Palm oil fuel ash application in cold mix dense-graded bituminous mixture

The performance of cold mix cold-laid emulsified asphalt mixtures is often improved by additives like rice husk ash, fly ash, fibres, and lime for varying applications. High void content, weak early strength, and slow rate of strength gain remain an unsolved challenge for cold mixtures. This study explored the feasibility of utilising palm oil fuel ash (POFA) in a fast-curing cold mix asphalt (CMA) as a filler replacement. Large volumes of POFA waste deposited in landfills continue to pose threats to the environment; thus, needs redress. This study employed a fine dense-graded CMA with a nominal maximum aggregate size (NMAS) of 4.75 mm (FGCMA-4.75 mm). This study aimed to improve CMA's volumetric and mechanical performance by reducing the inherent void content and enhancing the cracking, rutting, and moisture damage resistances. Ten mix types were cast with 1–4% POFA by dry weight of aggregate replacing granite filler. The study tested mixtures for Indirect Tensile Strength (ITS), Indirect Tensile Stiffness Modulus (ITSM), Tensile Strength Ratio (TSR), dynamic creep, Cantabro loss, and Marshall stability and flow including volumetric properties. Results showed that POFA addition in CMA yields a significant progressive improvement in Marshall volumetric properties due to its pozzolanic properties revealed by XRF and FTIR. There is improved ITS, ITSM, dynamic creep, and Cantabro loss between 1 and 3% POFA percentage replacements. Also, POFA waste had proven to be an excellent pozzolanic filler as translated by improvement in the ITS, coupled with up to 96% resistance to moisture damage that of an HMA. Furthermore, the minimal Cantabro loss – 33.85% and high ITS of 586 kPa revealed improved durability. The addition of 3% cement complements the POFA in producing a higher stiffness mixture while adequate strength was attained within 2–4 days of curing, signifying improved early strength gain. The research concluded that incorporating 3% POFA in FGCMA-4.75 mm mixtures has better mechanical performance with 3 – 5% voids similar for an HMA, against the usual voids of 5 – 10% common to CMA.