【正文】 e raw material mix and the same two plates and pouring, pouring the morning or afternoon, the emergence of cracks on the cast is basically not found. Different and the same construction of concrete cracks in the ranks of different levels, the construction technology and the environment that conditions on the nonstructural cracks in concrete play a decisive role. 3, the temperature of mass concrete cracks Hydration process of cement hydration have some heat, and most of its heat is released within three days, concrete is a poor conductor of heat, especially the large volume of concrete, resulting in a large number of hydration heat is not easy to distribute, the internal temperature rising , and the concrete surface heat faster, so have a temperature gradient inside and outside the crosssection, especially when the 4 temperature difference between day and night, the temperature difference between inside and outside the greater thermal expansion of concrete deformation of the internal pressure, external concrete shrinkage deformation, resulting in tensile stress, as the concrete in this when the lower tensile strength, internal tensile stress when the concrete tensile strength of more than concrete, the concrete will crack, the crack gap generally deeper, and sometimes a crosscutting nature, the basement of a project for film rib raft foundation beam, rib 900 1600mm beam surface coefficient small, each cement concrete 425 R amp。 預(yù)防的措施是在滿足泵送和施工的前提下盡可能減小混凝土塌落度，施工過程中應(yīng)經(jīng)常觀察模板的位移和混凝土澆搗的密實(shí)情況，不能漏振、過振，且在第一次振搗后間隔 20～ 30mm 后，進(jìn)行第二次復(fù)振。且相同的混凝土不同的施工隊(duì)伍裂縫程度不同，此說明施工工藝與 環(huán)境條件對混凝土非結(jié)構(gòu)性裂縫起決定性作用。 預(yù)防措施是配制大體積混凝土宜使用低水化熱水泥如礦渣水泥、摻加膨脹劑，更重要的是施工單位要設(shè)置測溫裝置，同時(shí)采取保溫措施，如采用塑料薄膜和草袋履蓋以確保內(nèi)外溫差小于 25℃ 。 6 塑性收縮裂縫 混凝土澆注后仍處于塑性狀態(tài)時(shí)，由于表面水分蒸 發(fā)過快而產(chǎn)生的裂縫，這類裂縫隙多在表面出現(xiàn)，形狀不規(guī)則、長短寬窄不一、呈龜裂狀，深度一般不超過 50mm，但薄板結(jié)構(gòu)如果混凝土中摻有含泥量大的粉砂則可能被穿透。 Engineering Industry Profile》 United Kingdom 5 商品混凝土早期裂縫的成因及防治措施 摘要：本文就工程實(shí)際中容易出現(xiàn)的早期裂縫進(jìn)行了分析和說明，同時(shí)也有針對性的介紹了一些防治措施。 混凝土是由固、液、氣組合而成的非均質(zhì)復(fù)合材 料，在成型后隨著溫度、濕度等環(huán)境條件的影響下會(huì)形成肉眼看不到的微裂縫，由于混凝土的組成材料和微觀構(gòu)造不同以及受環(huán)境影響的不同，混凝土產(chǎn)生裂縫的原因很復(fù)雜，本文中筆者僅就工程實(shí)際中遇到的情況對早期裂縫的成因及預(yù)防略加說明。 一般的塑性沉落裂縫和塑性收縮裂縫都屬于非結(jié)構(gòu)性裂縫，對結(jié)構(gòu)性能無大影響，塑性沉落和收縮有時(shí)沒有明顯區(qū)別，交織在一起，混凝土所用 原材料質(zhì)量有一定影響，但不起決定作用。 摘自 《 建筑與工程產(chǎn)業(yè)概況 》 英國