Optimization of paper mill sludge ash in sustainable concrete mixes for enhanced strength and durability performance

Abstract

This research studies the feasibility of paper mill sludge ash (PMSA) as a sustainable alternative to conventional cementitious materials to alleviate the environmental and economic issues due to the production of regular cement. The study was done with M30 concrete with water to binder (w/b) ratio of 0.38 to provide a common ground for strength and durability evaluation. Concrete mixes were prepared using 0–30% PMSA as cement replacement according to Indian Standard specifications. The fresh, mechanical and durability properties were tested using slump, compaction factor, fresh density, compressive strength, split tensile strength, flexural strength, water absorption, rapid chloride penetration test (RCPT) and sulphate resistance. As the PMSA content increases, the workability and fresh density decrease. The compressive and flexural strengths increase at moderate replacement level (8–10%) due to the increased pozzolanic activity. The durability tests indicated that the resistance to sulphate attack was improved at optimum replacement levels, but the chloride permeability was increased with higher doses of PMSA. In general, the results show that the PMSA can be an economical alternative for concrete production, effectively reducing cement consumption and environmental impact. An optimum replacement level of 8–10% gives a balanced combination of strength, durability and sustainability for M30 concrete.