Effect Of Particle Size Distribution Of Diatomite Fly Ash Blended Admixtures On The Pore Structure Of Concrete

In this paper,fly ash-diatomite composite prepared by mixing concrete,studied under different curing conditions(normal temperature and-10 ?)admixture particle size distribution of concrete mechanical properties,single-sided freeze-thaw durability and pore structure of the impact,The particle size distribution of fly ash-diatomite and the mathematical model of concrete pore structure were established by using the gray correlation particle size to study the correlation between particle size distribution and pore size characteristics of concrete.The main findings are as follows:The effects of particle size distribution of fly ash-diatomite admixture on the strength and durability of concrete were studied.The results showed that the particle size distribution and curing condition of concrete would affect the strength and durability of concrete.The early strength of concrete increases with the increase of particle size,while the strength and unilateral freeze-thaw durability of the concrete increase first and then decrease.Under the standard curing condition,when the D50 value of the blended material is 15.2 ?m,the mechanical property of the concrete is the best.When the D50 value of the blending material is 17.7 u m under the condition of low temperature-10 ?,the flexural strength of the concrete is the highest,When the material D50 value is 15.2?m,the flexural strength of concrete is the highest.When the admixture D50 value is 15.2?m,the durability of concrete is the best.The results show that the particle size distribution of fly ash-diatomite will affect the pore structure parameters of concrete obviously,and the effect of particle size distribution and curing condition on the pore structure of concrete will be affected by the particle size distribution of the admixture and curing conditions.The influence of concrete pore structure is more obvious.With the decrease of particle size,the number of harmless pores less than 20nm and the number of less harmful holes ranging from 20nm to 50nm were increased,and the number of harmful pores from 50nm to 200nm was significantly reduced.The trend is not obvious.The smaller diameter of the admixture of concrete on the early pore size distribution of concrete has been optimized.It was observed by SEM that the degree of hydration of concrete under standard curing condition was much higher than that of low temperature curing concrete,and the pore structure of the concrete was more compact and the pore size was smaller as the particle size of the admixture became thinner.Of the degree of hydration.The relationship between particle size distribution and curing condition of cement admixture and pore structure of concrete was analyzed by gray relational theory.The results showed that admixture particle size distribution,which are too small or more than a certain particle size distribution,will improve the porosity of concrete less.The influence of the particle size distribution of the admixture on the most probable pore size of concrete is relatively small compared with the effect on the concrete pore.However,under the standard curing condition,the grain size of 30-40?m interval has a relatively large influence on the most probable pore diameter of concrete.In the low temperature curing conditions,the 20-30?m of the size will impact the most possible pore size of the concrete more.Particle size distribution of the admixture almost has no significant correlation with median pore diameter of the concrete curing at low temperature.For standard cured concrete,only the finer size(0-20?m)particle of admixtures can significantly affect the median size of concrete.The influence of particle size distribution of mineral admixtures on the pore size of concrete under standard curing conditions is generally low,and there is no obvious regularity.The mathematical model of particle size distribution and pore structure of concrete was established.The results showed that the fitting curve of particle size distribution and porosity of the specimen under standard curing conditions:Y=-0.1895X1+0.2762X2+0.5839X3+0.1311X5+1.2366e-3.4323(X6-4.3377)2+0.3286X7+0.1584;under the standard curing condition,the relationship between the particle size distribution of the admixture and the median diameter of the specimen is fitted:Y=(1+10-0.5172(28.0020-X1))/0.8588+(1+10-0.2274(25.1857-X2))/2.3312+ 15.9503;under the standard curing condition,the relationship between the particle size distribution of the admixture and the median diameter of the specimen is fitted:Y= 2.4277 × e-17.8213(X6-4.3788)2 ?9.4949.The results show that the mathematical model can be used to characterize the relationship between the particle size distribution and the properties of concrete.