纳米二氧化硅改性SAP混凝土抗碳化性能研究与预测

Research and prediction on carbonization resistance of concrete using SAP as internal curing agent modified by nano-silica

混凝土中掺入高吸水性树脂(SAP)对内部湿度、水化程度和抗冻性具有积极作用,但对抗碳化性能有不利影响。基于快速碳化试验,对单掺、复掺纳米二氧化硅(NS)与SAP的混凝土抗碳化性能进行研究,重点分析其在不同碳化龄期下(3、7、14、28 d)立方体抗压强度和碳化深度的发展规律,并利用BP与RBF神经网络对其抗碳化性能进行预测。研究结果表明:(1)碳化作用会提高混凝土抗压强度,碳化后混凝土抗压强度随着SAP掺量的增加而降低,随着NS掺量的增加而提高;(2)单掺、复掺SAP和NS混凝土的碳化深度随NS掺量的增大而减小,随SAP掺量的增大而增大。由于NS超细颗粒尺寸和极高的火山灰活性较好地弥补SAP带来的负面影响,复掺0.16%SAP和1.0%NS混凝土抗碳化效果较佳;(3)通过对25组试验数据进行随机挑选训练集与测试集模拟发现,模型预测值与试验值吻合良好,为纳米二氧化硅改性SAP内养护混凝土抗碳化性能研究提供了重要依据。

The super absorbent polymer(SAP)has positive effects on the concrete internal humidity,hydration degree and frost resistance,but has negative effects on carbonization resistance.Based on an accelerated carbonation experimental analysis,it studied the carbonation resistance behavior of concrete by single-doping SAP,single-doping NS and double-mixed.With the focus on the analysis of the development law of the cubic compressive strength and carbonization depth under different carbonization ages(3,7,14 and 28 d),it also discussed how to employ BP neural network and RBF neural network system to predict the anti-carbonization performance of concrete.The results of the study showed that(1)Carbonation led to an increase of the cubic compressive strength,the compressive strength of concrete decreased with the increase of SAP content,and increased with the increase of NS content.(2)The carbonation depth of concrete by single-doping SAP,single-doping NS,and double-mixed decreased with the increase of NS content,and increased with the increase of SAP content.The negative impacts brought by SAP could be better made up for by the ultra-fine particle size of NS and its extremely high pozzolanic activity.The best effect on anti-carbonization of concrete was the mixture of 0.16%SAP and 1.0%NS.(3)According to the training simulation results of training sets and testing sets randomly selected from 25 groups of experimental data,the results of the model were shown in good agreement with the experimental results,which provided a reference for carbonization resistance of concrete using SAP as internal curing agent modified by NS.