Papers by Author: Kun Lin Ma

Abstract: Salt solution ingress into concrete will result in serious deterioration of concrete materials, and then bring concrete structure in danger. So researchers pay more attention to the transportation of salt solution in concrete. In this paper, the ingress of 5% NaCl, 5%Na2SO4 and H2O into concrete under capillary siphon effect were investigated, and the influence factors such as water to binder ratio, mineral admixture, porosity and pore structure were also analyzed by methods of capillary solution-absorption experiment and evaporated water test. Results show that in capillary siphon effect, first the salt solution ingress into concrete increase quickly in very short time and then with the increase of time the solution absorption mass keep stable gradually. The types of salt solution are not the decisive factors controlling the solution ingress. Addition proper mineral admixture such as compound of fly ash (FA) and silica fume (SF) can decrease solution absorption mass under capillary siphon effect efficiently. In capillary effect, pores with aperture above 30 nm have close relativity with solution absorption mass. The decrease of porosity and improvement of pore structure can reduce the ingress of solution into concrete.

Abstract: The physical crystallization action of sulfate in cement based material, which often occurs by dry-wet cycle, capillary rising and evaporating action, can damage seriously cement-based materials as compared to chemical corrosion by sulfate. The deterioration mechanism of cement-based materials by sulfate crystallization attack, experimental investigations of the process of sodium sulfate crystallization and the factors affecting the process, and the invading track of salt solution by capillary effect are presented in this paper. Results show that the crystal type and crystallization velocity of sodium sulfate is influenced greatly by relative humidity and ambient temperature. There is a close relationship between invading depth and the porosity of concrete. Addition of mineral admixture to concrete can significantly reduce the invading depth of sodium sulfate solution and thereby enhance the resistance of concrete to sulfate crystallization attack.The profile of invading track of salt solution by capillary effect is similar to the shape of concave parabola.