Sustainable Innovation Using Crushed Shell and Construction Waste as Sand Replacement in Concrete Mixture

Abstract

This study evaluated the effectiveness of using recycled crushed shells and construction waste as partial replacement of sand with particle sizes between 4.75mm to 0.15mm is the sand commonly used to produce concrete mixtures. Two replacement rates were tested: 15% (7.5% recycled crushed shells and 7.5% crushed shell) and 20% (10% recycled concrete blocks and 10% crushed shell), through slump and compressive strength tests. The slump test results showed values ​​of 37 mm for the 15% mixture and 48 mm for the 20% mixture, both meeting the JKR specifications. Increasing the replacement rate increased workability, facilitating pouring and compaction. Compressive strength tests showed consistent strength development throughout the curing period. The 20% mixture achieved a 28-day compressive strength of 22.167 N/mm², higher than the 15% which recorded 21.217 N/mm². Although the 20% replacement failed to meet the JKR standards at 7 days, the 15% mixture performed better and met the JKR standards. Overall, the use of 15% recycled concrete blocks and crushed shell provided a good balance between workability and compression strength and met the JKR standards for non-structural concrete applications. These findings support the use of sustainable alternative materials in concrete production.