外加剂对充填体强度和微观结构的影响

The Influence of Additive on Strength and Microstructure of Backfill

为提高充填膏体龄期强度,加速液压支架推移频率,对掺有不同含量硫酸钙的充填膏体试件的力学强度、水化产物、微观结构以及反应机理进行了测试和分析。结果表明:不同硫酸钙掺量的充填膏体试件随着养护时长的变化而表现出不同的峰值强度。适量的硫酸钙掺量可以提高充填膏体的峰值强度,而过量的硫酸钙掺量反而会降低充填膏体的强度。当试件养护28 d时,掺有0.5%硫酸钙含量的充填膏体试件峰值强度最大,为4.98 MPa;掺有3%硫酸钙含量的充填膏体试件峰值强度最小,为1.97 MPa。XRD图谱结果显示,掺有0.5%硫酸钙含量的充填膏体试件较掺有3%含量的试件具有更多和更强的C—S—H衍射峰。SEM结果显示,掺有0.5%和3%硫酸钙的充填膏体试件内部均出现了絮状的C—S—H凝胶和针棒状的钙矾石(AFt)。掺有0.5%硫酸钙含量的充填膏体试件内部结构更为致密,孔隙度更小,适量的硫酸钙可以提高试件峰值强度,是因为C—S—H凝胶和AFt等水化产物互相缠绕降低了试件质量的损伤,而过量硫酸钙试件强度较低的原因是膨胀性AFt破坏了试件内部空间结构,致使试件产生了微裂纹。

In order to improve the age strength of filling paste and accelerate the moving frequency of hydraulic support,the mechanical strength,hydration products,microstructure and reaction mechanism of filling paste specimens with different contents of calcium sulfate were tested and analyzed.The results show that the filling paste specimens with different calcium sulfate contents show different peak strengths with curing time.An appropriate amount of calcium sulfate can increase the peak strength of the filling paste,while an excessive amount of calcium sulfate will reduce the strength of the filling paste.When the specimens were cured for 28 days,the peak strength of the filling paste specimens with 0.5%calcium sulfate content was the highest at 4.98 MPa.The peak strength of the filling paste specimens with 3%calcium sulfate content was the smallest at 1.97 MPa.The XRD pattern results show that the filling paste specimen with 0.5%calcium sulfate content has more and stronger C—S—H diffraction peaks than the specimen with 3%content.SEM results show that the filling paste specimens mixed with 0.5%and 3%calcium sulfate showed flocculent C—S—H gel and needle-like ettringite(AFt).The internal structure of the filling paste specimen with 0.5%calcium sulfate content is denser and the porosity is smaller.A proper amount of calcium sulfate can increase the peak strength of the specimen.It is because the hydration products of C—S—H gel AFt and other hydration products are intertwined to reduce the damage of the specimen quality.The reason why the strength of the excess calcium sulphate specimen is lower is that the expansive AFt can destroy the internal spatial structure of the specimen,resulting in a micro crack.