硫酸长期腐蚀环境下赤泥-煤系偏高岭土地聚合物耐久性研究

Durability of Red Mud-Coal Metakaolin Geopolymer in Long-term Sulfuric Acid Corrosion Environment

以工业废弃物赤泥和煤系偏高岭土为原料,水玻璃和NaOH的混合溶液为激发剂制备赤泥-煤系偏高岭土地聚合物(RCG)试件。探究试件养护7 d后在pH值为2的硫酸溶液中浸泡3~112 d耐酸腐蚀性能。试件抗压强度、X射线光谱分析(EDS)及扫描电子显微镜(SEM)测试结果表明,赤泥-煤系偏高岭土地聚合物的聚合反应在酸液中浸泡14 d后基本结束,酸性环境下地聚合物发生解聚并在内部结构中形成裂纹,导致其抗压强度随浸泡时间延长而逐渐降低。酸液中不同浸泡时间下RCG的应力应变曲线上升段差异明显,随浸泡时间延长上升段斜率和峰值应力呈先增大后减小的趋势,浸泡过程中弹性模量与抗压强度具有良好的相关性。以复合幂指数非线性模型为基础,并考虑长期浸泡的因素,建立了模型各参数与酸液浸泡时间D(D≥14 d)的关系,为研究硫酸长期腐蚀下赤泥-煤系偏高岭土地聚合物的应力应变曲线提供了新方法。

Red mud and coal metakaolin were used as raw materials,and a mixed solution of sodium silicate and sodium hydroxide was used as an activator to prepare red mud-coal metakaolin geopolymers(RCG)specimens.The acid corrosion resistance of the specimens after 7 days of curing in a sulfuric acid solution with pH=2 for 3-112 days was explored.The results of compressive strength,X-ray spectroscopy(EDS)and scanning electron microscopy(SEM)of the specimens reveal that the polymerization reaction of RCGis almost finished after being soaked in acid for 14 days.Under the acidic environment,the geopolymer depolymerized and formed cracks in the internal structure,resulting in its gradual decreasein compressive strength with the immersion time.The stress-strain curve of RCG under different immersion time in acid solution exhibited significant difference in the rising section,and the slope and peak stress of the rising section first increased and then decreased with the immersion time.There was a good correlation between the elastic modulus and the compressive strength during the immersion process.Based on the compound power exponential nonlinear model,and by taking into account the factors of long-term immersion,the relationship between the parameters of the model and the immersion age D(D≥14 d)was established,which provides a new method for the study of the stress-strain curve of red mud-coal metakaolin geopolymer under long-term corrosion by sulfuric acid.