Effect of Water-Cement Ratio on Plastic Shrinkage Cracking in Self-Compacting Concrete

Plastic shrinkage cracking is a mechanical phenomenon that occurs in the first few hours after casting the concrete in its mould. It is commonly believed that rapid and excessive moisture loss of the fresh concrete, mainly due to evaporation, plays a decisive role in the early age shrinkage. However, it is not always possible to justify all the plastic shrinkage incidents based on water evaporation solely. Instead, it seems that and interconnected correlation between evaporation, capillary pressure and hydration rate may offer better explanation. In this paper effect of water-cement (w/c) ratio on plastic shrinkage cracking of self-compacting concrete (SCC) is investigates. Four recipes with different w/c ratios (0.38, 0.45, 0.55 and 0.67) are tested by using Ring test method (NT BUILD 433). During the experiments evaporation, capillary pressure and internal temperature of the specimens were recorded from 60 minutes after casting up to 18 hours, at which the length and width of the cracks were measured. The results show lower risk of cracking when w/c ratio is between 0.45 to 0.55. However, the specimens with 0.38 and 0.67 w/c ratio experienced higher cracking tendency, especially the latter, in which severe cracking was observed