硅灰粉煤灰对喷射混凝土性能影响

Effect on the performance of shotcrete mixed with silica fume and fly ash

为了解决现场喷射混凝土普遍存在强度低、喷层易开裂、回弹量大、粉尘浓度高等问题,在喷射混凝土中加入不同掺量的硅灰、粉煤灰替代水泥,并通过室内试验和现场试验研究硅灰、粉煤灰对添加铝酸盐液态速凝剂喷射混凝土性能的影响。结果表明:铝酸盐液态速凝剂掺量为3%时,凝结效果最好;单掺8%的硅灰能有效促进铝酸盐液态速凝剂的凝结效果,提高混凝土强度,增加粘聚性;单掺粉煤灰可以降低速凝剂的促凝效果、降低混凝土强度、提高和易性。硅灰、粉煤灰和铝酸盐液态速凝剂混掺,对混凝土1 d抗压强度影响由主到次为粉煤灰掺量>速凝剂掺量>硅灰掺量,28 d抗压强度影响由主到次为速凝剂掺量>硅灰掺量>粉煤灰掺量,从而得出三者最佳组合。并结合新型喷射工艺进行现场试验,得出最佳组合能有效减少水泥用量、提高喷射混凝土强度、减少开裂、降低回弹和粉尘的结论。

To solve the problems of shotcrete in the field, such as the low strength, much cracking, high rebound and dust concentration, adding different mass ratio of silica fume and fly ash to replace the cement in the shotcrete, the in- fluence of silica fume and fly ash on the performance of shotcrete with aluminate liquid accelerator was studied through laboratory and field tests. The results showed that the coagulation effect was the best when the dosage of aluminate liq- uid accelerator was 3% of cementing material. A silica fume dosage of 8% could effectively promote the coagulation effect of aluminate liquid accelerator, and improve the strength and the cohesiveness of concrete. The addition of fly ash could reduce the coagulation effect of accelerator, reduce the strength and improve the workability of concrete. The ad- dition of silica fume, fly ash and aluminate liquid accelerator affected the 1d compressive strength of concrete, and the order of influence factors was fly ash content 〉 accelerator dosage 〉 silica fume content. The order of influence factors for 28 d compressive strength of concrete was accelerator dosage 〉 silica fume content 〉 fly ash content. Based on the a- bove analyses, the optimal proportion was obtained. Combined with a new spraying technology in-situ, the best combina- tion could effectively reduce cement amount, improve shotcrete strength, reduce cracking, and lower rebound and dust.