Experimental Study On The Preparation Of High Performance Concrete By Ultra Plasticity Retention Polycarboxylate Superplasticizer

With the vigorous development of the construction industry,ordinary building materials are difficult to meet the requirements of various modern engineering for slump loss,mechanical properties and durability of concrete.The project has been synthesized ultra plasticity retention polycarboxylate superplasticizer basing on high water reducing polycarboxylate superplasticizer.This project synthesized a series of water reducing PC,using free radical copolymerization reaction.Designing L₁₆?4⁵?orthogonal test analyze the influence of various factors and determine the optimal ratio and process.Determine of highly water-reducing type polycarboxylate water reducing agent PC-C optimal formula,that is 5:1 ratio of acid to ether,4.5%of the amount of chain transfer agent,0.45%of the amount of initiator,drop time for 2.5hours,and incubated for 1 hour.Modification study for PCC was conducted using 2-acrylamide-2-methyl propane sulfonic acid?AMPS?and hydroxypropyl acrylate?HPA?,to study the flow retention of cement mortar.Test results show that when the AMPS substitution amount is 60%,the initial expansion and medium-term plasticity retention performance of the synthetic BTB are excellent;when the HPA substitution amount is 40%,the initial expansion and its later plasticity of the superplasticized polycarboxylate BTC is superior.It was studied that how different pH conditions influence of concrete performance and maintain water reducing agent storage time about BTC.The study found that when the pH value is maintained at about 7,the product performance is stable and the storage time is long.Using GPC test method to prove BTC and BTB molecular structure,analyze formula weight and molecular weight distribution.The test found that molecular weight distribution are in the best distribution range.Three kinds of commonly used mineral admixtures of fly ash,ground slag and silica fume was studied.The effects of the single blending of each mineral admixture and the mixed admixture of different mineral admixtures on the performance of high performance concrete were studied separately.It is found that with the increase of fly ash and ground slag content,the initial fluidity and late fluidity of the performance of HPC show an increasing trend on the whole,the 3d strength decreases,and the later strength is slightly improved.With the increase of the amount of silica fume,both the initial flow and late fluidity have a certain degree of reduction.Three kinds of mineral admixtures were mixed.The results showed that when the FA:KF:GH ratio was 13.5:13.5:3 and instead of 30%total amount of cement,the workability and strength of high performance concrete improved.Through the mixture of PCC,BTC and BTB,when the BTC:BTB:PCC ratio is 4:2:4,the high-performance concrete with mini slump meets the requirements of 160¹80mm,has good workability and low shrinkage,and has little change of 1h slump.The small slump concrete mixed with BTC,BTB,PCC and other admixtures has been successfully applied in the construction of underground continuous wall of Ji'nan rail transit R2 line,and has been tested by relevant departments.