Development And Performance Test Of Underwater Non-dispersive Concrete Under Moving Water

The anti-washout underwater concrete is called “epoch-making concrete or new generation underwater construction material” by scholars at home and abroad.The underwater non dispersive concrete has good fluidity and anti dispersion,which can self level and self compact,and has been widely used in underwater construction projects such as cross sea bridge.However,the concrete industry consumes a large number of natural tons of sand and stone resources,resulting in a serious shortage of high-quality sand and stone resources.Many areas are forced to excavate in some mountains and rivers with high mud content,resulting in the problem of high mud content in sand and stone.At present,the strength of the underwater non dispersive concrete is generally low,and the strength of the materials required in the project is higher and higher,especially for the special construction environment under high pressure and high water flow speed.Firstly,a kind of polycarboxylic acid water reducer with low absorption and mud resistance was synthesized through a series of experiments by using the orthogonal experimental method,and the influence of the acid ether ratio,temperature,the amount of chain transfer agent,the amount of initiator,the amount of phosphate anti mud monomer and other factors on the synthetic water reducer was analyzed.The structure characterization and anti clay mechanism of synthetic water reducing agent were studied by FTIR and XRD.On this basis,according to the characteristics of sulphoaluminate cement,an effective retarder is mainly developed,which can control the rapid setting of sulphoaluminate cement without reducing its strength,and solve the compatibility problems of retarder,flocculant and water reducer.By analyzing the fluidity and time loss of cement paste,setting time,compressive strength,p H value of cement mortar and suspended matter content of cement mortar The amount,turbidity,water land strength ratio.Based on the factor design method,the anti dispersion performance of the underwater non dispersible concrete is optimized and predicted to ensure the high workability and workability of the underwater non dispersible concrete.The main conclusions are as follows:(1)Based on the principle of free radical polymerization,acrylic acid and isopentenol polyoxyethylene ether are the main reaction materials,A kind of lowabsorption and mud resistant polycarboxylic acid water reducer(KN-PC)was synthesized.The KN-PC with the optimized performance can be obtained under the following conditions: a reaction temperature of 43°C;an acid-ether ratio of 4.2;amounts of sodium methyl vinyl sulfonate and initiator of 0.45% and 1.6%,respectively;amounts of acrylamide and phosphate ester clay-resistant monomer of0.7 mol and 1.2 mol,respectively;and dripping times of Solution A and Solution B of2 h and 2.5 h,respectively.The structure characterization and anti clay mechanism of KN-PC were studied by FTIR,XRD and TOC.Compared with the common polycarboxylic acid water reducer,the synthesized low absorption and anti mud polycarboxylic acid water reducer was less sensitive to montmorillonite,and there was no characteristic functional group of low absorption and anti mud water reducer after the interaction with Montmorillonite.The layer spacing was 1.50 nm.The low absorption and anti mud water reducer was in montmorillonite The adsorption capacity of soil is much less than that of PC.(2)The critical dosage of KN-PC and PC is 1.4% and 1.6% respectively.The dosage of water reducer is less than the critical dosage.With the increase of the dosage of water reducer,the fluidity of sulphoaluminate cement paste increases,the dosage of water reducer is greater than the critical dosage,and the fluidity of sulphoaluminate cement paste basically remains unchanged.The time-lapse loss of fluidity of cement mixed with kn-pc sulphoaluminate is less than that of PC.Compared with the sodium gluconate(PT),ZC(self synthesized)retarder has better retarding effect on the sulphoaluminate cement,increasing the initial setting time and final setting time,and the effect of the combination of ZC retarder and kn-pc on the compressive strength of sulphoaluminate cement is smaller.The experimental results show that when the water reducing agent is kn-pc,the dosage is 1.4%,the flocculant is hydroxypropylmethylcellulose(AWA),and the dosage is 0.8%,the anti dispersion performance of sulphoaluminate cement is the best.On the basis of the existing research on the mechanism of flocculant action,and according to the experiments,two mechanisms of anti dispersant action are proposed,which can be divided into adsorption bridge dispersion and surface activity bridge dispersion.(3)Factor design method is used to model and calculate the fluidity,scour resistance and the ratio of water to land compressive strength of underwater non dispersible concrete,which can reduce the number of test groups.The error analysis of the model shows that the error of the model is within the acceptable range,and itcan effectively predict the change of the performance of the new mixture designed in the range of test factors with the change of the mixture composition.The model can be used as an effective method to optimize the test of underwater non dispersive concrete.The optimum conditions for the performance of the underwater non dispersive concrete of KN-PC and AWA and W/B 1.468% and 0.858% and 0.388,respectively.Under these conditions,theoretically,the corresponding fluidity of the underwater non dispersible concrete is 183.994 mm,the content of suspended solids in the anti dispersibility test is 113.185 mg / L,and the strength ratio between water and land is 77.442%.