FT-IR analysis of polymerization degree of different origin slag Huang Xinliang1,Zhou Shenbo2,Liang Xiaoying3,Ren Tingting1,He Fan1(1.Shanxi Building Research Institute, Shanxi,Xian,710082) Abstract: Different origin of slag has quite different hydration activity due to the discrepancy in micro-sturcture, and by infrared spectroscopic analysis method,the hydration activity mechanism of slag was studied from the angle of polymerization degree. the results show that different origin of slag has quite different Si-O and Al-O chemical bond, therefore only a bit of silicate root polymerize to form gel at early hydration ages. Along with the hydration, there will be more silicon and aluminum exposure to the surface, slag hydration was accelerated, single silicate root ion polymerizing to form silicate speed up. As a result, the strength of the slag lime system increase larger at later hydration ages. Key words: blast furnace slag; polymerization degree; Si-O bond; Al-O bond; infrared spectroscopic analysis