【摘 要】
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It had gained wide acknowledgement that some phosphor and fluorine released from phosphorus slag had caused the set-retarding and low early-strength of cement and concrete with yet no solid explanatio
【机 构】
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Changjiang River Scientific Research Institute, No.269 Huangpu Avenue, River Bank District, Wuhan 43
【出 处】
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The 14th International Congress on the Chemistry of Cement (
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It had gained wide acknowledgement that some phosphor and fluorine released from phosphorus slag had caused the set-retarding and low early-strength of cement and concrete with yet no solid explanation.Soluble and insoluble phosphates and fluorides were incorporated into cement and time setting and hydration of pastes were investigated with employment of micro calorimeter and X-ray diffusion with object of disclosing its working mechanism.Results indicated that, when equivalent content of P2O5 and F ranged between 0.5%~1.5%,soluble phosphate Na2HPO4, Na3PO4 and insoluble CaF2 had significant retarding effect on cement setting,while insoluble CaHPO4, Ca3(PO4)2 and soluble NaF had not, with occasionally flash setting observed.Micro analysis disclosed that soluble Na2HPO4, Na3PO4 and insoluble CaF2 retarded cement setting by delaying its induction period.Retarding effect of soluble Na2HPO4 and Na3PO4 was implemented by decreasing pH value in liquid, producing aluminium phased hydration products and increasing thickness of hydration products over surfaces of un-hydrated particles while insoluble CaF2 conducting by absorption effect through hydrogen bond between cement hydration products and F.
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