246-TDC: Test methods to determine durability of concrete under combined environmental actions and

Technical Committee 246-TDC

General Information

Chair: Prof. Yan YAO
Deputy Chair: Prof. Ling WANG
Activity starting in: 2011
Activity ending in: 2018
Cluster B

Subject matter

By now there exist several methods to predict service life of reinforced concrete structures. In most cases one dominant deteriorating process such as carbonation or chloride penetration is taken into consideration. Experimental results as well as observation in practice show, however, that this is not a realistic and certainly not a conservative approach. A combination of mechanical and environmental loads may turn out to be much more severe than each single load alone. There are obvious synergetic effects, which have been widely neglected so far. The major aim of this proposed RILEM Technical Committee is to develop test methods to characterize the behaviour of concrete under combined actions such as mechanical load, freeze-thaw cycles, carbonation, and chloride penetration. The validity of the recommended test methods shall be checked by comparative test series carried out in a number of selected laboratories in different countries. Finally a RILEM recommendation for the newly developed test methods shall be published. Results of the suggested tests shall provide a solid basis for more realistic service life prediction.

Terms of reference

The necessary duration of this new RILEM TC is estimated to be four to five years. During the first year two aims must be achieved. A thorough literature review shall be undertaken compiling all relevant publications on concrete properties under combined actions. In addition a first series of comparative tests shall be prepared, based on the outcome of the literature review. A core group of members who are able and willing to participate in comparative test series will be composed by invitation. In addition volunteers from all countries are welcome. It is expected that National Delegates will nominate experts from their region. A comprehensive report with a complete bibliography of methods to predict service life and test methods to determine relevant material properties shall be established.

Detailed working programme

First year:
An extensive literature study shall be made and a comprehensive annotated bibliography shall be published. The bibliography shall be focused on theoretical concepts to describe the action of combined loads and on appropriate test methods to determine properties of concrete under combined environmental mechanical loads. At this stage concrete shall be investigated as a composite material. The behaviour of real structures shall be postponed to a follow-up committee. Finally a detailed test program for first comparative test series shall be worked out and distributed among the core members of the TC.

Second year:
Carrying out comparative test series in a number of participating laboratories (core group) according to detailed recommendations; evaluation of results and preparation of a summarizing publication. A second more specific series of comparative tests based on the results of the first test series is to follow. The most serious load combinations shall be identified and further studied.

Third year:
Carrying out the second more specific series of comparative tests; evaluation of test results and pointing out the relevance for prediction of service life of reinforced concrete structures; Organization of an international workshop on “Service life of Reinforced Concrete Structures under Combined Loads”.

Fourth and fifth year:
Summarizing most important results and publication of conclusions; Elaboration of recommendations for durable construction of reinforced concrete structures and a state-of-the-art report; Organization of a conference on “Prediction of Service Life of Reinforced Concrete Structures, Relevant Material Properties, and Most Severe Load Combinations”

As the scope of this RILEM TC is very wide and the subject is comparatively young, it will not be possible to solve all relevant problems within four to five years. Open questions and tasks for follow-up technical committees shall be formulated towards the end of the work of this TC.

Technical environment

RILEM has a long tradition with work on durability and service life. The TC 176-IDC has recently published a recommendation for testing freeze-thaw resistance of concrete. This method may be used in the proposed comparative test series to induce well defined frost damage, which may then be combined with application of an external load and determination of carbonation and chloride penetration. Cooperation with the recently created TC-FDS on durability design of SHCC will certainly be envisaged. Contacts with another newly created TC-MCT on multi-component transport in hardened cement paste will be beneficial for the work of the proposed new TC. A strong link will be established with RILEM TC 213-MAI, model assisted integral service life prediction. The work of other active technical committees such as 207-INR, 211-PAE, and 214-CCD deserve to be closely followed. Finally results of TC 221-SHC, self healing phenomena in cement based materials, may provide an important impact on the work of the TC proposed herewith.

In the Chinese Building Materials Academy a number of PhD theses on this subject have been carried out during the last ten years. Relevant tests have also been run in the Centre for Durability and Sustainability Studies at Qingdao Technological University. An international workshop on durability under combined environmental and mechanical loads has been organized in Qingdao in 2005. Pioneering work in this field has been initiated at Shenzhen University about ten years ago. A number of prospective members of the proposed TC are at the same time active in a Japanese working group on a similar subject. The proposed TC can take advantage of the wealth of information already available and to transform existing knowledge into a RILEM recommendation.

Once first results will be available contact with other international associations such as fib may be useful.

Expected achievements

More reliable prediction of service life of reinforced concrete structures is of utmost importance for more ecological and more economical construction in the future. The following deliverables will be produced by the new TC:
- A comprehensive bibliography on the subject
- Recommendation for test methods to characterize durability under combined actions
- An international workshop to bring together most of the international experts in this field
- An international conference to transfer most relevant results to the interested engineering community
- Experimental results shall serve as a basis for more realistic service life design
- Priorities and orientations for future research work on the effect of combined loads.

Group of users

Results of the proposed TC should be integrated in teaching of building materials on all levels. The expected RILEM recommendation for a test method will help testing laboratories to characterize different types of concrete with respect to their durability under combined mechanical and environmental loads. Ready mixed concrete producers may optimize their products with respect to service life under given environmental conditions.

The biggest advantage for the public will be the extension of service life of reinforced concrete structures. This will be a significant contribution to more ecological and more economical construction.

The obtained results will be a solid basis for groups dealing with the prediction of service life of concrete and concrete structures. It will enable these groups to further develop the existing models and to make the outcome of their statistical models more realistic.

Specific use of the results

Service life of existing reinforced concrete structures is in most cases too short. The cost for maintenance and repair has increased steadily and reached a level in most countries by now, which slows down further development in other areas. This is a most serious problem in countries, which develop quickly and have a construction boom nowadays. If construction will not be significantly more durable in the future, necessary repair con not be afforded and further development will be negatively influenced.

As soon as durability of concrete under combined loads can be quantified experimentally and taken into consideration in durability design, this situation may change rapidly. A rough estimation of the implied expenditures shows clearly the enormous potential for savings in construction.