Introduction
In the recent years, alkali silica reaction (ASR) has been regarded as
one of the relevant aspects for durable concrete design. Common practice is to
avoid the reactive aggregate, to use low-alkali cement or supplementary
cementing materials (SCMs), which are seemingly easy solutions. It is often too
risky for an engineering office to use one particular accelerated ASR test
result and design for a service life of decades. Or, as often encountered, it
is important to estimate the remaining service life of a structure showing ASR
cracks.
In The Netherlands, the first reference an engineer could consult for an ASR-proof structural design is CUR Recommendation No. 89. The parameters
involved are cement type and alkali content, aggregate type and results of
accelerated tests. This recommendation was later followed by CUR recommendation
102, which deals with inspection and evaluation of concrete structures with
symptoms of ASR damage. These recommendations mostly provide decision trees;
suggest a ‘GO-NO GO’ decision. This is a beneficial tool to examine a structure
showing symptoms of ASR damage and decide if the structural safety is still
guaranteed. However the propagation of the ASR mechanism and the consequences
for the structure is not part of the evaluation with CUR recommendation 102. Therefore
it lacks a precise recommendation on what the modification methods entail and the
possible consequences of modifications such as effect of limestone fillers or
SCMs.
Goal(s) of this research project
Durable concrete design requires an understanding of the possible deleterious reactions during the service life of a concrete structure. PAT-ASR project aims to create a tool for predicting the coupled effects of different material, environmental conditions and structural details on alkali silica reaction (ASR) performance, using a multi-scale approach to model the degradation mechanism. Project combines the tasks of internationally accepted recommendations on ASR prevention and control in a unique comprehensive integrated tool, in designing ASR-proof concrete. This final support tool will provide a guideline for engineers on ASR conscious design and a full-scale technical report on the subject. The model will also provide an option, a database to keep track of ASR related characteristics of concrete materials, structural properties and environmental profiles which enables transfer of knowledge to the future projects.
The project is divided into two interconnected PhDs and a post-doc project; experimental, micro/meso scale modelling and structural modelling studies. This project involves experimental studies, among others including the determination of mechanical properties of ASR gel. A computational model, in conjunction with the already developed Lattice Models, will be used for simulating crack patterns in a concrete matrix and a structural model to analyse the structural effects on the overall structure.
