風作用下におけるコンクリートの収縮特性に関する基礎的研究

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In order to clarify the effects of wind velocity on the drying shrinkage and development of shrinkage stress of concrete members, the shrinkage tests were performed by using an experimental blower and the analysis was made based on the diffusion theory proposed by Pickett. Mortar prisms having six kinds of mix proportions were used as the test specimens and three different wind velocities, 0, 5.6 and 9 m/sec, were examined. The results obtained are summarized as follows: (1) At the early stage of drying, shrinkage was enhanced in a windy condition more rapidly than in a windless condition. Its rate of increase was nearly proportional to wind velocity. The final shrinkage value estimated from the hyperbolic experimental equation also increased with wind velocity. (2) The loss of moisture was accelerated in the initial stage of drying as the wind velocity was increased. The younger the age of specimen tested, the more remarkable its tendency. It was confirmed that the mechanism of the increase in shrinkage due to wind action was closely related to that of moisture loss. (3) Both the diffusivity of shrinkage and the surface factor in the diffusion equation increased due to wind action, but the rate of increase for the surface factor was much larger than that of the diffusivity. (4) The shrinkage stress at the exposed surface of mortar evaluated by using the above factors showed the following trends. The maximum value of the shrinkage tensile stress became larger, the time to reach the maximum stress became shorter, and the stress fell more rapidly from the maximum in a windy condition than in a windless condition. (5) Prolonged wet curing and lowering the paste content are recognized effective in order to prevent the increase in shrinkage and the development of shrinkage cracks by wind action.
社団法人日本材料学会の論文
1979-02-15

著者

庄谷征美
秋田工業高等専門学校

風作用下におけるコンクリートの収縮特性に関する基礎的研究

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