|
In recent years, with the rapid development of infrastructure, mineral admixture such as fly ash (FA)and slag powder(SP) become shortage after many years use in cement and concrete. Thus it is necessary to develop a new mineral admixture which is of low-cost and high-quality. In the view of the shortage of FA and SP along the YiBa expressway in Hubei Province, with the local phosphorus slag powder (PSP) as the research object, the effects of PSP on mass concrete and the high-strength concrete were studied, which provide theoretical basis and technical support for application of phosphorus slag power concrete in bridge construction..Firstly, the influence of PSP on the physical and mechanical properties of cement and concrete was studied.The results show that there is a linear relationship between the setting time of PSP cement and the content of PSP,moreover the setting time prolongs with the increases of the specific surface area of PSP. Soluble F-(NaF) promotes the condensation of cementitious material, while soluble phosphate (NaH2PO4) retards the condensation of the harden of cementitious material. The incorporation of PSP improves the rheological properties of cement paste, and reduce its fluidity with time; with the increases of PSP content, the early strength of concrete gradually decreases, the later strength greatly increases, the adiabatic temperature rise of concrete also decline slightly.The strength of concrete increases with the increases of PSP specific surface area.Secondly, with the C30 mass concrete and C50 high-strength concrete as research object, the effects of PSP on durability and long-term performance of concrete have been investigated. The results show that the incorporation of phosphorus slag improves the impermeability, frost resistance, sulfate attack resistance of concrete. Carbonation resistance of concrete declined with the content of the PSP increasing, and enhanced with the increase of the PSP specific surface area; shrinkage of concrete gradually increased with the content and specific surface area of PSP increased. PSP has a similar performance to S95 grade slag powder with the same mixing content in concrete, and is better than grade I fly ash. Sum up, when C50 high-strength concrete was prepared, the PSP content should be 20%, and the specific surface area was about 400m2/kg, when it comes to C30 mass concrete,the content of phosphorus slag powder can up to 40%.Finally, hydration heat, chemical bound water, XRD, SEM and MIP tests showed that the hydration heat and exothermic rate of hydration decreases with the incorporation of PSP. Because of the volcanic activity and filling effects of PSP, Ca(OH)2 significantly reduced, C-S-H increased, the porosity decreased, pore refined, the structure of ITZ improved, the quality of cementitious materials was improved, so the performance of concrete improved.
|