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赤泥基膠凝材料穩定碎石抗裂性能及評價方法

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

  • 摘要: 路面半剛性基層具有強度高、穩定性好等優點,但在強度形成及后期服役過程中由于內部相對濕度和溫度變化會產生收縮應力,當收縮應力超過膠凝材料自身膠結力時,基層會發生干燥收縮裂縫和溫度收縮裂縫. 作為一種新型路面基層材料,赤泥基膠凝材料可100%代替水泥用于道路基層建設,然而赤泥基膠凝材料穩定碎石抗裂性能的經時演化規律尚不明確. 因此,本文以赤泥基膠凝材料穩定碎石干燥收縮、溫度收縮性能為研究對象,探究赤泥基膠凝材料摻量、養生齡期等因素對收縮性能的影響規律并運用灰色關聯度確定了干縮抗裂性能指標、溫縮抗裂性能指標與最大干縮應變、溫縮應變的相關性. 試驗結果表明赤泥基膠凝材料穩定碎石的干縮應變、溫縮應變隨膠凝材料摻量的增加先降低后升高且干縮應變、溫縮應變增長速率隨養生齡期的延長逐漸減小,基于灰色關聯度分析法確定了干縮抗裂性指數和溫縮系數為赤泥基膠凝材料穩定碎石抗裂性能的最優評級指標,確定了赤泥膠凝材料摻量為7%時,赤泥基膠凝材料穩定碎石抗裂性能最優.

     

    Abstract: 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%.

     

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