A.S. MENAKA(1), R.G.ROBINSON(2), and K.RAMAMURTHY(3), FIMS
(1) Research scholar, Building Technology and Construction Management Division, Department of Civil Engineering, Indian Institute of Technology Madras, Chennai 600 036, India
(2) Professor, Department of Civil Engineering, Geotechnical Engineering Division, Indian Institute of Technology Madras, Chennai 600 036, India.
(3) Professor, Building Technology and Construction Management Division, Department of Civil Engineering, Indian Institute of Technology Madras, Chennai 600 036, India,
ABSTRACT
The coal extraction process in open-cast mining involves removing excess quantities of topsoil (overburden), which is then deposited elsewhere, resulting in degradation of soil quality. Maintenance of this massive overburden is challenging as the fine particles from the dumps are prone to cause air pollution in surrounding areas. This study used clean sand with two fineness moduli sourced from mine overburden through a wet-sieving process as fine aggregate for mortar made using cement and hydrated lime. The properties were compared (benchmarked) when river sand was used as fine aggregate in the control mortar. Following ASTM C270, sand-to-binder ratios of 2.25 and 3 were adopted, and the percentage of lime used to replace cement in the mortar was between 10% to 46% ensuring in all mixes, a constant workability of 110% for all the combinations of mortar, resulting in varied water demand. Fresh properties, such as water demand and retention, and hardened properties, such as compressive strength, dry density, water absorption, sorptivity, vacuum-saturated porosity and leaching, were determined. Characterisation based on Zeta potential, Thermogravimetric analysis (TGA) and Mercury intrusion porosimetry (MIP) were related to water retention, compressive strength and sorptivity, respectively. The experimental results showed that the water retention characteristics significantly improved with an increase in lime replacement in mortar. Different mix proportions that satisfied ASTM C270, BS EN 998-2, and IS 2250 allowed for the emergence of various mortar designations based on the compressive strength of mortar.
KEYWORDS: mine overburden, fine aggregate, masonry mortar, water retention, hydrated lime.