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加气块有裂缝的原因

发布时间:2019-04-03    编辑:上海德新新型建材平安彩票    浏览次数:198次

平安彩票 1. 干缩变形产生裂缝

 
  加气混凝土砌块是高分散毛细孔结构,且大部分空洞呈封闭状态,随着时间的变化孔内的水分就不断减少,在表面张力的作用下,毛细孔内就形成收缩应力,当这种应力达到一定程度砌体就会产生干缩。干缩变形特征是早期发展快,以后逐渐变慢并在相当长的时期内延续,使整个砌体处于徐变状态。干缩裂缝分布广、数量多、裂缝强度较严重,干缩变形是产生裂缝的主要原因。
 
 2. 砂浆对裂缝的影响
 
  普通砂浆的导热系数约为0.9W/(m·K),线膨胀系数约为4×10-4mm(/m·℃),与加气混凝土砌块相差达到10倍左右,一旦环境温度变化一定程度,则在砌筑砂浆、抹灰砂浆与砌块之间产生温度应力,当该应力大于粘结强度时裂缝就产生,该裂缝主要表现在顶层梁底与墙体之间,门、窗框与墙体之间,裂缝呈水平裂缝与斜拉缝砌块。
 
 3. 施工不足产生裂缝
 
①未控制好砌块的含水率,加气混凝土砌块出釜时含水率大多在35~40%,砌块出釜(10~30d)后含水率在堆放正常的情况下可降至30%,此时方可上墙施工。
 
②砌筑时不按相关规范要求进行施工,砌块表层的含水率、砌块搭接长度、一次性砌筑高度不合理等造成裂缝。
 
③砌筑时未严格控制灰缝的饱满度。
 
④未合理设置拉结筋,或未按规范在跨度或高度较大的墙体内设置构造柱、圈梁。
 
⑤抹灰前不进行除尘、湿润墙面等措施。
 
⑥未在不同材料交界处进行加强措施处理。
 
 
1。 Dry shrinkage creates cracks

The aerated concrete block is a highly dispersed capillary structure, and most of the holes are closed。 With the change of time, the water in the hole continues to decrease。 Under the effect of surface tension, the capillary hole forms a contraction stress。 When this stress reaches a certain level, the masonry will produce dry shrinkage。 Dry deformation is characterized by rapid early development, gradually slowing down and continuing over a long period of time, leaving the entire masonry in a state of creep。 Dry shrinkage cracks are widely distributed, numerous, and the fracture strength is serious。 Dry shrinkage deformation is the main reason for cracks。

2。 Impact of mortar on cracks

The thermal conductivity of ordinary mortar is about 0。9 W /(M · K), the line expansion coefficient is about 4 × 10-4mm(/ M · °C), and the difference with the aerated concrete block is about 10 times, once the ambient temperature changes。 To a certain extent, The temperature stress is generated between the masonry mortar, the mortar mortar and the block。 When the stress is greater than the bond strength, the crack is generated。 The crack is mainly represented between the top beam bottom and the wall, between the door and the window frame and the wall。 The cracks are horizontal cracks and sloping seams。

3. Insufficient construction resulting in cracks

1 The water content of the block is not controlled properly。 The water content of the gas-filled concrete block is mostly 35 to 40 % when it is filled。 The water content of the block(10 to 30D) can be reduced to 30 % when the pile is normal。 At this time, construction can be done on the wall。

2 When masonry does not carry out construction according to the relevant specifications, cracks are caused by the water content of the surface layer of the block, the length of the block, and the unreasonable height of the one-time masonry.

3 The fullness of the gray seam was not strictly controlled when masonry was made.

4 There is no reasonable setting of tendons, or structural columns and girders are not installed in the walls with large spans or Heights according to specifications。

5 Do not carry out dust removal, wet wall and other measures。

Enhanced measures were not taken at the junction of different materials。
 



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