Protocols for investigating the reactivity of aggregates and alkali thresholds for ASR prevention
- Publisher:
- LABORATÓRIO NACIONAL DE ENGENHARIA CIVIL (LNEC)
- Publication Type:
- Conference Proceeding
- Citation:
- Proceedings of the 16th International Conference on Alkali-Aggregate Reaction in Concrete, 2021, 1, pp. 689-698
- Issue Date:
- 2021-01-01
Open Access
Copyright Clearance Process
- Recently Added
- In Progress
- Open Access
This item is open access.
Alkali in concrete pore solution and reactive silica in aggregate are integral features required for alkalisilica
reaction (ASR). When high amounts of alkali are present, expansive ASR gel forms that cause
cracking of concrete. Thus, limits have been imposed, restricting allowable alkali contents for use in
concrete. However, these limits are known to be generalised with a single limit specified for all aggregate
types. This study investigates the reactivity potential and critical alkali threshold for individual aggregates
and aggregate combinations, by increasing alkali content (0.60-1.25% Na2Oe) in concrete, varying
exposure temperature (38-80°C) and extending test duration. A combination of RILEM recommended
methods and modified versions of the standard accelerated mortar bar test (AMBT) and concrete prism
test (CPT) expansion test methods have been used. The key findings of this study suggest that the
potential exists for specifying a determined alkali threshold in concrete based on the reactivity
classification of aggregates used, thus, allowing a relaxation of the current alkali limit for concrete. This
approach permits greater flexibility in the potential safe use of reactive aggregates in concrete.
Furthermore, this study shows that the determination of an aggregate’s reactivity and potential to ASR
is not only highly dependent on its chemical composition and the alkali content in the concrete but also
the test method, exposure temperature and test storage age used to assess changes in expansion.
Please use this identifier to cite or link to this item: