Mechanical and Microstructural Performance of Concrete Incorporating River and Quarry Sand

Abstract

The increasing scarcity of natural river sand and the environmental impacts associated with its extraction necessitate systematic evaluation of alternative fine aggregates for sustainable concrete production. This study investigates the mechanical and microstructural performance of concrete incorporating river and quarry sands sourced from eight locations around Hawassa City, Ethiopia. Four river sands and four quarry sands were characterized for physical, chemical, and mineralogical properties in accordance with ASTM and Ethiopian standards. Concrete mixtures were proportioned using a constant water–cement ratio of 0.50 and a nominal mix ratio of 1:1.5:2.6, targeting a 28-day compressive strength of 33.5 MPa. Fresh concrete exhibited comparable workability, with slump values ranging from 76 to 82.5 mm and compaction factors between 0.816 and 0.853. At 28 days, compressive strength varied from 23.14 to 33.86 MPa, while splitting tensile strength ranged from 11.98 to 15.01 MPa. Water absorption results indicated lower permeability for concretes produced with well-graded sands. Scanning Electron Microscopy revealed pore area values between 17.96 % and 28.56 %, demonstrating a strong inverse relationship with compressive strength. X-ray Diffraction confirmed quartz as the dominant mineral phase influencing hydration behavior. The findings demonstrate that properly processed quarry sand can achieve mechanical and microstructural performance comparable to river sand when stringent quality control measures are applied.