Effect of Sawdust and Lightweight Aggregate on Thermal and Mechanical Properties of Concrete

Abstract

Wood-waste owing to landfilling space scarcity and environmental concerns require proper utilization through adequate measures for effective recycling and safe disposal. Moreover, the natural sand resources are depleting globally owing to excessive consumption by the construction sector. Incorporation of wood-waste in cementitious environment as partial replacement of sand provides viable source of raw materials. Present study aims at production of eco-friendly, sustainable, and thermal efficient concrete with the effective utilization of sawdust and lightweight shale aggregates. Conventional normal weight concrete containing 0, 5, 10, and 15% sawdust and light weight concrete containing 0 and 10% sawdust of total dry volume of sand cured for 7 and 28-days were studied in details in terms of volumetric shrinkage, water absorption, density, flexural strength, fracture toughness, compressive strength, thermal conductivity and energy efficiency. Sawdust was characterized for possible use as fine aggregate by determining its physical and chemical properties as well as morphology at micro and macro level. FESEM and AFM micrographs revealed well-defined channel like structure of sawdust with uniform distribution of micro pores. FTIR and DTA/TGA results endorsed presence of cellulosic, hemi-cellulosic and various hydroxyl compounds present in the sawdust. Substantial decrease of 42% in volumetric shrinkage, considerable decrease in concrete density and increase in water absorption of concrete samples were observed with the increase in sawdust percentage. Results of three-point bend test and compression test showed slight decrease in their values for both NWC and LWC with increase in sawdust loading, however improvement in failure strain and pre-crack toughness was observed due to added heterogeneity by sawdust intrusions in the form of internal voids. Furthermore, thermal conductivity test results exhibit significant decrease in heat transfer for both types of concrete with increase in sawdust loading. Utilization of sawdust in conjunction with lightweight aggregates presented significant reduction in Heating Ventilation and Air Conditioning (HVAC) by 21.42% and corresponding reduction in CO2 emissions. The FTIR analysis endorsed non-chemical interventions of sawdust with concrete. In addition, simulation of concrete beams carried out in ABAQUS software portrayed agreement to the experimental results.