CRTSⅢ型无砟轨道底座板防裂混凝土配合比控制技术研究

Research on Mix Proportion Control Technology of CRTSⅢ Ballastless Track Base Slab Anti-Cracking Concrete

为解决CRTSⅢ型无砟轨道底座板混凝土极易开裂的现象,通过分析混凝土表面裂纹形成的主要原因,研究出混凝土配合比原材料早期水化热、匀质性、表面裂纹外因等控制技术,并进行了室内模拟试验与现场应用验证。室内模拟试验结果显示,胶材用量为397 kg/m3,粉煤灰掺量25%,水胶比0.35,入模坍落度控制在140~160 mm,含气量在4%~6%范围内,振捣后的浮浆厚度在2~5 mm之间,最大芯部温度为56℃,最大温差为16℃,模拟试件56 d内均未发生裂纹现象。现场应用结果表明,结合现场施工控制措施,溜槽施工只出现3条裂纹现象,泵送施工未出现裂纹现象,泵送优于溜槽施工,极大降低了底座板混凝土的开裂机率。

In order to solve the problem that the concrete of CRTSⅢballastless track base plate is easy to crack,this paper analyzes the main reasons for the formation of concrete surface cracks,and studies the control technologies such as the early hydration heat,uniformity,and external causes of surface cracks of the concrete mix proportion raw materials,and carries out indoor simulation tests and field application verification.The indoor simulation test results show that the amount of cementitious material is 397 kg/m~3,the amount of fly ash is 25%,the water binder ratio is 0.35,the slump into the mold is controlled within 140~160 mm,the air content is within the range of 4%~6%,the thickness of laitance after vibration is between 2~5 mm,the maximum core temperature is 56℃,the maximum temperature difference is 16℃,and no cracks occur in the simulated test pieces within 56 d.The field application results show that,combined with the on-site construction control measures,there are only 3 cracks in the chute construction,and no cracks in the pumping construction.The pumping construction is superior to the chute construction,which greatly reduces the cracking probability of the base plate concrete.