Exploring the influence of geological characteristics, surface texture, and surface energy of crushed rock aggregates on the compressive strength of concrete

Abstract

Concrete is a globally used construction material valued for its strength, which has long been primarily determinant on the water-to-cement ratio. However, studies indicate that aggregate properties influence concrete strength. Therefore, this study aimed at assessing how geological characteristics, surface energy, and surface texture of crushed rock aggregates affect the compressive strength of concrete. The methods used in this study included Petrographic and TIMA analysis, UCS tests, SFE tests and Bond Strength tests. Dolomite, andesite, quartzite, ferro-quartzite and felsite aggregates were used to mix concrete with water-to-cement ratios of 0.4 and 0.6. The surface energy was measured on South Africa’s first Contact Angle Meter DMs-401 instrument, and mechanical bond strength was measured using 3-point bending tests. Results show that high mica contents weaken compressive strength, and its influence becomes more prominent as the water-to-cement ratio decreases; low SFE does not always result in high compressive strengths and these energies do not correlate with previous studies performed with different probe liquids; rough surface texture enhances the macro-mechanical bond between aggregate and cement, but detrimental minerals and structural features hinder bond strength from developing. In conclusion, it was found that the compressive strength is dependent on a combined influence of mineral characteristics, structural integrity, surface energy and surface texture. Therefore, fine grain size and rough, intact texture, high mechanical bond, little to no detrimental minerals and structural defects, and low surface energy are the properties that make the most suitable aggregates for high-strength concrete.