| Geopolymer is a new type of inorganic aluminosilicate gelling material which is obtained by the polymerization of aluminosilicate(such as fly ash,slag and metakaolin)excited by alkaline solution.It has wide range of raw material sources,low energy consumption.Meanwhile,it has good mechanical properties,excellent durability,and wide application prospects.As a common hydraulic structure,earth-rock dam has the advantages of wide use conditions,easy access to dam construction materials,strong terrain adaptability,and low cost.Core wall,as a key component of earth-rock dam,is one of the key points of earth-rock dam research,and the hydraulic fracturing of core wall is a common concern and urgent problem in hydraulic engineering.In this paper,metakaolin was used as silicaluminate material and sodium silicate is used as alkaline activator to prepare the soil curing agent of metakaolin base polymer.The influence of the modulus of alkaline activator,concentration,dosage of metakaolin and curing conditions on the mechanical properties of geopolymer cured soil was analyzed.And explored the strength development and durability of geopolymer-solidified soil at different ages.Finally,the solidification mechanism was revealed through microscopic test.The specific research contents of this paper was as follows:(1)The optimal mixing ratio scheme,admixture dosage and curing conditions were determined through the controlled variable test,that is,under standard curing conditions,the dosage of metakaolin was 15%,the modulus of the alkaline activator was M=1.1,and the concentration was 50%.The strength of the solidified soil increased after the admixture was added.When the level of the anionic surfactant SO was 1/200 of the water,the compressive strength had a certain gain;when the content of dispersible latex powder(SWF)accounts for 3%wt of the cementitious material,the strength improvement effect was more significant.(2)The unconfined compressive strength and splitting tensile strength of the geopolymer-solidified soll and the control group were explored with age.The early compressive strength of geopolymer-solidified soil specimens was higher than that of the control group,and the compressive strength increases with the increase of curing age.It can still maintain a certain growth rate after 60 days of age,and had higher strength.safety reserve.Splitting tensile strength and compressive strength have the same trend of change.(3)The mechanical properties,appearance and quality changes of solidified soils with different materials under the action of long-term soaking in water,alternating dry and wet,and freeze-thaw cycles were investigated.The strength of geopolymer-solidified soil specimens did not decrease after drying and wetting cycles,but increased slightly,with less water absorption and better integrity.Under the condition of long-term soaking in water,the strength increases,the mass loss was low,there is no block caving,and the water stability was excellent.After the freeze-thaw cycle,the quality was reduced,but the strength was still high.(4)The stabilized effect of geopolymer material is mainly realized by the effect of gel material generated by reaction to fill pores and encapsulate the particles.The addition of geopolymers significantly increased the levels of Na,Al and Si elements in the samples,and the Na/Al index can be used to make qualitative judgments.Higher concentration of alkaline activator makes the porosity smaller;with the increase content of metakaolin,the distribution of the internal pores of the specimen towards the middle pore size was more uniform at the optimal content level;the smaller the modulus of the alkaline activator,the smaller the porosity.The thermogravimetric differential thermal analysis test showed that the pyrolysis weight loss process of geopolymer materials was mainly the evaporation of free water and bound water around 200℃ and the decomposition of carbonate substances at around 700°C,and there was no Ca(OH)2 intermediate. |
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