Effect of de-icing salt and aluminous supplementary cementitious materials on the mechanisms of the alkali-silica reaction in concrete

本项目第二阶段的目的是描述在现场温度条件下，在氯化钠存在下，碱硅酸盐反应（ASR）与天然骨料的破坏过程，同时考虑到辅助胶凝材料（SCM）的铝含量。该项目的重点是在ASR凝胶的组成和膨胀性能的损害机制和过程中，具有高活性人工骨料的混凝土和具有低活性天然骨料的混凝土（例如，硅藻土、花岗岩）。特别是，ASR凝胶的形成被认为是一种新的方法，在混凝土孔隙溶液中的含水硅质物种的效果。反应骨料的性质（特别是矿物组成和微观结构）对反应有什么影响？此外，温度和渗透盐（如NaCl或KCl）的组成的变化对硅质物种的形成和稳定性的影响进行了研究。基于这些结果，凝胶的组成和膨胀性能之间的相关性，因此混凝土损坏makes.To进一步的第一个建议的调查，目前的混凝土棱柱体的储存期将被延长。如果再延长一个供资期，将可回答下列未决问题和新问题。在NaCl存在下，天然骨料中进行ASR期间，混凝土孔隙溶液中发生了什么长期变化？2.当使用目前被认为是非反应性的天然骨料（例如硅藻土和花岗岩）时，NaCl会在混凝土中引起破坏性ASR吗？3.在NaCl存在下形成的ASR凝胶的组成是什么？它如何受到粘合剂（水泥和SCM）和反应骨料的性质的影响？4.在NaCl或KCl存在下，混凝土孔隙溶液中会形成哪些硅质物种，它们如何影响ASR的严重性？5.尽管在较低温度下化学反应较慢，但在冬季温度（2 °C）下与除冰盐结合使用时，由于孔隙溶液成分的变化，破坏性ASR是否会增强？

The aim of the second phase of this project is to characterize the damaging process of alkali silica reaction (ASR) with natural aggregates under field temperature conditions in the presence of sodium chloride taking into account that the aluminium content of supplementary cementitious materials (SCMs) in the binder contribute to the composition and the swelling properties of ASR gels.The project focusses on the damage mechanisms and processes in concretes with a highly reactive, artificial aggregate and concretes with less reactive, natural aggregates (e.g. diabase, granite). In particular, the formation of the ASR gel is considered, as a new approach, in the light of the effect of aqueous siliceous species in the concrete pore solution. What effects do the properties (especially mineralogical composition and microstructure) of the reacting aggregate have on the reactions? Furthermore, the effect of variations in temperature and in composition of the penetrating salt (e.g. NaCl or KCl) on the formation and the stability of the siliceous species is investigated. Based on these results, a correlation between the composition and swelling properties of the gels and therefore concrete damage can be made.To further the investigations of the first proposal, the storage period of the current concrete prisms will be extended. A further funding period would provide answers for the following open and new questions.1. What long-term changes occur in the concrete pore solution during an ongoing ASR in natural aggregates in the presence of NaCl?2. Can NaCl cause a damaging ASR in concrete when natural aggregates (e.g. diabase and granite) are used which are at present considered as non-reactive?3. What is the composition of ASR gels formed in presence of NaCl and how is it affected by the binder (cement and SCM) and the properties of the reacting aggregate?4. Which siliceous species form in the concrete pore solution in presence of NaCl or KCl and how do they affect the severity of the ASR?5. Is damaging ASR enhanced at winter temperatures (2 °C) in combination with de-icing salt owing to changes in pore solution composition, despite a slower chemical reaction at lower temperatures?