The Influence Of Fly Ash To Concrete Pore Structure In Low Temperature

At present, the durability of concrete is a hot research topic at home and abroad. As early as the second concrete durability International Conference in 1990 s, Mehta stressed: "in today's world, the main causes of concrete damage are not only cold regions of freezing and thawing damage, but also the physical and chemical effects of steel corrosion and corrosion environment," The main problem is frost damage problem of concrete durability in northern china. The frozen concrete divided into many, mainly include: early age frost and freezing at young stage, age frost damage and final instar freezing. And concrete in the juvenile period and have to face the dangers of starvation and exposure damage[5]. On the concrete of the late durability will cause irreparable damage. So the prevention of concrete damage and have to face the dangers of starvation and exposure in the juvenile period is extremely important; and the study of the pore structure features of low temperature concrete, to prevent concrete in young during freezing injury, improve low-temperature late concrete durability has great effect.The traditional way of concrete construction in winter is the use of antifreeze antifreeze, but there are many shortcomings in. at present, domestic and foreign scholars in the winter construction adopted in concrete admixtures, prevent concrete under low temperature in young stage due to frost damage occurred. Most of the research is to fly ash, silica fume and other admixtures the effect of low temperature concrete strength, but studies on mineral admixture such as fly ash and low temperature concrete pore structure is less[6]. This paper uses the non adding antifreeze and by particle size change of fly ash and fly ash, with a constant negative temperature and Heng Zhengwen for curing conditions, the test of fly ash concrete the age of the pore characteristics, and to verify the development of porosity based on the corresponding age strength test, determine the reasonable dosage of admixture and curing for concrete construction in winter.In this paper, the effect of particle size distribution on mechanical properties and pore structure of low temperature concrete is studied by means of laser particle size analyzer, pressure mercury analyzer and scanning electron microscope[7]. The particle size distribution of fly ash is changed by laser particle size analyzer and scanning electron microscope. Secondly, by using the method of grey correlation analysis, the influence of the mechanical properties of low temperature concrete on the size range of the fly ash is determined. Finally, the relationship between the mechanical properties and the pore structure of the low temperature concrete mixed with cement was established by fitting the model.The results show that the incorporation of fly ash has a certain influence on the mechanical properties and the pore structure of low temperature concrete. When the amount of fly ash is the same, the fine particles in the particle size range of fly ash increases, and the compressive strength of concrete at different curing temperatures are increased. The content of 0-5 m, 5-10 m, 10-15 m was increased by and 10%, the content of fly ash was increased by and 20%. At the curing temperature of-5, the compressive strength of low temperature concrete mixed with fly ash is 10%, which is far better than the development of low temperature concrete with 20% and 30%. In the same amount of fly ash, the strength of concrete decreases with the decrease of temperature. At different curing temperatures, the total porosity of concrete decreases with the increasing of the particle size of fly ash. The total porosity of 10% is greater than the total porosity of 20% and 30%. At a temperature of- 10 DEG C, with fly ash particle size becomes smaller and the capillary porosity accounted for the total porosity ratio was significantly larger, and coarse porosity accounted for total porosity ratio was significantly smaller[8]. Under the condition of constant low temperature curing, with the increase of the amount of fly ash, the total porosity of the first increase, with the extension of curing time, the total porosity of concrete gradually decreases, when the content of fly ash is 20%, the total porosity of concrete is the largest when the content of-10 is. In the low temperature concrete, the harmful hole and the hole decrease with the decrease of temperature, and the harmful hole and the harmful hole in the low temperature concrete increase with the decrease of temperature. And the lower the temperature, the smaller the number of harmless holes and less harmful holes.