Study On Engineering Characteristics Of Cement Titanium Gypsum Improving Weathered Residual Soil In Red Bed

The mechanical properties of red bed weathered residual soil are poor,and it is easy to cause subgrade collapse,mud pumping and other phenomena when it is used as subgrade filling.In order to improve the bad engineering properties of red layer residual soil,based on the special engineering properties of cement and titanium gypsum,this paper proposes to use cement to improve the red layer residual soil and add titanium gypsum as cement retarder to improve its engineering characteristics.In this test,the additive dosage is 10% and 15%.Based on the test results,it is found that when the cement ratio is 6%,the strength of the improved sample can not only meet the strength standard of secondary highway subgrade filler,but also can reduce the cement consumption and improve the utilization rate of titanium gypsum.Then,the optimal ratio sample was used for dry and wet cycle test,and the cycle times were 3,5,7,10,15 and 20 times respectively.The above test was repeated at the end of the cycle.The experimental results are summarized as follows:(1)Using cement and titanium gypsum as additives can significantly improve the compressive strength of red bed weathered residual soil,and with the increase of curing age,the strength of each group of samples is improved.(2)When the curing age is 7 days and 14 days,the strength of the group with the highest cement addition is the highest.When the curing age is 28 days,the strength of the 10%-2:8 and 15%-3:12 groups is the highest,and the improvement effect is the best.(3)Scanning electron microscope analysis showed that ettringite grew well in each group of samples with 7-day curing age,titanium gypsum promoted ettringite growth,wrapped cement particles played a retarding role,and filled the gaps of soil particles to improve the late strength.(4)On the whole,the samples numbered 10%-4:6 and 15%-9:6 can not only meet the strength standard of secondary highway subbase in JTJ 034-2000 technical specification for construction of highway pavement base,but also make full use of titanium gypsum waste,reduce cement consumption,save cost and meet the needs of engineering,so the ratio of these two samples is set as the optimal ratio.(5)The samples were prepared with the optimal ratio to carry out the dry wet cycle test,and the unconfined compressive strength test was carried out on the samples after the completion of the dry wet cycle.This paper describes the morphological changes of the samples after different cycles of dry and wet,and the failure of the samples after unconfined compressive strength test,and analyzes the stress-strain curves of each sample,so as to summarize the durability of cement titanium gypsum improved red weathered residual soil.