At present, the development and widespread application of high-efficiency water reducing agents have brought fundamental changes to modern mortar concrete, but at the same time it has also increased the risk of cracking of modern mortar concrete. For modern mortar concrete Insufficient understanding of the design, construction and supervision of pumped mortar concrete. The development of pumped mortar concrete construction technology has also greatly increased the technical difficulty of crack control in mortar concrete. With the transformation of engineering construction methods, the excessive pursuit of project progress has not only led to insufficient maintenance of mortar concrete , and leads to the excessive pursuit of early strength of mortar concrete.
Cracks are not only a sign of poor construction quality, but also the most unfavorable factor that aggravates the deterioration of the durability of mortar concrete. Cracks in mortar concrete are inevitable, but the extent It is controllable. He concluded that the poor durability of mortar concrete is mainly due to the influence of the surrounding environment or the reaction with the surrounding medium, and is accompanied by performance failure phenomena such as expansion cracks, spalling and collapse.
The reason why cement mortar concrete is easy to crack is the nature of brittle materials. There are only weak physical bonds between particles, and the tensile strength is an order of magnitude smaller than the compressive strength. In recent years , the main causes of cracking of mortar concrete in our country are changes in cement, increase in pumped mortar concrete (additives, mortar bone ratio), improvement in strength grade of mortar concrete and improvement in the strength of mortar concrete. Increase the dosage of mortar concrete.
Cracks are the channels for the intrusion of all corrosive media. The growth of existing cracks is easier than new cracks, and the development of existing cracks is easier than new cracks. Therefore, early cracking and late cracking It is inevitable. Non-cracking in the later period is not necessarily non-cracking, but the shrinkage stress formed in the early stage should be reduced as much as possible. Controlling early cracks can reduce the width and number of later cracks.
Early shrinkage cracking is the main cause of cracking of mortar concrete structures. The temperature stress caused by excessive temperature difference between inside and outside is enough to cause mortar concrete to crack. The cracking stress is also related to the elastic modulus of mortar concrete, and the cracking is related to the cracking of mortar concrete. Stress is related to tensile strength. The results show that the water glue of modern mortar concrete is relatively low, the exudation rate is low, and the surface of mortar concrete is easier to dry. The initial curing time is significantly advanced, curing is required, and the curing method needs to be improved. However, traditional curing methods can no longer meet the development requirements of modern mortar concrete.
One is to control temperature and humidity; the other is to control temperature and humidity. The second is to reduce constraints; the third is to reduce the cracking sensitivity of mortar concrete, the maximum Minimize strength and water consumption, use crack-resistant cement, optimize aggregates, and use minerals with good crack-resistant admixtures; fourth, the construction of the molding process is the last key link. </p
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