| The raw soil material is an important building material, which left behind a brilliant one in the history of human social development,its excellence characteristics of heat insulation,low energy consumption and none pollution are still the targets that many building materials develop for. However, with the development of society, the material now is confronted with new challenges. On the one hand, as main raw material, high quality clay resources are limited to be used, meanwhile, the soil salinization is becoming serious,a large areas of saline soil is urgent to be exploited . On the other hand, the traditional raw soil material has fatal flaws, such as poor compressive strength, volume stability and low water resistance, which cannot meet the social development demands. Therefore, it is necessary to probe new ways to develop environment-protected materials and improve its performance, constantly expanding the application scope of the raw material.In this thesis, on the base of the physical and chemical performance of saline soil, analyzing its potential activity of silicon and aluminum that activated by alkali, and supplemented by fly-ash to form saline soil-fly ash composite system, the effect of technological influence factors on this system has been studied. The results show that the new composite cementitious system has higher strength and better duration. The reaction process and its products were also investigated by using equipment as XRD, FTIR and SEM etc. The reaction mechanism of composite gel system under the condition of alkali stimulation was preliminary discussed, the main conclusions were shown as follows:(1)The dissolution extent of active ingredients varies with temperature, dealing time and NaOH concentrations. The variety of mineral composition corresponds to the dissolution of SiO2 and Al2O3. The ideal processing conditions of active ingredients leaching test are: 10M NaOH, 60℃and 24h. The strength of Saline Soil-based cementitious materials will enhance 2-3 times. The bending peak related to Si-O and Al-O vibrates after alkali-activated, mineral structure appears a certain degree of destruction or disintegration, the activated silicon and aluminum dissolved from the saline soil can participate in the further reunion reaction.(2)The strength and durability of the sample is not so perfect by only the saline soil and activator. Cooperated with fly ash to constitute saline soil-fly ash system, when mixing 40% fly ash in this system can great improve activation effects, while the compressive strength increases nearly 1 times, soften coefficient enhance from 0.61 to 0.77 once fly ash mixing contend improve to 40%. Keep 60% fly ash in this system can be very good suppression of the material surface damage and reduce the specimen's quality loss. Base on the composite gel material strength variation trend, the concentration of NaOH in alkaline solution should be less than or equal to 10mol/L, appropriate proportion between sodium hydroxide and water is 1.0.(3)Overall, NaCl is harmful to the strength for saline soil - fly ash composite gel material, but the appropriate amount of NaCl in favor of materials'early strength ascending, such as ascension sodium chloride from 1% to 3%, the compressive strength value of the material can increase 19.1 %and 20.5%respectively for 3d to28d.(4)The XRD and FT-IR analysis indicated that the activity silicon and aluminum will depolymerize, and then reconstruct into zeolite-liked material, aluminum silicate network is also generated in product structure, which is the key to get superior performance.(5)The SEM and EDS studies show that the products microstructure and its elements migration are various with fly ash content changes in saline soil-fly ash composite gel system,it also has influence on the amount of the gel and compact structure. |
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