Study on Influence of Heat and Humidity on The Adhesive Performance of Base Mortar of External Wall.

按照去年的顺序，在砂浆浇筑的混凝土墙体上进行了试验。其中一些被红外灯加热到80ºC，然后冷却到环境温度（或+湿度），另一些则暴露在室外。砂浆与混凝土墙体接触面处于“正常”和“部分预裂”两种状态（参见图1，Type1）。今年，又进行了一些实验。预裂试件（1型、2型）按上述方法进行加热，并对预裂行为进行了检测。实验结果如下：(1)在仅加热的情况下，砂浆与混凝土墙体的粘结强度在一个月后降低了40%。(2)“正常”状态下（加热+加湿）粘接强度下降幅度小于单纯加热状态。另一方面，“预裂1型”胶黏剂在（加热+加湿）条件下的下降幅度远大于仅加热条件下的下降幅度。(3)试验开始90天后，“正常型”粘结强度降低7%，“预裂型1”粘结强度降低37%。(4)所有试件均出现砂浆开裂，其中“预裂1型”试件裂缝较宽。(5)在“预裂型1、预裂型2”的根部，观察到预裂型的延伸。这些是砂浆从混凝土墙上脱落的力学原因。2)用有限元法分析了红外灯加热后试样的温度分布。计算结果与实测温度吻合较好。3)根据第2)项计算的温度分布，计算试件的应力分布。结果表明，砂浆中存在足够大的拉应力使其发生开裂。

In the sequence from last year, the experiments have been carried out on the concrete walls finished by mortar. Some of them have been heated upto 80ﾟC at the face by infrared lamps and cooled down to circumstane temperature (or+humidity) and others exposed out door.The contact planes with mortar and concrete wall have been in two conditions, "normal" and "having partially pre-cracking" (Ref.fig-1, Type1).In this year, additional experiments have been done. The specimens with pre-crackings (Type1,2) have been heated up as same as above and the behavior of pre-cracking have been inspected.The exprimental results have been as follows ;(1) The adhesive strength with mortar and concrete wall has been lowered 40% after a month in the case of only heating up.(2) The drop in adhesive strength of "normal" was amaller in the case of (heating+giving humidity) than in the case of only heating. On the other hand, the drop in the adhesive of "pre-cracking Type-1" was much larger in the case of (heating+giving humidity) than in the case of only heating.(3) The adhesive strength of "normal" have been lowered 7% after 90 days from exprimental start and that of "pre-cracking Type-1" have been lowred 37%.(4) The cracking in mortar have been observed in all the specimens, especially the specimens with "pre-cracking Type-1" have had wider cracking.(5) At the roots of "pre-cracking Type-1,2", the extention of that have ben observed. These are a mechanical reason of mortar pealing off concrete wall.2) The temperrature distributions in the specimen which have been heated up infrared lamps have been analyzed by F.E.M.. The calculated results have agreed with the mesured temperature.3) The calculation of stress distribution in the specimen have been carried out based on the temperature distribution calculated in item 2). They are shown that the enough magnitude of tensile stress for cracking to occur exists in mortar.