Effects of Manufactured Sand on the Properties of Normal and High Strength Concrete

Abstract

Manufactured Sand (MS) has been introduced as a very effective fine aggregate and is being widely used in various construction activities. Large amounts of Manufactured Sand Fines (MSF) that are less than 75 µm in particle size, are produced during the production process. Costs are incurred in separating these fines from the crushed stone and are then dumped in landfills, thus causing serious environmental issues. Studies on MSF are not well established and a handful has been done on High Strength Concrete (HSC). The key objectives of this study were to study and compare the effects that MSF have on the properties of Normal Strength Concrete (NSC) and HSC and to propose effective fines percentages that could be incorporated in them. Tests were carried out by partial replacement of MS with fines in proportions of 10%, 15% and 20% for C30 and C60 concrete and were compared with the control mixes that contained 3.36% MSF. It was identified that a 15% replacement of MSF produced effective results with the highest compressive, splitting tensile and flexural strength results and minimum water absorption in both NSC and HSC. At 15% fines content, a strength of 35.3 MPa and 63.3 MPa was achieved by the C30 and C60 concretes respectively. However, the increment of fines decreased the workability significantly. The microstructure analysis proved the densification of the microstructure at 15% MSF content. The cost analysis showed that the availability of high fines content can deduct the cost of NSC by 1.8% and HSC by 1.6%. The 10% - 15% range was identified as the most effective fines content range that can be incorporated in NSC and HSC. Results of this study can contribute to develop concrete with better performance while addressing several environmental and cost issues related to the concrete industry. KEYWORDS: Manufactured sand, fines, partial replacement, normal strength concrete, high strength concrete.