INFLUENCE OF MACROMOLECULE-TYPE RETARDERS ON THE HYDRATION PROCESS OF BUILDING GYPSUM AND ITS RETARDING MECHANISM

The effect of macromolecule-type retarder bone glue on the hydration process,ion concentration in liquid phase and supersaturation degree,and crystal morphology of dehydrate of building gypsum was investigated.Furthermore,by using the X-ray photoelectron spectroscopy technique,its retarding mechanism was also studied.The results indicate that the addition of bone glue retards the early hydration of building gypsum,which leads to a delay in the hydration heat evolution.It can also decrease the hydration ratio at in the early stage and the prolong induction period of building gypsum.Bone glue has a minor effect on the crystal morphology of dehydrate and a lower negative effect on the strength of hardened gypsum paste than low molecule-type retarder.But it causes the large crystal sizes.Bone glue interacts with the Ca element on the crystal nuclei surface of dehydrates and forms a chemical adsorption layer,decreasing its surface energy,inhibiting its growth,and consequently slowing down the hydration process.