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为了研究硫酸盐侵蚀后喷射混凝土表面损伤层厚度变化,采用干湿交替方法,对同配合比模筑混凝土、喷射混凝土及钢纤维喷射混凝土进行硫酸盐侵蚀,利用超声波平测法对试件表层声时进行测定,采用回归方法对试验数据进行拟合,得出试件损伤层厚度。结果表明:随着干湿交替次数增加,试件表层超声波波速降低,试件密实度下降,损伤层厚度增大,用损伤层厚度表征试件硫酸盐侵蚀具有较好相关性。而后对硫酸盐侵蚀后喷射混凝土微观结构进行分析,发现喷射混凝土硫酸盐侵蚀破坏方式从初期钙矾石破坏转变为后期钙矾石、石膏复合破坏,且钙矾石及石膏含量随着交替次数的增多而增加;同时,对交替150次喷射混凝土试件进行钻孔分层取粉,对其进行物相分析及热分析,随着深度增加,试件中钙矾石含量先增大后减小继而平稳,但石膏含量持续减小,深度大于12mm时石膏含量为0。
In order to study the change of the thickness of the damaged layer on the surface of shotcrete after the sulfate attack, the wet-dry method was used to carry out the sulfate attack on the same mix concrete, sprayed concrete and steel fiber shotcrete. When the determination of regression methods used to fit the test data to obtain the damaged layer thickness of the specimen. The results show that with the increase of alternate wetting and drying times, the ultrasonic wave velocity decreases, the compactness decreases, and the thickness of damaged layer increases. It is found that there is a good correlation between the sulfate erosion and the damaged layer thickness. The microstructure of sprayed concrete after sulfate attack was analyzed. It was found that the failure mode of sulfate eroded shotcrete changed from initial ettringite destruction to later ettringite and gypsum composite destruction, and the content of ettringite and gypsum changed with the number of alternation Increase and increase; at the same time, the alternate 150 shotcrete specimens were stratified and take the powder, the phase analysis and thermal analysis of the specimen, as the depth increases, the content of ettringite first increased and then decreased Then it was steady, but the content of gypsum continued to decrease. When the depth was greater than 12mm, the gypsum content was zero.