Study On Hydration Properties Of Cementmineral Admixture-Expansive Agent Composite Cementitious System At Different Temperatures

Expansive Concrete has been widely used in structures such as self-waterproofing,long structure seamless construction,mass concrete and other fields.In this paper,some problems in the application,such as the concentrated release of hydration heat,lead to the hydration temperature of the concrete,which is higher than the normal temperature,which affects the hydration process of the cementitious material,the large amount of mineral admixture makes the hydration environment more complicated,studied effect of hydration temperature,mineral admixture content and expansive agent on hydration characteristics of cement-mineral admixture-expansive agent composite cementitious System.The main contents of the experimental study are: hydration temperature,mineral admixture content,expansive agent on the composite cementitious system mortar strength and restricted expansive ratio and the coordination between the two;The influence of different factors on the hydration kinetics was studied by Krustlovic-Dabic model.The chemical bound water of composite cementitious systems and reaction degree of material admixtures were determined.The mechanism of hydration temperature,mineral admixture and expansive agent was analyzed.Research results indicate:①Under different curing temperature,the higher the curing temperature,the faster the expansive effect of the expansive agent,the sooner the stability of the limiting expansion rate,the greater the restricted expansive rate;the influence of fly ash on the strength and expansive of the impact of the scope is larger than slag;higher hydration temperature promotes hydration,but also makes the contradiction between strength and expansive The HCSA expansive agent is better than ZY expansive agent under different curing temperature on the sensitivity to temperature.②Expansive agent will lead to the induction period of the composite cementitious system come earlier,mineral admixtures will delay the end of induction period;the HCSA expansive agent is faster than the hydration heat dissipation rate of ZY expansive agent,The final exothermic energy is affected by the factors such as mineral admixture type,dosage and expansion agent type,hydration temperature and other factors;temperature excitation and alkali excitation The role of superposition,you can let the early limited activity of mineral admixtures earlier and faster volcanic ash reaction.③The Krstulovic-Dabic model can be applied to the cement-mineral admixtureexpansive agent composite cementitious system,and its hydration reaction process undergoes crystallization nucleation and crystal growth process(NG),phase boundary reaction process(I)and diffusion process(D).Mineral admixtures,expansive agents,and hydration temperatures have distinct effect on the hydration kinetic parameters at each stage.The temperature sensibility of the ZY expansive agent is higher than that of the HCSA expansive agent.The addition of the mineral admixture to the whole hydration reaction is more moderate.Both the expansion agent and mineral admixture will reduce the apparent activation energy of the composite cementitious system.④With the growth of the age,the chemical bound water of the composite cementitious system and the reaction degree of mineral admixture also increased;the mineral admixture content is large,the reaction degree and the chemical bound water becomes smaller;The high temperature curing improves the reaction degree of the mineral admixture and the chemical bound water,and the improvement of the reaction degree to the slag is greater than that of the flyash.