用于喷射混凝土的低碱性速凝剂研究

选择低碱性速凝、早强物质，采用外加剂复配的方法，通过对水泥凝结时问，强度检验的手段。进行了正交试验，确定了一种喷射混凝土用低碱性速凝外加剂的配方。通过试验结果可以得出，Al2(SO4）3掺量在2％～4％之间时，随着掺量增大，初凝时间和终凝时间变短，掺量为4％时，初凝为14分，终凝25分；K2SO4掺量在2％～4％之间可以缩短水泥凝结时间，掺量为4％时，初凝为12分，终凝23分，当其掺量超过4％时，后期强度会下降；NaF的速凝效果十分显著，当掺量只有0．2％时就可以使水泥的初凝时间控制在5分钟，终凝控制在10分钟。与传统的高碱性外加剂不同，低碱性速凝剂可显著提高喷射混凝土早期强度，1天强度可达9．6MPa，而且后期强度发展良好，28天强度达到45．5MPa。

Research on the low-alkali accelerating admixture for shotcrete

Orthognal test was made through choosing low-alkali flash setting and early-strength materials,compounding with admixture and checking the cement setting time and strength.And the mixing method of shotcrete with low-alkali accelerating admixture was carried out.The result shows that the more the Al_2(SO_4)_3,the shorter time for prehardening and final setting;the more KSO_4,the shorter time for setting,while the amount is over 4% poststrength can be lower;0.2% NaF can control the prehardening time in 5 minutes and final setting time in 1 minute.Different from the high-alkali admixture,the low-alkali accelerating admixture can improve concrete early strength apparently from 9.6MPa in the first day to 45.5MPa in the 28th day.