Abstract:

Tannin extract is traditional forest chemical product in China, their demand now is decreasing, and it is essential to develop new use. The modification of myrtan tannin extract and the dispersing performances of modified myrtan tannin extract to cement were studied. The results indicated that when the mass fractions of tannin extract and modified tannin extract to cement were 0.5%, the waterreducing rate of concrete was 7.1% and 13.1% respectively, and the initial and final setting time of cement paste added modified tannin extract was shorter 3 h 15 min and 8 h 50 min respectively than that of cement paste added tannin extract. The surface activity of modified tannin extract was less than unmodified, and the modified tannin extract almost lost its foaming capability. When the mass concentrations of modified tannin extract and tannin extract were 2.0 g·L^-1., their adsorptive amount on surface of cement particles was 7.39和5.91 mg·g^-1. respectively. When the mass concentrations of modified tannin extract and tannin extract were 1.0 g·L^-1., the ξ potentials on surface of cement particles added tannin extract and modified tannin extract was -22.13 and -25.53 mV respectively. Therefore the waterreducing and dispersing capability of tannin extract to cement increased significantly after being modified.

Key words: tannin extract, modification, cement, dispersion, retardation