Effect Of Admixture On Performence Of Steam Curing Concrete

Steam curing is a common technology to produce prefabricated concrete components,which could improve the early strength of concrete，accelerate the circulation of moulds andincrease the productivity. Usually，superplasticizer and early strength agent could improve theearly strength of concrete under steam curing，but the report to effect of single doped anddouble mixing of superplasticizer,early strength agent,air entraining agent,expansive agentand retarder on process of cement hydration and strength under steam-curing is less.In the project, effect of single and double doped admixture on the process of cementhydration and concrete strength under steam curing was systematically studied. Effect ofdifferent kinds of admixture on hydration peak and its appearing time, hydration heat andproduction of Ca(OH)2of steam curing cement paste was investigated by using directthermometry and X-ray diffraction technique(XRD). Effect of single doped and doublemixing of superplasticizer, early strength agent, air-entraining agent, expansive agent andretarder on concrete strength under steam curing was analysed.Test results shown that effect of different admixture on cement hydration and concretestrength is different. Polycarboxylate superplasticizer, sodium phosphate, glucose and citricacid could postpone the hydration peak，and reduce the hydration heat, the quantity ofCa(OH)2and steam curing strength，that is to say those admixtures delay the cementhydration. Excessive polyethylene glycol reduces theconcrete strength under steam curing.Polynaphthalene sulphonate, Na2SO4, calcium chloride and appropriate amount oftriethanolamine could obviously advance the hydration peak, increase the cumulativehydration heat and the quantity of Ca(OH)2,and also improve the concrete strength So these admixtures can promote the cement hydration. Besides, amino superplasticizer increases thesteam curing concrete strength.The Sodium dodecyl sulfate and the compound expansion agent have little effect onhydration process of cement and steam curing concrete strength Compared with the singledoped superplasticizer，double doped Polycarboxylate superplasticizer and early strengthagent, Polynaphthalene sulphonate and early strength agent, superplasticizer and airentraining agent, superplasticizer and retarder reduce the steam curing concrete strength.Compared with the single doped Polynaphthalene sulphonate，double doped Polynaphthalenesulphonate and early strength agent increases the steam curing concrete strength.