Synthesis And Performance Of An Ettringite Crystallization Inhibitor

The formation of expansive ettringite will cause cracks in concrete structure. With appropriate molar ratio of diethylenetriamine, formaldehyde and phosphorous acid, a new ettringite crystallization inhibitor- an organic phosphonate inhibitor is synthesized at a certain temperature after a certain reaction time.An "internal mixing" method, using inhibitors as admixtures directly incorporated into the cementitious materials was adopted. Using mortar bar test, the researchers studied the inhibition effect of ettringite crystallization inhibitors with different dosages on the expansion properties of reference cement doped with sulphoaluminate expansive agents, and confirm the inhibition effect of ettringite crystallization inhibitors on expansion. With the increase of inhibitor dosages, the inhibition effect differs notably at different ages. This paper presents the inhibition mechanism and suggests an optimal inhibitor dosage of 0.1%-0.2%. Ettringite crystallization inhibitors have the effect of retarding and slow down the hydration process of cement, but have no effect on strength of mortar with a proper inhibitor dosage.An "External Mixing" method, immersing the fabricated concrete specimens in Na2SO4 solution mixed with inhibitors to simulate the erosion of concrete in the sulfate environment, was adopted. The results confirm that the presence of sulfate ions in environment can cause the formation of expansive ettringite. Ettringite crystallization inhibitors can effectively inhibit the formation of ettringite so as to reduce the harden paste expansion caused by ettringite.