【正文】 ng this scheme, applicable to the general structure of planar size shoulds not be too big, when construction from the short side began to push along the long side, is more appropriate. When necessary, can be divided into two sections from middle to both ends to or from the middle and construction. Section 2 layer: Concrete casting, starting from scratch, casting a certain distance to the second floor, so after pouring in other layers on casting. Due to the total number of layers, therefore, after the first layer top pouring concrete yet at the end of the beginning of the second period, and can turn from layered casting. This scheme is applicable to units within the time required, the supply of concrete less like the first option on that. This scheme is applicable to structure is too big and thickness of large area or length. Incline stratified: Requirements of slope not greater than cant 1/3, applicable to greatly exceed the length of the structure of the thickness of the three times. From the bottom layer of concrete casting, gradually move. measures Maintenance of mass concrete construction is a vital work. Maintain proper maintenance is mainly to control temperature and humidity, temperature, promote concrete outside the normal development of the strength of concrete and prevent the cracks of concrete and development. According to the specific circumstances of should as far as possible much maintenance period of time, after dismantling formwork should immediately, covering protection to prevent recent climate, sudden cold temperature, prevent and control in early concrete cracks and medium. The massive concrete curing, not only to satisfy the need that still should increase by artificial temperature control, due to temperature caused by deformation of the concrete cracking. After the pletion of the concrete curing time to keep the concrete surface spraying maintenance, such as reducing often humid heat outside pour cans, and prevent dry crack and promote the stable growth of concrete strength. In general 18h 12 ~ after pouring in immediately start maintenance, maintenance time not less than 28d or design age. 4 Cooled If in the hightemperature seasonal construction, should be in early general refrigeration adopted to reduce the water temperature, but the peak of concrete, water cannot too long, for a long time can cause excessive temperature range of temperature stress caused by large. In order to cut inside and outside, still should temperature in summer jiamoqiuchu undertake metaphase is cooled by water, river, general middle water lasted about two months. Later, water is made concrete cylindrical blocks the necessary measures to juncture grouting, generally USES water and cooling water through the bination scheme. Third, the conclusion Concrete crack, especially large volume concrete crack is currently scholars and engineering is an important problem of attention, through the above analysis, the material of mass concrete crack is mainly posed of temperature stress and concrete39。s shrinkage, the author thinks carefully select material, and in the use of reasonable construction method, can effectively prevent the cracks. 混凝土施工裂縫原因及防治 混凝土施工裂縫原因不外乎外因和內(nèi)因。內(nèi)因主要指混凝土的初始缺陷：在混凝土初期硬化過(guò)程中，其內(nèi)部會(huì)存在眾多的 微孔隙、氣穴和微裂縫；外因是指非荷載原因：溫度裂縫、干縮作用等。在這些作用下，混凝土?xí)a(chǎn)生各種形式的裂縫。施工過(guò)程中要掌握好原材料的配置，在澆筑過(guò)程中把握好進(jìn)度和厚度，及時(shí)做好養(yǎng)護(hù)工作，這樣就可盡量避免混凝土裂縫了。 一、裂縫產(chǎn)生原因 混凝土是一種由砂石骨料、水泥、水及其他外加材料混合而形成的非均質(zhì)脆性材料。在混凝土硬化初期，由于混凝土的施工和本身變形、約束等一系列問(wèn)題，硬化成型的混凝土中會(huì)存在眾多微孔隙、氣穴和微裂縫，通常把這稱(chēng)作混凝土的初始缺陷。微裂縫通常是一種無(wú)害裂縫，對(duì)混凝 土的承重、防滲及其他一些使用功能不會(huì)產(chǎn)生危害。但是混凝土在受到荷載、溫度、收縮等作用下，微裂縫就會(huì)不斷擴(kuò)展和連通，最終形成肉眼可見(jiàn)的宏觀裂縫，也就是混凝土工程中常說(shuō)的裂縫，這會(huì)對(duì)混凝土結(jié)構(gòu)的使用性能和耐久性產(chǎn)生不利的影響。 由于混凝土的抗拉強(qiáng)度很小，當(dāng)結(jié)構(gòu)或構(gòu)件的某一部分由于外部作用產(chǎn)生的拉應(yīng)力大于混凝土的抗拉強(qiáng)度時(shí)，就會(huì)出現(xiàn)裂縫。因此，混凝土在荷載與非荷載作用下，都可以產(chǎn)生裂縫。對(duì)于荷載產(chǎn)生的裂縫，可以通過(guò)合理設(shè)計(jì)與施工來(lái)防止。而對(duì)于非荷載產(chǎn)生的裂縫，由于原因復(fù)雜，則很難處理和防止。一 般常見(jiàn)的非荷載因素有溫度作用、干縮作用、沉降收縮變形、塑性收縮變形作用等，在這些作用下，都會(huì)使混凝土內(nèi)部產(chǎn)生拉應(yīng)力。 3. 大體積混凝土裂縫形成的原因 大體積混凝土 裂縫產(chǎn)生的原因可分為兩類(lèi)：