ABSTRACT:The main objective of this study was to investigate the potential of using fly ash as a mineral filler in asphalt mixtures to reduce the amount of fly ash generated from coal-based power plants in Bangladesh requiring disposal. To achieve this, several mix designs which included fly ash were developed and compared with mixtures using cement as a mineral filler, with mixtures of cement and fly ash with different ratios considered and their performances evaluated. It was found that the design with a bitumen content and fly ash as a mineral filler was within the economical range and, when its Marshall stability and flow values were compared with those of cement, it was found to be satisfactory. Also, the moisture susceptibility of an asphalt mixture with fly ash was checked through immersion-compression tests and compared with that of one with cement as a mineral filler. As it was observed that fly ash generated from coal-fired power plants can reduce the damage caused to asphalt by moisture and is more cost-effective than conventional fillers, it is proposed that using it as a filler material in pavements could reduce the substantial damage suffered by the environment.

An extended study was carried out to explore the possibility of recycling of concrete made with brick aggregate as coarse aggregate. Demolished concrete blocks were collected from six demolished building sites and then crushed into coarse aggregate manually. Physical properties of the coarse aggregate collected from the blocks were evaluated. Cylindrical concrete samples (100 mm by 200 mm) were made using recycled aggregates with W/C = 0.40, 0.45 and 0.50. The specimens were tested for compressive strength, tensile strength, and Young's modulus of concrete at the ages of 7, 14, and 28 days. Control specimens were also made using virgin brick aggregate to compare with the results of recycled aggregate. The experimental results revealed that recycled brick aggregates have lower absorption capacity compared to the virgin brick aggregate. The average strength of concrete made with recycled brick aggregate was found to be 29 MPa and 23.5 MPa for W/C=0.45 and 0.55 respectively.