STUDY ON INFLUENCE OF MOISTURE CONTENT ON STRENGTH DEVELOPMENT OF HIGH-STRENGTH CONCRETE

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Strength development of concrete is affected by the temperature and moisture conditions during curing. High-strength concrete contains barely sufficient water from the beginning due to its low unit water content.In this study, the authors experimentally examined the effects of moist curing conditions on concretes having different strengths to elucidate and quantitatively evaluate the effect of moist curing conditions on the strength development of high-strength concrete.In addition we examined behavior of water content in structural concrete by using thermo-elements and ceramic sensor.The results are summarized as follows ;(1) The curing with lower relative humidity leads to lower long-term strength development.(2) The effect of moist curing conditions on the water content of high-strength concrete is marginal.(3) The equation for calculating the strength development, in which the rate of cement paste formation is expressed by the water content of concrete, unhydrated cement content, and content of hydrated cement paste formed is proposed. According to this equation for calculating strength development, hydration in concrete with a higher strength tends to stagnate while unhydrated cement content and water content remain higher.(4) The surface layer of concrete in structure has less water content than the internal parts when drying condition, and it became conspicuous when the water-cement ratio became higher.(5) High temperature curing of concrete in structural causes water movement internal parts to surface layer affected by partial pressure of water vapor. And rapid hydration at internal parts by high temperature curing causes water movement surface layer to internal parts. These behaviors were complicated and different of compressive strength between internal parts and surface layer became closer in long term, and it became conspicuous when the strength became higher.