早强剂对充填膏体宏观力学性能和微观结构的影响

The Effect of Early Strength Agent on the Macro Mechanical Properties and Microstructure of Filling Paste

为了尽快提高充填膏体的早期强度,从而加速采-充循环频率和控制顶板下沉,对内掺不同含量硫酸钠早强剂的充填膏体试件进行了单轴抗压强度试验,并分析其微观结构变化和反应机理。试验结果表明:掺有硫酸钠早强剂的充填膏体试件在不同龄期内的单轴抗压强度均远高于对照试件。当养护3d和7d时,掺量为2%的硫酸钠早强剂对充填膏体强度提升最大,分别提高了131%和116%;当养护28d时,掺量为1%的硫酸钠早强剂对充填膏体强度提升最大,提高了135%。扫描电镜结果显示,掺有1%和2%硫酸钠早强剂的充填膏体试件内部结构致密性更好,针状晶体更粗、絮状凝结物更多。硫酸钠作为一种早强剂掺入充填膏体后能与水泥水化产物氢氧化钙发生反应生成二水硫酸钙,进一步与水化产物铝酸钙(C3A)迅速反应生成水化硫铝酸钙针状晶体(AFt),在充填体内部形成早期骨架从而提高早期强度。

In order to improve the early strength of the filling paste as soon as possible to accelerate the mining-filling cycle frequency and control the roof subsidence,the uniaxial compressive strength test was carried out on the filling paste specimens with different contents of sodium sulfate early strength agent.And the microstructure changes and reaction mechanism of the specimens were analyzed.The test results showed that the uniaxial compressive strength of the specimens with sodium sulfate early strength agent was much higher than that of the blank specimens in different curing time.The strength of the specimens with 2%of sodium sulfate early strength agent increased the most in 3 days and 7 days,by 131%and 116%respectively.And the strength of the specimens with 1%of sodium sulfate early strength agent increased the most in 28 days,by 135%.Scanning electron microscopy(SEM)results showed that the filling paste specimens with 1%and 2%of sodium sulfate had better internal structure compactness,thicker acicular crystals and more flocs than other specimens.As a kind of early strength agent,sodium sulfate after adding into the filling paste can react with calcium hydroxide-a cement hydration product to generate calcium dihydrate sulfate,and further react with calcium aluminate(C3 A)-a hydration product to quickly generate calcium sulfoaluminate needle-shaped crystal(AFt),forming an early skeleton so as to improve the early strength.