Investigation Of Influencing Factors And Its Mechanisms On The Carbonation Curing Process Of C₃S And β-C₂S

Recently,greenhouse gas emission reduction technology has received more and more attention,thus the research of using carbon dioxide（CO₂）as a curing method for cement-based materials has been promoted to a new height.However,due to the carbonation curing of cement-based materials is a complex process involving various of minerals react with CO₂,and there are also many influencing factors.Therefore,its important to clarify the carbonation curing process of cement-based materials by studying the influencing factors and its mechanisms on the carbonation curing of various minerals in cement.In this thesis,the two most important minerals in cement minerals（C₃S andβ-C₂S）were used to explore the effect of hydration time,CO ₂pressure and curing temperature on the carbonation curing process of C ₃S andβ-C₂S pastes and its mechanism.The main conclusions are as follows:1.The early hydration reaction of C₃S paste is fast,a large number of C₃S hydration products are generated in the accelerated period.increasing of early age hydration time over a short period（<4 hours）can improve the carbonation degree of C₃S paste.However,when the early age hydration con tinuous for more than 8 hours,the further increase of early hydration would hinder the carbonation degree of C ₃S paste.Thus,the optimal early age hydration time of C ₃S is between 4 and 8 hours.The early hydration reaction ofβ-C₂S paste is slow and the content of hydration products is low.The carbonation curing degree ofβ-C₂S paste increased with the increase of early age hydration time.Calcite,aragonite and vaterite are produced in the C₃S pastes after carbonation curing,vat erite and calcite are formed in carbonatedβ-C₂S pastes.Early age hydration time has no effect on the crystal forms of calcium carbonate formed in the carbonated pastes.2.CO₂ absorption and carbonation degree of C₃S paste are firstly decreased and then increased with the increase of CO₂ pressure,all of the carbonated C₃S pastes contain vaterite and calcite,but some of the carbonated C₃S pastes has aragonite.The contents of vaterite and aragonite in C ₃S paste fluctuated slightly with the increase of CO₂ pressure,and the calcite content was more affected by CO ₂pressure.While the CO₂ absorption and carbonation degree ofβ-C₂S paste increased with the increase of CO₂ pressure.The content of calcite inβ-C₂S paste increases with the increasing of CO₂ pressure,but the content of vaterite was slightly affected.3.CO₂ absorption and carbonation degree of C₃S paste decreased gradually with the increase of curing temperature,the content of calcite in C₃S paste is greatly affected by curing temperature,while the relative content of vaterite and aragonite is slightly affected.The content of calcite and aragonite/aragonite in the carbonated pastes is reversed when the curing temperature between 40-60℃.The CO₂ absorption and carbonation degree ofβ-C₂S paste firstly increased and then decreased with the increase of curing temperature.the carbonation curing degree ofβ-C₂S paste can be improved by increasing of curing temperature within 20-40℃.And carbonation reaction ofβ-C₂S paste during curing will be hindered by increasing curing temperature above 40℃,the degree of hindrance will be intensified with increasing of temperature.