Effect Of Early Strength Agent Mixed With Polycarboxylate Superplasticize On Strength Of Steam-cured Concrete

Polycarboxylate sperplasticize as the third generation of high performance waterreducing agent,which has comprehensive technical performance with low dosage,high water reducing rate,collapsed and good performance,low harmful substance content and so on,but the unique molecular structure characteristics of PC will delay the cement hydration,affect the early strength development of concrete,limit the application in prefabricated and other projects.It is simple and easy by the method of compound to product PC with early strength performance.In this paper,the early strength agent such as organic salt and inorganic salt were mixed with anionic polycarboxylate superplasticizers?PC-O?and amphoteric polycarboxylate superplasticizers?PC-E?respectively.The effect of performance of the different kinds of and different dosages of early strength agents mixed with PC-O and PC-E on mortar and concrete were investigated,Not only the performance of PC with early strength property under standard-curing and steam-curing were investigated by experiments,but also the effect of the different kinds of early strength agents mixed with PC on the peak of cement hydration temperature and time were studied by the methods of direct thermometry,the amount of Ca?OH?2 was investigated by XRD,the mechanism of action of early strength agent mixed with polycarboxylate superplasticize were studied,the main research contents and results are as follows:Firstly,the different performance of PC-O and PC-E were compared,in order to determine the optimal dosage,the effects of two different proportion of PC-O and PC-E on the law of flow property,setting time and strength of mortar were compared,the results showed that when the PC-E content was 0.34% and PC-E content was 0.36%,two groups of cement paste have good fluidity and the smaller the loss,and initial setting and final setting time is short,in additon,the compressive strength of one day age mortar of is maximum.Secondly,the early strength agents?TEA?Li₂CO₃?Na₂SO₄?were mixed with PC-O,compared the different effect of different proportion of early strength agents mixed with PC-O on mortar under the condition of standard and steam-curing and steam-curing concrete,the results showed that under the condition of standard curing.PC-O mixed with early strength agents didn't play an important role in promoting the early strength of mortar.but it will impove the early strength obviously under 80°C steam-curing condition when TEA content was 0.06%,Li₂CO₃ content was 0.06% and Na₂SO₄ content was 0.6%.Then,the early strength agents(Na₂SO₄?Na NO2?C₁₆H₃₄O)were mixed with PC-E,the results showed that under the condition of standard curing and 50°C,80°C steam-curing,the early strength agents mixed with PC-E not only improve the early strength apparently,but also improve post-strength of mortar when Na₂SO₄ content was 0.6%⁰.8%,Na NO2 content was 0.6%⁰.8% and C16H34 O content was 0.03%⁰.05%.especially in the 80°C condition,it's more distinct.the significance of effect is C₁₆H₃₄O>Na₂SO₄>Na NO2.Finally,temperature-time curves and XRD analysis indicated that the early strength agents mixed with PC-E can improve the cement hydration temperature more than mixed with PC-E.the early hydration of C3 S were promoted and more C-S-H and Ca?OH?2 were generated when that the early strength agents mixed with two different kinds of PC was added in the cement paste.