Study On Application Of Circulating Fluidized Bed Ash And Slag In Cement Stabilized Crushed Stone

Cement stabilized crushed stone is the main choice for pavement base in my country.Due to the limited raw materials and my country’s increased efforts to protect the ecological environment,the supply of crushed stone exceeds supply,and the cost of road base construction has increased sharply.In recent years,circulating fluidized bed(CFB)combustion technology has been widely used in my country.The annual displacement of CFB ash and slag in my country can reach 120 million tons.The large amount of CFB ash and slag has a serious impact on the ecological environment.An effective way to ash and slag.This paper proposes the use of CFB ash and slag to prepare a new type of cement stabilized crushed stone pavement base material,analyzes the physical and chemical properties of CFB ash and slag,explores the mechanical properties,crack resistance,and water stability of cement stabilized crushed stone with single/combined CFB ash and CFB slag And the influence law of frost resistance,the microstructure and hydration products of the new CFB cinder pavement base material were analyzed by XRD and SEM.Research indicates:When the single content of CFB slag is 30% to 45%,the 7d unconfined compressive strength is higher than 3.0MPa and lower than 5.0MPa,and the indirect tensile strength is higher than 1.2MPa,which meets the strength requirements of the base layer.When the CFB slag single When the content is 35%,the 7d unconfined compressive strength can reach 3.8MPa,the 90 d unconfined compressive strength is 6.3MPa,and the 90 d indirect tensile strength is 1.5MPa.When the single content of CFB ash is 10%,the 7d unconfined compressive strength of the cement stabilized crushed stone system is up to 6.4MPa.When CFB fly ash replaces 12% of aggregate,the 7d unconfined compressive strength is5.3 MPa.When CFB slag is mixed with CFB ash(CFB ash and slag for short),When the single content of CFB ash is higher than 15%,the unconfined compressive strength drops significantly.When compounded with 15% CFB ash and 30% CFB slag,the 7d unconfined compressive strength is 6.8MPa,and the 90 d unconfined compressive strength is 10.6MPa.The water stability of cement stabilized crushed stone was 79%,and the 28 d water stability of CFB slag was 81.3%.The water stability can reach 103.2% when mixed with CFB ash and slag.The unconfined compressive strength of 35% CFB slag alone,15%CFB ash and 30% CFB slag after being immersed in water for 21 days were 3% and 30%higher than that of cement stabilized crushed stone,respectively.After 5 freeze-thaw cycle tests,the BDRs of cement stabilized gravel,cement-CFB slag,and cement-CFB slag were 89.7%,91.6%,and 94.4%,respectively.According to XRD and SEM analysis,the main hydration products of CFB ash and slag cement stabilized crushed stone are needle-shaped AFt,long columnar CaSO4·2H2O and fibrous C-S-H,but there are certain differences in the degree of hydration.When CFB slag is added alone,The degree of hydration at 28 d is lower than when CFB ash and CFB slag are mixed together,and the quality of the cement produced by hydration is less.That is,when CFB ash and CFB slag are mixed together,the hydration rate of cement stabilized crushed stone is high,which can promote early development of mechanical properties of pavement base materials.