Application Of Organic Silicon Water Repellents In Dry-mixed Mortar And Discuss Waterproof Mechanism

The waterproof materials usually used in buildings, through plugging pores of materials to exclude aggressive water. As the pores are blocked, the wall is not ventilated. While the buildings which use organic silicon water repellents can not only maintain ventilated, but also exclude water abidingly. Organic silicon water repellent is a novel rigid waterproof material with good prospective application.This study shows comprehensive performance of different organic silicon waterproof powder used in three types of dry-mixed mortar system (anti-cracking mortar of insulate board, waterproof skin coat and tile grout). And find out the best operational version for different organic silicon waterproof powder used in the dry-mixed mortar. Then, determine the optimized dosage to make sure mortar has good working performance, mechanical property and durability. On this basis, through micro-testing methods (XRD, FTIR, SEM and AFM), we know the waterproof mechanism of organic silicon water repellents and consummate the theoretical basis of the reaction. The comprehensive performance index include water absorption, ratio of compressive to flexural strength, adhesive strength, freeze thawing cycle, heat resistance, alkali resistance and dry shrinkage etc.The study found these six types of silicone waterproof repellents could be applied to dry-mixed mortar, and waterproof property is good. In the best condition, water absorption of mortar reduced by 90%. Water absorption of organic silicon water repellents is not increasing when the dosage of water repellents increases, but there is a suitable dosage. Different types of organic silicon water repellents, waterproof effect would be different. Compared to the other types of organic silicon water repellents, the compositive performance of single-component silicon water repellents is not remarkable; polymeric siloxane compound with the best waterproof effect, and also improve some of mortar performance. Silicone-modified water repellents obviously improve waterproof and the other performance of mortar. Inclusion silicone could increase adhesive strength of matrix and also improve resistance to water of materials. The mechanics of organic silicone water repellents have two sides: in the first place, organic silicone water repellents form a firm hydrophobic surface layer in mortar pores and capillary. This silane film is hydrophobic and reticular, has low surface tension and can uniformly distributed in the porous silicate substrate. This film make the wall of micro-hole has a good repellency. In the second place, organic silicone water repellents react to -OH group in the cement. Then, -OH group of the cement decrease. So organic silicone water repellents reduce surface tension of capillary and enhance cement density in some degree, thereby the waterproof performance of mortar improved.