How to solve the secondary grouting weaknesses

A well-known secondary grouting defects is the combination of cast-in-place concrete with the original base than poured firmly for the first time? So the question is why the second grouting process of cast-in-situ concrete and the combination of the original foundation is better than the first firm? Among the traditional secondary grouting construction, the materials are generally choose, net fine stone concrete in cement slurry under dry conditions can cause shrinkage of concrete; In wet conditions ( Or in the water) Volume swells. This phenomenon had appeared earlier at the Portland cement soon to attention by people. But how to solve this phenomenon, but until today is still a debate endlessly. Choose the right material is the key, the problem until the emergence of the epoxy grout is resolved, epoxy cement grout is as the main raw material, but in the production of epoxy grout added expansion agent, make its have to expand the characteristic of contractive close-grained, concrete and combined with the unstable problem of the original structure.