Synthesis Of A New Water-reducing And Collapse Composite Polycarboxylate Superplasticizer And Its Application In Concrete

With the rapid development of high-speed railways,intercity railways,expressways and commercial houses,the use of concrete in China has been greatly increased.With the improving of the usage of concrete,the high-quality raw materials of concrete are becoming less and less.Large amount of defective raw materials flooded into the market.This defective raw material will affect the performance of concrete.Water reducer as a concrete regulator,it must adapt to this kind of raw materials,to improve the workability of concrete,improve the working performance of concrete.Therefore,the water reducer with a single performance can no longer fully apply to the existing market,and it is urgent to develop a comprehensive water reducer with multiple properties.The objective of the present study is to synthesize a novel water reducer（PCA）which could keep better water reducing ability,slump preserving ability,mud resistance and machine-made sand adaptability at the same time.According to the flexibility of the side chains of polycarboxylate superplasticizers,maleic anhydride（MA）monomer was introduced into the reaction systems.Methyl allyl polyoxyethylene ether（HPEG）was used as a synthesis of monomer while acrylic acid（AA）was added as the synthesis of monomer.Hydrogen peroxide（H₂O₂）and vitamin C（V_C）initiator system was used and mercaptopropionic acid（MPA）was added as chain transfer agent.Univariate analysis of variance was performed to find the optimum molar ratio of each additives.Finally,the optimum molar ratio of each additive was:n_（HPEG）:n_（AA）:n_（MA）=1:1.6:0.6 and the total amount of initiator accounted for 0.4%of the total amount of large monomer（HPEG）with m_（H2O2）:m_（VC）=0.7:1,n_（MPA）:n_（HPEG）=0.10:1and a synthesis temperature of 30℃.The effect of the present novel synthetic water-reducer on cement was evaluated by comparison with other water-reducing agents（PCD）purchased on the market via studying the water reduction rate,as well as the flow rate,metamorphosis performance（viscosity,yield stress and tactile denaturation）and the test of hydration heat of cement.The results showed that the water reduction rate of the glue sand was more than 40%and the loss rate of 2 hours of gum sand flow was only 16.7%when the dosage of PCA（40%containment）was 0.3%.Moreover,the novel PCA had a higher water reduction rate and better collapse preservation compared with PCD.Compared with the blank sample,1d hydration heat reduced by 35.2%and 3d hydration heat reduced by 7.6%.This suggested that novel PCA had a certain slow coagulation effect.Under the same flow conditions,the plastic viscosity and touch ring area of the novel PCA was lower than that of PCD while the yield stress was much more greater than PCD.Hydrocement fluidity,coagulation and structural stability of the novel PCA were also much more better than those bought PCD.In order to evaluate the adaptability of the new novel PCA on montmorillonite and machine-made sand,the fluidity,time-loss,the performance of net slurry rheomorphism and its time-varying,the adsorption of montmorillonite and the stone powder in the machine-made sand to the PCA were studied and compared to those bought PCD.The results showed that:1)When montmorillonite was added into the cement-based material,for all those water-reducing agents:the flow of the pulp body decreased,the loss increased during menstruation,the viscosity and yield stress increased The effect of the montmorillonite on the novel PCA was much more smaller than that of the commercial PCD.2)When the machine-made sand was less than 30%of the total cement-based material,the flow of the slurry body and longitude loss of the novel PCA kept almost the same.However,when the machine-made sand was greater than 30%,the flow of the slurry body and longitude loss of the novel PCA were increased.The influence of the novel PCA was much more smaller than that of the commercial PCD.3)Adding the stone powder in the machine-made sand had little effect on the initial viscosity of the slurry,but had a great effect on the time changing of viscosity and the yield stress of the slurry.The effect of the dosage of machine-made sand on the PCA was smaller than that of the commercially available PCD.4)The adsorption of the novel water reducer PCA on montmorillonite and machine-made sand were less than that of PCD.Moreover,the adaptability of PCA to montmorillonite and machine-made sand is better than that of PCD.Finally,the application of this novel water reducer had been confirmed via experiments on three kinds of underwater concrete,three kinds of beam body concrete and one kind of self-compacting concrete.In all these experiments,the properties of the new synthesized PCA were evaluated by concrete slump,slump flow,gas content,compressive strength and other indicators.The results had shown that the new synthesized water reducer performed well in the above concrete.