Research on preparation and early performance of mixed phase phosphogypsum-based cementing materials
Mixed phase phosphogypsum was used as the main raw material,and slag,red mud,metakaolin and clinker were added to prepare mixed phase phosphogypsum-based cementing material.Its early performance was studied by compressive strength,pH and leaching toxicity tests,and the hydration mechanism was elaborated by X-ray diffraction(XRD),scanning electron microscope(SEM)and Fourier transform infrared spectroscopy(FT-IR)tests.The results showed that 53.76%(mass fraction,the same below)of mixed phase phosphogypsum,9.68%of slag,9.68%of red mud,16.13%of metakaolin and 10.75%of clinker could prepare the mixed phase phosphogypsum cementing material with optimized performance,and its compressive strength at the 3,5 d and 7 d were 8.93,10.99 MPa and 13.14 MPa respectively.Its pH alkalinity was lower than that of traditional cement-based materials,and the leaching concentration of PO43-and F-were lower than the limit of the integrated wastewater discharge standard.The results of microscopic analysis showed that phosphogypsum was calcined at 400℃for 60 min to form hemihydrate-anhydrate mixed phase phosphogypsum,in which the relative contents of hemihy-drate and anhydrate gypsum were 31.7%and 68.3%respectively.The hydrated calcium silicate gel,ettringite and brushite generated by hydration of mixed phase phosphogypsum-based cementing materials formed dense structures,which would improve the strength of materials and block the leaching of pollutants.The mixed phase phosphogypsum-based cementing material had good mechanical properties and environmental compatibility,which provided a new potential way for the large-scale consumption of phosphogypsum.
NETL
NSTL
万方数据
