| At present,the research on alkali-activated materials is mainly to solve the environ-mental impact of ordinary Portland cement production,but the use of extremely corrosive and viscous alkaline solutions has greatly hindered its application.Therefore,the preparation of one-part alkali-activated materials by solid alkali activator is more promising,but due to the problem of mixing and dissolution,it is difficult for solid alkali activator to fully react with raw materials in a short time,resulting in mechanical properties not as good as traditional alkali-activated materials.In addition,there are few studies on the preparation of alkali-activated materials from construction waste.In this study,the feasibility of preparing OP-WAAMs by compression molding was mainly aimed at the mechanical properties of one-part alkali activated materials(OP-WAAMs)prepared by red brick powder.The preparation process was designed by studying the effects of molding pressure,alkali activator(Sodium silicate nonahydrate,hydrate lime)ratio and water-solid ratio on OP-WAAMs.Composite OP-PWAAMs were prepared by using phosphorus residue as auxiliary cementitious materials,and the performance of OP-PWAAMs was optimized by adjusting the phosphorus slag content and high temperature curing parameters.The polymerization degree and phase content of the samples were finely analyzed with FTIR-spectral deconvolution and XRD full spectra.The main conclusions are as follows:(1)Compression molding can improve the mechanical properties of OP-WAAMs,the forming pressure exceeds 10 MPa,and the compressive strength is not further improved.The single alkali activator is not as effective as the compound activator,and the 28d compressive strength of OP-WAAMs prepared with sodium silicate nonahydrate as the activator is only1.65 MPa.The water-solid ratio,alkali activator ratio and dosage had the best values of 0.26,20 wt.%,hydrated lime:sodium silicate nonahydrate=1,and the 28d compressive strength of the prepared OP-WAAMs was 12.53 MPa.(2)The amorphous content of red brick powder was only 24.16 wt.%,and the high polymerization unit content in silicon-oxygen tetrahedron was 60.9 wt.%,which was not conducive to the development of compressive strength of OP-WAAMs.The addition of highly active phosphate residue could significantly improve the mechanical properties of OP-WAAMs,and the 28d compressive strength of OP-PWAAMs was 35.34 MPa with a phosphate residue content of 29 wt.%.A phosphorus residue content of 46 wt.%will lead to rapid accumulation of C-S-H gel,which will affect the progress of alkali activation reaction and the enrichment of calcium phosphate crystals in the system,resulting in a decrease in compressive strength.(3)The 28d compressive strength of OP-PWAAMs did not shrink within 15h of curing at60℃,but decreased with the increase of high temperature curing time.At 80℃ and above curing,except for 3h,the 28d compressive strength of the specimen was regressed,and it first decreased and then increased with the increase of high temperature curing time,but the 28d compressive strength still increased compared with room temperature curing.The optimal high-temperature curing parameters of OP-PWAAMs were 80℃-3h,the compressive strength of 7d was 34.64 MPa,close to room temperature curing for 28d,and the compressive strength of 28d was 41.30 MPa.(4)The introduction of Ca from phosphorus residue leads to a decrease in the polymerization of the gel product and the formation of more silica-rich gels,but this adverse effect can be attenuated by high-temperature curing.At not less than 80℃,increasing the curing temperature or prolonging the curing time at high temperature can significantly increase the content of Q~4(1Al)in the system,indicating that the degree of crosslinking of gel products is increased and more aluminum-rich gels are formed,thereby improving the compressive strength. |
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