消泡剂和增稠剂复掺对模袋混凝土抗冻性的影响

Effect of compounding of antifoaming agent and viscosity enhancing agent on frost resistance of mold bag concrete

为使模袋混凝土在大流动性下达到高抗冻性,应用正交试验法研究了含气量、消泡剂和增稠剂对混凝土工作性和抗冻性的影响。结果表明,含气量和消泡剂掺量是影响模袋混凝土相对动弹性模量的显著因素,且含气量影响效果显著大于消泡剂掺量,增稠剂掺量对相对动弹性模量的提高幅度较小。消泡剂和增稠剂复掺能够达到协同改善模袋混凝土工作性、孔结构和抗冻性的效果,当含气量为5vol%~6vol%时,0.15wt%消泡剂和0.03wt%增稠剂复掺使模袋混凝土含气量损失率减小了64.28%、扩展度损失率减小了55.04%;主要消除有害大气泡数量达81.38%,增加小气泡数量达14.89%,使气泡间距系数减小了11.54%,气泡比表面积减小了20.49%,相对动弹性模量增大了11.97%。气泡间距系数和气泡比表面积均与相对动弹性模量具有良好的相关性;当气泡间距系数不大于361μm、气泡比表面积不小于16.13 mm^(-1)时,模袋混凝土抗冻等级可达F300。通过对试验结果的回归分析,建立了模袋混凝土抗冻性预测模型。

For the requirement of mold bag concrete to achieve high frost resistance under large flowability,the effects of air content,antifoaming agent and viscosity enhancing agent on the workability and frost resistance of concrete were studied by orthogonal test.The test results show that the air and antifoaming agent contents are significant factors that affect the relative dynamic elastic modulus and the air content of mold bag concrete is significantly greater than antifoaming agent content;the viscosity enhancing agent increases the relative dynamic elastic modulus to a lesser extent.The compounding of antifoaming agent and viscosity enhancing agent can achieve the effects of synergistically improving the workability,pore structure and frost resistance of mold bag concrete.When the air content is 5 vol%–6 vol%,the compounding of 0.15 wt%antifoaming agent and 0.03 wt%viscosity enhancing agent can reduce the air content loss rate and the slump flow loss rate by 64.28%and 55.04%,respectively.The number of harmful large bubbles is eliminated by81.38%.The number of air bubbles is increased by 14.89%,.The spacing factor is decreased by 11.54%.The specific surface area is increased by 20.49%.The relative dynamic elastic modulus is increased by 11.97%.Both the spacing factor and the specific area have a good correlation with the relative dynamic elastic modulus.The frost resistance grade of the mold bag concrete with spacing factor not more than 361μm and specific surface area not less than 16.13 mm^(-1)can reach F300.The test results are regressed,and the prediction models of the frost resistence of the mold bag concrete are obtained.