FEASIBILITY STUDY OF USING SILICON-RICH PHOSPHOGYPSUM AS SUPPLEMENTARY CEMENTITIOUS MATERIAL

摘要

This paper reports the results of an attempt of using silicon-rich phosphogypsum (SRPG) to develop greener supplementary cementitious material (SCM). The higher strength SRPG-SCM is optimally designed as a results of reactions between SRPG and fly ash at the lower calcination temperature condition. The high levels of Si can promote the production of more silicon aluminum active minerals and undecomposed CaSO4 can not only be used as cement retarder, but also contribute to the formation of AFt. In this paper, the preparation methods, mechanical properties and microstructure are investigated. The optimal process conditions have been proposed: calcination temperature '200°C, holding time 30 min, activated carbon '0 and hydraulic module (HM) '.3. The f-CaO content was far lower than '.0 and the decomposition rate was 84.46. The compressive strength ratio of SRPG cement to OPC (pure Portland cement) at 3, 7 and 28 days are 115.82, 104.07 and 98.29, respectively, which are much higher than slag and fly ash cement. The mineral compositions mainly include C2S, C2AS, C3S and C3A. Its harden hydration structure can be described as AFt is framework filled by gel-like CSH and AH3, which formed the dense network structure and exhibited superior mechanical performance.