The Influence of Alternative Materials on Alkali Aggregate Reaction (AAR) Induced Development in Concrete

Abstract

Portland cement (PC) production is the main responsible for concrete’s carbon footprint, accounting for about 7% of the annual man-made CO2 emissions. Currently, concrete industry faces important challenges of finding cost-effective strategies to reduce the embodied energy associated with the production and use of PC in concrete. Therefore, the use of “conventional” by-products from other industries (i.e. supplementary cementing materials – SCMs) have been implemented with success in the concrete construction for many years. However, recent studies verified that the short and especially long-term availability of SCMs will not be enough to correspond to the rise in PC’s demand, which reinforce the need for alternative solutions to partially replace PC. Amongst possible alternatives, biomass waste (i.e. wood-ash - WA) and mineral fillers (MF) are seen as viable products due to their large availability and interesting physicochemical features. Yet, the short and long-term behaviour of concrete incorporating WA or MF are still unclear, particularly their durability performance against important distress mechanisms such as alkali-aggregate reaction (AAR). In this context, this Thesis aims to assess the behaviour of concrete mixtures incorporating WA and MF against AAR-induced development. Concrete mixtures containing reactive and non-reactive coarse and fine aggregates were fabricated with a) WA at distinct replacement levels (i.e. 10, 20, 50 and 60%, by mass) and, b) four types of MF (i.e. reactive and non-reactive) replacing either PC or fine aggregates at a fixed replacement level of 15% (by mass). Accelerated mortar bar and concrete prism tests (i.e. AMBT and ACPT, respectively) along with the conventional concrete prism test (CPT) were performed. In summary, AMBT results indicate a potential benefit of using WA to mitigate AAR-induced expansion and deterioration whereas the ACTP clearly demonstrated that WA is not effective to supress AAR. Otherwise, CPT results suggest a potential interest of using MFs to lower AAR-induced development, especially while replacing PC and depending upon the MF type. Furthermore, supplementary test procedures (i.e. chemical, mechanical and microscopic) were conducted to appraise the impact of these alternative materials on AAR-induced development. Finally, statistical analysis (i.e. analysis of variance – ANOVA) was conducted to prove the data and discussion made over this work.