Effect Of Different Mixing Methods On Performance Of Porous Aggregate Concrete

This paper discusses influences of the advancing mixing method(aggregate enveloped with cement paste)on the performance of coral concrete and ceramsite concrete,at the same time,mechanism of its action was discussed,and limestone concrete was analyzed for comparing.The main research contents and results are as follows:The physical properties like water-absorption,density,voidage,strength of column compression,crushing value and needle and plate particle content of three kinds of coarse aggregate,which called coral,ceramsite,limestone were tested.Take aggregate enveloped with cement paste as an advancing mixing method to improve the strength of aggregate concrete.Influences of the advancing mixing method on the workability of porous aggregate concrete were discussed through testing fluxility,gas content bleeding,and the interaction mechanism was analyzed.The results indicated:the advancing mixing method can enhance the fluxility of concrete,thereby reducing the dosage of plasticizer;The advancing mixing method can reduce the gas content of concrete,and the reduction is bigger in low water cement ratio,the reduction of porous aggregate concrete 's gas content is bigger than limestone concrete's;The coral concrete and ceramsite concrete bleeding seriously for low density,limestone concrete did not bleed,the advancing mixing method can improve the workability of porous concrete,and the effect is better in low water cement ratio.Influence of coarse aggregate on the compressive strength of concrete was discussed,and influences of the advancing mixing method on the compressive strength and durability of porous aggregate concrete were discussed.The results indicated:the compressive strength in the same water cement ratio as follows:limestone concrete>ceramsite concrete>coral concrete,the gap of strength between porous aggregate concrete and limestone concrete increases with the decrease of water cement ratio.The advancing mixing method can improve the compressive strength of concrete,and the porous aggregate concrete 's compressive strength increases more than limestone concrete's,when the water-cement ratio is low,the advancing mixing method can,t improve the compressive strength of porous aggregate in the early stage,the increase becomes apparent with the growth of age,and decline slightly then tends to be stable in the middle and late stage,when the water-cement ratio is high,the advancing mixing method can also improve the compressive strength of concrete and the increase is stable.when the water-cement ratio is low,the advancing mixing method can improve the resisting chloride permeability and the ability of anti-Carbonation of porous aggregate concrete slightly,the increase of the resisting chloride permeability would decrease W:ith the growth of age,but the increase of the ability of anti-Carbonation is stable.There is no effect when the water-cement ratio is high.Influences of the advancing mixing method on the preliminary performance of porous aggregate concrete were discussed by MIP method.Form a correlation analysis between pore structure and compressive strength,durability of concrete.The results indicated:the advancing mixing method can reduce the porosity of porous aggregate concrete especially the coral concrete,and the effect is more remarkable when the water-cement ratio is low,the lower the porosity,the higher the compressive strength;The advancing mixing method can reduce harmful pore of concrete,the rate of improvement as follows:limestone concrete>ceramsite concrete>coral concrete;The advancing mixing method can reduce pore volume of concrete especially the coral concrete,that means the connectivity of pores is reduced,the Cl-electric flux keeps good linear relationships with total pore volume.