre length (mm)6max Bulk density (g/cm 3)

1.10–1.25

MB-16

872

D.Lo Presti /Construction and Building Materials 49(2013)863–881

3000r.p.m,at a temperature in excess of180°C but not more than 220°C and for short periods before the introduction of rubber.Dur-ing the addition of the rubber component,the blend cools down considerably and has to be re-heated to a temperature of190–200°C to ensure proper digestion of the rubber in the bitumen. Special manufacturing equipment is required to manufacture this highly viscous material.The product has a limited useable life of 4–6h and,therefore,manufacture usually takes place onsite,or very close to the construction site.Bitumen Rubber binder can be used for surface dressing operations,in which case it is applied with binder distributors specially designed to handle this highly viscous binder.For surface dressing applications,the bitumen–rub-

ber binder is manufactured using the‘‘wet process’’,which is also the most used for the manufacture of bitumen–rubber hot-mix as-phalt.The blending unit consists of a small tank equipped with a high speed stirring device that ensures proper‘‘wetting’’of the rubber by the binder and prevents the formation of rubber lumps in the?nal product.From the blending tank the product is trans-ferred to a digestion tank which could also be a specialised binder distributor.In the digestion tank the product is continually agi-tated while being heated to the?nal temperature.

The ratio of components varies depending on the bitumen source,the climatic conditions and the application.The more reli-able manufacturers in South Africa nowadays prefer to standardise on20%rubber content and also to preselect the type of tyres for the modi?cation process.Following the addition of the rubber,a diges-tion period is required for the rubber to swell and partially dissolve in the bitumen/extender oil blend.The rubber never completely dissolves in the bitumen and the product is thus classed as a non-homogenous binder.The Bitumen Rubber blend is then circu-lated in a holding tank and heated at high temperatures(190–210°C)to facilitate the chemical digestion process.

The extender oil could either be added to the penetration grade bitumen before delivery or to the bitumen on site.The require-ments of the extender oil are such that it should have a?ash point of greater than180°C and the percentage by mass of aromatic unsaturated hydrocarbons be greater than55.To prevent sticking of rubber particles,also an addition of calcium carbonate or talc up to4%by mass of rubber is permitted.On completion of the digestion period,a hand-held viscometer is used to perform a vis-cosity test on the product to con?rm that suf?cient digestion has taken place(Table10).If approved,the product is ready for appli-cation[38].

3.2.

4.Bitumen Rubber storage

Bitumen Rubber degrades rapidly at

which are in excess of200°C.Therefore the

Rubber generally takes place in close proximity

or asphalt mixing plant.On completion of the

the product generally has a further useable life at

temperature of approximately4h.The rate of

vary depending mainly on the application

be monitored on-site with a hand held

turer of the Bitumen Rubber should supply

showing the changes in the properties over time.

Fig.16shows typical changes in the viscosity

Bitumen Rubber at different temperatures over

cient quantities of Bitumen Rubber should be

in accordance with what can be sprayed or mixed

cation viscosity window of the product.

for changing weather conditions and

planning and close cooperation between the

tor is essential to limit the over production of

which may result in unnecessary degradation of

ber over prolonged periods of heating.Product

heated if it is not going to be used.This will be superheated at a later stage for reuse if it is still within speci?-cation.If it happens to be out of speci?cation then only25%of the product can be re-blended with new bitumen and RTR.Table11 shows the recommended temperatures and time limits for the short-term handling,storing,spraying,mixing and application binders modi?ed with Bitumen Rubber.S-R1is a Surface Seal,A-R1is for hot mix while C-R1is a Crack sealant and all of them are Bitumen Rubber binders.

3.3.Crumb Rubber Modi?ed binder(AUS&NZ)

Bitumen technologists in Australia have been looking into using rubber in bitumen since the early1950s,when a surface dressing trial utilising5%vulcanised reclaimed rubber in R90bitumen (100pen)with10mm aggregate was applied on the Prince High-way at St.Peters in New South Wales.However,there was not much development until the mid-1970s,when the Road authority of the state of Victoria(VicRoads)in conjunction with the Austra-lian Road Research Board(ARRB)started using Crumb Rubber Modi?ed bitumen in spray seal in urban and rural applications.It has been used extensively as a bitumen modi?er in sprayed bitu-minous seals and occasionally in bitumen applications in Victoria. Thanks to this experience VicRoads,in collaboration with the Roads and Traf?c Authority(RTA),New South Wales and the Main roads by Western Australia,have prepared the‘‘Scrap rubber bitu-men guide’’.

Since1986,success has been reported using rubberised bitu-men in Australia,mainly RTA and VicRoads,speci?cally when used as a crack resisting layer,e.g.thin bitumen overlay over concrete, Stress Absorbing Membranes or Stress Absorbing Membranes Interlayers.In2006,Austroads published technical speci?cations framework AP-T41coupled with a guide to the selection and use Table10

Properties of Bitumen Rubber surfacing seals and asphalt,adapted swfrom[38].

Property Unit Test method Class

S-R1A-R1 Softening point1°C MB-1755–6255–65

Dynamic viscosity@190°C dPa s MB-1320–4020–50

Compression and recovery5min MB-11>70>80

1h%>70>80

4days>25n/a Resilience@25%MB-1013–3513–40 Flow Min MB-1215–7010–50

Fig.16.Typical changes in viscosity values from Bitumen Rubber at different temperatures over time,adapted from[38].

D.Lo Presti/Construction and Building Materials49(2013)863–881873

An important component of this Crumb Rubber speci?cation is the role of laboratory testing as explained later.

3.3.1.CRM requirements

In Austroads(2006),two levels of rubber content,nominally15 and18are speci?ed for Crumb Rubber Modi?ed binder obtained through the wet process.Another level,from25to30%,is de-signed for the dry process.Crumbs have only2sizes,namely16 (coarse)and30(?ne).Bulk density(max350kg/mc),grading, maximum particle size,steel content(<0.1%),moisture(<1%)and other properties must be speci?ed by the contractor.All CRM shall be less than3mm in length and the rubber shall not contain any foreign material such as sand,?bre or aggregate.All this info is summarised in Table12.

3.3.2.Base bitumen requirements

The only requirements related to the most suitable bitumen to be used as base for the Crumb Rubber Modi?ed binders,is indi-cated in the‘‘Crumb Rubber Protocol’’of the technical guide of Austroads[41],which speci?es to use Bitumen Class170corre-sponding to a Penetration grade of85/100(Table13).

3.3.3.Crumb Rubber Modi?ed binder production

As mentioned previously,the Austroads guide for Selection and use of Polymer Modi?ed Binders AP-T42[41],gives a major impor-tance to the a priori laboratory testing.In fact,the design process requires a laboratory exercise to be undertaken using the following procedure:

1.A trial mix is prepared for each of an appropriate series of

rubber concentrations such that the speci?cation limits

for the selected binder grade are met in at least one of

the mixes(mixing temperature195°C,digestion period

45min for size16rubber and30min for size30).

2.The measured properties are plotted against rubber con-

centration and the concentration at which the speci?cation

limits are complied with is identi?ed.This rubber concen-

tration is deemed to be the design concentration.

3.A rubber extraction is performed on the design mix using

AG:PT/T142Laboratory method for determining Crumb

Rubber concentration.The determined concentration of

rubber is used as a check for the analysis of?eld collected

samples.

The diagram in Fig.17illustrates the key steps.In the Austroads 2006speci?cations,S40R,S45R/S50R and S55R were replaced by S15RF,S18RF,for asphalt application,and S55R was kept for sprayed sealing.Plant protocols may require different procedures to the?eld de?ned system and the contractor will be responsible for the binder design.Crumb Rubber Modi?ed binders are pro-duced with production routes:factory and?eld produced rubber-ised bitumen.

Factory produced Crumb Rubber Modi?ed binders:usually include combining oil and lower concentrations of rubber

than their?eld produced counterpart.Factory produced

Crumb Rubber Modi?ed binder are used for hot mix asphalt

by using the wet process.This has been shown to improve

the mix properties but requires relatively high binder con-

tents.Since the concentration of rubber is an important

performance controlling factor,generally the higher the

volumetric concentration,the more effective will be the

binder in more demanding applications.Flux oil should

only be added to the CRM classes and the manufacturer’s

recommendations should be followed.It is important to

Table11

Typical temperature/time limits for Bitumen Rubber,adapted from[38].

Binder class Short term handling Storage Spraying/asphalt mixing/application

Max temp(°C)Max holding time(h)Max temp(°C)Max holding time(h)Max temp(°C)Min temp(°C)Max holding time(h)

S-R116524150240210195Refer to time/viscosity curve A-R116524150240210190

C-R116524––190180–

Table12

Austroads speci?cation for Crumb Rubber for bitumen modi?cation,adapted from

[41].

Test Methods Size16Size30

Grading

Passing2.36mm AG/PT1:43100100

Passing1.18mm AG/PT1:4380(min)100

Passing0.60mm AG/PT1:4310(max)40(max)

Passing0.15mm AG/PT1:435(max)

Bulk density AG/PT1:44350kg/m3350kg/m3

Water content AG/PT1:43<1%<1%

Steel content AG/PT1:43<0.1%<0.1%

Table13

Summary of the most important speci?cation requirements for RTR-MBs.

Properties ASTM2009Caltrans2006AsAc2007Austroads2007 Type I Type II Type III

Base bitumen requirements

Penetration:dmm85–100120–150200–300120–15060–10085–100

Crumb Rubber requirements

Passing sieve:mm 2.36 2.36 1.18 2.36 Rubber content:%P1518–2218–2415–18

Additives

Extender oils:%– 2.5–60–4–

Caclium carbonate/Talc:%0–4–0–4–

Processing conditions

Temperature:°C177190–220180–220195 Mixing speed:rpm––3000rpm–

Mixing time:min45+reaction45–60–30–45

874 D.Lo Presti/Construction and Building Materials49(2013)863–881

use the ?ner CRM in order to achieve a reasonable level of digestion in the binder in the short time that the material remains hot.

Field produced Crumb Rubber Modi?ed binders :are pro-duced for sprayed sealing.They are a high temperature blend of bitumen and CRM without combining oils,and may contain up to 25%by mass of rubber;these formu-lations are not suitable for long distance transportation or extended storage but represent the highest performing materials within their class when optimally digested.The properties of the ?eld produced rubberised bitumen are generally controlled by their softening point,elastic recovery and/or torsional recovery [41].3.3.4.Crumb Rubber Modi?ed binder storage

When ?eld mixing Crumb Rubber binders,the material must be continually circulated to minimise settling out of any rubber parti-cles.Failure to do this will most likely result in blockages of the spraying jets and/or pipework.Do not store ?eld produced Crumb Rubber mixtures in bitumen sprayers,road tankers or bulk storage because of the potential problem of segregation and settling out of the rubber particles resulting in blocked pipework etc.

It is worth to highlight that current work in Australia is focus-sing on the use of Crumb Rubber as a substitute for other modi?ed binders in more conventional applications while using similar de-sign criteria,with particular interest in the use of pre-blended products which behave much more like other pre-blended modi-?ed https://www.doczj.com/doc/cf16968269.html,boratory investigations with pre-blended Crumb Rubber Modi?ed binders indicate satisfactory performance but at higher binder contents (>8%).

Table 13summarises some of the most important speci?cations requirements for the RTR-MB production around the world.3.4.Wet process-high viscosity:bene?ts,issues and limitation Extensive literature clearly shows the numerous successes ob-tained using rubberised bituminous mixtures produced with the wet process-high viscosity.However,this technology is not a

panacea.This section was thought to explain the main bene?ts provided by the usage of this technology and the issues that still exist and,in some cases,limit its extensive application.

3.4.1.Bene?ts

The primary reason for using RTR-MBs is that it provides signif-icantly improved engineering properties over conventional paving grade bitumen.As for Asphalt-Rubber binders,they can be engi-neered to perform in any type of climate as indicated in ASTM D 6114.At intermediate and high temperatures,the RTR-MB shows physical and rheological properties signi?cantly different than those of neat paving grade bitumens.The rubber stiffens the binder and increases elasticity (proportion of deformation that is recover-able)over these pavement operating temperature ranges,which decreases pavement temperature susceptibility and improves resistance to permanent deformation (rutting)and fatigue with lit-tle effect on cold temperature properties [36].

As demonstrated by various researchers,RTR-MBs obtained through the wet process have reduced fatigue and re?ection crack-ing,greater resistance to rutting,improved aging and oxidation resistance and better chip retention due to thicker binder ?lms [42–45,39,46].Also Asphalt-Rubber pavements have been demon-strated to have lower maintenance costs [47],lower noise genera-tion [48–50]higher skid resistance and better night-time visibility due to contrast in the pavement and stripping [51].A summary of the bene?ts of using High-viscosity RTR-MBs for road pavement applications is given below:

High Viscosity RTR-MBs have: Increased viscosity that allows greater ?lm thickness in paving mixes without excessive drain down or bleeding.

Increased elasticity and resilience at high temperatures.High Viscosity RTR-MBs pavements have:

Improved durability.

Improved resistance to surface initiated and fatigue/re?ec-tion cracking due to higher binder contents and elasticity. Reduced temperature susceptibility.

Improved aging and oxidation resistance due to higher bin-der contents,thicker binder ?lms,and anti-oxidants in the RTR.

Improved resistance to rutting (permanent deformation)due to higher viscosity,softening points and resilience (stif-fer,more elastic binder at high temperatures).

Lower pavement maintenance costs due to improved pave-ment durability and performance.In addition,High Viscosity RTR-MBs pavements and binders can result in:

Reduced construction times due to thinner lifts. Reduced traf?c noise (primarily tyre noise).

Improved safety due to better long-term colour contrast for pavement markings because carbon black in the rubber acts as a pigment that keeps the pavement blacker longer. Savings in energy and natural resources by using waste products and not contributing to the stockpiles.3.4.2.Limitations

Wet process-high viscosity materials are useful,but they are not the solution to all pavement problems.The Asphalt-Rubber materials must be properly selected,designed,produced,and con-structed to provide the desired improvements to pavement perfor-mance.Pavement structure and drainage must also be adequate.Limitations on the use of Asphalt-Rubber include [36]

Fig.17.Austroads laboratory procedure for Crumb Rubber modi?ed binders,adapted from [41].

Materials 49(2013)863–881875

High Viscosity RTR-MBs are not best suited for use in dense-graded HMA.There is not enough void space in the dense-graded aggregate matrix to accommodate suf?cient rubberised binder content to enhance performance of dense-graded mixes enough to justify the added cost of the binder.

Construction may be more challenging,as temperature require-ments are more critical.Asphalt mixtures with High Viscosity RTR-MB must be compacted at higher temperatures than dense-graded HMA because,like polymers,rubber stiffens the binders at high temperatures.Also,coarse gap-graded mixtures may be more resistant to compaction due to the stone nature of the aggregate structure.

Potential odour,also if it seems to not be harmful(see environ-mental issues).

It is not possible to store High Viscosity RTR-MB at elevated temperatures without equipping storage tanks with augers or paddles.Furthermore,

these binders cannot be stored for prolonged period.If work is delayed more than48h after blending the High Viscosity RTR-MB may not be usable.Takallou and Sainton[52],said‘‘the rub-berised binder must be used within hours of its production’’. The reason is that if over-processed the CRM will be digested to such an extent that it is not possible to achieve the minimum speci?ed viscosity even if more CRM is added in accordance observe that High Viscosity RTR-MB is presently very attractive in cost when particularly examined in light of actual usage.With the RTR being a very cheap waste material the RTR-MBs technolo-gies are increasing their appeal also from the economical point of view.

Lifecycle economics.As in any economical evaluation,cost effec-tiveness should be evaluated using Life Cycle Cost Analysis.Again, Hicks and Epps(2003)showed that evaluating different scenarios, in terms of pavement design,maintenance and rehabilitation strat-egies,the following was concluded:

High Viscosity RTR-MB(Asphalt-Rubber)is a cost effective alternate for many highway pavement applications mainly

due to the ability to reduce thickness when using rubber-

ised asphalt.But also that,

High Viscosity RTR-MB(Asphalt-Rubber)was not cost effective in all applications.

When variability is considered in the inputs(cost,expected life,etc.),the Asphalt-Rubber alternates would be the best

choice in most of the applications considered.

Other studies conducted at the Arizona State University[47] compared maintenance and user costs trends for the conventional bituminous pavements and Asphalt-Rubber pavements(Fig.19).

Fig.18.Crude oil,Fuel,Bitumen and rubber cost’s trends,adapted from[54]. 876 D.Lo Presti/Construction and Building Materials49(2013)863–881

From an investigation made in2007in UK by the Waste&Re-sources Action Programme[18]in order to study a possible adop-tion of this technology,resulted that the approximate cost for importing/hiring and running the blending plant for5to7days of rubberised bitumen production is estimated to be between ￡60,000and￡90,000(70.000–105.000€).This is because none spe-cial mixing units described above is currently available in the UK, and therefore requires importing/hiring from either the US or mainland Europe.Moreover,for the installation of a Portable rub-berised bitumen mixing plant,an area of not less than150m2will be required,depending upon the model and make of the mobile plant[18].It is worth highlighting that mobilisation and set up of the?eld-blends binder production equipment cost as much for small jobs as for big ones,but large projects spread mobilisation costs over more asphalt tonnage.The memo suggests that smaller projects may not be cost effective with respect to initial cost. Although the break point for project size may have changed since then,unit costs of small projects(three days paving or less)should be evaluated by LCCA during the design phase[36].

3.4.3.Environmental Issues

High Viscosity RTR-MBs provides the obvious environmental bene?t of using waste tyres.Nevertheless,their production and their applications in asphalt presents the following issues: Hazardous Emissions.Fume emissions have been studied exten-sively in a number of Asphalt-Rubber projects in USA since1989. Different studies,performed also by the National Institute for Occupational Safety and Health(NIOSH),Federal Highways Admin-istration(FHWA),[55],determined that use of Asphalt-Rubber does not appear to increase health risks to paving personnel.In these studies the following is reported:‘‘...risks associated with the use of Asphalt-Rubber products were negligible’’and also ‘‘Emission exposures in Asphalt-Rubber operations did not differ from those of conventional asphalt operations’’and also‘‘...the ef-fect of CRM on emissions may be relatively small in comparison to the effects of other variables’’[36].Those variables include the fueling rate of the dryer,mix temperature,asphalt throughput rate and asphalt binder content.

However,some agencies also concluded that the rubber modi-?ed mix had an objectionable odour[21].Moreover,in Colorado while researching and developing speci?cations for the use of rub-berised asphalt for the2006paving season,local contractors ex-the Warm mix technology have shown a signi?cant reduction of emission during?eld operations due to an important decrease of the mixing and compaction temperatures[57,21].Therefore,envi-ronmental concerns upon the widespread usage of the wet process still exist,but the development of these technologies is proving that also this issue can be signi?cantly reduced.

Recyclability.Before1992,in USA Asphalt-Rubber pavements had been performing well and the replacement/recycling of them was not necessary.As some sections of Asphalt-Rubber pavements have met their service life span,recyclability became an issue.Carl-son and Zhu[58]report of two jobs occurred in the USA where As-phalt-Rubber mixes were successfully recycled.One example is the recycling job occurred in the City of Los Angeles,California[59], where the initial placement of the Asphalt-Rubber pavement oc-curred in1982.In1994the pavement was milled and stockpiled at a nearby asphalt plant.The Asphalt-Rubber grindings were added to the virgin rock and oil so that the grindings composed 15%of the?nal mix.At another location,the grindings were put through a microwave process where nearly100%of the output was composed of recycled Asphalt-Rubber.This project demon-strated that Asphalt-Rubber can be recycled using either micro-wave technology or conventional mix design technology.Air sampling during paving and recycling determined that employee exposures to air contaminates were well below the Occupational Safety and Health Administration permissible exposure limits, and in most cases below the detection limits.

4.Wet process-No-Agitation

No-Agitation Recycled Tyre Rubber Modi?ed Bitumen(No-Agi-tation RTR-MB),technology was?rst used in Florida and Texas in the mid-1980s and till nowadays it seems to have been used only in some other states of the USA.This is a form of the wet process where CRM is blended with hot bitumen at the re?nery or at a bitumen storage and distribution terminal and transported to the asphalt plant/job site for use.In fact the main intuition behind this technology is to take advantage of the engineered properties of the RTR by using the CRM as an alternative modi?er to produce storage stable modi?ed bitumen.These binders are often labeled as termi-nal blends,although nowadays they may also be?eld-blended at the asphalt plant.Furthermore,this terminology could sound restrictive also because some of the terminal-blended RTR-MBs,

Fig.19.Maintenance cost(left)and User cost comparison between conventional bituminous mixes(AC)and Asphalt-Rubber mixes(ARAC).

D.Lo Presti/Construction and Building Materials49(2013)863–881877

4.1.Production

In this process,no modi?cations to the asphalt plants are re-quired because the No-Agitation RTR-MBs are manufactured with speci?c pressure,temperature,time and agitation requirements similarly to polymer modi?ed bitumen.In the wet process-No-Agi-tation CRM and bitumen are blended through the continuous blending-reaction systems.No reaction tanks are provided.The bitumen is heated under a controlled environment in a tank to an elevated temperature and high shear stress.The CRM is then introduced into the tank and digested into the bitumen.The char-acteristic swelling process of the RTR-MB technologies is replaced by the depolymerisation/devulcanisation and optimised dispersion of the rubber into the bitumen by using high processing conditions (temperatures between200and300°C,shear stresses in the order of few thousands RPM and eventually with pressure higher than 1atm),resulting in a smooth,homogeneous product.In the past, rubber contents for such blends have generally been610%by weight of bitumen or total binder,but some products now include even25%CRM[61].

There are some proprietary and other non-proprietary pro-cesses.Some of them also include small percentage of other poly-mers(e.g.SBS),or other additives,to produce a combined homogeneous material that exhibits excellent storage stability and compatibility with the?nished binder formulation.Such bind-ers are typically modi?ed with CRM particles?ner than the 300l m(No.50)sieve size that can be digested(broken down and melted in)relatively quickly and/or can be kept dispersed by normal circulation within the storage.During this process,the operator takes samples and runs a solubility test to ensure the rub-ber is completely digested.Most manufacturers used a high shear process to make sure the CRM is completed digested.The solubility of the?nished product is generally above97.5%.The binder is then delivered to the hot mix plant by truck as a?nished product with no additional handling or processing.After mixing with aggregate material is shipped to the job and no special equipment is required for paving,or odour/fume control.Moreover,the RTR mix is com-pacted like regular hot mix asphalt[62].

4.2.Storage stability

The wet process-No-Agitation aims to produce bitumen-Recy-cled Tyre Rubber blends which do not occur in eventual phase sep-aration of the CRM from the binder during storage or transportation.The mechanism of phase separation is related to the differences in the properties,mainly physical,of the material constituents in the blends.After production of the blend,the pres-ence of non-dissolved CRM particles in bitumen leads to phase separation,particularly when the blends are stored at high temper-atures.As a result,the swollen CRM particles are considered to settle down quickly due to initial higher density than the bitumen phase[63].On the other hand,migration of the CRM particles to the top of the storage container due to a reduced density after swelling has also been reported in some research studies[64,65]. These different mechanisms lead to an unstable condition which results in a rubberised blend with varied properties after the storage.

The improvement of the settling properties of the No-Agitation RTR-MBs is often linked to the careful selection of the blend’s com-ponents usage of high-curing conditions[66]which ensures a high level of solubilisation of the CRM within the bitumen matrix.Some patented procedure states that as long as the CRM is fully digested into the binder(solubility is above97%)it is possible to store them without phase separation[62].However,at this stage the effect of the modi?cation is signi?cantly reduced.In fact,CRM is shown to a number of studies to effectively modifying the bitumen when it is still in the swollen state and not completely devulcanised/depoly-merised(Fig.10c).In order to maintain a convenient level of mod-i?cation,recent studies have shown that is possible to improve the storage stability of RTR-MBs also by adding substances to operate a chemical stabilisation of the blends[67],by mixing rubberised bitumen blends in presence of a low percentage of polymers [68],with compatibiliser to activate the CRM[69],or with sulphur to improve crosslinking[64].Another study[70]shows that hot storage stability of rubberised bitumens could be improved by blowing oxygen gases through these blends.In addition,pre-treat-ment of CRM particles with hydrogen peroxide has also resulted in a more stable RTR-MBs[71,72].Furthermore,Attia and Abdelrah-man[68]suggest improving the stability of modi?ed binders also by lowering the storage temperatures.In any case,the stability of No-Agitation RTR-MBs during prolonged storage seems to be similar to other blended PMBs and the man role in improving the settling properties of bitumen-RTR blends is covered by an accu-rate selection of the processing conditions(Lo Presti et al.2012).

4.3.Properties(Like a PMB)

Although such binders may develop a considerable level of rub-ber modi?cation,rotational viscosity values rarely approach the minimum threshold of1500cPs at177°C,that is necessary to sig-ni?cantly increase binder contents above those of conventional as-phalt mixes without excessive drain down[36].Recently in the United States the speci?cations used for terminal blend(PCCAS, 2008)have utilised the PG grading system,named PG-TR system, similar to the ones used for polymer modi?ed bitumen (Fig.4.33).In California,PG-TR grades are speci?cally targeted for use in the same applications for which PG-PMB binders are used, including dense-graded mixes for thick structural sections.The ter-minal blends now meet the ASTM de?nition for minimum CRM content[73].

Within the No-Agitation RTR-MBs production,two main prop-erties are of concern:?rst,the development of performance-re-lated properties and,second,binder compatibility or storage stability.The literature indicates that performance-related proper-ties develop early in the process while compatibility requires few hours to stabilise[74].Few investigators have conducted studies on the rheological properties of these binders.For example,Thode-sen et al.[75]evaluated several binders using the multiple creep recovery tests.Among the binders studied were an Asphalt-Rubber binder and a No-Agitation RTR-MB that uses10%CRM and1%SBS polymer.The results showed that the analysed RTR-MB exhibited the least creep and the highest percentage recoveries under vari-ous loading and temperature ranges.Another example is given by Attia and Abdelrahman[68],which investigating the possibility of producing high-performance terminal blends,suitable for SuperPave applications,found that by accurately regulating the processing conditions it is possible to balance the development of performance-related properties and storage stability.The same researchers proposed a procedure consisting in blending bitumen with5%of CRM and2%of SBS at elevated shear stress(30–50Hz)and with the processing conditions shown in Fig.4.38.They found that the?nal products have performance and binder stabil-ity(increasing shearing speed to50Hz)comparable to those of patent or proprietary products.Hence,interaction temperature on binder stability was not evaluated.Moreover the authors sug-gest enhancing the stability of binder by reducing the storage tem-perature at the plant.

4.4.Applications

No-Agitation RTR-MBs can be used with rubber contents as low as5%and as high as25%,depending on the application and the

878 D.Lo Presti/Construction and Building Materials49(2013)863–881

project’s requirements.These products can be used in all paving and maintenance applications as a replacement of the polymer modi?ed bitumens:[60]:

Recycled Tyre Rubber Modi?ed Paving Grade Bitumens.

Standard PG grades–dense graded mixes.

PG plus grades–high performance mixes.

Warm mix standard grades–dense and open/gap graded mixes.

Warm mix polymer modi?ed grades–dense and open/gap graded mixes.

Hot applied chip seal binders–neat and polymer modi?ed.

Recycled Tyre Rubber Modi?ed Cutback Bitumens.

(MC)Medium Cure Graded.

(SC)Slow Cure Graded.

Recycled Tyre Rubber Modi?ed Bitumen emulsions.

Rapid set chip seal.

Micro surfacing slurry seals.

Standard slurry seals.

Cold in-place recycling.

Cold Mix.

Recycled Tyre Rubber Modi?ed Seal Coats.

Recycled Tyre Rubber Modi?ed Surface Sealer.

Recycled Tyre Rubber Modi?ed Fog Seals.

5.Discussion and conclusion

High Viscosity RTR-MBs and No-Agitation RTR-MBs are differ-ent products and should not be interchanged(Fig.20).However, both provide superior cracking performance at reduced thickness, when compared to conventional dense graded hot mix asphalt pavement.Only when there are construction issues the products are not be expected to perform in a superior manner.

In terms of binder properties,the main differences between these products are the viscosity and their storage stability.Viscos-ity for No-Agitation RTR-MB can range between500and1000cen-tipoises at135°C,much lower than the viscosity for High Viscosity RTR-MB which is in the range of1500–5000centipoises at177.5°C (Table8).With regards to the storage stability,No-Agitation RTR-MB born with the idea of obtaining a RTR modi?ed binder compa-rable to the normal PMBs,therefore on contrary to High Viscosity RTR-MB,it is usually possible to store it as conventional PMBs.Fur-thermore,a recent study[76]highlights that the storage tempera-ture of the No-Agitation RTR-MB could be signi?cantly decreased (i.e.15°C)if compared to the?eld blended High Viscosity RTR-MB.Considering also the need of the?eld blends to be stored in agitated tanks,from this point of view the terminal blends leads to signi?cant energy and money savings.

On the other hand,asphalts obtained by using High Viscosity leads to an asphalt mix with signi?cantly high binder content (about7–9%)and with widely proven reduced oxidation,increased durability and increased resistance to re?ective cracking.All these bene?ts are reduced when High Viscosity RTR-MBs is used for Dense-Graded hot mix projects since the dense gradation cannot adequately accommodate the rubber particle size,?lm thickness is reduced(9micron)as well as acceptable binder content(about 5%)and the RTR-MBs needs to be produced with much lower rub-ber content(about10%).The use of special equipment is not any-more justi?ed by the signi?cant bene?ts of a thicker coating, therefore in the case of Dense-Graded asphalt mixes the No-Agita-tion RTR-MBs are the most suitable.On this regard,they are more likely to compete with polymer modi?ed bitumen rather than High Viscosity RTR-MB.

No-Agitation RTR-MBs have been successfully used for a much wider range of products as for instance chips seal applications, open graded and gap graded mixes and emulsions.Basically,No-Agitation RTR-MBs can be used wherever conventional asphalt mixes or asphalt surface treatments are needed.The lower viscos-ity of No-Agitation RTR-MB implies the usage of less binder per unit area(5–6%binder content)indicating less performance life than if High-Viscosity RTR-MB is used(8–10%binder content).In fact,the ability to inject more binder in the mix translates to better fatigue and re?ective cracking performance.

In conclusion,the main advantages of the usage in asphalt mix-ture of the wet process-No-Agitation in lieu of the wet process–High Viscosity method at the contractor’s plant include: No need for costly specialised equipment at the asphalt plant.

No portable plants required for blending of Crumb Rubber with asphalts.

No additional holding areas for storing the Crumb Rubber product.

Easiest for the contractor to incorporate into their tradi-tional manufacturing process.

Mixing,laying and compaction temperatures are compara-ble to standard mix applications with PMBs.

Works with all mix designs;does not require any special adjustments to gradation or mix design parameters.

Being prepared at the re?nery,completely eliminates potential problems with heating and blending of Crumb

Rubber and asphalt products and

Eliminates smoke and particulates from entering the atmosphere.

The binder can be Performance Graded and emulsi?ed

The few available analyses on the sustainability of the product show that No-Agitation leads to economical saving

and environmental bene?ts.

Fig.20.RTR-MB from Wet process(left)and Wet Process-No-Agitation(right),adapted from[73].

D.Lo Presti/Construction and Building Materials49(2013)863–881879

Some have expressed concern that there is no way to verify the amount of CRM used in No-Agitation RTR-MBs.

Moisture susceptibility of asphalt mixture containing No-Agitation RTR-MB is still not clear.

5.1.Conclusions

The author believes that the widespread use of the RTR-MBs technologies within the road pavement industry is advisable.In fact the several bene?ts provided to the asphalt pavement perfor-mance,and to the overall sustainability of the infrastructure,are so evident that it is strongly advised to consider RTR-MBs technolo-gies as a?rst option to the binders currently used in road https://www.doczj.com/doc/cf16968269.html,panies,road authorities,etc.have to evaluate if it is convenient to use the High Viscosity wet process technology, which proved widely to provide several bene?ts,in particular it al-lows highway designers to reduce pavement layer thickness due to the proven properties of rubberised bitumen,but presents some challenges as:the need for suitable blending and mixing equip-ment,the cost of such equipment and the degree of dif?culty in preparing asphalt mix design.The other option is to choose the wet process-No-Agitation technology which solves several issues but leads to asphalts pavements with,so far,uncertain long term performance.In both cases the implementation of these technolo-gies still presents issues as:the lack of availability of suitable RTR processing facilities in the vicinity and the cost of such facilities, the lack of rubberised bitumen binder and mix standards,the uncertainty on the environmental performance of these products and the lack of trained personnel particularly for accurate labora-tory analyses,of raw materials and?nal blends,which are neces-sary to optimise the modi?cation process and the performance of the?nal https://www.doczj.com/doc/cf16968269.html,cation and training are indeed another key aspect for a successful application of RTR-MBs in road asphalt mix-tures also because new procedures are being developed to perform an enhanced laboratory design of these technologies[77]as well as reducing limitations to their applicability in the?eld.Examples are given by the increasing number of rubberised asphalt applications with additives able to reduce paving temperatures(i.e.warm mix technologies)[21,57],but also from the invention of a new form of product delivery as the case of the rubberised pellets[78].Another important aspect to clarify is the cost of this technology:it is true that initial costs are still an issue but the rapid cost increase of bitumen and results of lifecycle cost analyses indicate that RTR-MBs are in many cases an economically convenient option.At last, there is evidence that a closer involvement of local and national governments with policies supporting the RTR industries and the major investments on training and research could de?nitely help to decrease the costs of implementing RTR-MB technologies as well as solving the several issues indicated within this manuscript.A proof of this statement is given by the state of California(USA) where since2005a government mandate[79]supports the increasing adoption of these technologies in asphalt mixture and from the January2013the usage of rubberised asphalt pavements needs to reach at level of at least35%of the total weight of asphalt paving materials produced in the country.The main reason of this mandate is the prediction of substantial savings in the long term. References

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D.Lo Presti/Construction and Building Materials49(2013)863–881881

幼儿园大班美术活动教案《种子粘贴画》

大班美术活动教案《种子粘贴画》活动目标： 1、能利用种子进行粘贴作画，根据种子不同的外形特征表现一定的物体形象。 2、发现自然材料的美，体验成功的乐趣。 3、能在活动中耐心、细心完成作品。活动准备： 1、收集不同种类的种子如“瓜子、芝麻、绿豆、黑米、大红豆等，每组提供一份。 2、不同颜色卡纸画、胶水、棉签、卫生纸若干。 3、课件《种子粘贴画》。活动过程： 1、出示“种子盒”，导入活动，激发幼儿兴趣。教师摇动盒子，请幼儿根据声音来猜测盒子里装的是什么。猜完之后，导入透明盒子里请幼儿看一看都有哪些种子。 2、小朋友想一想种子可以用来做什么？幼儿自由回答。教师小结：小朋友刚才说了种子可以发芽，可以做粥等等。今天老师带来了许多好看的图画，我们一起请它们出来好不好？ 3、播放课件，边看边讲解操作过程和注意事项。

（1）、出示种子示范画，引导幼儿欣赏观察。教师：小朋友们，种子宝宝们可真厉害啊，这些图画可真漂亮啊！由各种各样颜色和形状的种子宝宝组成的的图画就叫做种子粘贴画。（2）、教师边示范边讲解。教师：刚才看了这么多好看的种子粘贴画，相信小朋友们很好奇是怎么做出来的吧！下面就跟着老师一起看看样该怎样操作。首先，用棉签沾上胶水涂在图画里，不能涂的太多哦！然后选择你喜欢的种子宝宝粘在胶水上面，粘上后用嘴巴吹一吹。如果是小米可以直接撒在上面。拿种子的时候要互相谦让。保持画面的干净。这样我们的图画就会变的漂亮了。 4、展示作品、进行点评。活动延伸：我们的种子粘贴画都完成的不错，下面我们把它放到作业袋里面吧。你可以请好朋友去和你一起欣赏哦。《种子粘贴画》反思通过这节课，孩子们利用种子进行粘贴，让孩子们初步认识了种子，了解它们除了可以食用，还可以制作种子画。激发了孩子们好奇心和探索欲望，让孩子们体验成功的乐趣。

中班美术活动种子粘贴画教案反思

中班美术活动种子粘贴画教案反思中班美术活动种子粘贴画教案反思主要包含了活动目标，活动准备，活动过程，活动延伸，活动反思等内容，能利用种子进行粘贴作画，根据种子不同的外形特征表现一定的物体形象，发现自然材料的美，体验成功的乐趣，适合幼儿园老师们上中班美术活动课，快来看看种子粘贴画教案吧。活动目标： 1、能利用种子进行粘贴作画，根据种子不同的外形特征表现一定的物体形象。 2、发现自然材料的美，体验成功的乐趣。 3、能在活动中耐心、细心完成作品。　 4、引导幼儿能用辅助材料丰富作品，培养他们大胆创新能力。 5、让幼儿体验自主、独立、创造的能力。　活动准备： 1、收集不同种类的种子，如“葵花子、白芝麻、绿豆、黑米、红豆等，每组提供一份。 2、画有各种图案的彩色卡纸、胶水、棉签、湿毛巾若干。 3、《种子粘贴画》ppt 。活动过程： 1、出示“种子瓶”，玩《听音辨物》游戏导入活动，激发幼儿参与活动的兴趣。教师摇动装有种子的瓶子，让幼儿根据声音来猜测盒子里装的是什么。猜完之后，导入透明盒子里请幼儿看一看都有哪些种子。 2、讨论：种子可以用来做什么？幼儿自由回答。教师小结：小朋友刚才说了很多种子的用途，老师也用种子做了许多好看的东西，你们想知道吗？那我们一起来看吧。 3、播放《种子粘贴画》ppt，引导幼儿欣赏观察。（1）、刚刚你们都看到了哪些漂亮的图片？谁来告诉大家这些漂亮的图片都是用什么东西做成的？　教师：小朋友们，种子宝宝们可真厉害啊，变出了这么多的漂亮图片，我们把这些漂亮图片叫做种子粘贴画。（2）、教师边示范边讲解。教师：刚才看了这么多好看的种子粘贴画，你们想不想也用种子来做一幅漂亮的图画呢？那现在我们就一起来看一看种子粘贴画是怎么完成的。首先，取出一张画有图案的画纸，根据图案想一想，选择哪些种子来进行粘贴，接着，用棉签沾上胶水涂在图画里，注意不能涂的太多哦！然后，用你选择的种子宝宝粘在胶水上面，并轻轻地按一按，将图案里都粘贴上了种子宝宝，种子粘贴画就完成了，图案不同的地方我们可选择不一样的种子，而且拿种子的时候要小心，不能将种子撒了。（教师边讲解，边示范制作过程） 4、幼儿动手制作种子粘贴画。幼儿制作时，教师巡回观察，提醒幼儿注意胶水不能太多，拿种子时要小心，注意谦让等。 5、展示作品、进行简单点评。活动延伸：将幼儿制作的种子粘贴画创设一个作品展示栏，让孩子们进一步感受自然材料的创作之美，体验成功感的快乐。活动反思：原来的粘贴相框的活动只是单一的技能要求以直线条为主，这一操作任务对孩子已经不再具有挑战性了，这就向我们发出信号，提醒我们要调整材料，作出应答。这正是《纲要》中提倡的教师在组织实施教育活动时应“关注幼儿在活动中的表现和反应，敏感的觉察他们的需要，及时以适应的方式应答，形成合作探究式的师幼互动。”

英语四级作文 Recycling Waste-废物的回收利用

英语四级作文 Recycling Waste-废物的回收利用 Recycling Waste European countries are now making an active effort to reuse materials more than they used to. This is called recycling.Materials such as paper，glass or metal are collected， sorted，treated and used again. Old papers are recycled. The ink is taken out by a special technique， and new paper is made. Oil from fatories and motor oil can be treated and resued. In many cities in Europe rubbish is collected separately. Empty glass bottles are collected， and the glass is broken and reused for making new bottles. Developing countries all over the world already recycle materials. In India， waste paper is collected， sorted and recycled. Paper bags are made from unsold newspapers. In Egypt， waste is collected by rubbish cars and sorted. Leftover food is given to pigs and vegetable matter is put back onto the fields. In some Asian countries， shoes are made from the rubber of old car tyres. The Chinese government is also working hard against pollution. More than 60，000 small factories which seriously polluted the enrivonment were shut down in 1996. Many materials like used rubber

汽车轮胎参数

图：轮胎表面的参数解读 https://www.doczj.com/doc/cf16968269.html, 2009年07月23日21:33 腾讯汽车综合我要评论(3) 有许多有用的信息被模制到轮胎的胎侧上，例如轮胎种类、花纹、规格、有无内胎、速度级别、载重指数、扁平比以及重要的安全标示等等。轿车轮胎的胎侧例: P215/65R15 89H “P” 是指轿车轮胎。(用以区别卡车或其他车型适用的轮胎) “215”指的是轮胎断面的宽度，是两个胎侧之间的宽度(以毫米为单位)。此宽度随轮胎所匹配轮辋宽度的不同而不同：宽轮辋配宽轮胎，窄轮辋配窄轮胎。一般在胎侧上所标示的胎宽，是指当轮胎安装到所建议宽度的轮辋时的宽度。 “65”是轮胎的扁平比，是胎宽与胎高的比例，这里指胎高占胎宽的65%，数值越小，越显扁平。

“R”是指轮胎的结构，表示此轮胎为子午线结构，也就是说它的帘布层是呈辅射状排布在胎体内的。“B”表示轮胎为斜交结构，目前斜交结构的轿车轮胎已不复存在。 “15”表示轮辋直径(以英寸为单位)，此轮胎必须匹配15英寸(1英寸等于2.5400厘米)的轮辋，否则无法安装。 “89”表示载重指数：此轮胎最高载重为1,279磅（1磅=0.45359237千克）。不同的载重指数代表不同的最高载重(通常以磅或公斤为单位)。 “H”表示速度级别：此轮胎最高时速为每小时130英里（1英里=1.609344千米）。旧式欧洲胎边标示系统中以215/65HR15表示。不同的英文字母表示不同的速度级别。 “DOT”则表示此轮胎符合美国交通部(U.S. Department of Transportation, DOT)规定的安全标准。“D OT”后面紧挨着的11位数字及字母则表示此轮胎的识别号码或序列号。胎侧通常也显示帘线种类、胎侧和胎面帘布层数。轮胎分级：统一轮胎品质分级系统(Uniform Tire Quality Grading System, UTQG) 除雪地胎外，DOT要求制造厂依据“胎面磨耗” “抓地力” 及“耐高温”三个性能要素将轿车轮胎分级。胎面磨耗率超过100-较优 100-标准低于100-较差。磨耗等级是根据在美国政府指定的试验场地，按标准条件测试的磨耗率换算得出的。如某轮胎磨耗等级为200，则表示它在政府指定的试验场地上比等级为100的轮胎可以多跑一倍的时间。而实际上

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垃圾的分类 The classification of garbage Hello, everyone! I am glad to have this chance to share some ideas about the classification of garbage with you. When walking in the campus, you usually ask yourself，“where is the garbage can?”，in order to lose rubbish in your hand. In the past, I think it is a fairly easy thing to throw rubbish. The only thing which waste my time is to find a garbage can in the nearby. Then I would throw the garbage into the trash can with giving a whistle. But now things are changing. Along with the environmental policy，I find that more and more garbage can with novel style appeare in the campus. They ordinarily consist of two parts. One used to hold the recyclable garbage, and another used to store unrecyclable garbage. So when I’m ready to throw rubbish, I need to stop and think. What type of garbage does it belong to in my hand? Recyclable? Unrecyclable? Then I must to bent down to see what is written on the barrel. Which one is recyclable barrel? Which one is unrecyclable barrel? Because I’m nearsighted. Although this process wastes my some time, when I put the rubbish into the right position, I will arise spontaneously a sense of achievement. Because I think I have done a little useful thing for the great cause of environmental protection. But sometimes ,it is not a simple thing to make sure the type of

轮胎型号大全

各种车辆用的型号: 195/50 R15 82V 捷达GIF、斯柯达FABIA 195/55 R15 85V POLO、标致206、雨燕、凯越、塞纳、福美来、普利马、哈飞赛豹205/50 R15 86V 雷诺风景II、沃尔沃S40 T5、现代酷派 205/55 R15 88V 马自达626、现代MARIX、丰田CELICA 205/45 ZR16 87W 奔驰A160、SMART、标致206CC 205/50 ZR16 87W 伊兰特1.8、塞拉图Sports、丰田CELICA、雷诺风景、MINI 205/55 ZR16 91W 奥迪A6、马自达6、宝马318i、蒙迪欧、福克斯、景程SX、标致307CC、大众甲壳虫、途安、帕萨特、中华尊驰 215/55 ZR16 93W 奥迪A4、A6、雪铁龙C5、欧宝VECTRA、萨博95 215/60 R16 95V 丰田锐志、佳美、本田奥德赛、现代NF、双龙主席 225/50 ZR16 92W 宝马Z3、奔驰CLK 级、SLK 级 225/55 ZR16 95W 奥迪A6L、宝马5 系、凯迪拉克CTS、美洲虎S-TYPE、雷克萨斯G300、IS200、奔驰SL 级、

E级、三菱3000GT 205/50 ZR17 89W 沃尔沃S40、宝马530i 215/45 ZR17 91W 富士翼豹、雷克萨斯IS200 215/50 ZR17 95W 欧宝VECTRA、三菱GTS 215/55 ZR17 94W 丰田皇冠、锐志、标致407、富士森林人、傲虎、风度V6 3.0、天籁350 V6 225/45 ZR17 91W 宝马Z4、无限G35、帕萨特W8、奥迪TT，奔驰C系 225/50 ZR17 94W 奥迪A6L、宝马5 系、凯迪拉克CTS、沃尔沃S80、索纳塔NF，标致607 3.0V6 225/40 ZR18 92W 奔驰CLK 级、SLK 级、克莱斯勒CROSSFIRE 225/45 ZR18 95W 无限G35、马自达RX8、奥迪A8L 235/50 ZR18 97W 奥迪A8、凯迪拉克XLR、美洲虎XJ6 245/40 ZR18 97W 美洲虎S-TYPE、雷克萨斯SC430、奔驰CLS 级 245/45 ZR18 96W 宝马645i、奔驰CL 级、S 级、日产350Z 255/35 ZR18 90W

幼儿园小班美术教案种子粘贴画(三篇)

教学资料参考范本幼儿园小班美术教案种子粘贴画(三篇)目录：幼儿园小班美术教案种子粘贴画一幼儿园小班美术教案笔宝宝走路二幼儿园小班美术教案篮子里的蔬菜三

幼儿园小班美术教案种子粘贴画一【活动目标】 1、能利用种子进行粘贴作画，根据种子不同的外形特征表现一定的物体形象。 2、发现自然材料的美，体验成功的乐趣。 3、能在活动中耐心、细心完成作品。【活动准备】 1、收集不同种类的种子如瓜子、芝麻、绿豆、黑米、大红豆等，每组提供一份。 2、不同颜色卡纸画、胶水、棉签、卫生纸若干。 3、课件《种子粘贴画》。【活动过程】 1、出示“种子盒”，导入活动，激发幼儿兴趣。教师摇动盒子，请幼儿根据声音来猜测盒子里装的是什么。猜完之后，导入透明盒子里请幼儿看一看都有哪些种子。 2、小朋友想一想种子可以用来做什么? 幼儿自由回答。教师小结：小朋友刚才说了种子可以发芽，可以做粥等等。今天老师带来了许多好看的图画，我们一起请它们出来好不好? 3、播放课件，边看边讲解操作过程和注意事项。 (1)出示种子示范画，引导幼儿欣赏观察。

师：小朋友们，种子宝宝们可真厉害啊，这些图画可真漂亮啊!由各种各样颜色和形状的种子宝宝组成的的图画就叫做“种子粘贴画”。 (2)教师边示范边讲解。师：刚才看了这么多好看的种子粘贴画，相信小朋友们很好奇是怎么做出来的吧!下面就跟着老师一起看看样该怎样操作。师：首先，用棉签沾上胶水涂在图画里，不能涂的太多哦!然后选择你喜欢的种子宝宝粘在胶水上面，粘上后用嘴巴吹一吹。如果是小米可以直接撒在上面。拿种子的时候要互相()谦让。保持画面的干净。这样我们的图画就会变的漂亮了。 4、展示作品、进行点评。

全球回收标准GRS4.1培训教材

全球回收标准GRS4.1 培训教材 2020.04.23

Textile Exchange Global Recycled Standard纺织品交易所回收标准GRS 4.1替代GRS 4.0，自2019年5月8日起生效。

前言 A部分 - 基本信息和要求 GRS认证的原则 / 回收材料要求 / 供应链要求 B部分 – 社会要求 B1 – 社会政策 / B2 – 社会要求 C部分 – 环境要求 C1 - 环境管理体系 C2 – 环境要求 C2.1 能源使用 C2.2 用水 C2.3 废水/污水C2.4 废气排放 C2.5 废物管理D部分 - 化学要求 D1 – GRS 化学品管理 / D2 - GRS中的受限制化学物质附录

Introduction简介 The Global Recycled Standard (GRS) is an international, voluntary, full product standard that sets requirements for third-party certification of Recycled Content, chain of custody, social and environmental practices, and chemical restrictions. The goal of the GRS is to increase use of Recycled materials in products and reduce/eliminate the harm caused by its production. 全球回收标准（GRS）是一项国际、自愿和全面的产品标准，规定了回收内容、产销监管链、社会和环境实践以及化学品限制的第三方认证要求。GRS 的目标是增加产品中回收材料的使用，并减少/消除其生产所造成的危害。

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According to our experience, the following materials account for majority cost of the products based on LEED scope, and most of them will have great contribution to ensure related LEED credits. MR 4 Recycled Content: Material Recycled Content Recycled Content type Weighted Percentage Possible Brand Carpet made of synthetic materials Industrial Nylon Post- consumer Up to 100％Interface Gypsum wall board Gypsum ceiling board Desulfo－ Gypsum Pre- consumer 90％Lafarge Furniture PET (plastic bottle) / Recycled Aluminium Post- consumer Above 80% Haworth Ceiling Tile (矿棉板) Wasted newspaper Post –consumer 40% Armstrong Glass Cullet /wasted glass Pre-consumer /Post-consumer 10%~30% ALL Cement Fly ash Pre-consumer 30%~50% ALL Concrete Fly Ash Pre-consumer 5% ALL Aluminium Panel Recycled Aluminium Post- consumer 20% Alucobond Steel Waste steel Post- consumer 25% Default value Marble N/A particle board 刨花板 Wood chips Pre-consumer 100% ALL 细木工板 N/A 中密度板wood chips Pre-consumer

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(1) (5) (7) (9) .............................................................................. 11 (1) 4 (1) 6 (18) MICHELIN Primacy HP (29)

225/55R17 97 W 梅赛德斯奔驰 S600 V12;路虎神行者V6;上海通用别克君威 2.0L 225/50R17 98 W 凯迪拉克 CTS;宝马 530i;华晨宝马530i;沃尔沃 S80 3.2; 205/55R16 91 W 斯巴鲁力狮;北京现代伊兰特悦动1.8;上海大众帕萨特领驭 1.8T 205/50R16 87 W 北京现代伊兰特 1.8 GLS;南汽名爵3SW 1.8;沃尔沃 S70 T5; 235/60R16 100 V 奇瑞瑞虎 2.4L;梅赛德斯奔驰 300 SEL;上海通用凯迪拉克 SRX 4.6L;沃尔沃 XC90 3.2 AWD 205/60R16 92 V 雷诺风景;长安铃木天语;北京现代索纳塔 GLS V6 GOLD 215/60R16 95 V 北京现代御翔 24S;一汽丰田皇冠ROYAL;一汽丰田皇冠;斯巴鲁森林人 225/60R16 98 W 梅赛德斯奔驰 S280;上海通用别克君威;上海通用别克君越;梅赛德斯奔驰 S350 225/55R16 99 W 宝马 528i;凯迪拉克 CTS;北京梅赛德斯奔驰 E280;沃尔沃 S80 2.5T 215/55R16 97 W 梅赛德斯奔驰 E200;萨博 9-5;奥迪A4;上汽荣威荣威 195/50R15 82 V 一汽大众捷达 GIF;斯柯达 ELEGANCE FABIA 1.4 16V;大众高尔夫 195/65R15 91 V 标致 307;一汽大众新宝来 1.6;上海大众朗逸 1.6;北京现代伊兰特悦动 1.6; 205/65R15 94 V 宝马 520i;广州本田雅阁 2.4;北京现代索纳塔;尼桑风度 V6 3.0GV 225/60R15 96 V 宝马 528i; 195/55R15 85 V 上海通用别克凯越;海南马自达福美来;上海大众波罗 205/60R15 91 V 宝马 318i;东风日产蓝鸟;一汽奥迪A6;东风悦达起亚远舰 GL 215/65R15 96 V 东风风行;马自达 MPV 3.0i V6;北京现代御翔 2.0 195/60R15 88 V 比亚迪汽车 F3;本田雅阁 2.2;北京现

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害啊，这些图画可真漂亮啊！由各种各样颜色和形状的种子宝宝组成的的图画就叫做种子粘贴画。 2.教师边示范边讲解。教师：刚才看了这么多好看的种子粘贴画，相信小朋友们很好奇是怎么做出来的吧！下面就跟着老师一起看看样该怎样操作。首先，用棉签沾上胶水涂在图画里，不能涂的太多哦！然后选择你喜欢的种子宝宝粘在胶水上面，粘上后用嘴巴吹一吹。如果是小米可以直接撒在上面。拿种子的时候要互相谦让。保持画面的干净。这样我们的图画就会变的漂亮了。幼儿欣赏制作过程，了解一些制作的注意事项。通过教师的边示范边讲解，让幼儿知道制作过程。四、展示作品、进行点评。活动延伸：我们的种子粘贴画都完成的不错，下面我们把它放到作业袋里面吧。你可以请好朋友去和你一起欣赏哦！幼儿把自己的作品放到作业袋，相互欣赏、点评作品。通过欣赏和点评让幼儿体验成功的快乐。七、教学反思:

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国家标准《废弃电工电子产品回收利用术语》（征求意见稿）编制说明一.标准工作概况 1.1 前言随着科技的飞速发展，电子行业成为数量和更新换代速度增长最快的领域之一，也导致电子产品使用寿命越来越短，报废电子设备的数量迅猛增加。同时大部分报废电工电子设备中含有有害物质，如未经技术处理直接进行焚烧、掩埋将会造成地下水和大气的严重污染。而另一方面来说，废弃电工电子产品中有许多有用的资源，如铜、铝、铁及各种贵金属、玻璃和塑料等，具有很高的再利用价值。目前从国际到国内已经越来越加强了对废弃电工电子产品回收处理的管理，出台了多项相应的法律法规和技术标准。我国将于2011年1月1日开始实施中国版WEEE：《废弃电器电子产品回收处理管理条例》。本条例对电子产品的生产者和回收企业都提出了相应的要求，规定生产者要交纳废弃电器电子产品处理基金，并在产品上或者产品说明书上按照规定提供有关有毒有害物质含量、回收处理提示性说明等信息，回收企业要符合国家环保标准等规定。目前国内也在开展一系列配套技术标准的制定工作。而标准体系的制定需要建立统一的术语定义，以协调各标准的一致性和科学性，促进产业的规范化管理和国内外的管理与技术交流。 1.2 任务来源本标准的制定来自于国家标准委2009标准制修订计划，计划项目号为20090089-T-469，旨在分析国内外电工电子产品资源循环利用法律法规及该领域标准化工作现状，建立适应我国国情和生产力发展水平的标准化体系框架，并制定一系列废旧电工电子产品回收过程、处理方法、污染控制、相关组织的管理评价方法，为行业发展提供技术支撑，提升我国相关产业的生产技术水平。

轮胎公司简介

山东玲珑轮胎股份有限公司简介山东玲珑轮胎股份有限公司位于中国金都－招远市，是一家专业化、规模化的技术型轮胎生产企业。公司主导产品轮胎涵盖高性能轿车子午线轮胎、乘用轻卡轿车子午线轮胎、全钢载重子午线轮胎等10000多个规格品种，连续多年入围世界轮胎20强，中国轮胎前五强。自主创新能力突出，掌握行业核心技术。公司拥有国家级企业技术中心和国家认可实验室，是国内同时拥有国家级企业技术中心与博士后科研工作站为数不多的企业之一，建设了行业内第一家噪声实验室和低滚动阻力实验室，其中低滚阻实验室于2012年6月份与欧盟相关滚阻检测机构完成对标，具备独立检测滚阻的能力，获得欧盟认可；公司还组建了院士工作站、哈工大玲珑轮胎研究中心，斥巨资购进动态印痕实验机、滚动阻力试验机、LMS系统等世界领先试验检测设备500多台套，为产品质量检测、新产品研发及性能提高提供了强有力的硬件保障。公司科研团队承担了多项国家863计划、多项火炬计划等国家级技术攻关课题，主导和参与制定及修改了60多项国家及行业标准，取得三百多项国内外专利，形成了一批行业领先、国内一流的关键技术和高新技术产品： Green-max UHP轮胎在2011年夏季芬兰轮胎世界评测中以7.6分的综合得分位列第四位，与米其林等两大世界一线品牌并驾齐驱，成为历次测试中表现最好的中国轮胎。公司自主研发的“低断面抗湿滑低噪音超高性能轿车子午线轮胎”，先后获得“山东省科技进步一等奖”和2010年度“国家科技进步二等奖”，是中国轮胎产品截止目前获得的国家科技进步奖最高奖项。倡导低碳，绿色先行，进入21世纪，玲珑轮胎将环保理念倾注到经营管理的每一个环节，以“安全、高环保、低消耗、操控性能好、驾乘舒适度好”等要求为目标，致力于绿色环保轮胎的研发与推广，截止2014年六月底，公司通过Smartway认证的产品数量已经达到58个，总数位居世界各轮胎品牌第一。在欧盟标签法应对上，个别产品达到A级、部分达到B级、大多数处于C级，达到国际先进水平。管理精益求精，产品质量稳定可靠，成就挺进中高端轮胎配套市场有力依托。玲珑人始终坚持“管理就是执行、管理就是服务、管理就是改善创新”的现代化管理理念，在管理上精益求精，借助信息化技术，实现异地协同办公、深度开发ERP系统综合管理功能，推进服务器与桌面虚拟化，为公司业务的高效运转提供了基础保障。利用MES系统、产品PDM、硫化群控、信息集成等信息技术，推行“目视化、现场5S、设备TPM、质量QC、作业标准化”五大管理模板，

轮胎部位和部件术语

轮胎部位和部件术语 3. 1 胎冠cap，外胎两胎肩之间的整个部位，包括胎面、缓冲层（或带束层）和帘布层等。 3. 2 胎面tread，胎冠部位缓冲层（或带束层）或帘布层以上的外胎胶层。 3. 3 胎面行驶面tread cap，胎面两胎肩间与地面接触部位。 3. 4 胎面基部tread base，胎面花纹沟底以下至缓冲层（或带束层）或帘布层之间的胶层，分为基部胶和过渡胶。 3. 5胎面基部胶tread slab base，胎面花纹沟底以下至胎面过渡胶之间的胶层。 3. 6 胎面过渡胶transition rubber of tread，胎面基部胶以下至缓冲层（或带束层）或帘布层之间的胶层。 3. 7 缓冲层breaker，斜交轮胎胎面与胎体之间的胶帘布层或胶层。 3. 8带束层belt，在子午线轮胎的胎面基部下，沿胎冠中心线圆周方向箍紧胎体的材料层。 3. 9 缓冲胶片breaker strip，加贴在缓冲层或带束层上、下的胶片。 3. 10包边胶tie-in strips，包覆在钢丝帘布层和带束层两端的胶片。 3. 11冠带层cap ply，加贴在带束层上面或活胎面基部的胶帘布层。 3. 12胎体carcass，通常为由一层或数层帘布与胎圈组成整体的充气轮胎的受力结构。 3. 13帘布层cord ply，胎体中由覆胶帘线组成的布层。 3. 14隔离胶insulation rubber，加贴在胎体帘布层之间的薄胶层。 3. 15封口胶sealing rubber，加贴在胎圈补强带或胎体帘布两端的胶片或胶条。 3. 16胎里tyre cavity，有内胎轮胎胎里表面的胶层。 3. 17内衬层inside liner，有内胎轮胎胎里表面的胶层。 3. 18气密层innerliner，无内胎轮胎胎里及胎圈与轮辋胎圈座接触面上的耐透气胶层。 3. 19胎肩shoulder，胎冠两侧边缘部位。 3. 20胎肩区shoulder area，胎冠与胎侧之间的过渡区。 3. 21胎肩垫胶shoulder wedge，带束层两端之下的三角形垫胶。 3. 22胎侧sidewall，胎肩至胎圈之间的部分。 3. 23屈挠区flexing area，轮胎在行驶过程中，胎侧频繁的弯曲变形的部分。 3. 24胎侧胶sidewall rubber，胎侧外层帘布层上的胶层。 3. 25装饰胎侧decorative sidewall，颜色不同于外胎表面其他部位的胎侧。 3. 26装饰线decorative rib，模压在胎侧上凸起的装饰性线条。 3. 27装配线fitting line，模压在胎侧与胎圈交接处的单环或多环胶棱，主要用以指示轮胎正确装配在轮辋上的标线。 3. 28防擦线kerbing rib ，模压在胎侧上，用以保护胎侧不被擦伤的环形凸起胶棱。 3. 29胎圈bead，轮胎安装在轮辋上的部分，由胎圈芯和胎圈包布等组成。 3. 30钢丝圈bead ring，由钢丝按一定断面形状排列制成的刚性环。

轮胎等级分类

有许多有用的信息被模制到轮胎的胎侧上，例如轮胎种类、花纹、规格、有无内胎、速度级别、载重指数、扁平比以及重要的安全标示等等。请点击轮胎示意图上的任意部位获取该部位的相关信息。轿车轮胎的胎侧例: P215/65R15 89H “P” 是指轿车轮胎。(用以区别卡车或其他车型适用的轮胎) , “215”指的是轮胎断面的宽度，是两个胎侧之间的宽度(以毫米为单位)。此宽度随轮胎所匹配轮辋宽度的不同而不同：宽轮辋配宽轮胎，窄轮辋配窄轮胎。一般在胎侧上所标示的胎宽，是指当轮胎安装到所建议宽度的轮辋时的宽度。 “65”是轮胎的扁平比，是胎宽与胎高的比例，这里指胎高占胎宽的65%，数值越小，越显扁平。“R”是指轮胎的结构，表示此轮胎为子午线结构，也就是说它的帘布层是呈辅射状排布在胎体内的。“B”表示轮胎为斜交结构，目前斜交结构的轿车轮胎已不复存在。 .“15”表示轮辋直径(以英寸为单位)，此轮胎必须匹配15英寸的轮辋，否则无法安装。 “89”表示载重指数：此轮胎最高载重为1,279磅。不同的载重指数代表不同的最高载重(通常以磅或公斤为单位)。 “H”表示速度级别：此轮胎最高时速为每小时130英里。旧式欧洲胎边标示系统中以215/65HR15表示。不同的英文字母表示不同的速度级别。 “DOT”则表示此轮胎符合美国交通部(U.S. Department of Transportation, DOT)规定的安全标准。“DOT”后面紧挨着的11位数字及字母则表示此轮胎的识别号码或序列号。胎侧通常也显示帘线种类、胎侧和胎面帘布层数。轮胎分级：统一轮胎品质分级系统(Uniform Tire Quality Grading System, UTQG) 除雪地胎外，DOT要求制造厂依据“胎面磨耗” “抓地力” 及“耐高温”三个性能要素将轿车轮胎分级。胎面磨耗率超过100-较优 100-标准低于100-较差。磨耗等级是根据在美国政府指定的试验场地，按标准条件测试的磨耗率换算得出的。如某轮胎磨耗等级为200，则表示它在政府指定的试验场地上比等级为100的轮胎可以多跑一倍的时间。而实际上轮胎的磨耗率与使用条件有关，例如：驾驶习惯，路面状况，气候，定位等皆会影响。注：磨耗率只能适用于同一制造商的产品进行比较，不同品牌不能予以比较。抓地力 A-最佳 B-中等 C-一般抓地等级，是指轮胎按标准条件在美国政府指定的测试场地，在湿滑柏油路面和水泥路面所表现的直线行驶刹车性能，不包括转弯性能。温度等级 A-最佳 B-中等