Road performance and microscopic action mechanism of low liquid limit silt solidified by AT curing agent

This study investigated the road performance and microscopic action mechanism of low liquid limit silt solidified by AT curing agent: firstly, carrying out the compaction test of low liquid silt solidified by different contents of AT curing agent; secondly, according to different curing ages, carrying out the CBR test in laboratory; thirdly, simulating the local seasonal frozen environment and carrying out the unconfined compressive strength (UCS) test under the action of freeze–thaw cycles; and lastly, on this basis, using x-ray diffraction (XRD) and scanning electron microscopy (SEM) to further research the micro-mechanism formed by UCS of low liquid limit silt cured by AT curing agent. The results show that the content of AT curing agent has little effect on the optimum moisture content of low liquid limit silt; compaction degree and curing age are very important to increase CBR strength of solidified low liquid limit silt. The UCS of solidified low liquid limit silt increases with the increase of content; especially at 5% content, the UCS of the sample has a particularly obvious improvement; under the condition of 96% compaction degree and 28 days of curing, the CBR strength of samples with 5% AT curing agent is 1.85 times, 1.58 times, 1.25 times, and 1.07 times of samples with 0.5%, 1%, 2%, and 3% AT curing agent. The UCS of low liquid limit silt solidified by AT curing agent with different contents decreases with the increase of freeze–thaw cycles and tends to be steady after 8 freeze–thaw cycles. Microscopic analysis results show that compared with sodium silicate, AT curing agent can produce more cementing substances, which can be cemented with soil particles and make soil more compact, as well as with the increase of curing agent content, the cementing substances also increase; as a result, silica gel, N(C2H4ONa)3·mSiO2·nH2O composite crystal, and aluminum silicate produced by the reaction can effectively improve CBR strength, UCS, and stability of soil samples. Finally, carrying out the field test of solidified low liquid limit silt subgrade, it is found that the solidified low liquid limit silt with 1% AT curing agent can meet the filling requirements of roadbed on expressway and first-class highways.