The Mechanical Properties Of Cement Soil Improved By The Admixture Of Steel Slag Powder And Its Activators

Steel slag is a kind of waste residue generated in the metallurgical industry. With the rapid development of the iron and steel industry, more and more steel slag is being generated year by year. Too large amount of steel slag not only occupy too much land but also causes serious environment pollution. As a result, the treatment and rational utilization of steel slag has become a problem of much attention and concern from all circles. The muddy soil has the properties of high compressibility,low strength, low permeability, and heterogeneity, which can not satisfy the engineering requirement. In the earlier stage result, it has been found that muddy soil will possess higher strength by mixing it with 10%cement and 10% SSP (steel slag powder). On the basis of previous result,various activators were added into the SSP-cement soil, and its reinforcement mechanism on the SSP-cement soil were studied by the unconfined compression strength(UCS), X ray diffraction(XRD) and scanning electron microscope(SEM) test. The main results are as fallow:(1)Added the NaOH, Silica fume(SiO2), and CaCl2 into the SSP-cement soil in accordance with a certain proportion (0.3%, 0.6%?0.9%, 1.2% and 1.5% separately) and prepared testing samples. Cured the samples in the curing box (maintains at the temperature of 20? and relative humidity of 95%). Took the samples out of the curing box when the curing age get 7, 28, and 90 days curing age. The strength, E50, Ec and failure characteristics of the samples were measured by UCS test.The results showed that NaOH and SiO2 can effectively enhance the strength, E50 and Ec of SSP-cement soil at the appropriate content and the damage characteristic of the samples were transformed from ductile to brittle. However the addition of CaCl2 has a negative effect on the mechanical properties of cement soil.(2) Fixed the content of NaOH and SiO2 at 0.3% and 0.6%respectively, and changed the content of Na2SO4. Compounded the three materials above , added them into the SSP-cement soil and prepared testing samples. Cured the samples in the curing box(maintained at the temperature of 20? and relative humidity of 95%). Took the samples out of the curing box when it get 7, 28, and 90 days curing age. The strength, E50, Ec and failure characteristics of the samples were measured by UCS test. The following results were founded: the strength of cement soil increased at first and then decreased with the content of Na2SO4 increased and the cement soil gains its largest strength, E50 and Ec at 0.6% Na2SO4, and its damage characteristic were also transformed from ductile to brittle.(3) The chemical and mineral composition of SSP and cement, and the interaction mechanism of the activators on the SSP-cement soil were analyzed by SEM and XRD test: the chemical and mineral compositions of SSP are similar to that of cement, but the hydration of the former are far from the latter; The hydration process of SSP were accelerated by the admixture of NaOH; The SSP and cement can get the opportunities of rehydration by the admixture of SiO2; The compound activators have the two advantages above, besides hydrated alumina minerals were produced by the admixture of Na2SO4, which further improves the strength of cement soil block.