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

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%.