Experimental Research On Durability Of Engineered Cementitious Composite With High Volume Fly Ash

Engineered Cementitious Composite (ECC) is featured with strain-hardening and multiple cracking as a new material of fier reinforced concrete. During the recent two decades, many researches on the properties of ECC have been carried out at home and abroad. However, the research mainly focuses on the theoretical study, as well as the mechanical properties such as tensile, flexure, shear and so on, and the properties of shrinkage cracking. Few researches are about the durability of ECC. Therefore, starting with the freezing-thawing resistance, permeability, carbonation resistance, chemical resistance and the resisitance to corrosion of steel, the durability of ECC with low water-cement ratio and high volume fly ash is investigated in this paper, compared with ordinary concrete with the same compressive strength.Accelerated freezing and thawing test has been conducted, and the mass loss, changes of dynamic elasticity modulus, and changes of flexural properties are analysted. Furthermore, the influence of freezing and thawing medium on ECC is investigated compared with ordinary concrete. The results show that ECC has stronger resistance to spalling. Whiletime, the initial crack load and ultimate load decrease, and flexural deflection enhances, especially for the specimens under freezing and thawing cycles in the salt solution. The flexural toughness index arrives maximum at 150 cycles in the water and 50 cycles in the salt solution respectively. According to the rapid chloride ions penetration test, the permeability of ECC with high volume fly ash is higher, of which diffusion coefficient is 8.095×10^-10cm/h, compared with 2.95×10^-10cm/h of ordinary concrete. The results show that the flexural and compressive strength and initial cracking load decrease, but flexural deflection increases after immersed in HCl. However,the influence of NaOH on ECC is not so obvious. Additionally, the flexural and compressive strength slightly enhance, initial cracking load increase and flexural deflection decreases after immersed chlorate and sulphate.Compared with ordinary concrete, the carbornation of ECC is relatively easy due to its non coarse aggregate and high volume fly ash used through the accelerated carbornation method. The initial cracking load decreases and the flexural deflection increases after carbornation. Furthermore, the accelerated corrosion of steel test has been conducted to compare the ability of resistance to corrosion of steel between ECC and ordinary concrete. And the influence of different loads and carbornation on the resistance to corrosion of steel has been investigated. The results show that ECC has a strong ability of corrosion resistance compared with ordinary concrete.