纳米SiO2超高强高流态混凝土及改性机理

Study on nano-SiO2 ultra-high strength and high-flow concrete and modification mechanism

通过正交试验提出纳米超高强高流态混凝土的胶凝材料配合比设计参数,并研究了纳米SiO2的掺入对传统掺硅灰、粉煤灰超高强水泥基胶凝材料强度及工作性能的影响。在保证水胶比不变的条件下,开展了混凝土配合比试验,并研究了纳米SiO2对混凝土抗压强度的影响及其微观机理。结果表明:超高强高流态混凝土中胶凝材料最优比例为:纳米SiO2:硅灰:粉煤灰:水泥=1:8:20:71;在胶凝材料用量为600~1 000kg/m3范围内,随着其掺量的增加,混凝土流动度不断增加,抗压强度先增大后减小,当其掺量为800kg/m3时,抗压强度最大。分析认为,纳米SiO2、硅灰与粉煤灰形成的三元多尺度堆积体系能优化粉体材料在混凝土中的微集料密实填充效应,纳米SiO2的二次水化反应也有效改善了硬化水泥石的微观结构,并优化其形态分布,进一步增大其强度。

The design parameters of cementitious materials mixture ratio of nano ultra-high strength and high-flow concrete were proposed by orthogonal test,and the influence of nano-SiO2 on the strength and workability of traditional ultra-high strength cement-based material doped silica fume and fly ash was studied.Same water-binder ratio,the concrete mix proportion test was carried out.Afterwards,the effect and mechanism of nano-SiO2 on the compressive strength of concrete were explored.The results indicated that the optimum ratio of cementitious material in ultra-high strength and high-flow concrete is:nano-SiO2:silica fume:fly ash:cement=1:8:20:71.In the range of 600~1 000 kg/m3,its fluidity has increased with increase of cementitious material,the compressive strength first increases and then decreases,with the maximum compressive strength of cementitious material of 800 kg/m3.It is concluded that the ternary multiscale stacking system formed by nano-SiO2,silica fume and fly ash can optimize the compaction effect of powder materials in concrete micro-aggregates.Additionally,the secondary reaction of hydration reaction of nano-SiO2 also improves the micro-structure of hardened cement stone and optimizes its morphology distribution,further increased its strength.