Results are given of flexural strength and fatigue tests on small unreinforced beams of pavement quality concrete to study the effects of various moisture conditions. Subsidiary tests included dynamic modulus of elasticity and equivalent cube crushing tests on the fractured specimens. The report is in two parts:- part 1 effects of moisture condition at the time of test. Beams were cured under water for 26 weeks and then tested either wet, surface-dry or oven-dried. The highest flexural and fatigue strengths were obtained with oven-dried specimens and the lowest with specimens that were air-dried for seven days. There was no correlation between these results and the corresponding equivalent cube strengths, where the effects of air drying were reversed. Part 2 method of curing. Beams were cured for 26 weeks under various combinations of immersion in water, air-drying, fog room and surface coatings. Immersion in water for one to four weeks followed by air-drying gave the highest flexural and fatigue strengths. Specimens which were air-cured for the whole period were significantly weaker. There was little correlation between compressive strength and flexural strength related to curing conditions. The importance of considering moisture states that may occur in practical structures under service conditions is emphasised, as is the need for standardising moisture conditions for research tests. (Author/publisher)
Samenvatting