Aggregate Reactions in Concrete: Addressing the Needs for test Methods, Preventive Measures, and Mitigation

据报道，混凝土中的骨料反应会对结构造成重大损害。在某些集料中，碱-硅反应（ASR）和硫化物相氧化是导致混凝土严重损伤的两种主要集料反应。在加拿大的许多地方，骨料的稀缺性可能会推动使用新来源的骨料，这需要进行资格预审。因此，需要快速可靠的资格预审测试方法。如果发现所审议的骨料具有反应性，则必须有办法确定适当的预防措施。这是因为经济和环境可行性可能需要使用这种骨料，而不是从遥远的地方运输非反应性骨料。******自20世纪40年代发现ASR以来，ASR一直是许多研究项目的重点，这些研究项目产生了测试方法、预防措施和管理受影响结构的方法。然而，关于ASR测试仍有一些未解决的问题。具体来说，最可靠的实验室测试-混凝土棱镜测试(CPT) -被发现高估了一些预防措施的功效。除了需要改进当前的测试方法之外，研究人员和从业人员还可以从一种更好的方法中获益，这种方法可以基于一种更精确的识别聚合体反应性的方法来规定预防措施的类型和水平。******另一种骨料反应是在某些类型的骨料中发现的硫化物相的氧化。自20世纪初以来，这种反应造成的损害在世界各地的许多地方都有报道。最近发生的三河流域、qubec和美国康涅狄格州的案例由于损害程度和经济损失引起了相当大的关注。虽然最近提出了筛选骨料的测试，但尚未制定具体的测试。这个测试可以用来评估可能的预防措施的效果。******本方案解决了上述技术需求。在ASR方面，将研究一种新的识别聚合反应性的创新策略。这将有助于更精确地确定补充固井材料（SCMs）的水平——ASR的常见预防措施——以减轻膨胀。此外，将评估一种改进的检测方法。新方法减少了测试过程中样品的碱损失，从而获得更准确的膨胀值。******对于骨料中硫化物相的氧化，本提案中的活动将侧重于开发具体测试。申请人最近的工作已经阐明了在实验室条件下可以产生膨胀的测试制度。此外，将研究一种新的方法，该方法需要将混凝土样品暴露于富氧环境中，在相对湿度下维持氧化。

Aggregate reactions in concrete have been reported to cause major damages to structures. Alkali-silica reaction (ASR) and oxidation of sulphide phases in some aggregates are two major aggregate reactions that have been associated with severe damages to concrete. The scarcity of aggregates in many locations in Canada may push for the use of aggregates from new sources which need to be prequalified. Quick and reliable prequalifying test methods are therefore in need. If the aggregate under consideration is found reactive, the availability of ways to identify adequate preventive measures will be essential. This is because the economic and environmental feasibility may require the use of such aggregate rather than hauling non-reactive aggregates from distant locations. ******Since its discovery in the 1940's, ASR has been the focus of many research projects that produced test methods, preventive measures, and ways to manage affected structures. However, there are still some unresolved issues pertaining to ASR testing. Specifically, the most reliable lab test – Concrete Prism Test (CPT) – was found to overestimate the efficacy of some preventive measures. In addition to the need for improvement in current test methods, researchers and practitioners can benefit from a better way to prescribe the type and level of preventive measures based on a more precise way of identifying the reactivity of aggregates.******Another type of aggregate reaction is the oxidation of sulphide phases found in some types of aggregates. Damages due to this type of reaction have been reported in a number of locations all over the world since the early 1900's. The relatively recent cases of Trois-Rivières, Québec, and Connecticut, USA have attracted considerable attention due to the level of damage and economic loss. While tests to screen aggregates have been recently proposed, a concrete test is yet to be developed. This test can be utilized to evaluate the efficacy of possible preventive measures. ******This proposal addresses the above technical needs. In terms ASR, a new innovative strategy to identify aggregate reactivity will be investigated. This will help achieving a more precise determination of the levels of Supplementary Cementing Materials (SCMs) – common preventive measures for ASR – required to mitigate the expansion. In addition, an enhanced method of testing will be evaluated. The new method reduces the loss of alkalis from the sample during the test resulting in more accurate expansion values. ******For the oxidation of sulphide phases in aggregate, the activities in this proposal will focus on developing a concrete test. Recent work by the applicant has shed light on testing regimes that can produces expansion under lab conditions. In addition, a new approach will be investigated which entails exposing the concrete samples to oxygen-rich environment under a relative humidity that sustains oxidation.