试验方法对喷射混凝土用液体无碱速凝剂检测结果的影响

Influence of test method on test results of liquid alkali-free flash setting admixtures for shotcrete

对比了我国5个有关液体无碱速凝剂标准中的检测项目、指标和试验方法,对实际试验过程中存在的问题进行了归纳总结,探究了不同试验方法对液体无碱速凝剂检测结果的影响。结果表明:采用离子色谱法对液体无碱速凝剂中的游离氟离子含量进行定性检测相对准确;采用150℃卤素水分测定仪可实现液体无碱速凝剂产品生产线快速检测,且根据其测得的含固量与直接烘干法测得的含固量偏差在±1%以内;与常温稳定性相比,低温(-10℃)稳定性问题主要为黏度增大、上层分层、底部结晶或沉淀等;无振动、采用典型或代用振动台振动均会造成基准砂浆表面泌水,使实际水灰比低于理论值0.50;适当降低灰砂比有利于改善基准砂浆的泌水问题;采用基准水泥时,按1.0 MPa抗压强度限值要求,受检砂浆的6 h和8 h抗压强度合格率分别为30%和40%。

The test items,indicators and test methods in five domestic standards for liquid alkali-free flash setting admixtures were compared,and the problems existing in the actual test process were summarized.The influence of different test methods on the test results of liquid alkali-free flash setting admixtures was explored.The results show that based on ion chromatography method,the free fluoride ion content of liquid alkali-free flash setting admixtures can be determined qualitatively,with relatively accurate results.The rapid detection of solid content of liquid alkali-free flash setting admixtures can be realized by using Halogen moisture meter method at 150℃,and the deviation of test results is limited within±1%compared to direct drying method.Compared with room temperature stability,the stability issues at low temperatures(-10℃)mainly include increased viscosity,upper layer layering,bottom crystallization or precipitation,etc.No vibration,using a typical or substitute vibration table vibration can cause surface bleeding of reference mortar,resulting in the actual water cement ratio lower than the theoretical value of 0.50.Reducing the cement sand ratio of reference mortar is beneficial for improving the bleeding problem.When using reference cement,according to the requirement of 1.0 MPa compressive strength limit,the qualification rates of 6 h and 8 h compressive strength of the tested mortar are 30%and 40%,respectively.