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Study on water content and dynamic mechanical properties of fly ash concrete under water confining pressure
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摘要: 为了研究粉煤灰对水围压下混凝土的含水量及其动态力学特性的影响，对粉煤灰掺量为0、20%和40%的混凝土试件（F00、F20和F40）进行了不同水围压（1、3和5 MPa）和不同应变速率（10−5、10−4、10−3和10−2/s）作用下的动态压缩试验，同时还开展了大气环境中干燥混凝土试件的动态压缩试验。分析了水围压、粉煤灰掺量对混凝土含水量的影响，并结合含水量数据，进一步研究了粉煤灰掺量、水围压和应变速率与混凝土动态强度间的关系。研究结果表明：①相同粉煤灰掺量下，混凝土的含水量随着水围压的增加呈现先增大后减小再增大的趋势；在相同水围压条件下，F00混凝土含水量最大，F40次之，F20最小，说明粉煤灰掺量对混凝土的含水量有显著影响。②可用三次函数描述了不同粉煤灰混凝土的含水量与水围压之间的关系。③不同水围压条件下，粉煤灰混凝土单位体积含水量所对应的混凝土动态强度增加值与应变速率呈二次函数关系，并建立了不同水围压条件下粉煤灰混凝土的动态强度增加值与应变速率之间的关系式。Abstract: In order to study the effect of fly ash on the water content and dynamic mechanical properties of concrete under water confining pressure, different concrete test specimens (F00, F20, F40) with fly ash contents of 0%, 20% and 40% were made. The dynamic compression tests under water confining pressure (1, 3 and 5 MPa) and different strain rates (10−5, 10−4, 10−3 and 10−2/s) were conducted. Dynamic compression tests of dry concrete specimens in atmospheric environment were carried out as well. The effects of water confining pressure and fly ash content on concrete moisture content were analyzed, and the relationship between fly ash content, water confining pressure and strain rate and concrete dynamic strength was further studied in combination with water content data. The research results show that: ①Under the same fly ash content, the water content of concrete shows a trend of first increase, then decrease, and then increase with the increase of water confining pressure. Under the same water confining pressure, F00 concrete has the largest water content, followed by F40 concrete. F20 concrete is the smallest, indicating that the amount of fly ash has a significant effect on the water content of concrete. ② A cubic function is used to describe the relationship between the water content of different fly ash concretes and the water confining pressure. ③ Under different water confining pressure conditions, the increase value of concrete dynamic strength corresponding to the unit volume of water content of fly ash concrete is a quadratic function relationship with strain rate, and the relationship between dynamic strength increase value of fly ash concrete and strain rate under different water confining pressure conditions is established.
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Key words:
- fly ash concrete /
- water confining pressure /
- water content /
- strain rate
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图 1 不同围压下含水量试验数据与拟合曲线
Figure 1. Experimental data and fitting curves under different confining pressures
图 2 不同围压下3种粉煤灰混凝土ΔVd值试验数据与拟合曲线
Figure 2. Experimental data and fitting curves of ΔVd values of three kinds of fly ash concrete under different confining pressures
表 1 不同水围压下的混凝土含水量
Table 1. Water contents of concrete under different confining pressures
P/MPa 混凝土含水量/mL F00 F20 F40 0 0 0 0 1 122.9 50.6 92.9 3 122.5 58.1 105.9 5 147.1 105.9 123.3 注：表中含水量数据为3次试验的平均值。 
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表 2 不同围压和应变速率下混凝土的抗压强度
Table 2. Compressive strength of three kinds of fly ash concrete under different confining pressures and different strain rates
孔隙结构 水围压/MPa 不同应变速率下的抗压强度/MPa 10−5/s 10−4/s 10−3/s 10−2/s F00 干燥 48.3 60.2 64.8 68.2 1 51.1 61.9 65.4 65.1 3 51.6 66.8 73.6 84.7 5 54.2 69.0 80.7 87.6 F20 干燥 46.1 54.3 62.2 64.7 1 48.1 51.9 53.6 69.8 3 55.6 59.9 68.9 76.3 5 50.5 58.6 66.4 80.4 F40 干燥 43.8 50.6 58.3 59.5 1 42.6 52.5 58.9 59.5 3 51.6 61.5 65.3 73.7 5 53.8 65.8 71.3 80.8
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表 3 不同水围压下3种粉煤灰混凝土
ΔVd与lg $ \dot{\varepsilon } $ 的拟合参数Table 3. Fitting parameters of ΔVd and lg
$ \dot{\varepsilon } $ of three kinds of fly ash concrete under different water confining pressures混凝土种类 水围压为1 MPa 水围压为3 MPa 水围压为5 MPa A B C R2 A B C R2 A B C R2 F00 −0.39 −1.21 −0.23 0.99 3.55 0.28 −0.08 0.96 2.46 −0.18 −0.13 1.00 F20 12.89 5.61 0.61 0.85 7.42 2.17 0.14 0.98 6.03 1.90 0.14 0.99 F40 0.56 −1.14 −0.25 1.00 3.01 0.41 −0.04 0.93 3.04 0.35 −0.05 0.96
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