水化龄期对喷射混凝土微观结构和力学性能影响研究

Study on the influence of the microstructure and mechanical properties of sprayed concrete by difference hydration age

喷射混凝土因其水化过程与普通混凝土不同,故其终凝时间极短,早龄期强度高。为了研究喷射混凝土水化过程,采用X-射线衍射(X-ray diffraction,XRD)、热重-差热扫描分析(TG-DSC)、扫描电子显微镜(scanning electron microscope,SEM)对不同水化龄期普通水泥净浆及掺4%速凝剂水泥净浆微观结构进行观察;同时对喷射混凝土立方体抗压强度及劈裂抗拉强度经时变化和关系进行试验研究。结果表明:速凝剂的掺入显著影响水泥水化进程。在水泥-速凝剂-水体系中,NaAlO_2及Na_2CO_3令石膏缓凝作用失效,C_3A快速水化生成板条状水化铝酸钙晶体,并与针状钙矾石及棒状钠长石晶体形成网络结构对水泥颗粒产生"桥连"作用而实现速凝。同时,大量水化热促进水泥熟料矿物水化速率加快,净浆密实度快速增加,使喷射混凝土具有高早龄期强度。

Be due to different of hydration process by normal concrete,sprayed concrete has very short of final setting and high early aging mechanical properties.In order to research the hydration process of sprayed concrete,the microstructure of cement paste with and without accelerator by difference hydration age was studied by using the method of X-ray diffraction（XRD）,comprehensive thermal analysis（TG- DSC） and scanning electron microscope（SEM）,respectively.At the same time,the ongoing change of cubic compressive and splitting tensile strength was also studied.The result show that it is significantly influenced the hydration process of cement with the addition of accelerator.In the system of cement-accelerator- water,the retarded action of gypsum was disappeared under the effect of NaAlO_2 and Na_2CO_3.C_3A was hydrated quickly to form CAH crystal and a mesh structure was formed by needle- like ettringite,rod-like ablite and CAH crystal.While,a large amount of hydration heat improved the hydration rate of cement clinker mineral and made the quickly increased the density of paste.It could be made the early aging mechanical properties.