防冻剂对混凝土性能影响研究及配比优化

发布时间：2018-06-03 18:20

  本文选题：混凝土 + 防冻剂　； 参考：《辽宁工程技术大学》2014年硕士论文

【摘要】：高纬度季冻区冬季时间长、气温低,混凝土的应用受到限制。为保证低温季节混凝土顺利施工,掺加混凝土防冻剂成为一个较为方便和经济的手段。但目前防冻剂多为复合型防冻剂,成分复杂,难于清楚了解防冻剂对于混凝土性能的影响,严重影响产品的应用与推广。针对目前防冻剂应用混乱的情况,系统研究各防冻组分对混凝土性能的影响规律,揭示防冻组分的影响机理,为季冻区混凝土防冻剂的应用提供技术参考。首先讨论了不同防冻组分对混凝工作性、力学性能与抗冻融耐久性的影响。结果表明：CaCl_2使初始坍落度减小,坍落度损失增大。Ca(NO_2)_2、Ca(NO_3)_2对初始坍落度有提高,但坍落度损失增大。乙二醇提高了初始坍落度,坍落度损失也减小。CaCl_2、Ca(NO_2)_2、 Ca(NO_3)_2、乙二醇均能起到一定的防冻效果,-10℃时,防冻效果对比有CaCl_2Ca(NO_3)_2乙二醇Ca(NO_2)_2。随着CaCl_2、Ca(NO_2)_2掺量的增加,混凝土抗冻性能明显减弱。乙二醇在较低掺量时,能提高混凝土的抗冻性能。其次通过研究防冻组分对掺减水剂混凝土工作性的影响,结果显示,防冻组分对减水剂的性能影响不大。其影响主要表现在掺减水剂混凝土坍落度损失增大。接着建立了水泥稀浆摇泡中的气泡指数衰减模型,指数衰减模型能够较好的拟合气泡体积随时间的变化规律,其参数能够表征不同引气剂的特征参数。应用此模型研究了防冻组分对两种不同引气剂气泡稳定性的影响,并测定了混凝土拌合物含气量。结果表明,对于皂苷类引气剂,CaCl_2降低了气泡稳定性和混凝土拌合物含气量,Ca(NO_2)_2、Ca(NO_3)_2降低了溶液的起泡能力而使含气量也减少。乙二醇对泡沫的稳定性有所提高,但起泡能力显著下降,新拌混凝土含气量也降低。对于苯磺酸盐类引气剂,CaCl_2使其气泡能力下降,Ca(NO_2)_2则主要降低了泡沫的稳定性,Ca(NO_3)_2不利作用不显著,但掺三种盐类混凝土拌合物含气量均降低。乙二醇则提高了气泡稳定性与新拌混凝土含气量。最后通过响应曲面法研究防冻剂各组分间配比的确定方法,结果显示,响应曲面法回归方程能较好预测混凝土负温强度、坍落度、含气量随各参数的变化规律。最佳配比为：硝酸钙掺量为4.79%,减水剂为0.21%,引气剂为0.31%。实验结果与预测值相差很小,表明响应曲面法能够优化防冻剂配比。
[Abstract]:The application of concrete is limited because of long winter time and low temperature in high latitude seasonal freezing area. In order to ensure the smooth construction of concrete in low temperature season, adding concrete antifreeze has become a more convenient and economical means. But at present, the antifreeze is mostly compound antifreeze, the composition is complex, it is difficult to understand clearly the influence of antifreeze on concrete performance, which seriously affects the application and popularization of the product. In view of the confusion in the application of antifreeze agents at present, the effects of various antifreeze components on the performance of concrete are systematically studied, and the influence mechanism of antifreeze components is revealed, which provides a technical reference for the application of antifreeze agents in seasonal freezing areas. The effects of different antifreezing components on coagulation performance, mechanical properties and freeze-thaw resistance durability were discussed. The results show that the initial slump decreases and the slump loss increases. Ethylene glycol increases the initial slump and reduces the slump loss. CaCl _ 2CaN _ (2) C _ (2) C _ (2) C _ (2), CaNO3 / T _ (2), ethylene glycol can all play a certain antifreeze effect at -10 鈩，

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