Investigation Of Key Transform Technology On The Application Of High Performance Cement

This project was from of the national basic research plan ("973" project, named basic research of the production and application of high performance cement). Focus on the two important scientific issues of this project, works were carried out to provide basal theories for the application of high performance cement (short for HPC thereinafter). The differences of the hydration characteristics of HPC and traditional Portland cement (short for TPC thereinafter) were studied multi-angle. Based on it. the mechanisms of chemical admixtures on the initial hydration process of HPC and the control technologies in corresponding conditions were investigated. The main achievements are listed as follows.1. Hydration characteristics of HPCThe differences of the hydration characteristics of HPC and TPC were significant, which are direction of the application of chemical admixture in HPC. The results show that the initial hydration heat parameter, paste electricity and macroscopical physical performance were different with TPC, but show themselves some regulations and relationships. From the view point of the application of chemical admixtures, it showed that the early workability between HPC and TPC is parallel but is distinct in the later workability. The chemical shrinkage of TPC is higher than HPC, but very impressible to water-reducing agents (short for WRA thereinafter). HPC shows more sensitive than TPC to the delayed effect of retarders. Shrinkage-reducing agent (short for SRA thereinafter) enhanced the mechanical performance of TPC, but had a weakening effect with varying degrees to HPC. In the conditions of low dosage level of coal-gangue, compared with HPC, TPC had a lower compressive strength, but higher chemical shrinkage.2. Controls and mechanisms of chemical admixture on initial hydration of HPCWRA promote the first peak primarily due to the increase of wetting heat, but the second peaks in hydrated temperature curve are retarded and weakened. The heat process and the structure formation reflected by resistivity were inconsistent because of the air introduction by calcium lignosulphonate, this shows that the use of heat-Electric models (in short H-E model) to online describe the hydration process and structure formation of instantaneous state can effectively compensate for the structural formation of a single thermal model described. The effects of sugar and itsderivatives to heat parameter and electrical performance are both common and differences, related to their molecular structure. Their role was mainly to delay the hydration of C3S, but accelerated initial hydrolysis of C3A. TEA exist double threshold dose 0.02% and 0.15%.3. Chemical admixtures compound optimizationThe relationship between early cement paste fluidity, resistivity and the mechanisms of retarders to the hydration of C3A was consanguineous. There were critical effects on compressive strength when sulphate compounded with WRA. and the fluidity of paste was weakened. The relativity of exothermic time with the highest rate and structure formation in the corresponding cement specimen were obvious. The drying shrinkage characteristics curve A L/At-t acted as "w'\ which reflected different mechanisms in the drying shrinkage process. Both of the peaks were weakened remarkably by the compound of water-reducer agent and shrinkage-reducing agent, which was not exist in each member solely.4. The control mechanism of chemical admixtures affected by environmental factorThere is a mutation of the paste fluidity added with WRA when the environmental temperature going up. The retarders had dose critical effect on the setting-time of cement, and critical dosage reduced when temperature went up. The relationship of relayed effect of sugar and temperature are special. Role in the chemical admixtures, when environmental factor changed, the electrothermal performance and the marco and micro structure performance had a confirmation mutual relationships, particularly for the relationship between the characteristics of resistivity each stage, pore distribution and macroscopical mechanical performance. By means of optimization, fine tuning and compound technology, the compatibility of chemical admixture and high performance cement can be solved without raising costs.