Study On Compressive Strength And Corrosion Resistance Of Modified Pisha Sandstone Geopolymer Material

Pisha sandstone(PS)is a special interbedded rock with severe weathering,loose and broken.It is concentrated in the border area of Shanxi,Shaanxi and Mongolia,covering an area of 11,700～32,000 km~2.PS suffers from multiple erosion,and soil erosion is serious in its distribution area,which is the main source of coarse sediment in the Yellow River.The prevention and control of soil erosion in the PS area and restoration of its ecology are important to improve the water-sand relationship in the Yellow River and slow down the uplift of the riverbed downstream.In this paper,the resource utilization of PS was studied by using industrial waste to improve its properties and develop it into a material with higher strength,good corrosion resistance,and potential for engineering applications.The main research contents and conclusions are as follows:(1)The modification effect of the auxiliary modifier-weakly alkaline salt solution and the effect of the modulus and dosage of sodium silicate solution on the compressive strength of the material were studied.The results show that the weakly basic salt solution can provide an alkaline environment,the sodium carbonate solution does not significantly improve the strength of the material,and the sodium sulfate solution is not conducive to the long-term development of strength.While the modifying effect of sodium silicate solution is significant,the modulus and dosage have a greater effect on the strength the material.When the modulus is too high(M_s=3.0),with the increase of dosage,the strength will continue to grow.When the modulus is too low(M_s=1.5),the modifier will lead to a decrease in the strength of the material in excess.(2)The effects of the dosage and the compound ratio of mineral additives on the compressive strength of the material were studied.For the single-doped mineral Pisha geopolymer material,the higher the dosage of mineral additives with higher activity,the more significant the modification effect;the lower activity of mineral additives with higher dosage,the strength improvement of the material is relatively small.For the composite mineral Pisha geopolymer material,the high activity mineral additives can still obtain high strength at a lower substitution rate,while the composite effect of low activity mineral additives is not obvious.(3)The effects of the curing mechanism on the compressive strength of the material were studied using the curing temperature,curing humidity and curing age as considerations.The results show that with the increase of the curing temperature,the activity of mineral additives is stimulated,the compound effect of minerals is highlighted,the degree of polycondensation reaction is improved,and the strength is greatly improved.The high temperature curing mainly improves the early strength,and the later strength develops slowly with the growth of age,and the development stagnates or even shrinks backwards.While under the normal temperature curing,the material strength increases more uniformly with the growth of age,but the highest strength value was low.For the material with high early strength,the brief high humidity curing inhibits the inversion of strength and cracks in the late stage of the material.And for the material with slow early strength development,the low humidity maintenance is more beneficial to the long-term development of strength.(4)The microstructure morphology and hydration product types of modified Pisha sandstone geopolymer material(MPSGM)were analyzed by XRD,SEM-EDS and TG-DTG to investigate the modification mechanism.The results show that the internal denseness of the material is good,the pore structure is greatly improved,and the hydration products are mainly C-S-H gel,Si-Al gel and zeolite,which play the role of constructing the skeleton structure and filling the pores.(5)The resistance of different MPSGM to water,acid,alkali and sulfate erosion was studied by testing the water absorption,softening coefficient,The overall mass and strength loss is not significant.The results show that the material has basically good corrosion resistance,softening coefficients above 0.76,low water absorption,low mass and strength loss.In the early stage of immersion(within 7d),the rate of mass loss and strength loss grew faster,and after 28d of immersion,the mass loss and strength loss grew slowly with immersion time.