Abstract
The quality of the the existing concrete surface in its repairing and strengthening is the key factor affecting the together working performance. The effective method to solve this problem is to use permeable crystal waterproof material to strengthen the existing concrete surface. In view of the existing old concrete which lacks free Ca2+ in the interior, the method of compensating calcium ion strengthening is proposed based on the action mechanism of permeable crystalline waterproof material. On the basis of DPS, calcium ion compensating agent Ca (OH)2, Na2SiO3(sodium silicate) and Na2CO3(potassium carbonate) solutes are added to prepare composite reinforcement solution for impregnation strengthening of concrete. Scanning electron microscopy (SEM) was used to observe the microstructure of the concrete before and after strengthening. It showed that after the entry of silicate ions, C-S-H colloid was formed by reaction with Ca (OH)2, and C-S-H gel blocked some pores, which made the inner microstructure more compact. The results of compressive strength before and after concrete strengthening show that the strengthening effect of calcium ion compensation method for low-strength concrete is better than that of permeable crystallization material strengthening method. The strength of C5 and C15 grade concrete is increased by 36.1% and 6% respectively, and the surface strength of 13.7 MPa concrete is increased by 16.7%.
Highlights
The building materials industry of our country issued the JCT 1018-2006 .Jiang Qian [4] applied water-based permeable crystalline material (DPS) on the surface of concrete with different strength grades, the compressive strength and chloride ion penetration resistance of concrete were significantly improved, and the improvement degree decreased with the increase of concrete strength grade.Gong Yunli[5] used three kinds of water-based osmotic crystallization materials to do the test of improving the strength of concrete
The strength of C5 concrete is increased by 33.4%, and that of C15 concrete is only increased by 6%.Low strength concrete has larger water cement ratio, more internal pores and poor anti permeability, which makes it easier for DPS to penetrate
(2) The results show that the compensation calcium ion reinforcement method is better for low strength concrete, the strength of C5 concrete is increased by 36.1%, and the strength of C15 concrete is increased by 6%
Summary
Existing concrete is required to have a certain strength in the repair and reinforcement of the existing concrete base.For example, the various reinforcement methods in the GB 50367-2013 require that the positive tensile bonding strength of the substrate surface of the concrete is not less than 1.5MPa and the strength is above C10 or C20 when the concrete is reinforced.JGJ/T259-2012 divides the repair construction into four processes: base treatment, interface treatment, repair treatment, and surface treatment. base treatment and interface treatment are important measures to ensure the bonding effect between the base concrete and the repair material.The base treatment is mainly to solve the existing concrete foundation hollowing, cracking, loosening, steel corrosion and other problems that affect the repair treatment and durability in the later use, and create good base conditions for the restoration.Whether it is the repair or reinforcement of the concrete structure, the quality of the existing concrete base and the treatment method of the bonding surface are the key factors that affect the bonding of the existing concrete and the repair or reinforcement materials to form a common force[1].In order to ensure the quality of the existing concrete base, surface treatment methods such as flower hammers, grinders or high-pressure water jets are required to remove loose aggregates, gravel, scum, leaked cracks and dirt or damaged concrete, surface chiseling, surface cleaning, etc[2]. The results show that DPS improves the compressive strength and chloride ion resistance of concrete,and the penetration depth of DPS is about 2 cm.Zhang Yongchun [7] sprayed concrete with permeable crystalline material for 72h. Some researchers have shown that the penetration depth of the substance can reach 1.2m, and the active ingredients will continue to penetrate with the passage of time [13] These studies and engineering practices have proved that both water-based permeable crystalline materials and cement-based permeable crystalline materials can improve the compressive strength and durability of concrete on the basis of increasing the waterproof capacity of concrete base. Basic attribute name Environmental protection Acid and alkali resistance, gasoline and freeze thaw resistance
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