Study On Mechanical Properties And Frost Resistance Of High Performance Self-compacting Concrete

As a kind of high performance concrete with high filling and stability,self-compacting concrete usually needs to add some mineral admixtures and additives to improve its performance.Zeolite powder is a kind of powder material with very small particle size formed by grinding zeolite rock,and it is also a kind of admixture with excellent performance commonly used in concrete.Zeolite rock has huge reserves in China,and it is cheap and easy to exploit.Adding appropriate amount of zeolite powder in self-compacting concrete can not only improve the working performance of self-compacting concrete mixture,but also improve its mechanical and durability performance.Therefore,zeolite powder used to prepare high performance self-compacting concrete has a better economic and applicability.In this paper,theoretical and experimental studies on the performance,mechanical properties and frost resistance of self-compacting concrete with zeolite powder and fly ash are carried out.The main work is completed and the corresponding research conclusions are obtained.（1）The working performance of 21 groups of self-compacting concrete was studied with slump expansion,T₅₀₀00 and J-ring expansion as indicators.The results show that the fillability of self-compacting concrete is greatly influenced by the mineral admixture content,especially the zeolite powder content.The larger the zeolite powder content,the bigger the T₅₀₀00 of the mixture,while the smaller the slump expansion and J-ring expansion,but the smaller the impact on the PA value,which is basically maintained in the range of 10 mm to 25 mm.The addition of zeolite powder can significantly reduce the fluidity and filling property of the mixture,but has no significant effect on the clearance trafficability.（2）The mechanical properties of 21 groups of self-compacting concrete with different zeolite powder content were studied.The results show that with the increase of zeolite powder content,the basic mechanical indexes such as compressive strength and splitting tensile strength of each age increase slightly at first and then decrease gradually.When the content of zeolite powder is between 2.5%and 5%,the basic mechanical properties are the best.The mechanical properties of mineral admixtures are similar to those of mineral admixtures.The mechanical properties of mineral admixtures with 12.5%to 17.5%are the best.（3）Four groups of the most representative concrete were selected for the frost resistance test.The mass loss of concrete specimens decreases first and then increases under the action of water freezing and salt freezing,and the loss of dynamic elastic modulus and compressive strength increases all the time.There is a good correlation between the two,and the damage of concrete under the action of salt freezing is more serious.The frost resistance of four groups of concrete is in turn:F10Z05.0（10%fly ash and 5%zeolite powder）is better than F15Z02.5（15%fly ash and 2.5%zeolite powder）is better than F00Z00.0（0%fly ash and0%zeolite powder）is better than F15Z00.0（15%fly ash）.The frost resistance and durability of self-compacting concrete can be improved by mixing appropriate amount of zeolite powder and fly ash in self-compacting concrete.The mechanism of freeze-thaw damage was analyzed by scanning electron microscopy.The freeze-thaw damage of concrete was caused by the frost heave of water and the expansion of salt crystals.The dynamic elastic modulus loss rate and strength loss rate are equivalent to freeze-thaw damage degree,and the concrete freeze-thaw damage evolution model based on Weibull probability distribution function with two parameters has a high fitting degree.