Effect of glass fibers on restrained plastic shrinkage cracking of HPC with silica fume

摘要

This paper presents effect of silica fume on plastic shrinkage cracking (PSC) of high performance concrete (HPC). Test specimens of fresh concrete were subjected to a simulated hot dry environmental conditions (temp., 45℃ & 52℃; relative humidity, 40±5%; wind velocity, 2.8 m/s) immediately after casting. After studying the crack patterns, glass fibers (length, 12 mm; diam, 0.014 mm; volume fractions, 0.05-0.3% at increment of 0.05%) were added. In a new technique, fiber reinforced concrete to be tested was laid on top of a fully hardened base concrete, which provides the bottom restraint resulting in cracking in the freshly placed overlay. The effect of mineral admixtures towards the development of PSC and the effectiveness of glass fibers in controlling PSC were studied. It was observed that 0.3% volume fraction fibers are required for 10% silica fume replaced concrete.