TEST AND STUDY FOR 'DRY SACKING' METHOD FOR REPAIRING SURFACE DEFECTS ON CONCRETE WITH FINE CEMENT MORTAR

摘要

(1) Washing test shows that the "sack rubbed" finish can withstand the water flow at 10m/s safely. This method can be applied to repair the defects on the concrete water retaining faces, exposed faces and water flow faces in low flow area such as bug hole less than 10mm in depth and voids less than 5mm in depth which don't need to be chipped off. (2) The concrete surface repaired by "sack rub" method has a great improvement on flatness. Furthermore, its appearance is consistent with the base concrete, which can avoid using other materials to repair such defects to cause big differences on the appearance. (3) Repairing materials include Gezhouba Jingmen moderate heat cement No.525, manufactured sand or river sand which the grain size is smaller than 0.63mm after screened, recommended admixture SP-8N. The water-cementitious material ratio shall from 0.45 through 0.55. The strength class of cement mortar shall be one class (at least) higher than that of concrete surface to be repaired. (4) Since humidity and curing is critical for good repairing quality, which shall be controlled carefully. (5) "Dry sacking" operation shall follow the experiences from the productive test strictly. For this work, there must be a special team. The operators shall not be allowed to work until trained. (6) Based on the application of this method, further test and study can be carried out for the possibility to repair the surface defects on concrete water flow face at flow velocity more than 10m/s. (7) If conditions are available, abrasion test can be performed in the laboratory or field for quantitative analysis.