粉煤灰基地聚物混凝土的耐久性研究新进展

Review of Recent Progress in Durability of Fly Ash Based Geopolymer Concrete

地聚物是近10余年来国际上研究非常活跃的一种新型化学激发胶凝材料,可能成为大量取代水泥的绿色胶凝材料.针对碱激发粉煤灰(AAFA)地聚物的耐久性问题,分别从抗碳化性能、抗冻融性能、抗氯离子渗透性能、抗酸和抗硫酸盐侵蚀能力及抗风化性能等方面对AAFA地聚物混凝土的国内外研究现状进行了系统的整理与分析.结果表明:1)AAFA混凝土的抗碳化能力不如水泥混凝土(OPC)的,碳化后的地聚物的孔隙率增加,力学性能下降,热固化、添加Ca(OH)_(2)、OPC、矿渣粉和纳米TiO_(2)等可以改善AAFA混凝土的抗碳化性;2)AAFA混凝土的抗冻融性能较OPC的低,添加矿渣、偏高岭土等可以提高AAFA混凝土的抗冻融性能;3)AAFA混凝土的氯离子渗透率较高,掺入矿渣粉、降低液固比、高温固化及延长固化时间可以增强AAFA混凝土的抗渗透性;4)AAFA混凝土的抗硫酸、盐酸、硝酸、乙酸及硫酸盐的能力较强,吸水率较低;5)AAFA混凝土的抗风化能力较差.延长热固化时间,掺入富铝添加剂、降低目标钠与铝的摩尔比、减少地聚物的含水量、添加纳米SiO_(2)和硅烷表面改性都可以增强AAFA混凝土的抗风化性能.

Geopolymer is a new type of chemically activited cementitious material which has been actively investigated across the world for more than 10 years.It may become a green cementitious material to replace cement.In view of the relatively weak durability of alkali activated fly ash(AAFA)geopolymer,recent research progress in AAFA geopolymer based concrete worldwide is systematically reviewed in terms of carbonation resistance,freeze-thaw resistance,chloride ion penetration resistance,acid and sulfate resistance,and weathering resistance.Literature survey results can be summarized as follows:1)Compared with ordinary Portland concrete(OPC),the anti-carbonization ability of AAFA concrete is weaker,so the carbonized AAFA concrete has an increased porosity and decreased mechanical properties.High temperature curing and addition of Ca(OH)_(2),OPC cement,ground granulated blast furnace slag(BFS)and nano-TiO2 can improve the carbonation resistance of the AAFA concrete.2)The freeze-thaw resistance of AAFA concrete is generally low.Adding BFS and metakaolin can improve the freeze-thaw resistance of AAFA concrete.3)Compared with OPC,AAFA concrete has higher Cl-permeability,and the addition of BFS,lower liquid-solid ratio,high temperature curing,and prolonging curing time can improve the Cl permeability performance of AAFA concrete.4)AAFA concrete has strong resistance to sulfuric acid,hydrochloric acid,nitric acid,acetic acid and sulfate,and has low water absorption.5)The efflorescence resistance of AAFA is relatively weak.This is closely related to porosity.Extending the heat curing time,adding aluminum-rich additives,lowering the target sodium to aluminum molar ratio,reducing the water content of the geopolymer,adding nano-SiO2 and silane surface modification can improve the efflorescence resistance of the AAFA concrete.