Abstract:

To solve the durability of structures caused by shrinkage and crack of concrete,we prepared an shrinkage-reducing polycarboxylate superplasticizer(PS) with high water-reducing rate and good cementitious compatibility.Firstly,an ester macromonomer was prepared by using acrylic acid,neopentyl glycol and water-carrying agent in association with polymerization inhibitor and catalyzer.Then,the shrinkage-reducing PS of TX-938 was synthesized by using the ester monomer,isoamyl alcohol polyoxyethylene ether,acrylic acid and dipropylene glycol with the combined effect of the oxidation-reduction initiator and chain-transferring agent.The performance that we tested shows that,as for cement dispersion property and adaptability,the shrinkage-reducing PS of TX-938 is almost equal to TX-50H,which is a kind of normal PS;moreover,TX-938 can significantly decrease the surface tension from 72.3 mN/m(without TX-938 ) to 31.6 mN/m with the blending ratio of 2.5%;then,the drying shrinkage of mortar blended with TX-50H and TX-938 decreases by 10.5% and 29.1% respectively when compared with that of mortar without PS;72 hours after initial set ,the drying shrinkage of concrete is 452×10^-6 and 399×10^-6 respectively,in other words,the drying shrinkage of concrete with TX-938 was only 88% of that of concrete with TX-50H,and the 28d drying shrinkage of concrete with TX-938 is only 35.6% of that of concrete without PS,less than 50% of that of concrete with TX-50H;finally,the water-reducing rate of TX-938 is up to 29.4% and TX-938 has no negative effect on compressive strength of concrete at different ages.

Key words: shrinkage-reducing type, polycarboxylate, superplasticizer, synthesis, strength of concrete, shrinkage of concrete