内养护混凝土收缩和早期抗裂性能试验研究

发布时间：2018-08-14 09:44

【摘要】：高性能混凝土因其高强度、高工作性能和高耐久性能等优点而被广泛应用,但其低水胶比的特征而引起的混凝土收缩开裂问题逐渐突显,严重危害了工程结构的安全性和耐久性。混凝土的内养护技术为解决混凝土收缩和开裂提供了新思路。本文采用非接触式法和平板法,考虑内养护剂掺量、粒径、引水方式和种类,通过试验研究,分析了内养护材料对混凝土早期力学性能、收缩和抗裂性能的影响规律,并与基准混凝土进行了对比。建立了适用于内养护混凝土收缩的预测模型,对内养护材料在实际工程中的应用提供指导。(1)SAP对混凝土的7d抗压强度和7d抗折强度有类似的影响规律。10倍吸水方式对混凝土强度产生不利影响,随着SAP掺量的增加,强度降低程度越明显;10倍吸水且扣水方式和0倍吸水方式对混凝土强度有增强效果。(2)收缩试验结果表明,混凝土在开始测试数小时后都出现了明显的膨胀现象,掺入SAP或LWA可以提高混凝土的早期膨胀量且使膨胀时间延长。有效水胶比相同时,随着预吸水SAP掺量的增加,混凝土的收缩减缩率呈现出先增大后减小的规律,合理掺量为0.2%;减缩率最大的引水方式为10倍吸水方式;粒径为100目的SAP对混凝土收缩变形的改善效果比60目明显;综合考虑7d强度试验结果和收缩试验结果,SAP比LWA更适宜用于混凝土的内养护中。内养护混凝土产生的内养护作用更多地体现在混凝土养护早期。(3)根据内养护混凝土长达180d的收缩试验结果,建立了两种收缩预测模型,提出了内养护混凝土收缩计算公式,计算值与实测值吻合程度较好。(4)抗裂试验结果表明,SAP和LWA的加入,对混凝土的早期抗裂性能有明显的提高。对于掺入100目0倍吸水SAP的混凝土,随着SAP掺量的增加,初裂时间逐渐推迟,开裂面积逐渐减小;三种引水方式中,10倍吸水且扣水方式的抗裂效果较好。掺加SAP的混凝土比掺加LWA的混凝土在初裂后相隔相同时间对混凝土的开裂面积有更明显的降低效果。
[Abstract]:High performance concrete (HPC) is widely used because of its high strength, high working performance and high durability. However, the shrinkage and cracking of high performance concrete caused by its low water-binder ratio is becoming more and more serious. It seriously endangers the safety and durability of engineering structure. The internal curing technology of concrete provides a new way to solve the shrinkage and cracking of concrete. In this paper, non-contact method and plate method are used to analyze the influence of internal curing materials on the early mechanical properties, shrinkage and crack resistance of concrete by considering the amount of internal curing agent, particle size, water diversion method and type. And compared with the reference concrete. A prediction model for shrinkage of internally cured concrete is established. It provides guidance for the application of internal curing materials in practical engineering. (1) SAP has a similar effect on the 7d compressive strength and 7d flexural strength of concrete. The water absorption mode of 10 times has a negative effect on the concrete strength, and with the increase of SAP content, The more obvious the decrease of strength is, the more 10 times of water absorption and the way of water entrainment and the way of water absorption of 0 times can enhance the strength of concrete. (2) the results of shrinkage test show that the concrete has obvious expansion phenomenon after several hours of initial test. The addition of SAP or LWA can increase the early expansion of concrete and prolong the expansion time. When the effective water-binder ratio is the same, with the increase of SAP content, the shrinkage and shrinkage rate of concrete increases first and then decreases. The effect of SAP on shrinkage and deformation of concrete is better than that of 60 mesh, and considering the results of 7d strength test and shrinkage test, SAP is more suitable than LWA for internal curing of concrete. The internal curing effect of internal curing concrete is more reflected in the early stage of concrete curing. (3) based on the shrinkage test results of 180 days, two kinds of shrinkage prediction models are established, and the formula for calculating shrinkage of internal cured concrete is put forward. (4) the results of crack resistance test show that the addition of SAP and LWA can obviously improve the early crack resistance of concrete. With the increase of the amount of SAP, the initial crack time is delayed and the crack area is gradually reduced for the concrete mixed with 100 mesh and 0 times water absorbent SAP, and the anti-cracking effect of the three water diversion methods is better than that of 10 times water absorption and water impingement method. The concrete with SAP is more effective to reduce the crack area of concrete than the concrete with LWA at the same time after the initial crack.
【学位授予单位】：郑州大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TU528

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