Investigation into mechanisms and mitigation of alkali-silica reaction in sustainable portland cement concrete containing recycled glass materials.

摘要

A significant portion of recycled glass from municipal waste streams is not found to be suitable for reuse as cullet in the production of new glass containers, and as a result it is disposed in landfills. One of the appropriate ways to reduce the disposal of waste glass in landfills is by using it in portland cement concrete as an aggregate material and/or supplementary cementitious material to replace portion of portland cement. The high silica content of the soda glass can potentially behave as a pozzolanic material when finely ground, which may enhance the mechanical and durability properties of concrete. On the other hand, due to the significant source of reactive silica in glass structure, this material is a highly reactive material in terms of alkali-silica reaction distress in concrete. Silica and alkalis from glass can react with the hydroxyl ions present in the pore solution of concrete to produce ASR gel, which can cause significant expansion and cracking in concrete, often referred to as ASR distress. Therefore, concrete containing glass aggregate is more susceptible to ASR distress compared to the concrete containing mineral reactive aggregate. Thus, the use of glass in concrete as an aggregate may or may not be beneficial, depending on the physical and chemical characteristics of the glass, mixture proportions of concrete and the environmental exposure conditions. However, the use of glass powder with its pozzolanic behavior can enhance the durability properties of concrete and potentially mitigate the ASR distress in concrete.;Past studies on using recycled glass in concrete have focused efforts in using this material as an aggregate replacement material. While this approach allows for using a significant quantity of material, the use of glass aggregate has known to create problems with alkali-silica reaction (ASR) in concrete, particularly if the alkali content of the cement is not controlled. Furthermore, the alkali content of the recycled glass itself is high creating a potential to supplement the alkali loading in concrete. The reactivity of the recycled glass is not only a function of its chemical composition but also its particle fineness. To the best of the author's knowledge no published study has been carried out to evaluate the incorporation of glass powder and glass aggregate in concrete simultaneously, by which optimum amount of waste glass can be used in concrete.;In this study, the use of recycled glass as either a finely ground cementitious material or as an aggregate material by themselves, or in combination were explored to maximize the amount of waste glass used in concrete. These strategies were considered to not only maximize the level of waste glass used in concrete, but also to benefit from the pozzolanic and ASR mitigation ability of fine glass powder. In addition, fundamental investigations were done to evaluate the influence of alkalis from glass structure on the ASR distress in mortar bars or concrete prisms. In this regard, several laboratory tests such as the accelerated mortar bar test (AMBT), the miniature concrete prism test (MCPT) and the concrete prism test (CPT) were conducted to address the influence of curing time and exposure on the ASR distress in mortar bars or concrete prisms. Also, the pozzolanic reactivity and mitigation performance of ternary blends containing glass powder and other conventional SCMs such as fly ash, slag and meta-kaolin were evaluated and were compared with that of the binary blends containing individual components. In all studies the microstructural analysis was conducted to evaluate the performance of mortar and concrete specimens. Finally, the fresh and hardened properties of concrete containing glass powder or/and glass aggregate were evaluated.;Results from this investigation showed that pozzolanic behavior of glass powder was related to the average particle size of the ground glass powder. Increase in the fineness of glass powder particles resulted in increase in the pozzolanic reactivity. Also, the ternary blends of fly ash and glass powder showed synergic effect. In terms of ASR, the use of glass powder as cement replacement material showed promising ASR mitigation performance when a reactive mineral aggregate is used. Based on the AMBT results, the use of glass powder as either glass aggregate replacement material or as mineral aggregate replacement material showed promising ASR mitigation performance; however, in concrete tests, the use of glass powder as mineral aggregate replacement showed the more promising ASR mitigation performance, compared to when glass powder was used as a cement replacement material. The pore solution analysis results showed that the alkali content of the pore solution in specimens containing glass powder was significantly higher than that of the control specimens without any glass powder, indicating the alkali release from glass matrix. (Abstract shortened by UMI.).