Effect of water/cement ratio on the early age tensile strength of concrete

Following Hannant's research in the United Kingdom, the authors measured the tensile strength of concrete between the ages of 2 and 8 hr after batching. Water/cement ratios varied from 0.3 to 0.7, and water content varied from 198.6 to 220 kg/m(3) (327 to 377 lb/yd(3)). It appears that there is a dormant period from 2 to about 4 hr when tensile strength was immeasurably low. Pragmatically this corresponds to the time period when plastic shrinkage cracking is frequently initiated. Tensile capacity developed very rapidly after the dormant period, and in all cases development of tensile strength was more rapid the lower the water/cement ratio.