战胜重要(国外英文资料).doc

克服紧张(国外英文资料)Causes and prevention of concrete cracks in commoditiesStrictly speaking, there is almost no structural uncracked structure, and the key is how to control the emergence of harmful cracks, which is harmful and harmless.In general, the harmful cracks are 0.3 mm above the width of the outside, which is affected by the rain and exposure to the outside. Indoor harmful crack width is 0.6 mm above.The shrinkage of concrete and its influencing factorsThe shrinkage of concrete is mainly plastic shrinkage, contraction, drying shrinkage and carbonization. Plastic shrinkage{plastic shrinkage is the shrinkage of new mixed concrete. It is caused by dehydration of the surface.{the space between the droplets in the fresh concrete completely filled with water, when a high wind speed, low relative humidity of concrete, high temperature and high temperature bonding effect, moving water from the slurry to the surface, dehydration from the surface, at this point, the capillary negative pressure, with the increase of filtration, the capillary tube negative pressure increases gradually, contraction force, make the slurry produces contraction. When the contraction force is greater than the tensile strength of the matrix, it causes the surface to crack.The maximum velocity of the early plastic shrinkage of the concrete occurred within one to four hours after pouring and then flattening.{so special protection measures should be taken to avoid cracking of concrete during periods of high shrinkage.Chemical reductionChemical reduction is mainly caused by chemical reaction of cement and water.Chemical reduction in silicate cement is about 25 percent of the chemical hydration. So you can think of the chemical combination of water mud, which is the ultimate chemical reduction.The constituent minerals of silicate cement have different chemical contractions, and C3As chemical reduction is the largest. The C3A rate is three times the C2S, almost five times the C4AF. Therefore, the C3A hig