Research on preparation of C40 high performance concrete by phosphogypsum based cementitious material and aggregate
The preparation of concrete by phosphogypsum based cementitious material and aggregate can provide a new idea for the high consumption of phosphogypsum solid waste.However,there are few reports on the use of phosphogypsum as cementing material and ag-gregate in the preparation of concrete.The effects of the composition,aggregate grading,sand rate and water-binder ratio on the properties of concrete based on phosphogypsum were studied,and the mechanism was investigated by XRD and SEM.The results show that when the cementing material made of 5%P·O 42.5 cement,30%phosphogypsum and 65%mineral powder is added with 0.5%NaOH+5%sodium silicate and 1%NaAlO2 composite activator,the dosage of cementing material is controlled by 600 kg/m3.Phosphypsum crushed sand re-places 40%river sand with sand rate of 0.41 and water-binder ratio of 0.34.The preparation has good working performance,initial setting time is greater than 25 h,compressive strength is greater than 20.0 MPa,48.0 MPa and 55.0 MPa for 3 d,28 d and 60 d,and adiabatic tem-perature rise is lower than 35℃.High volume phosphogypsum based C40 low-temperature micro-expansion high performance concrete with a 60 d expansion rate greater than 180 με.The main hydration products of concrete cementing materials are AFt and C-S-H gels.The cementite can penetrate the surface void of phosphogypsum aggregate and produce mechanical interlock effect to bind phosphogypsum ag-gregate and cementite matrix more closely.
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