Khalid S. Hashim

Investigation into the stiffness improvement, microstructure and environmental impact of a novel fast-curing cold bituminous emulsion mixture

Cold bituminous emulsion mixtures (CBEMs) have environmental advantages over conventional hot mix asphalt as they are cold products and are safe to use whilst also reducing energy. However, their low early strength and long curing time have been cited as the main barriers for their wide utilisation. This study describes the development of a new fast-curing CBEM incorporating binary blended cement filler (BBCF) containing high calcium fly ash (HCFA) and high aluminosilicate waste material (HASW) to replace the commercial limestone filler. In addition, a waste alkaline NaOH solution was used as a replacement for the prewater. The new CBEM needs only ambient temperature curing in order to achieve strengths comparable to the traditional hot mixture in a very short time (less than one 1 day). Water sensitivity of the mixtures was assessed by the Stiffness Modulus Ratio (SMR). Scanning electron microscopy (SEM) was employed to characterise the surface morphologies. Furthermore, the environmental impact of using these waste materials in CBEMs was assessed by using a toxicity characteristic leaching procedure (TCLP).The results indicated a significant improvement in the indirect stiffness modulus (ITSM) test and water sensitivity compared to hot mix asphalt. Moreover, SEM analysis confirmed the formation of hydration products after various curing ages. Furthermore, the TCLP test for environmental impact revealed that the heavy metal concentration in the leachates satisfied the required criteria.