赤泥基胶凝材料稳定碎石抗裂性能及评价方法

Study on crack resistance and evaluation method of red mud–based cementitious material stabilized stone

路面半刚性基层具有强度高、稳定性好等优点,但在强度形成及后期服役过程中由于内部相对湿度和温度变化会产生收缩应力,当收缩应力超过胶凝材料自身胶结力时,基层会发生干燥收缩裂缝和温度收缩裂缝.作为一种新型路面基层材料,赤泥基胶凝材料可100%代替水泥用于道路基层建设,然而赤泥基胶凝材料稳定碎石抗裂性能的经时演化规律尚不明确.因此,本文以赤泥基胶凝材料稳定碎石干燥收缩、温度收缩性能为研究对象,探究赤泥基胶凝材料掺量、养生龄期等因素对收缩性能的影响规律并运用灰色关联度确定了干缩抗裂性能指标、温缩抗裂性能指标与最大干缩应变、温缩应变的相关性.试验结果表明赤泥基胶凝材料稳定碎石的干缩应变、温缩应变随胶凝材料掺量的增加先降低后升高且干缩应变、温缩应变增长速率随养生龄期的延长逐渐减小,基于灰色关联度分析法确定了干缩抗裂性指数和温缩系数为赤泥基胶凝材料稳定碎石抗裂性能的最优评级指标,确定了赤泥胶凝材料掺量为7%时,赤泥基胶凝材料稳定碎石抗裂性能最优.

The semirigid pavement base is known for its high strength and good stability.However,it faces challenges owing to the generation of shrinkage stress during the development of its strength subsequent service.This stress arises from internal changes in relative humidity and temperature.When this shrinkage stress exceeds the bonding force of the cementitious material,the base may develop dry shrinkage cracks and temperature shrinkage cracks.Addressing this issue,cementitious material based on red mud emerges as a novel solution for roadbed construction,potentially replacing traditional cement entirely.Despite its promise,the crack resistance evolution of this material is still unclear.This study focuses on the dry shrinkage and temperature shrinkage properties of the stabilized gravel layer made from red mud-based cementitious material.It investigates how various factors,including the content of red mud-based cementitious material and duration of maintenance,affect these shrinkage properties.Additionally,it establishes a correlation between dry shrinkage,temperature shrinkage,and their maximum strain values through grey correlation degree analysis.Experimental results reveal a positive correlation between the cumulative dry shrinkage strain of stabilized crushed stone based on red mud cementitious material and the curing age,with the growth rate diminishing over time.The cumulative dry shrinkage strain first decreases and then increases as the content of red mud cementitious material rises,hitting its lowest point at 7%content.The cumulative dry shrinkage coefficient of stabilized crushed stone of red mud–based cementation material reaches the peak value at the age of 1 d and before gradually decreasing and stabilizing.Notably,at an 8%dosage,this coefficient is significantly higher than in other groups.Regarding temperature shrinkage,the coefficient first increases and then decreases with rising temperature.The average temperature shrinkage coefficient follows a similar pattern based on the content of red mud-based cementitious material,with the 7-day coefficient substantially exceeding the 28-day figure.Microcracks fill the stable gravel matrix at 7 days of age,whereas at 28 days,the matrix becomes denser owing to the increase in hydration products.Scanning electron microscope morphology analysis further elucidates the mechanisms of dry and temperature shrinkage.Employing grey relational analysis,the study identifies the dry shrinkage resistance index and temperature shrinkage coefficient as optimal indicators for assessing the cracking resistance of stabilized crushed stone using red mud-based cementitious material.Optimal cracking resistance is achieved when the content of red-mud cementitious material is 7%.