Experimental Study On The Self-gelling Property Of Hydrated Calcium Silicate Crystal Seed Powder To Excite Sediment Based Mortar Materials

In order to further solve the current situation of dust pollution and waste of land resources caused by silt removal from Wuhai Lake in the Inner Mongolia section of the Yellow River occupying the land on either side of the Yellow River,the sediment material is taken as an available resource to stimulate its gelatinability instead of cement-based material and applied in the paving of road base,channel lining and slope protection of mine landfills.The realization of safe disposal and high ecological value use of sediments has significant economic and environmental benefits and practical engineering importance.In this thesis,the lake sediment of Wuhaihu River in Inner Mongolia is taken as the research object,and the self-cementing property of the sediment is activated by the self-made calcium silicate hydrate as the crystal seed,and the ordinary sediment base mortar and self-cementing sediment base mortar are prepared instead of cementitious materials,so as to explore the influence of different sediment base materials and dosage on the working performance,mechanical properties and long-term properties of the sediment base mortar.In this study,the mechanical properties and durability were analyzed by means of pressure testing machine and low temperature test chamber.Microscopic analysis involves the use of an X-ray diffractometer,scanning electron microscope,nuclear magnetic resonance instrument,and other equipment to explore mortar phase composition,micromorphology,changes in pore structure,and mechanism of action.Relevant research findings include:（1）The crystal seed powder of calcium silicate hydrate was prepared by hydrothermal synthesis method.Based on the orthogonal test,the crystal seed powder under different synthesis systems was developed.The crystal seed powder obtained by different synthesis systems was used as cementing material instead of cement.Using range analysis and variance analysis,the best preparation results of calcium silicate hydrate crystal seed powder were obtained as the calcium-silicon ratio set 1.5,reaction temperature set 120°C,reaction time set 6h.The microstructure and composition of the products under this synthesis system have better morphology and crystallinity.（2）According to the adsorption principle of maximum specific surface area of the bottom slime and the crystal seed powder obtained under the optimal preparation conditions,the physical adsorption was carried out to prepare cement mortar to verify the self-cementification of the bottom slime-based material.The research showed that the self-cementification index of the obtained self-cementification bottom-cement mortar specimen was significantly higher than that of the ordinary bottom-cement mortar group,and the cementification index was increased by 20%,showing a good excitation effect.Therefore,it is feasible for self-cementing sludge base material to replace cement as cementing material.（3）As the curing time increases,the mechanical properties of the mud base mortar gradually increase,and decrease gradually with increasing mud base material content,albeit at the same age,the mortar made of self-cementing mud-base material has a significant increase in strength,and the strength does not shrink in the later period;When the amount of sediment material reaches 15%,the mechanical strength loss rate of the two mortars is the lowest,indicating that when the content of sediment is 15%,the consumption of sediment and the strength loss of mortar are more appropriate.（4）Using XRD and SEM microscopic analysis,it is found that the incorporation of self-cementing bottom mud-based materials can provide additional nucleation sites,significantly reduce the nucleation barrier of C-S-H to promote the rapid hydration of cement,and stimulate the activity of Si O₂and other substances in the bottom mud,which is easy to produce volcanic ash effect,resulting in secondary hydration of cement and increased hydration products.And in combination with each other,not only constitute a continuous network structure but also fill internal cement stone holes,voids,improve the phase composition of the hydration product of the mortar interface zone.The results of the NMR tests show that the internal pores of the slurge-based self-cementing mortar prepared by the slurge-excited material are efficiently refined,and the cement stone structure is denser,which improves the strength of the slurry-based mortar.Simultaneously,based on gray system theory,the GM gray prediction model（1,3）was established to theoretically predict the compressive strength of the self-cementing bottom mud base mortar,which has good predictive accuracy.（5）Compared with ordinary bottom mud base mortar and self-cementing sediment base mortar under different bottom mud content,in terms of working performance,the consistency of mortar increases with the increase of bottom mud content,which will affect the workability of bottom mud base mortar to a certain extent,while the addition of self-cementing bottom mud base material can adjust the consistency of mortar to improve the workability;In terms of long-term performance,the mud-base material has good water absorption performance.Under the condition of high pore water content,the addition of self-cementing mud-base material will fine the internal pore structure of mortar,improve the compacting property of mortar and reduce the pore water content of mortar,which not only reduces the dry shrinkage value of mortar,but also hinders and delays the internal damage of mortar and reduces the strength loss rate and quality loss rate.Then the anti-freezing property of the bottom mud base mortar is improved.