Compounding And Engineering Application Of Polycarboxylate Superplasticizer

As the most popular type of concrete admixture,polycarboxylate superplasticizer(PCA)has attracted more and more attention because of its flexible molecular structure,low dosage,high water reduction rate and environmental protection.However,a single polycarboxylate superplasticizer mother liquor is difficult to meet the construction requirements due to that their performances are easily to be influenced by cement,mineral admixture,sand and stone used in actual engineering applications,as well as the regional and climatic factors of the project.Furthoer more,the cost performance is low when polycarboxylate superplasticizer mother liquor used alone in actual engineering applications.In view of this,this paper intends to develop compounding technology applying for polycarboxylate superplasticizer,and to obtain pumping agent;to evaluate the pumping agent's performances in fresh concrete through commercial concrete(fluid concrete),high throw self-compacting concrete(high fluid concrete),combining with laboratory image processing software to evaluate the apparent molding quality of hardened concrete.The ultra-slow release polycarboxylic acid pumping agent was prepared by the compounding idea of "water-reducing polycarboxylate mother liquor + slow-release polycarboxylate mother liquor + retarder".The self-made water-reducing polycarboxylate mother liquor(PC4)and the selected slow-release polycarboxylate mother liquor(PC340)from market and retarder(sodium gluconate(PN))were selected as raw materials,their ratio in ultra-slow release polycarboxylic acid pumping agent was confirmed through single factor test combined with orthogonal test:(?)PC4(9%)+ PC340(2%)+ PN(2.2%),the water reduction rate was 26.7%,the fresh concrete kept with workability for 2 h;(?)PC4(8.5%)+ PC340(3%)+ PN(2.5%),the water reduction rate is 27.2%,the fresh concrete kept with workability for 3 h;(?)PC4(8%)+ PC340(5%)+ PN(2.9%),the water reduction rate is 28.5%,the fresh concrete kept with workability for 4 h;(?)PC4(7.5%)+ PC340(7%)+ PN(3.5%),water reduction rate of 29.1%,the fresh concrete kept with workability for 5 h;and the comprehensive cost of materials for each ultra-slow release polycarboxylic acid pumping agent is below 1900 yuan / ton.For a high-rise building project in Chengdu Longquan,which was constructed in July(30 °C~35 °C),the fresh concrete transportation time is about 3 hours.The ultra-slow release polycarboxylate pumping agent designed by compounding technology(?)can meet the transportation and construction requirements,the slump loss of fresh concrete after 3 hours is less than 20 mm.The strength of C30 concrete sample and structural solid concrete is above 36 MPa,which meets the engineering quality requirements.High throw self-compacting concrete polycarboxylic acid pumping agent is prepared according to the compounding idea of "water-reducing polycarboxylate mother liquor + slow-release polycarboxylate mother liquor + viscosity-reducing polycarboxylate mother liquor + anti-segregation component(thickener)+ retarder + defoamer".For the characteristics of high throw self-compacting concrete,the self-made water-reducing polycarboxylate mother liquor(PC7),slow-release polycarboxylate mother liquor(PC3),viscosity-reducing polycarboxylic acid mother liquor(PC2),market-preferred hydroxypropyl Methyl cellulose ether(HPMC),sodium gluconate(PN),and defoamer(JDU)were employed as raw materials.Their ratio in high throw self-compacting concrete polycarboxylic acid pumping agent was optimized by the control variable method: PC7(4%)+ PC2(6%)+ PC3(3.5%)+ PN(1.5%)+ HPMC(0.02%)+ JDU(0.1%).The performances of the optimized compounded product are: slump/expansion: 260/685 mm,T500: 4.5 s,U-box height difference: 31 mm,7d-strength: 47.7 MPa,the cost is about 1700 yuan / ton.This product is applied to the steel pipe column of the terminal of Chengdu Tianfu International Airport(column height 14 m,medium-high grade concrete).The fresh concrete kept in good condition during construction,the liquidity is 700 mm,and there is little slump loss for 2 h,T500 for 3.2 s,the U-box height difference is 30 mm,and the 28-day strength is 58 MPa.The structure of cured concrete is monitored by ultrasonic,which is compact and fully meets the design requirements of medium-high grade concrete high throw self-compacting concrete.The apparent quality of hardened concrete(such as porosity,chromatic aberration,pitting,etc.)was improved by using the comprehensive function of “polycarboxylic acid superplasticizer compounding technology + sand and stone-optimization + component ratio-optimization + construction process-optimization,etc”.The pore area in the hardened concrete's surface was analysized and quantified by laboratory image software.The commercially available polycarboxylate superplasticizer(HLP),the preferred aoki oil defoamer and the rosin air entraining agent(CAB)are compounded to optimize the compound sample which is favorable for the apparent molding quality of the concrete.The compound sample was labeled as HXY: HLP(1.6%)+ aoki oil defoamer(0.3%)+ CAB(0.3%);In addition,the effects of sand(fineness modulus),stone(powder content),sanding rate,mold release agent,and vibrating process on the apparent quality of concrete were also studied.The comprehensive research results show that when the strategy of "HXY + sand ratio 41% + sand fineness modulus 2.5 + stone powder content 11% + water-based release agent + external vibration + vibration once" was applied,the total area of the stomata on the hardened concret's surface is the lowest,which is 83.26% and 84.82% lower than that of HLP and HXY.And the forming surface is basically free of porosity,chromatic aberration and pitting.The appearance quality of the hardened concrete is the best.In this paper,through the compounding technology of polycarboxylic acid superplasticizer,the ultra-slow release polycarboxylic acid pumping agent and the high throw self-compacting concrete polycarboxylic acid pumping agent were prepared to improve the performances of fresh concrete,which were successfully applied in engineering;combining the polycarboxylate superplasticizer compounding technology with the quantitative processing technology of laboratory image analysis software,the apparent quality of the hardened concrete is improved.Therefore,the research work on the compounding technology of polycarboxylate superplasticizer has significant practical value.