Influence Of Binding Material Composition And Temperature On The Deformation Of Shrinkage-Compensating Concrete

Expansive mortar and expansive concrete of composite cementitious materials wereinvestigated. The influence of factors on the expansion efficiency of expansive agentwas studied by orthogonal test and parallel test and the influence of high temperaturecuring on the expansive efficiency was discussed emphatically. The hydration process,hydration products, and microstructure of shrinkage-compensating composite binderwere studied by hydration heat, non-evaporable water, XRD, SEM. The main contentsand results are listed as follows:Sulfoaluminate–calcium expansive agent can produce a larger expansion and agreater expansion speed at early ages. The restrained expansion rate (RER) of mortarcured moistly, RER residue and expansion decline of mortars after dry shrinkage arewell consistent with each other to assess the expansion performance of expansive agent.The increased content of expansive agent and the decreased content of fly ash canincrease RER. The amount of expansive agent is the major factor of expansionperformance, followed by content of fly ash and water-binder ratio, but not the onlydecisive one. By adjusting composition of binding materials, different expansionexpectation can be achieved.During the hydration process, when the water is sufficient, expansive agent andcement promote hydration with each other in early ages. While the water is insufficient,the competitive demand of water between expansive agent and cement makes expansiveagent hinder hydration of cement. The hydration of expansive agent is faster than thecement, so it obtained the water firstly and produces appropriate expansion. Hightemperature can not only improve the hydration of expansive agent; but also make thecompetitive water-demanding show up, so the conclusions got under the condition ofroom temperature don’t work at high temperature. In high temperature the RER can beclose to or reach the maximum value at1d，but develop very slowly at later ages; thelarge expansion in the early stage can hinder compressive strength of mortar, make itselfno longer agree with the development of strength.Temperature has an important role inthe influence trend of water-binder ratio on the RER of mortar. The effect that RERincreases with water-binder ratio rising at40℃is opposite to that at20℃and60℃. The RER declines with the increase of fly ash; this influence trend of fly ash on theRER of mortar is the same under different temperatures;The addition of fly ash can promote the expansion of expansive agent, properdosage of fly ash can increase expansion significantly, but larger dosage of fly ashdecreases the increase variation of expansion because of low early strength. Forconcrete with fly ash and HCSA, the minmum dosage of expansive agent can be lowerand shrinkage can be totally compensated by appropriate composition of bindingmaterialsExpansive agent can reduce the autogenous shrinkage of concrete with lowwater-binder ratio after1d. The elevated fly ash amount and water-binder ratio canimprove the compensating efficiency of expansive agent.6%HCSA can generateenough expansion to compensate all autogenous shrinkage of concrete underwater-binder ratio of0.34, make concrete expand after30h.