Study On The Preparation Of Tricalcium Silicate By Electric-Microwave Heating And The Hydration Process

This paper is based on National 973 Key Basic Research Development Program in China, complicated component interaction in concrent,whice is the project of "Basic research of environmentally friendly moder concrent"(NO.2009CB623201).In this paper, we have discussed a new preparation method of tricalcium silicate, and hydration process, development of initial structure and mechanism of cement with water reducer and retarder.Multiple measurements are unfolded in this paper. Through f-CaO testing,and XRD, we have researched the performance of new preparation tricalcium silicate, and confirmed the technological parameter of the new preparation methord of tricalcium silicate. Through heat of hydration and chemically combined water testing, the hydration process, the initial structures of tricalcium silicate hydration are studied. Further more, the structure formation and development of paste together with chemical admixtures (water reducer and retarder agent) are investigated systematically and comprehensively. In addition, regulative mechanisms of chemical admixtures to hydration process are discussed thoroughly by microstructure analysis techniques.The results are listed as following:1. First we have discussed a new preparation method of tricalcium silicate—electric heating assisting with micro-wave heating. Comparaed with tricalcium silicate which preparaed through using foreign oxides, we have confirmed the technological process and parameter as following:using calcium hydroxide as calcareous raw material, and usingβ-SiO2 as siliceous raw material; pressing into wafers shaped under 40MPa; sintering in the furnace for 2 hours under 1450℃, then quickly placing in the microwave oven, sintering 30 minutes; adding 4% of the CB after cooling, grinding 50 minutes, and then using the microwave heating 30 minutes; repeat the process until the calcined sample qualified.2.After adding water-reducing agent,because of its adsorption and dispersion effection, the hydration process of tricalcium silicate has changed, and the effects of different water-reducing agent are obvious different:sodium lignosulphonate has the lower water reducing ratio. Therefore,under the larger dosage, it played a significant role in delayed and prolonged tricalcium silicate hydration at the early age, and the effect is lasting at the following hydration age; Naphthalene superplasticizer also has conducted a delay effect at the early age of tricalcium silicate hydration prcess, but the effect is not obvious, and played a role in promoting hydration at the later age of hydration;Polycarboxylate superplasticizer has a higher water reducing ratio.So even a little content, it also can conducts a obvious effect. It played a significant role in delayed and prolonged tricalcium silicate hydration at the early age, but played a role in promoting hydration at the later hydration age.3.After adding the retarder agent, the hydration process of tricalcium silicate has changed significant. Sodium gluconate can effectively delay the initial hydration process of tricalcium silicate, because of its molecular structure containing hudroxyl and carboxyl, and in an alkaline environment,they can form an unstable complex with Ca2+. Thus it can prolong the tricalcium silicate hydration induction period, and play a role in retarding; Sodium tripolyphosphate can also effectively delay the hydration of tricalcium silicate in the initial reaction, because it has a strong ability to complex alkali metal ions, can take chemical reaction with Ca2+ in the solution. Thus it can extended the initial hydration induction period of tricalcium silicate. As complex products, the initial hydration products and adsorption layer coverage, so that the tricalcium silicate particle agglomerated. Thus the late hydration process also affected.