Development of an optimum mix for paving blocks using waste steel slag and crushed tile waste as part replacement of aggregates
Authors:   Department of Civil Engineering, University of Moratuwa, Sri Lanka, Gamage J.C.P.H. , Chandrathilaka E.R.K. 
Published: October 2024

In contemporary construction practices, paving blocks are essential for creating durable and aesthetically pleasing surfaces in urban and suburban areas, such as pedestrian walkways, driveways, and plazas. However, traditional paving blocks are often associated with considerable weight and high production costs, which can limit their widespread use and contribute to environmental degradation due to the extensive use of natural aggregates. This research aims to address these challenges by developing a lightweight and cost-effective mix design for eco-friendly paving blocks. The proposed design incorporates waste materials from the steel industry, specifically steel slag, as well as crushed tile waste from construction industry, both of which are typically discarded as industrial and construction waste. By repurposing these materials, the study seeks to minimize the environmental impact of paving block production while providing a sustainable and economical alternative to conventional paving blocks. The experimental program involved replacing traditional fine aggregates in the paving block mix with steel slag at varying proportions of 10%, 20%, and 30% by volume. Additionally, coarse aggregates were partially substituted with 25% crushed tile waste. The mechanical performance of the various paving block mixes was thoroughly assessed through a series of standardized tests, including density, compressive strength, split tensile strength, and flexural strength. These tests were conducted to determine the structural integrity and suitability of the eco-friendly paving blocks for practical applications. The results of the study revealed that the paving block mix containing 30% steel slag and 25% crushed tile waste achieved an optimal balance between weight reduction, cost efficiency, and mechanical performance. This mix exhibited a compressive strength of 16.6 MPa after 28 days, making it suitable for non-traffic areas such as walkways, garden paths, and recreational spaces. Although this strength is marginally lower than the compressive strength of 17.5 MPa observed in conventional paving blocks, the eco-friendly mix offers several advantages, including a significant reduction in weight and production costs. Furthermore, a detailed cost analysis was performed to compare the economic feasibility of the eco-friendly paving block mix with that of traditional paving blocks. The analysis indicated that the use of waste materials such as steel slag and crushed tile waste not only reduces the consumption of natural resources but also results in considerable cost savings. The cost of paving blocks decreases with the substitution, showing a reduction rate of approximately 4.6% from Mix 01 to Mix 02, and continuing consistently up to Mix 05, making it economically feasible. In conclusion, this study contributes to the ongoing efforts to develop sustainable construction materials by demonstrating the viability of using industrial and construction waste in paving block production.