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 (10 mm) on fresh and hardened properties of concrete. Previous researches were conducted on the MAS of 12.5 mm, 19 mm, 25 mm, 37.5 mm and 50 mm (T. Uddin, 2017). This is the continuation of the previous work of lower MAS. 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 10 mm with varying sand to aggregate volume ratio (s/a) (0.40, 0.45 and 0.50), W/C ratio (0.45, 0.50, and 0.55), and cement content (375 kg/m3 and 400 kg/m3). A total of 18 different cases were considered and a total of 144 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 and 28 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 (10.0 mm) give lower compressive strength and splitting tensile strength. 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 lower for the MAS of 10.0 mm of brick coarse aggregate. Based on the experimental results, relationship between compressive strength and w/c ratio, tensile strength and w/c ratio, UPV, cement content and s/a ratio are proposed for MAS of 10.0 mm of brick aggregate.