基于再生微粉的复合胶凝体系水化特性研究

Study on the hydration characteristics of composite cementitious system based on the recycled micro powder

为了解基于再生微粉的复合胶凝材料的水化硬化机理,本文将再生微粉和粉煤灰单掺或与硅灰复掺以50%、60%、70%的取代率取代水泥制备水泥净浆试件,研究其抗压强度、水化放热速率、放热量及水化产物的变化规律。结果表明:随着取代率增加,胶凝材料抗压强度降低,取代率为50%时,胶凝材料力学性能最佳,其中复掺再生微粉和硅灰龄期为7d时,其抗压强度达到了29.1MPa;复掺再生微粉和硅灰的早期放热速率与复掺粉煤灰和硅灰基本一致,但加速了二次放热且放热量均低于纯水泥组;通过XRD试验可以发现,随着取代率增大,复掺再生微粉和硅灰的Ca(OH)2衍射峰逐渐减弱,表明其促进了二次水化,也证明了再生微粉具有火山灰活性,且再生微粉的火山灰活性大于粉煤灰。该结果可为研发生态建筑材料提供理论支撑。

In order to explore the hydration and hardening mechanism of composite cementitious materials based on the recycled micro powder,recycled micro powder and fly ash are used to prepare cement paste specimens by replacing cement with the substitution rates of 50%,60%and 70%respectively in the form of single mixing or mixing with silica fume.The variation rules of their compressive strength,hydration exothermic rate,exothermic heat and hydration products are investigated in the study.The results show that the compressive strength of cementitious materials decreases with the increase of substitution rate.The mechanical properties of cementitious materials are the best with the substitution rate of 50%.The compressive strength of the materials reaches 291 MPa when the recycled micro powder and silica fume are mixed at 7 days;the early exothermic rate of mixing the recycled micro powder and silica fume is basically the same as that of mixing fly ash and silica fume,while the secondary exothermic rate is accelerated and the hear release of both combinations is lower than that of pure cement group;it can be found through XRD test that the diffraction peak of Ca(OH)2 of mixing the recycled micro powder and silica fume gradually weakens with the increase of substitution rate,which indicates that the secondary hydration is improved.It also proves that the recycled micro powder has pozzolanic activity which is greater than that of fly ash.The results can provide theoretical support for the research and development of ecological building materials.