The Hydration Mechanism Of The BFS And Fa Cement Based Materials

With the rapid development in the economy, and great progress in science and technology of ourcountry, an enormous amount of Portland cement are required, resulting in a significant pressure to theenergy and resource. In addition, the serious environment pollution caused by the production of Portlandcement is threatening to the health and existence of human being. So, replacing more Portland cement withthe industrial waste residues (such as fly ash, slag) as much as possible has already become one of our goalsduring the cement production and manufacture of high performance concrete.However, it has been proved that the application of waste residues, especially when high volume anddifferent kinds of waste residues are used to replace Portland cement, will lead to the obvious difference inthe chemical compositions, microstructure and hydration process between cement pastes with waste residuesand cement pasts without waste residues. In some cases, some negative effects will take place such as lowearly strength, the requirement of good curing, the low resistance to freeze-thaw cycles, large autogenousshrinkage, and carbonization acceleration, etc. As a result, it will be required that a systematic research onhydration process, the amount, compositions, the types of hydration productions in Portland cement-wasteresidues system in order to better understanding of the positive and negative effects when different types,amount, adding approaches of the industrial waste residues are introduced to the Portland cement paste.In this paper, the two types of waste residues—slag and fly ash, which are widely applied in the world,are investigated in detail. The reaction degree of the two types of waste residues, the content of CH,non-evaporable water, pore structure and the mechanical properties of Portland cement-waste residues pastesin the case of different W/B, different curing ages, are systematically studied when different types of,different amount of, different ratio of cement to waste residues are employed. Based on the experimentalresults mentioned previously, the hydration process of Portland cement-waste residues, the amount, chemicalcompositions, and microstructure of hydration productions will be analysized in order to better understandingof the positive and negative effects, a reasonable application of industrial wastes.On basis of the experimental results and theoretical analysis, the reaction degree of slag and fly ash isquantitative determined; the demand-offering mode of CaO is also presented during hydration process ofcement-slag or fly ash pastes according to the amount, microstural characteristics of hydration products; asuperposing and complementary model of waste residues and Portland cement is established; The optimummass ration of cement to waste residues in cement-slag or fly ash pastes, cement-slag-fly ash pastes isproposed to obtain a better microstructure of pastes than pure Portland cement pastes. In the last, a optimumreplacing amount and the corresponding theoretical basis of different waste residues (fly ash, slag) isestablished in the case of meeting the requirements of physical, mechanical and durable performance.The experimental results and theoretical model presented in this paper will provide a scientific basis inorder to take advantage of waste residues, better develop the great potential, establish a mixture designmethod of Portland cement-waste paste system and realize the prediction of properties.