碳化养护对磷石膏基复合胶凝材料力学性能与耐水性的影响及机理研究OA

Phosphogypsum-based materials have poor water resistance and insufficient strength,which limits their large-scale resource utilization.In this paper,phosphogypsum-based composite cementitious material(PGC)was constructed by using hemihydrate phosphogypsum as the main raw material,mixed with cement,fly ash and quicklime.The effects of standard,water bath and carbonation curing on the mechanical properties,water resistance and microstructure of PGC were studied.The results show that the 28 d compressive strength of PGC under three curing conditions is significantly higher than that of single phosphogypsum system,and the compressive strength under standard curing is the highest,reaching 33.78 MPa.Under carbonation curing,PGC has both high strength and excellent water resistance.The 28 d compressive strength is 27.68 MPa,the compressive softening coefficient is 1.0.The results of TGA,XRD,FTIR and SEM show that calcium silicate hydrate(C-S-H),AFt and CaCO3 are synergistically formed by cement hydration,fly ash-lime pozzolanic reaction and carbonation deposition.CaCO3 is mainly deposited in crystal gaps,gel pores and local microcracks,and improves the continuity of microstructure together with hydration products.Carbonation curing can effectively improve the strength-water resistance synergy of PGC,which can provide reference for high-value utilization of phosphogypsum,CO2 sequestration and development of low-carbon cementitious materials.