Experimental Study On Key Performance Of Fair-faced Concrete

In this paper,the effects of the coagulation component triethanolamine,aluminum sulfate single doping and complex doping,the retarding component citric acid and sodium hexametaphosphate on the setting time and strength of cement samples were studied.After the test,it was concluded that triethanolamine The coagulation inhibition is unstable,which will reduce the strength;the coagulation time and strength are best when the content of aluminum sulfate single doping is 4%,and the final setting time becomes stable after compounding with triethanolamine,but the strength loss is large;citric acid and Sodium hexametaphosphate has a significant retarding effect on cement samples.The effect of citric acid on strength is first reduced and then increased,while sodium hexametaphosphate is used to reduce strength.Finally,the amount of aluminum sulphate mixed with 4% was mixed into the mortar as the base material of the fair-faced concrete.On this basis,the orthogonal test is designed based on the rheological factors of water-cement ratio,rubber-sand ratio and water-reducing agent.The fluidity,compressive and flexural strength of the base material and the volume stability of the shrinkage rate are tested respectively.And the extreme difference and variance analysis of the sand flow,3d and 28 d compressive strength,3d shrinkage value,the following conclusions are drawn:(1)The influence degree of each basic rheological factor on the fluidity of the mortar is as follows: the amount of water reducing agent > water-cement ratio > mortar ratio.When the amount of water reducing agent is 1.5%,the water-cement ratio is 0.35,and the ratio of rubber to sand is 1:0.8,the fluidity of the mortar is the largest.The change of the amount of water reducing agent has a significant effect on the fluidity of the clear water concrete.The ratio of water to cement and the ratio of rubber sand have no significant effect on the fluidity of the sand.(2)The compressive and flexural strengths of 3d and 28 d were the highest in Group 1,the ratio of water-cement ratio was 0.33,the ratio of sand to sand was 1:0.8,and the amount of water-reducing agent was 1.3%.The influence degree of the factors on the 3D compressive strength of fair-faced concrete is as follows: water-cement ratio>additive amount of water-reducing agent>sand-sand ratio,the influence degree of 28 d compressive strength is as follows: the amount of water reducing agent> Water-cement ratio > mortar ratio.(3)The shrinkage rates of 3d and 7d were the largest in Group 9,and the ratio was: water-cement ratio of 0.35,mortar ratio of 0.8:1,water-reducing agent dosage of 1.4%;14d and 28 d shrinkage.The ratio is the largest in the eighth group,and the ratio is: water-cement ratio is 0.35,rubber-sand ratio is 0.8:1,and water-reducing agent is 1.3%;the influence degree of each factor on 3d shrinkage is : Water-cement ratio > dosage of water reducing agent > mortar ratio.When the water-cement ratio is 0.33,the water reducing agent dosage is 1.5%,and the rubber sand ratio is 1:0.8,the 3d shrinkage rate of the fair-faced concrete is the smallest.Select the best ratio of fluidity of the mortar(1.5% water reducing agent,0.35 water-cement ratio,1:0.8 sand ratio)for the next step,on which the admixture(silica ash)is added.,fly ash)and admixtures(expansion agent,defoamer)were tested in parallel to test the effect on the slurry fluidity,compressive flexural strength and shrinkage.The results are as follows:Silica fume will reduce the fluidity,the strength will increase first and then decrease,and the maximum will be at 8%.The amount of more than 8% will increase the shrinkage rate;the effect of fly ash on the fluidity will increase first and then decrease,and the dosage will be 20%.The maximum time,3d intensity change has no obvious law,28 d strength first increases and then decreases,15% dosage is the largest;silica fume and fly ash recombination,silica fume 8%,fly ash 15% fluidity is best Give full play to the advantages of silica fume to improve early strength,and also reduce the drying shrinkage by the addition of fly ash,reflecting the "super-stacking effect" of composite materials.When the amount of expansion agent is 6%,the fluidity is the smallest,but the strength is the highest,and the shrinkage rate is basically reduced to zero.When the amount of defoaming agent is 0.3%,the fluidity is the best,and when the dosage is 0.5%,the strength is the highest.As the amount increases,the shrinkage rate gradually decreases.