Rheological Evaluation of High ReclaimedAsphalt Content Modified with Warm MixAdditive
Lillian Gungat and Meor Othman Hamzah
Abstract High temperature for producing reclaimed asphalt mixture becomes themain concern in recycling as this will further age the reclaimed asphalt binder.Highly stiff binder causes workability and compatibility problems, hence affects thedesirable performance of pavement. Warm mix asphalt additive is able to decreasethe production temperature by reducing the binder viscosity. The synergy of warmmix asphalt and reclaimed asphalt mixtures resulted in a more environmental andenergy savings benefits. The effects of a warm mix additive on the rheologicalproperties of conventional asphalt binder containing a high proportion of recoveredreclaimed asphalt binder were evaluated. Reclaimed asphalt were obtained fromtwo sources and modified with a warm mix additive named RH. The recoveredbinders were blended with conventional binder at proportion of 0, 30 and 40 % andthen tested for viscosity, stiffness and frequency dependency. Fuel usage andgreenhouse gas emission were estimated based on the required fuel to heat up theaggregate and binder from ambient temperature up to the mixing temperature. Theaddition of RH improves the flow of binders by reducing the viscosity, thusdecreases the construction temperature. The initial stiffness of reclaimed asphaltbinders influences the effects of RH on the complex modulus and phase angle. Thecomplex modulus increases while the phase angle decreases as the frequencyincreases, which indicates the binders have become stiffer. The differences in themagnitude of complex modulus are more noticeable at lower frequency and it getsclose to each other at the higher frequency. This indicates that in the long run, the
L. Gungat (&) M.O. HamzahSchool of Civil Engineering, Engineering Campus, Universiti Sains Malaysia (USM),Nibong Tebang, Penang, Malaysiae-mail: firstname.lastname@example.org
M.O. Hamzahe-mail: email@example.com
Springer Science+Business Media Singapore 2015R. Hassan et al. (eds.), InCIEC 2014, DOI 10.1007/978-981-287-290-6_105
performance of modified reclaimed asphalt binders will be slightly better than theconventional hot mix asphalt. The warm mix additive and reclaimed asphaltcomposite in this study has the potential to reduce the fuel usage and green housegas (GHG) emission by 21 %.
Keywords Reclaimed asphalt Viscosity Construction temperature Stiffness Frequency-dependence
The awareness of environmental and sustainability issues of road constructionmaterials in asphalt industry has led to the widespread recycling of secondary mate-rials. The reuse of valuable old asphalt pavement can be considered as cost effectiveapproach for new road construction or rehabilitation. The cost saving will be more onthe materials as 70 % of the cost to produce hot mix asphalt (HMA) are frommaterials. Based on comparative life cycle assessment (LCA) studies on reclaimed asphalt(RA) the materials that were used in pavement for base and sub-base layers couldpotentially reduce global warming (20 %), energy consumption (16 %), water con-sumption (11 %), life-cycle costs (21 %) and hazardous waste generation (11 %) .It was reported that the total expenditure for road maintenance program in Malaysiahad increased to 2.16 billion in the year 2008 . The author highlighted that pave-ment recycling is quite new in Malaysia, but has grown dramatically over the last fewyears as the preferred way for rehabilitation of an existing pavement. The pavementcould be recycled partially or fully with the aid of recycling agents depending on theexisting road defect. The performances of reclaimed asphalt (RA) pavement incor-porated into new HMA are comparable with virgin HMA .
Nevertheless, increased stiffness of RA needs higher production temperature andthis is the main concern in recycling as this will further age the RA binder. Highproduction temperatures are needed to allow the asphalt binder to become viscousenough to completely coat the aggregate, have good workability during laying andcompaction as well as durability during traffic exposure. To compensate the furtheraging of RA binder, utilization of additives, rejuvenator and lower grade of binderhas been suggested . Too stiff binder leads to workability and compactibilityproblems and causes fatigue failure in the long run. Warm mix asphalt (WMA)additive is able to reduce the production temperature as the result of viscosityreduction. The combination of WMA and RA technology leads to more environ-mental and energy saving benefits especially during the asphalt production. Theincorporation of WMA additive allows more RA content to be incorporated into themixtures due to improved blending and workability, despite lower productiontemperature [6, 7]. Various WMA technologies such as organic (wax based),chemical and foamed can be selected to be added with RA .
1188 L. Gungat and M.O. Hamzah
2 Literature Review
In the past, a number of researches had been conducted related to the integration ofWMA technology to RA. There are two main effects of WMA additive to the RAmixtures namely: reduction of the production temperature and improved blendingand workability. The benefits of lower production temperature in the RA-WMAmixtures are: minimized the further aging of RA due to heating temperature, aid incompaction, fewer emission during the production and paving, shorter constructionduration and cost saving. Workability refers to the ease of compaction of the RA-WMA mixture. The workability of RA-WMA to produce porous asphalt based onCompaction Energy Index (CEI) concept was evaluated . The WMA additivesdecreases the energy used during the production of RA mixture. The workableWMA produced a better degree of blending of RA with virgin binder .
The incorporation of RA into WMA mixtures can improve the moisture sensi-tivity [11, 12]. Other researchers indicated that low production temperature did notexhibit any negative effects on the water sensitivity. Therefore, addition of highpercentage of RA to WMA mixtures might be an alternative to reduce the moisturesusceptibility regardless of WMA technology and pavement layer . The stiffnessof the RA-WMA mixture at various percentages (10, 20, 30, 40, and 50 %) of RAwith different penetration grades of binders were blended with organic, chemical andfoaming WMA additives . Generally, the Marshall quotient (MQ) valuesincreased linearly with RA percentage, while the organic WMA additive exhibitedhigh MQ values indicating a high stiffness. Investigation on the permanent defor-mation of surfactant additive with 50 % RA for mixtures consisting RA-HMA,HMA and WMA using wheel tracking tests investigated in . The RA-WMAmixture improved rutting resistance as demonstrated by lowest rut depth.
The type of WMA additives affects the rheological and mixtures performance.Generally, commercial waxes are use as a flow improver which can reduce theviscosity. Therefore a lower construction temperature can be achieved .Nevertheless, it has different effects on rheological properties of asphalt binder andmixture performance. RH is a new type of wax additive which was produced fromcross-linked polyethylene. It is designed to reduce the viscosity of asphalt binder athigh temperature while strengthening the asphalt crystalline structure at lowtemperature.
Most studies in the past related to RA incorporating WMA additive focused onmixture performance due to high cost of extracting and recovering the RA binder.The incorporation of high RA content will affect the rheological properties andmixture performance. Therefore, the study on the rheological properties as theresults of binder modification will enhance the knowledge related to application ofRA and WMA. This paper presents the rheological evaluation of conventionalbinder containing high proportion of recovered RA binder modified with a WMAadditive. The effects of WMA wax additive on the source and amount of RA binderadded have been evaluated using Dynamic Shear Rheometer (DSR) and rotationalviscometer (RV).
Rheological Evaluation of High Reclaimed Asphalt Content 1189
3 Materials and Methods
1. Asphalt BinderConventional asphalt binder 80/100 pen which equivalent to PG64 was used inthis study. This type of asphalt is normally used for local road construction inMalaysia. The asphalt binder was supplied by SHELL Sdn. Bhd. The rheologicalproperties of the virgin binder are shown in Table 1.
2. Reclaimed Asphalt BinderReclaimed asphalt (RA) was obtained from the milled roads of Jabatan KerjaRaya (JKR) and Projek Lebuh Raya Utara Selatan (PLUS). The recoveredbinder from RA was extracted by means of solvent to separate the binder fromthe aggregate, followed by recovery using the rotary evaporator. To make surethe consistency of binders recovery, the penetration of every extracted RAbinder were tested. The recovered binder from the RA was blended with thevirgin binder at 140 C in proportion of 30 and 40 % by mass of asphalt binder.The fundamental properties of the blended RA binder are indicated in Table 1. Adesignation was adopted to simplify the identification of the asphalt blend. Thefirst number denotes the percentage of RA content followed by the source of theRA. For example, 30JKR means that 30 % RA content from the JKR road.
Table 1 Fundamental properties of binders
Binder Source of RA Fundamental rheological properties
Penetration Viscosity at 135 C (Pa s)
VirginVirgin + RH
RA JKR 12
30 % 42 0.615
40 % 31 0.735
30 % 49 0.580
40 % 38 0.685
RA + RH JKR
30 % 53 0.440
40 % 46 0.500
30 % 63 0.420