Study Of Hydration And Carbonation Mechanism Of Natural Hydraulic Lime And Modification Of Its Mortars

The application of natural hydraulic lime (NHL) has been a long history, the widely use of Portland cement lead to the shrinkage of its application.Recently, because of the superiority of NHL in old relic’s restoration field,its application is experiencing resurgence. However, there are scarce research reports on NHL and deep research is deficient. In order to make clear the hydration and carbonation mechanism of NHL, modify the NHL-based mortars and further provide materials with beneficial properties for relic restoration, this dissertation carries out experiment from the following points:the effect of outside condition and water binder ratio on the hydration and carbonation of NHL, the effect of diatomite and carbon fiber addition on the properties of NHL-based mortars. The experiment results show that, the contact between NHL paste and outside condition noticeably affect its hydration and carbonation process within 90 days of curing in this dissertation. There is still C2S and Ca(OH)2 after 90 days when NHL paste does not fully contact with outside condition. Hydration almost complete within 28 days when NHL paste fully contact with outside condition, and Ca(OH)2 almost complete its carbonation after 14 days. Carbonation rate of Ca(OH)2 is greater than that of CSH in the paste and the carbonation promotes the hydration of NHL paste. Water binder ratio has effect on the early hydration and carbonation of NHL paste as well. The use of diatomite as a partial replacement of NHL lessen the density of manufactured NHL-based mortars and it will consume smaller amount of total raw materials, especially the amount of NHL, to prepare hydraulic mortars. The introduction of diatomite enhances strength of mortars and improves hydrochloric acid resistance, freeze and thaw resistance and sulfate resistance property. And these can be attributed to the pozzolanic reaction between diatomite and Ca(OH)2 in the mortars.The mortars prepared with carbon fiber and diatomite modified carbon fiber addition show a greater flexural strength than the control. Diatomite plays a certain role in modifying the surface of carbon fiber, it can react with Ca(OH)2 leading to the link between carbon fiber and the mortar matrix, which further enhances strength of mortars. The addition of superplasticizer greatly improves both the compressive and flexural strength of mortars for the reason that superplasticizer is propitious to the uniform dispersion of mortar matrix.