Development And Application Of A New Polyether Concrete Pumping Admixture

Pumping is the main pouring method of modern concrete,due to the shortage of high-quality aggregate and the variability of raw materials,the performance of concrete pumping admixture is particularly important,especially the compatibility between pumping admixture and other raw materials,which directly related to the quality of construction projects or the long-term cooperative relationship between concrete factory and client.Therefore,it is extremely essential to prepare a new type concrete pumping admixture to reduce cost and improve product quality for concrete production plant,so as to meet the fierce market competition environment.In this paper,a new polyether slump retaining SRA-Ⅰwas synthesized,and a new polyether concrete pumping admixture JY-I was developed with SRA-Ⅰas water-reducing component.Using（2+2）new polyether macromonomer EPEG,acrylic acid and hydroxyethyl acrylate as comonomers and mercaptopropionic acid（MPA）as chain transfer agent,In the redox initiation system composed of H₂O₂-Vc-Fe _SO₄,According to the theory of free radical copolymerization,a new polyether slump retaining agent SRA-Ⅰwas synthesized by normal temperature process,the effects of acid ether ratio,ester ether ratio,initiator system,chain transfer agent,synthesis temperature and the relationship between dropping time and the performance of water reducing was studied by single factor test.The optimum synthesis process of SRA-Ⅰwas determined:acid ether ratio n（AA）:n（EPEG）=3.5:1,ester ether ratio n（HEA）:n（EPEG）=2.0:1,the dosage of hydrogen peroxide,MPA and ferrous sulfate solution were 0.8%,0.33%and 0.22%of the mass of macromonomer EPEG respectively,n（H2O2）:n（Vc）=5:1,reaction temperature 20℃and dropping time is 1 h.A new polyether concrete pumping agent JY-I was compounded by using the synthesized SRA-Ⅰas the water reducing component and optimized with retarder,air entraining agent and thickener.The formulation of retarding components is comprehensively evaluated from the aspects of compatibility between retarding components,plasticizing effect and slump retention,setting time,bleeding and compressive strength.It is obtained that the best formulation of retarding components is sucrose,sodium tripolyphosphate and sodium hexametaphosphate,accounting for 1.0%in the pumping admixture respectively.Keep the water reducing and retarding agent in the pumping admixture unchanged,with K12,AES,AOS is used as air entraining component.The formula of air entraining component is comprehensively evaluated from the aspects of concrete fluidity and time loss,bleeding rate ratio,air content and time loss,compressive strength and so on.The best formula of air entraining component is that AOS accounts for 0.1%of pumping admixture.Maltodextrin,hydroxypropyl methylcellulose（HPMC）,polyacrylamide（PAM）and self-made viscosity modifier MS-01 are used as thickening components.Through the influence of different thickening components and dosage on the fluidity,time loss,bleeding rate ratio,expansion time t500,compressive strength and other properties of concrete,the best thickening component formula is MS-01,accounting for 1.5%of pumping agent.The industrial production of new polyether slump retaining SRA-Ⅰand JY-I pumping admixture was carried out.In the specific project,JY-I pumping admixture is used to prepare C50 and C70 pumping concrete respectively.Compared with the pumping admixture of different manufacturers,it shows that this kind of pumping admixture can meet the actual needs of the project and achieve the expected effect.