Effects of exposure sequence and GGBS cement replacement on performance of concrete subjected to carbonation and chloride ingress

IF 3.4 3区 工程技术 Q2 CONSTRUCTION & BUILDING TECHNOLOGY
Grace A. Blackshaw, Jessica C. Forsdyke, Janet M. Lees
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Abstract

In a variety of applications, such as in tidal zones, abutments of bridges and concrete tunnel linings, reinforced concrete is exposed to both carbonation and chloride ingress. The exposure can be either simultaneous or sequential. However, durability design rarely considers synergistic effects due to carbonation and chloride ingress, even though this may have detrimental consequences for performance. Comparative implications of exposure sequence across different concrete compositions are also unknown. In this study, an experimental investigation on the effects of the sequence of carbonation and chloride ingress was conducted, using two concretes which differ by 50% cement replacement with ground granulated blast furnace slag (GGBS). Specimens were exposed to a combination of 10% CO2 accelerated carbonation and immersion in 3% sodium chloride solution, in either sequence, and compared with companion samples subjected to only one of these aggressive environments. The extent of carbonation was measured using phenolphthalein indicator solution, while silver nitrate and Rapid Chloride Testing provided indicators of the chloride ingress. For both concrete mixes, specimens with prior chloride ingress exhibited a decreased rate of carbonation when compared to specimens with no prior exposure. Conversely, specimens with prior carbonation displayed an increased rate of chloride ingress compared to non-carbonated counterparts and a step in the acid soluble chloride content in the region of the carbonation front. The concrete composition appeared to play a role since a greater increase in chloride diffusion coefficient due to prior carbonation was observed in the mix with 50% GGBS replacement than the mix without. These findings suggest that in concrete structures exposed to air and saline environments, the effects of sequential exposure should be characterised.

Abstract Image

暴露顺序和 GGBS 水泥替代物对受碳化和氯化物侵蚀的混凝土性能的影响
在潮汐区、桥墩和混凝土隧道衬里等各种应用中,钢筋混凝土都会受到碳化和氯化物侵蚀的影响。这种暴露可以是同时发生的,也可以是连续发生的。然而,耐久性设计很少考虑碳化和氯化物侵入的协同效应,尽管这可能会对性能产生不利影响。不同混凝土成分的暴露顺序的比较影响也不为人知。在本研究中,我们使用两种不同的混凝土对碳化和氯离子侵入顺序的影响进行了实验调查,这两种混凝土的不同之处在于用磨细高炉矿渣(GGBS)替代了 50%的水泥。将试样置于 10% CO2 加速碳化和 3% 氯化钠溶液中浸泡,任选一种顺序,并与仅置于其中一种侵蚀性环境中的同类试样进行比较。碳化程度使用酚酞指示溶液进行测量,而硝酸银和快速氯化物测试则提供了氯化物侵入的指示。对于这两种混凝土混合物,与之前未接触过氯化物的试样相比,之前接触过氯化物的试样的碳化率有所下降。相反,与未碳化的试样相比,碳化过的试样的氯化物吸收速度加快,而且碳化前沿区域的酸溶性氯化物含量出现阶跃。混凝土成分似乎也起了一定的作用,因为在添加了 50% GGBS 的混合料中,与未添加 GGBS 的混合料相比,事先碳化导致的氯化物扩散系数增加幅度更大。这些研究结果表明,在暴露于空气和盐水环境中的混凝土结构中,应确定连续暴露的影响。
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来源期刊
Materials and Structures
Materials and Structures 工程技术-材料科学:综合
CiteScore
6.40
自引率
7.90%
发文量
222
审稿时长
5.9 months
期刊介绍: Materials and Structures, the flagship publication of the International Union of Laboratories and Experts in Construction Materials, Systems and Structures (RILEM), provides a unique international and interdisciplinary forum for new research findings on the performance of construction materials. A leader in cutting-edge research, the journal is dedicated to the publication of high quality papers examining the fundamental properties of building materials, their characterization and processing techniques, modeling, standardization of test methods, and the application of research results in building and civil engineering. Materials and Structures also publishes comprehensive reports prepared by the RILEM’s technical committees.
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