Influence of Foundry Sand and Natural Pozzolans on the Mechanical, Durability and Micro-structural Properties of Lightweight Concrete

This paper presents the results of an experimental investigation on the use of waste foundry sand as fine aggregate replacement to produce lightweight concrete (LWC) with Portland volcanic ash based blended cement (PVC) and coarse pumice aggregate. The effect of foundry sand as replacement of river sand (from 0 to 30%) on fresh (slump and air content), mechanical (density, compressive/tensile strength, and modulus of elasticity), durability (drying shrinkage, water permeability, rapid chloride permeability and carbonation) and micro-structural (porosity, pore size distribution, micro-hardness, interfacial transition zone) properties is described. Other variables in the study include: water-to-binder ratio (W/B) by mass, aggregate-to-binder ratio (A/B) by mass, total binder content and cement types (ASTM type I cement and PVAC). The properties of LWC is influenced by water to binder ratio (W/B), binder content, foundry sand content and the presence of volcanic ash in blended Portland cement. The investigation leads to the production of foundry sand based LWCs for structural applications having satisfactory strength and durability characteristics. The foundry sand induces the beneficial effect of reducing drying shrinkage and water permeability as well as refinement of pore structures and better interfacial transition zone (ITZ). Results have indicated that foundry sand has potential for being used as fine aggregate in producing durable concrete. The utilization of natural pozzolan (volcanic ash) and waste (foundry sand) not only makes LWC economical, but also do help in reducing disposal problems and promote sustainable construction.