DOC : Degradation of organic coating materials and its relation to concrete durability
Deputy Chair: Prof. Kei-Ichi IMAMOTO
Recently, the rapid deterioration of the reinforced concrete structures due to chloride-induced corrosion, alkali-aggregate reaction and early carbonation has become a serious problem. Coating materials act as texture of structure to coordinate its appearance. On the other hand, they are also expected to act as protection of structural concrete to prevent ingress of harmful components from outside. In laboratory condition, the effect of coating materials to prevent the ingress of CO2 and/or Cl- have been verified throughout accelerated test. And, for example, the effect of coating materials on suppression of carbonation in concrete is described in Japanese Architectural Standard Specification for Reinforced Concrete Work “JASS5”. However, organic coating material such as multi-layer coating material will degrade by ultra violet light and/or heat and its barrier effect might be reduced. This RILEM Technical committee focuses on degradation of coating materials under actual environmental condition and its relation to concrete durability.
CIB W080 “Prediction of Service Life of Building Materials and Components” dealt with durability of coating materials. Relationship between chemical deterioration mechanisms and transport of substances has been clarified by analyse technique. Exact expectation of life time of structures has become possible, taking the effect of coating into account on the durability design.
The target of this TC is not to just develop durable coating agent but to evaluate the impact of deterioration of coating materials on durability of concrete.
Some coating such as acrylic coating is of course durable, but there will be many kinds of coating materials for RC buildings. In many cases, coating materials will be selected from viewpoints of not only durability but also aesthetic and so on. At the time, coating materials would be deteriorated with time due to sunshine and rain effect. Many coating materials may affect durability of concrete even though they are selected from aesthetic. Hence, evaluation of “deterioration of coating materials and its durability of concrete” would be valuable.
This RILEM Technical Committee will conduct scholarly activities towards developing deeper fundamental understandings of the mechanisms of degradation of coating materials and its relation to concrete durability under actual environmental condition. This activity will create new research field of concrete technology.
Terms of reference
The activities of the new TC are proposed to be conducted over a 5-year time period. Members will be recruited from academia and industry, based on their experience with coating materials and concrete.
The work will include literature research, exchange of good practices information, journal publications and/or state-of-the-art report regarding the following items;
- Suppression effect of CO2 ,Cl- and moisture ingress by coating materials at laboratory condition
- Deterioration mechanisms and modelling of degradation of coating materials
- Accumulation of information on suppression effect of CO2 ,Cl- and moisture ingress by coating materials under actual environmental condition
Detailed working programme
- Start-up meeting (2020): introduction of members, suggestion of new members, overview of members’ competences and experience, plan of activities, organisation of initial workshop
- Small session (2020) will be planned at international symposium on durability of building materials and components (DBMC) held at Barcelona on 2020, in order to get an overview of experience, problems and points of attention related to degraded coating materials and its relation to concrete durability.
- Next workshop and exchange of information between TC members (2021); compilation of sheets with the best available technique and the best practices; round robin test if appropriate
- International symposium on regeneration and conservation of structures (RCS) will be organised during RILEM Week at Kyoto on 2022.
- Summary of TC findings in one or more journal publications, STAR and/or recommendation (2023-4)
The study of the new TC fits into the scope of RILEM as an organisation dealing with a range of construction materials and structural performance. The work will be an extension of the previous TCs which relate to coating materials, repair materials and durability of concrete. Other active TCs correlated to the subject are:
- 270-CIM : Benchmarking Chloride Ingress Models on Real-life Case Studies: Theory and Practice
- 281-CCC : Carbonation of concrete with supplementary cementitious materials
- IMC : Durability of Inorganic Matrix Composites used for Strengthening of Masonry Constructions
CIB W080 conducted durability of coating materials so far. At present, many of researchers have retired and there are few researches on coating materials and its relation to concrete durability. This TC would be a trigger to create a new research field considering the interaction between concrete and coating materials.
Expected benefits are:
- publication of the state-of-the-art report
- improvement of the knowledge related to the mechanisms of deterioration of coating materials and its relation to concrete durability.
- establishment of network among researchers working in the field of coating materials and concrete durability.
Group of users
Academics, testing laboratory workers, industrialists, practitioners and designers
Specific use of the results
- Strengthening ISO standard “ISO/CD 15686-7 Buildings and constructed assets — Service life planning — Part 7:Performance evaluation for feedback of service life data from practice, Annex C "Prediction of the performance development over time by Markovv Chain" to expect degradation of coating materials under actual environmental condition
- Creation of new technical fields
- Proper communication between users and providers of coating materials and concrete.
Extending the life time of the concrete structures is quite important. Coating materials contributes to this trend by acting not only as texture of building but also as protection of reinforced concrete structure against from harmful substances. Best practices related to the study of concrete with coating materials will lead to the development of new materials and practices.