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Research Project: Evaluating packing density and reactivity of waste quarry dust for use in concrete

Large amounts of waste dusts generated by quarries are available worldwide. Quarry dusts (QD) if not managed properly may cause serious threats to air, land and water if dumped in open landfills. Finding ways of optimizing the use of QD is important to help improve the environment by reducing waste created by quarries and carbon dioxide emissions due to cement replacement. QD may play a big role in creating eco-efficient concrete. Fine filler materials are known to improve the packing characteristics of cementitious mixes and can be reactive. Hence, identification and modification of QD characteristics might make them apt for use as a supplementary cementitious material (SCMs) and/ or filler.

Most QD contain high amounts of silica and alumina (except special cases like limestone). Hence, QD treated through mechanical grinding to micro-meter sizes might also possess some pozzolanic properties. The effect of QD as a cement replacement or filler has been studied extensively. However, there is lack of understanding on the combined effects of finely processed QD on packing density and their contribution in improving reactivity. Mixtures used are usually of a constant w/b ratio and a pre-selected percentage of partial replacement without considering packing density. With appropriate design of mixtures, QD have the potential to improve rheology, mechanical and durability characteristics of concrete. It is predicted that the optimum size of QD will contribute to the effective packing density of QD-cement paste which will result in lower usage of cement and lower amounts of w/b ratio. It will also increase the rate of early cement hydration by providing increased surface area for the nucleation and growth of hydration products. Moreover, the optimum QD size will change the crystalline structure into amorphous and enhance the pozzolanic reaction of QD-cement paste.

This research aims to utilize mechanically processed waste quarry dust as SCMs/filler in cementitious mixes. The study will focus on the properties of fine quarry dust by optimizing its packing density and identifying the effect of particle morphology to its packing state and propose improvements to the Compressive Packing Model (CPM) by introducing particle morphology. The optimum amount of quarry dust will be used to evaluate its effect on concrete performance and durability. This study will provide a new pathway for the development and promotion of low carbon and green binding materials.