Design Of Mixture Proportions And Study On Performance Of High Fly Ash Content Concrete

Aimed at the shortcoming of the design theory of mixture proportions of fly ash concrete at present, regarded fly ash as an independent component, the effect of fly ash in concrete and the design theory of mixture proportions of high fly ash content concrete (HFCC) are studied in this thesis. The major contents are summarized as follows:1. The study on calculation theory of ordinary concrete mixture proportionsThe calculation theory of ordinary concrete mixture proportions is studied. Thehalf-empirical formula between relative strength fcu.O/fc and cement-water ratio C/W isbrought up according to the large numbers of information. The formula of water dosage (W) is deduced according to Bingham model theology. The mathematics model of sand-aggregateratio (Sp) is established based on the tight filling and improving the workability of fresh concrete.2. The study of fly ash cementitious coefficientThe fly ash cementitious coefficient β is defined. In different ages, β can be expressed as the function of fineness, water requirement and loss on ignition of fly ash. Experiment constants in the mathematics model of β are confirmed according to the tests. The cementitious coefficient β reflects the synthetical effect of fly ash in concrete. It can be used in the appraisement of fly ash quality and the design of mixture proportions of high fly ash content concrete (HFCC).3. The appraisement of fly ash qualityThe cementitious coefficient β is a basic parameter decided by the performance of fly ash, and β reflects the gelatinization of fly ash. It could be used to classify fly ash, appraise the quality of fly ash used in concrete. This new method adopts β as the combinational factor, and reliability is high. The method of classification and applicability of each grade of fly ash is brought forward, and it is contrasted with other methods used to appraise fly ash.4. The study on design theory of the mixture proportions of HFCCBased on the cementitious coefficient β, regarded fly ash as an independent component, and differentiated the different action of fly ash in concrete, the four basic parameters of the design of mixture proportions of HFCC are brought forward. The formulas of the four basicparameters are deduced, and a new design method of mixture proportions of HFCC is established.5. Study on the mechanical performance and the durability of HFCCThe main mechanical performances and the durability of HFCC are studied according to the tests, and they are contrasted with the ordinary concrete. The influencing rule and mechanism of fly ash quality and mixture proportions on the mechanical performance and the durability of HFCC are analyzed. The durability of HFCC is appraised according to the tests and analysis.