The Strength Properties Of Compacted Cement Loess

Collapsible loess in Ningxia has a wide distribution and a strong damp, which often needs to be improved as a building foundation. Economy of Ningxia is relatively backward, the loess area is multi-storey building mostly, foundation treatment is based on lime soil or soil replacement method. In recent years, there are often some buildings has big wet subsidence due to cushion failure, affecting the normal use. Strength, stiffness and anti-permeability of cement soil are better than lime soil, besides its very cheap, which expands its application in cushion foundation and subgrade. In order to explore the application of soil cement in collapsible loess foundation treatment, and to increase the utilization of fly ash, magnesium slag industrial waste expansion, taking Ningxia concentric collapsible loess as the research object, unconfined compressive strength of compacted cement loess were determined by fully automatic three axis instrument, and then an orthogonal test scheme were designed, effect of cement, fly ash, magnesium slag content and compaction degree on compacted cement loess strength were studied in the experiment, the variation of the strength of cement soil were analyzed by using orthogonal experiment method, variance analysis method were used to analyze the significant of each factors, finally regression model of cement soil strength with all the factors were established in application of least square method. The results show that:(1) the strength of compacted cement loess increases approximately linearly with the increase of cement content; increases nonlinearly with the increase of fly ash content and magnesium slag content, strength growth faster when fly ash and magnesium slag content is low, strength increase slowly under larger content; increases nonlinearly with the increase of compaction degree, and the strength of growth rate is gradually increased.(2) the strength of compacted cement loess determined in 56d is stronger than 28d, and the later strength is strong, which is the embodiment of the two hydration and ion exchange effect of fly ash. The strength of compacted cement loess at the later stage is large, and the experiment should be designed with strength of the later period.(3) the positive effect of magnesium slag and fly ash composite on unconfined compressive strength increase of cement loess growth was far greater than the single doped fly ash or single doped magnesium slag. Magnesium slag and fly ash could promote each other, complement each other. Magnesium slag hydration generated Ca(OH)2 is the activator and the material basis of fly ash hydration reaction. Fly ash hydration consumes the hydration products of magnesium slag, and in turn accelerated and induced the hydration reaction of magnesium slag.(4) the impact significant order of each factors all are cement content, compaction degree, fly ash content and magnesium slag content(5) model of compacted cement loess strength established is significant, has a correlation with each factor and a high fitting degree.