Performance of fine dense-graded cold mix asphalt incorporating spent garnet and palm oil fuel ash

Abstract

Cold mix asphalt (CMA) is preferable than hot mix asphalt (HMA) or warm-mix asphalt (WMA) due to minimal energy requirement, cost, and fumes emission in road construction. Efforts in mitigating CMA limitations of low early strength, slow curing, and high void content remained significant for further investigation. Moreover, CMA lacks a unified acceptable mix design method. The inclusion of industrial by-products and binder modification are several strategies aimed at solving these problems. However, there is limited research on the addition of spent garnet, palm oil fuel ash (POFA), and fast setting emulsions in CMA. This study adapted the International Slurry Surfacing Association (ISSA A-143) dense gradation with a nominal maximum aggregate size (NMAS) of 4.75 mm. The gradation with 10% fine content passing the 0.075 mm sieve was used to develop fine dense-graded cold mix asphalt (FGCMA-4.75). The study was carried out in three phases. The first phase entails assessing and characterising the constituent material in terms of its microstructural, physio-mechanical, morphological, and rheological properties. A rapid setting conventional emulsion (RS-1K) and a quick setting polymer-modified emulsion (CQS-1h) in addition to 3% of cement were used as the binders. The second phase involved designing eight (8) different mixtures, including the control mix using the Asphalt Institute (AI) modified Marshall design method. A performance-based mix design was then proposed, employing indirect tensile stiffness modulus (ITSM) and Cantabro loss test results. The FGCMA-4.75 mm consists of a 7 – 9% emulsion content range, 1 – 4% POFA and 50% and 100% spent garnet replacement. A final optimised mix (FGCMA-GP) consisting of 3% POFA and 100% spent garnet as fine aggregate and filler replacements, respectively, was selected using grid analysis. The final phase centred on the engineering properties and performance of the FGCMA-GP. The mixtures were tested for ITSM, dynamic creep, moisture damage, indirect tensile strength (ITS), and wheel tracking tests. The result shows that the Marshall stability, flow, void content, and density of all the modified mixtures met Malaysian Public Works Department (JKR) and India’s Ministry of Road and Transportation (MoRTH) specifications. The results revealed that the replacement of up to 3% POFA increased the ITS and ITSM but reduced the void content of the mixture. All CMA samples have better rutting resistance than HMA. Emulsion comparison showed that mixtures with CQS-1h emulsion have higher cracking, abrasion and rutting resistance than RS-1K. Meanwhile, FGCMA-GP has good rutting resistance and a 20% higher tensile strength ratio (TSR) than the control sample. Generally, FGCMA-GP with 100% spent garnet and 3% POFA can be used in CMA for restoration works and pavement wearing course.