掺粉煤灰建筑混凝土在冻融-干湿循环作用下的碳化性能研究

Study on Carbonation Behavior of Building Concrete Mixed with Fly Ash under Freeze-thaw-dry-wet Cycle

为了探究复杂环境下粉煤灰混凝土的碳化性能,对掺0、10%、20%以及30%粉煤灰混凝土进行了基准碳化、冻融-碳化、干湿-碳化和冻融-干湿-碳化耦合损伤试验。研究结果表明:动弹性模量随循环次数的增加逐渐减小,相同环境和循环次数下,20%粉煤灰掺量时的动弹性模量最大;干湿循环对粉煤灰动弹性模量的影响大于冻融循环对动弹性模量的影响;掺加粉煤灰的混凝土抗碳化性能减弱,掺量越大,碳化深度越大;粉煤灰掺量和龄期一定时,冻融-干湿-碳化深度>冻融-碳化深度>干湿-碳化深度>基准碳化深度,冻融损伤对粉煤灰混凝土碳化性能的影响大于干湿作用;基于研究成果,建立起考虑多因素共同作用的粉煤灰混凝土碳化模型,可以较好地模拟不同环境条件下粉煤灰的碳化深度,可为相关工程实践提供借鉴。

In order to explore the carbonation performance of fly ash concrete in complex environment,the damage tests of benchmark carbonation,freeze-thaw-carbonization,dry-wet-carbonization and freeze-thaw-dry-wet-carbonization were carried out with fly ash concrete mixed with 0,10%,20% and 30% respectively.The results show that the dynamic modulus of elasticity decreases with the increase of cycling times,and the maximum dynamic modulus is at 20% fly ash content under the same environment and cycling times;the effect of dry-wet cycling on the dynamic modulus of elasticity of fly ash is greater than that of freeze-thaw cycling;the carbonation resistance of concrete with fly ash decreases,and the greater the content of fly ash,the greater the carbonation depth.When the dosage and age are fixed,freeze-thaw-dry-wet-carbonization depth> freeze-thawcarbonization depth> dry-wet-carbonization depth> reference carbonization depth,the effect of freeze-thaw damage on the carbonation performance of fly ash concrete is greater than that of dry-wet effect Based on the research results,a carbonation model of fly ash concrete considering the combined action of multiple factors is established,which can better simulate the carbonation depth of fly ash under different environmental conditions.It can provide reference for relevant engineering practice.