纳米SiO_(2)改性粉煤灰混凝土力学性能及吸水特性研究

Study on mechanical properties and water absorption characteristics of fly ash concrete modified by nano-SiO_(2)

为了探索粉煤灰混凝土的高性能,开展了纳米SiO_(2)改性粉煤灰混凝土的力学和吸水试验,研究了粉煤灰取代率和纳米SiO_(2)掺量对混凝土力学性能(抗压强度、劈拉强度、动弹性模量)和吸水特性的影响。结果表明:粉煤灰混凝土的力学性能指标均随纳米SiO_(2)掺量的增加先增大后减小;当纳米SiO_(2)掺量从0%增加至2%时,粉煤灰混凝土28 d抗压强度、劈拉强度和动弹性模量分别提高了12.90%、7.53%和5.85%,可见纳米SiO_(2)对抗压强度影响更显著;当粉煤灰取代率从10%增加至30%时,混凝土28 d抗压强度、劈拉强度和动弹性模量分别降低了7.24%、2.61%和9.87%,可见粉煤灰对动弹性模量影响更显著;随纳米SiO_(2)掺量增加,粉煤灰混凝土的毛细吸水系数呈现出先下降后上升的趋势;随粉煤灰取代率增加,混凝土毛细吸水系数增大,且纳米SiO_(2)对混凝土毛细吸水系数影响也越显著;粉煤灰取代率和纳米SiO_(2)掺量对混凝土力学性能与毛细吸水系数之间的相关性无显著影响,混凝土抗压强度、劈拉强度以及动弹性模量与毛细吸水系数均呈现负相关性,其中抗压强度与毛细吸水系数相关性最好。

In order to explore the high performance of fly ash concrete,the mechanical and water absorption tests of nano-SiO_(2) modified fly ash concrete were carried out.The effects of replacement rate of fly ash and nano-SiO_(2) content on the mechanical properties(compressive strength,splitting tensile strength and dynamic elastic modulus)and water absorption characteristics of concrete were studied.The results show that the mechanical properties of fly ash concrete increase first and then decrease with the increase of nano-SiO_(2) content.When the nano-SiO_(2) content increases from 0%to 2%,the 28 d compressive strength,splitting tensile strength and dynamic elasticity modulus of fly ash concrete increase by 12.90%,7.53%and 5.85%,respectively.Therefore,nano-SiO_(2) has a more significant impact on the compressive strength.When the replacement rate of fly ash increases from 10%to 30%,the 28 d compressive strength,splitting tensile strength and dynamic elastic modulus of concrete decrease by 7.24%,2.61%and 9.87%,respectively,so the influence of fly ash on the dynamic elastic modulus is more significant.With the increase of nano-SiO_(2) content,the capillary water absorption coefficient of fly ash concrete shows a trend of first decreasing and then increasing.The capillary water absorption coefficient of concrete increases with the increase of replacement rate of fly ash.The higher the replacement rate of fly ash,the more significant the influence of nano-SiO_(2) on the capillary water absorption coefficient of concrete.The replacement rate of fly ash and the content of nano-SiO_(2) have no significant influence on the correlation between the mechanical properties of concrete and the capillary water absorption coefficient.The compressive strength,splitting tensile strength,and dynamic elastic modulus of concrete have negative correlation with the capillary water absorption coefficient,and the compressive strength has the best correlation with the capillary water absorption coefficient.