Study outline

Concrete is a heterogeneous building material consisting of natural and man made products. The inherent heterogeneity of these material makes it hard to set a standard procedure for reactivity assessment. Common practice is to avoid reactive aggregates, where reactivity tests are either time consuming (impractical for engineers) or not reliable enough. Thus, there exists no internationally accepted ASR performance testing procedure; however studies on RILEM AAR-4 performance testing procedure is still in progress, yet not published. It is still a challenge to estimate the ASR effect on the existing structures together with potential impacts. There exist several recommendations, around the world, on ASR detection and prevention around the world. None, so far, has been internationally accepted.

In Netherlands, CUR regulations committee, CUR Technical Committee VC 62: Alkali Silica Reaction in concrete was set up in 2000. After severe criticism on CUR recommendation 38 (1994), the new committee published CUR recommendation 89 – ‘Measures to prevent damage to concrete by alkali-silica reaction (ASR)’ in 2002, which was followed by CUR recommendation 102 ‘Inspection and assessment of concrete structures in which the presence of ASR is suspected or has been established’. These recommendations are mostly provide decision trees suggest a ‘GO-NO GO’ decision.

A great number of studies, carried out worldwide, investigate the material performance considering various aspects of ASR effect. Most of these studies aim to determine the sole effect of ASR on micro-to-macro structural elements. Yet, there are missing links between chemical reaction parameters and gel product’s deleterious behaviour. Due to discontinuity of material properties in a mix, there may occur variations between laboratory test results and real structure measurements. A statistical approach to sample space data, harvesting available literature, can be used to increase the reliability of such a prediction model.

The aim of the project is to develop a material performance model for simulation of ASR effect on concrete durability. The final outcome of this project is an integrated support tool for engineers for ASR conscious design – a guideline for engineers.

How to achieve this goal
Putting together existing knowledge for alkali-silica reaction requires a medium for interaction and communication from engineering and geological perspectives. Establishment of ASR conscious design is only possible if one can make use of the studies in materials science. Such an iterative support tool can be promoted via user friendly and easy-to-use interface. Our aim is to provide a platform which will promote experts in this field to share their knowledge and studies, in a common, standardized and supervised space. This platform will provide a backbone structure for the users to compare and run simulations via:
- Several material databases, including aggregate distribution maps, aggregate properties atlas, cement and SCM material providers list, geographical distribution, products and information lists.
- National and internationally accepted regulations and limitation on ASR
- Simulation modules for various ASR effect on structures, up-to-date list of available models on the subject
- An updated information cloud which can be extracted to other durability assessment issues in concrete


Figure 1: Draft flowchart for performance assessment tool summary for ASR.

CLUSTERS & WORK-PACKAGES

Cluster One: ASR Reactivity Assessment

Work package 01 (WP01): Assessment of Chemical Reaction parameters
We are currently working on our own test schedule in TU, Delft. These tests include AAR-2, AAR-3 and AAR-4 application on reference aggregates (more details on this will be published later)
Work package 02 (WP02): Developing a Statistical/computational model for ASR effect

Cluster Two: Assessment of ASR Effect on concrete structures

Work package 03 (WP03): ASR gel analysis, stress formation, link to parameters in chemical reaction, crack formation modelling
Work package 04 (WP04): Micro to Macro Scale Deformation model, simulation of ASR Effect on larger structural elements.

Resources for our study:

Experimental part includes mortar bar, concrete and small scale testing together with petrographic analysis and exposure site, hopefully. Validation test will be carried out by Norwegian reference aggregate. We are in progress to finalize the test set-up assembly and material supply. There are on-going discussions on possible collaborations between institutions from Netherlands, Norway, Iceland and Turkey. We are currently in touch with technical committees (e.g. RILEM), test institutions and industry partners, to exhibit our case and mature objectives for further studies with expert opinions on the issue.