矿物掺合料对桥面板蒸养混凝土强度和抗渗性的影响

Effect of Mineral Admixture on Strength and Permeability Resistance of Steam-cured Concrete for Bridge Deck

为获得性能优异的C55预制桥面板蒸养混凝土的配合比,研究了单掺粉煤灰10%~30%、单掺矿粉10%~30%及复掺粉煤灰与矿粉20%~35%对蒸养混凝土抗压强度和抗氯离子渗透性的影响,并采用X-射线衍射仪和扫描电镜研究了复掺粉煤灰与矿粉对胶凝材料浆体微结构的影响。结果表明:粉煤灰降低了蒸养混凝土的脱模强度,矿粉提高了蒸养混凝土的脱模强度;无论是单掺粉煤灰、矿粉还是二者复掺,均可以改善蒸养混凝土的后期强度增进率,提高其抗氯离子渗透性。综合考虑脱模强度、后期强度和抗氯离子渗透性,预制桥面板C55蒸养混凝土的掺合料以复掺12%粉煤灰和18%矿粉为最佳,其机理在于蒸汽湿热作用下粉煤灰和矿粉的火山灰活性早期得以激发,在吸收Ca(OH)2的同时形成了较多胶凝产物,改善了混凝土的微结构和界面过渡区结构。

In order to obtain the mix proportion of C55 strength steam cured concrete for precast bridge deck slab with excellent performance,the effects of fly ash(FA)replacement of 10~30%,ground blast furnace slag(GBFS)replacement of 10~30%and the replacement of FA and GBFS composite mineral admixtures of 20~35%on the compressive strength and chloride diffusion coefficient of the steam cured concrete were studied.The results showed that addition of FA reduced the strength for demoulding of steam cured concrete,while addition of GBFS increased the strength for demoulding.No matter whether adding FA or GBFS alone or the composite of FA and GBFS,which all increased the the rate of later strength development of steam cured concrete and improved its resistance to chloride ion permeability.Moreover,the improvement effect of GBFS on the chloride ion permeability resistance of steam cured concrete is better than that of FA.C55 steam curing concrete prepared with 12%FA and 18%GBFS has the most obvious advantages in demoulding strength,later strength and chloride ion permeability resistance.The main reason is that the pozzolanic activity of FA and GBFS can be excited in the early stage under the action of steam thermal curing,and more cementitious products are formed while absorbing Ca(OH)2,which improves the microstructure of concrete And interface transition zone structure.