Study On Application Of Red Sandstone Aggregate In Cement Stabilized Base Of Xiyu Expressway In Shanxi

Red sandstone is a kind of sedimentary rock formed by weathering,migration and deposition,and the strength and water stability of different red sandstone are quite different.About 21 million tons of red sandstone waste rock are produced during the excavation of Xiyu Expressway subgrade in Shanxi Province.If it is prepared into water-stable base material,it can not only alleviate the shortage of limestone supply,but also absorb highway waste rock,which has good social and economic benefits.In this thesis,after selecting high-quality red sandstone parent rock,the physical and chemical properties of red sandstone aggregate were studied by comparing with limestone aggregate,and the influence of red sandstone aggregate replacement rate,cement dosage and mixture gradation on the 7d unconfined compressive strength of cement stabilized base mixture was discussed.The durability of red sandstone cement stabilized base mixture was tested and the corresponding test section was paved.The results show:The internal sediments of red sandstone are complex,including sandstone and mudstone,sandstone and limestone.The chemical composition is mainly Si O₂,Al₂O₃and Ca O.In addition to quartz and calcite,it also contains kaolinite and illite clay minerals.The clay mineral content of fine aggregate of red sandstone is higher than that of coarse aggregate of red sandstone.Compared with cement stabilized limestone,with the increase of red sandstone aggregate replacement rate,the strength of cement stabilized base decreases,while the red sandstone 9.5～26.5 mm coarse aggregate replaces the limestone aggregate to prepare the cement stabilized base.The strength reduction rate is the smallest and the later durability is better.The cement-stabilized base mixture prepared by replacing limestone aggregate with 9.5～26.5 mm coarse aggregate of red sandstone is prepared under C-B-1 gradation and 5%cement dosage.The unconfined compressive strength of7 d reaches 4.1 MPa,which meets the strength requirements of the subbase of extremely heavy and extremely heavy traffic expressways and first-class highways.The softening coefficient of 90 d reaches 0.91,and the BDR reaches 90%after 5 freeze-thaw cycles of28 d.The microscopic test results show that the clay minerals in the fine aggregate of red sandstone soften and disintegrate,expand and loosen,and weaken the cementation between the aggregate and the cement transition zone.Therefore,the cement-stabilized base prepared by the fine aggregate of red sandstone has poor durability and is not suitable for cement-stabilized base.After paving the test section with the water-stabilized base mixture prepared by red sandstone coarse aggregate,it is tested to meet the design strength and have good durability,and has good economic and social benefits.