Effect of Chelating Additive on Pore Structure and Mechanical Property of Mortar under Different Curing Conditions

Effect of chelating additive on microstructure, hydration products and mechanical property of mortar under different curing conditions was investigated. The microstructure was tested by nuclear magnetic resonance and scanning electron microscope. And the chemical composition of hydration products was analyzed by X-ray diffraction. The compressive strength was measured under different curing conditions at different curing age, including standard curing, water immersion, seawater immersion and salt mist curing. After curing for 28 days in water, compared to control mortar, the reduction ratio of harmful pores whose size larger than 0.1μm in mortar with chelating additive (CA mortar) was 14.6%, followed by 8.9%, 9.2% and 2.9% which was under standard curing, seawater immersion and salt mist curing, respectively. From the scanning electron microscope image, there were more needle-like and bar-like crystals in CA mortar making it more compact, which was mainly calcium silicate hydrate through component analysis. Besides, the raising percentage of compressive strength of CA mortar under water immersion is 28.6% compared to control mortar at the age of 28 days, followed by 26.8%, 21.8% and 16.3% which was under standard curing, seawater immersion and salt mist curing, respectively. The results indicate that chelating additive can enhance compactness and compressive strength of cement-based materials especially under water immersion by promoting the formation of calcium silicate hydrate.