Study On Mix Proportion Design And Durability Of Solid Waste Foamed Lightweight Soil

With the rapid development of highways in China,reconstruction and expansion projects are increasing popular and severe differential settlement has been a significant problem in road and bridge transition sections and the new and old roadbeds,which threaten the service life of roads and traffic safety.Foamed lightweight soil,a lowdensity and high-strength material,can efficiently reduce the post-work settlement of the new roadbed.However,the high cost puts a limit on its widely use in road engineering.At the same time,a large amount of industrial solid waste is produced every year in China,but a small percentage of the waste is reused.A large amount of land is occupied by solid waste,which cause serious pollution to the surrounding environment.Based on the above problems,two bulk industrial solid wastes sintered red mud and CFBC fly ash in Shandong Province was selected as raw materials for foamed lightweight soil.Corresponding activation methods was put forward.Mechanical properties,durability and dynamic performance of solid-waste foamed lightweight soil was systematically studied.The following conclusions was obtained in the thesis.(1)DEIPA can significantly improve the strength of CFBC fly ash-based foamed lightweight soil at an early age and also increase the post-strength.Mechanical grinding slightly improves the flow value of sintered-red-mud foamed lightweight soil and significantly improves the pre-strength of foamed lightweight soil and also improves the post-strength.However,mechanical grinding of CFBC fly ash will help release the expansion source in CFBC fly ash,which is harmful to the formation of bubble pores and results in the increase of foamed lightweight soil density.(2)The mass and moisture content of the foamed lightweight soil increased in the early stage of the wet-dry cycle,and then leveled off;the strength ratio of the sintered red mud foamed lightweight soil with 0.6g/cm3～1.2g/cm3 was 85.23%～69.18%after the wet-dry cycle,and the resistance to wet-dry cycle of the CFBC fly ash foamed lightweight soil was slightly worse than that of the sintered red mud foamed lightweight soil,and the strength ratio was 84%after the wet-dry cycle.The strength ratio is 84%;therefore,when sintered red mud foamed lightweight soil is used as roadbed filler in areas where dry and wet cycles occur,it is recommended to control the density of 0.6g/cm3 and cement admixture of not less than 300kg/cm3,and when CFBC fly ash foamed lightweight soil is used,the cement admixture should be not less than 300kg/m3.(3)The wet mass of foamed lightweight soil shows a trend of increasing first and then decreasing with freeze-thaw cycle;the strength ratio of sintered red mud foamed lightweight soil with density of 0.6g/cm3～1.2g/cm3 is between 74.23%and 87.50%after freeze-thaw cycle,and the strength ratio of CFBC fly ash foamed lightweight soil is only 62.20%.Therefore,it is not recommended to use CFBC fly ash slag foamed lightweight soil in the road section with frost resistance requirement,and it is recommended to use sintered red mud foamed lightweight soil with density of 0.6g/cm3 and cement admixture of not less than 300kg/m3.(4)The permanent strain of the specimen in the natural state tends to be stable during the cyclic loading,and the permanent strain is within 0.2%;the permissible dynamic stress level of the water-filled specimen with density of 0.6g/cm3～1.0g/cm3 is less than 0.2qu,and the permanent strain of the water-filled specimen with density of 1.2g/cm3 tends to be stable when the stress level is not greater than 0.3qu,therefore,in the high water table section,it is recommended to use sintered red mud foamed lightweight soil with density of 1.2g/cm3.It is recommended to use foamed lightweight soil with a density of 1.2g/cm3,if 0.8g/cm3～1.0g/cm3 density foamed lightweight soil is used,water isolation and drainage measures should be done.(5)The dynamic modulus of foamed lightweight soil in natural state is between 90MPa～269MPa,which decreases to 84MPa～240MPa after immersion,which is greater than the dynamic modulus of conventional soil and meet the requirement of dynamic modulus of subgrade.It is smaller than the damping ratio of conventional soil.