【正文】 尺寸穩(wěn)定性 在養(yǎng)護(hù)期間，材料的收縮要保持到最小，為了防止修復(fù)失敗、材料的尺寸變化應(yīng)與基層材料相當(dāng)接近。例如，熱天會阻礙水泥的水合作用從而使局部修復(fù)的普通水泥發(fā)生變質(zhì)，為了防止發(fā)生這種情況，養(yǎng)護(hù)期間應(yīng)對其作特別的保護(hù)。 外觀 修復(fù)材料與現(xiàn)有混凝土 的匹配程度取決于所修補(bǔ)的結(jié)構(gòu)和業(yè)主的要求。 修復(fù)方法的選擇 適當(dāng)?shù)男迯?fù)就是消除與結(jié)構(gòu)使用有關(guān)的所有缺陷。這些因素包括： 如果活動裂縫里填的是剛性材料，那么不但填補(bǔ)材料會斷裂，而且舊裂縫周圍也會產(chǎn)生新的裂縫，修復(fù)活動裂縫的方法是要么采用柔性材料以適應(yīng)結(jié)構(gòu)位移，要么在修復(fù)之前采取一定措施消除結(jié)構(gòu)位移。 如果裂縫里有水氣、水和雜物時，要先補(bǔ)好漏洞。 工人所采用的修復(fù)工藝是另一個與修復(fù)有關(guān)的因素，有時它意味著水久性修復(fù)或者修復(fù)材料過早損壞。 修復(fù)部位的表面可能很難看，特別是當(dāng)它處于建筑物顯眼的地方時。 中國地質(zhì)大學(xué)長城學(xué)院 2021 屆畢業(yè)論文 7 外文原文 Concrete Placing Curing Abstract Viewed in terms of accepted practices, concrete construction operations leave much to be desired with respect to the quality, serviceability, and safety of pleted structures. The shortings of these operations became abundantly clear when a magnitude earthquake struck northern Pakistan on October 8, 2021, destroying thousands of buildings, damaging bridges, and killing an estimated 79,000 people. The unusually low quality of construction operations prevalent was a major cause of the immense devastation. Keywords: Concrete。 Curing 中國地質(zhì)大學(xué)長城學(xué)院 2021 屆畢業(yè)論文 8 1Placing Concrete If concrete is placed in the surface, the surface should be filled with water sufficiently to prevent it from absorbing the concrete of its water. If fresh concrete is to be placed on or nearby to concrete that has solidified, the surface of the placed concrete should be cleaned absolutely, preferably with a highpressure air or water jetor steelwire brushes. The surface should be wet, but there should be no much water. A little quantity of cement grout should be brushed over the whole area, and then followed immediately with the application of a 1/2in Layer of mortar. The fresh concrete should be placed on or against the mortar. In order to decrease the disintegration resulting from carriage after it is placed. The concrete should be placed as nearly as probably in its final point. It should be placed in layers to permit uniform paction. The time interval between the placing of layers should be limited to assure perfect bond between the fresh and previously placed concrete. In placing concrete in deeper patters, a vessel should be used limit the free fall to not over 3 or 4 ft, in order to prevent concrete disintegration. The vessel is a pipe made of lightweight metal, having adjustable lengths and attached to the bottom of a hopper into which the concrete is deposited. As the patters are filled, sections of the pipe may be removed. Immediately after the concrete is placed, it should be pacted by hand pudding or a mechanical vibrator to eliminate voids. The vibrator should be left in one position only long enough to reduce the concrete around it to a plastic mass。 lower temperature will decrease the rate of setting, while a higher temperature will decrease the ultimate strength. 3Placing Concrete in Cold Weather When the concrete is placed during cold weather, it is usually necessary to preheat the water, the aggregate, or both in order that the initial temperature will assure an initial set and gain in strength. Preheating the water is the most effective method of providing the necessary temperature. For this purpose a water reservoir should be equipped with pipe coils through which steam can be passed, or steam may be discharged directly into the water, several outlets being used to given better distribution of the heat. When the temperatures of the mixtures are known, some specific charts may be used to calculate the temperature of concrete. A straight line pass all three scales, passing through every two known temperatures, will assure the determination of the third temperature. If the surface of sand is dry, the fact lines of the scales giving the temperature of concrete should be used. However, if