Reaction Kinetic Studies of the Electrical Conductivity in Dissolution Experiments for the Identification of Alkali-Reactive Aggregate

Citation
8th World Congress on Civil, Structural, and Environmental Engineering (CSEE 2023)
Contribution to Conference
8th World Congress on Civil, Structural, and Environmental Engineering, CSEE 2023  
Publisher DOI
10.11159/icsect23.147
Scopus ID
2-s2.0-85166406484
ISBN
978-1-99080-018-4
The alkali-silica reaction (ASR) is still a significant damage process in concrete structures. During an ASR poorly crystalline aggregate reacts with alkalis to form an alkali-silica gel. The alkali-silica gel causes damage by expansion within the concrete structure through the absorption of water. Since stopping an ASR is often not possible, costly and, time-consuming, preventive measures are taken and the use of reactive aggregates is avoided. Various test methods for the identification of alkali reactive aggregates already exist worldwide. However, there is currently no test method that can evaluate an aggregate in the short term without prior analysis, as in the case of an incoming goods inspection. In the Institute of Materials, Physics and Chemistry of Buildings at Hamburg University of Technology (TUHH) a new fast test method to identify alkali-reactive aggregates is being worked on. The test method is an accelerated dissolution experiment with ground aggregate like chemical testing methods, such as ASTM C289. But in the new approach, the reactivity of the aggregate is derived from the change in several chemical parameters due to a dissolution process. The dissolution process of the aggregate takes place in hot alkaline solution with an excess of alkalis. During the experiment, the pH-value, the electrical conductivity, and the redox potential are recorded as a function of time. Conspicuous points, such as extreme points and stationary states of these functions are to be used to evaluate the reactivity of the aggregate. It is assumed that the alkali reactivity of the aggregates is essentially reflected in the chemical parameters and thus, in reverse, a specific evaluation of the functions could provide indications of the reactivity of the aggregate. In this paper we present results regarding reaction kinetics and show possibilities to use this new method as an indicator for the reactivity of an aggregate.
Subjects
ASR
ASR testing method
durability
electrical conductivity
reaction kinetics
DDC Class
621: Applied Physics