碱、盐环境下不同应力水平FRP筋抗压强度试验与理论研究

为了研究温度、应力水平等因素对纤维增强聚合物(Fiber Reinforced Polymer,FRP)筋在碱、盐环境下抗压强度衰减规律的影响,将FRP筋分别置于60℃和25℃的碱、盐溶液进行加速腐蚀试验,然后测定其抗压强度衰减规律。60℃下FRP筋的压应力水平分别为0%、20%和40%,腐蚀时间分别为10d、21d、42d;25℃下FRP筋压应力水平为0%,腐蚀时间分别为36d、64d、100d。通过观察腐蚀前后FRP筋表面形貌的变化,可以得出:FRP筋表面侵蚀程度随腐蚀时间的增加而增加;同条件下,碱溶液对FRP筋的表面侵蚀程度大于盐溶液。对腐蚀后的FRP筋进行抗压强度试验,结果表明:应力和温度的提高加速了FRP筋抗压强度的退化,在60℃碱溶液中腐蚀42d后,应力水平为0%和40%的玻璃纤维增强聚合物(GFRP)筋、玄武岩纤维增强聚合物(BFRP)筋和碳纤维增强聚合物(CFRP)筋抗压强度分别下降了31.8%、43.6%、51.5%和44.2%、54.8%、57.1%,60℃盐溶液中腐蚀42d后,应力水平为0%和40%的GFRP、BFRP和CFRP筋抗压强度分别下降了22.2%、31.8%、18.1%和29.0%、37.2%、23.5%。基于Fick定律,提出了考虑应力水平、温度和腐蚀时间的FRP筋抗压强度预测模型,该模型可用于预测FRP筋在实际工况下抗压强度衰减规律。

Experimental and theoretical study on compressive strength of FRP rebars under different stress levels in alkali and salt solution

To study the influence of temperature,stress level and other factors on the compressive strength of FRP (Reinforced Plastic Fiber)rebars in alkali and salt solution,FRP rebars were placed in 60℃ and 25℃ of alkali and salt solution,respectively.The compressive stress levels of FRP rebars at 60℃ were 0%,20% and 40%,exposed for 10 d,21 d and 42 d,and the stress levels of FRP rebars at 25℃ were 0%,exposed for 36 d,64 d and 100 d.By observing the surface topography,the surface erosion degree of FRP rebars increases with time.Under the same conditions,the surface erosion degree of FRP rebars in alkali solution is greater than that in salt solution. Compressive strength tests of FRP rebars after erosion show that the increase of temperature and stress accelerate the degradation of FRP rebars.After 42 d of exposure of alkali solution,compressive strength of glass fiber rein-forced polymer(GFRP),basalt fiber reinforced polymer(BFRP)and carbon fiber reinforced polymer(CFRP)rebars at 0% stress are decreased by 31.8%,43.6% and 51.5%,while the compressive strength at 40% stress level are decreased by 44.2%,54.8% and 57.1%.After 42 d of exposure of salt solution,compressive strength of GFRP, BFRP and CFRP at 0% stress are decreased by 22.2%,31.8% and 18.1%,while the compressive strength at 40%stress level are decreased by 29.0%,37.2% and 23.5%.Based on Fick's law,a compressive strength prediction model of FRP rebars was proposed,which considers stress level,temperature and time and can be used to predict the degradation of FRP rebars under actual conditions.