Effects of Maximum Size of Brick Coarse Aggregate on Fresh and Hardened Properties of Concrete

Abstract

Investigation was carried out to study the effects of maximum aggregate size (MAS) of brick coarse aggregate (12.5 mm, 19.0 mm, 25.0 mm, 37.5 mm, and 50.0 mm) on fresh and hardened properties of concrete. For investigation, first class bricks were collected and broken into pieces to make coarse aggregate according to the gradation requirements of ASTM C 33. The aggregates were tested for specific gravity, absorption capacity, unit weight, and abrasion resistance. Cylindrical concrete specimens of diameter 100 mm and length 200 mm were made for MAS of 12.5 mm, 19.0 mm, 25.0 mm, and 37.5 mm with varying sand to aggregate volume ratio (s/a) (0.40 and 0.45), W/C ratio (0.45, 0.50, and 0.55), and cement content (375 kg/m3 and 400 kg/m3). For MAS of 50.0 mm, cylindrical concrete specimens of diameter 150 mm and length 300 mm were made with varying s/a ratio (0.40 and 0.45), cement content (375 kg/m3 and 400 kg/m3), and W/C ratio of 0.45. A total of 52 different cases were considered and a total of 552 concrete specimens were made for testing. The specimens were tested for splitting tensile strength at the age of 28 days, and compressive strength, stress-strain curve, and Young's modulus at the age of 7 days, 28 days, and 90 days. Ultrasonic Pulse Velocity (UPV) through the specimens was measured using Portable Ultrasonic Non-destructive Digital Indicating Tester (PUNDIT).The rebound number on the specimen surface was also measured using a Schmidt hammer. Results have revealed that for a higher cement content, smaller sized brick coarse aggregate (12.5 mm) gives higher compressive strength, splitting tensile strength, and Young’s modulus of concrete. But for a lower cement content, and lower W/C ratio, these properties tend to increase with an increase in maximum size of aggregate up to 37.5 mm. The compressive strength of concrete increases with an increase in s/a ratio from 0.40 to 0.45. Moreover, the UPV is higher for concrete made with larger MAS. Based on the experimental results, relationships between compressive strength and Young's modulus, compressive strength and tensile strength, compressive strength and UPV, Young’s modulus and UPV, compressive strength and rebound number are proposed for different MAS of brick aggregate.