The Chairlady of TC-TDC, Prof. Yao Yan, welcomed at the beginning of the meeting all participants warmly. She briefly introduced herself and summarized the work that the members of RILEM TC-TDC have done in the past two years. The main task of Group A is to compile an annotated bibliography on durability of reinforced concrete under combined mechanical and environmental actions. On the occasion of the first plenary meeting of RILEM TC-TDC in Beijing, a first draft of the bibliography was discussed. After in-depth discussions the structure was slightly modified and a number of new papers were added. With the help of several TC members specific introductory remarks were prepared for each chapter to make the collection of relevant references a real “annotated” bibliography. The main task of Group B is to prepare a list of existing relevant test methods to characterize durability of concrete exposed to combined actions. A report on the achievements shall be published finally. During recent discussions members of TC-TDC came to an agreement to work on suitable test methods.

It is hoped that we can be finalize after in depth discusssions within Group A the annotated bibliography and that we will find an optimum solution for its publication and distribution. Then we have to decide on the final design of the test rigs and specify the concrete composition and the test procedure. Finally, as mentioned already Group A and Group B can be considered to be dissolved after this TC meeting as they have fulfilled their mission. The question arises if it will be reasonable to form new working groups for the second period of activities of our TC. We may for instance form one group, which concentrates on carbonation under the influence of mechanical load and another group, which concentrates on chloride penetration under the influence of mechanical load.

Prof. Zhao Tiejun, Vice-President of QTECH, also made a warm welcome speech and shortly introduced QTECH and Qingdao city.

Dr. Li Juan, on behalf of the Secretary of TC-TDC，gave a short overview on the main tasks of TC-TDC and main progress in the past one and a half years. She also introduced the website www.rilem.cn in detail. The aim of the website is to serve as an online platform for all members of TC-TDC, as well as a communicating channel of RILEM in China and across the world. It started running on March 1, 2012. Important informations about RILEM TC-TDC are permanently updated on the website, including informations concerning all members of TC-TDC, meetings, specific tasks, and so on. There is a Chinese item in the website, it is added following the request of Prof. De Schutter, the Development Director of RILEM. He suggested the Secretary of TC-TDC may translate some webpages of RILEM into Chinese. These informations are subdivided into six chapters: (a) About RILEM, (b) Mission of RILEM, (c) History of RILEM, (d) Organization, (e) Honors and awards and (f) How to join RILEM. The spcial Chinese section on www.rilem.cn is meant to serve as a window for Chinese colleagues to facilitate access to RILEM activities and to provide general information on RILEM.

Prof. Folker H. Wittmann, Chairman of Group A, underlined that the main task of Group A is to publish an annotated bibliography containing complete references and summaries of all papers available in the literature in which results of studies to investigate durability of cement-based materials under combined actions are described. Then he introduced the structure of the content and details of procedure of publication of the bibliography.

Dr. Wang Zhendi, the secretary of Group A, made an introduction on the background, the main aim, progress made so far and still existing problems to be solved, such as 20 missing abstracts, missing introductory notes of Chapter 2 and Chapter 8 and so on. In Sep. 2011, during the inauguration meeting it was decided to prepare and finally publish a comprehensive annotated bibliography. From March 3rd, 2012, members of the TC-TDC were invited to send publications to the secretary, Dr. Wang Zhendi. On May 16th, 2012, members of the TC-TDC classified all papers collected. From Sep. 2nd, 2012, selected members of the TC-TDC started to add introductory remarks for each section and details of the publication procedure were fixed.

The main aim of this annotated bibliography is to serve as a reference book for those who are active in this field. It should be easy for all TC members at the first stage and for all colleagues who are active in this field or who want to start to work on similar topics. It is hoped that the annotated bibliography will help to provide easy access to the state-of-the-art to all our colleagues and to avoid unnecessary duplications. The selection criteria of the papers are based on the topic described and limited to common combinations.

1) The deadline for paper collection is May 31, 2013, that means soon after this meeting.

2) After discussions, a decision has been taken on the final structure of the document; see Attachment 1.

3) The format for the names of authors is as: Wittmann F. H. For Chinese names, the format for the names of authors is as: Wang Zhendi.

4) For the 20 missing abstracts, Prof. Nele De Belie suggested to circulate the list of all missing abstracts to all members, so that if someone who has a copy, he or she can the missing abbstract to the secretary Wang Zhendi.

5) Introductory notes are still missing for Chapter 2 and 8, and the secretary will contact Prof. Xing Feng and Prof. Weiss by email and ask them to submit their contribution within two weeks.

6) It was considered to be helpful to number the lines on all pages before distributing to all members. In this way corrections can be easily indicated.

7) The bibliography will be sent to all members as a pdf document, one month after having received all missing data for further and fiinal comments.

8) A CD with full papers will also be published together with the published bibliography. If the inclusion on the CD is not free of payment, only an internet link to the full length papers will be provided on the CD.

9) Prof. Wittmann will contact the RILEM Office to obtain agreement for the official publication of the bibliography.

Chairlady of Group B, Prof. Wang Ling presented the objectives, tasks and achievements of Group B. The objectives of Group B are: (a) the collection and critical comparison of existing test methods, and (b) a proposal of a most promising test method for comparative test series. The actual tasks of Group B are to finish the compilation of the standards and recommendations for test methods, combination of environmental actions and mechanical load and selection of the most promising test methods and characterization parameters.

For the compilation of standards & recommendations for test methods, Prof. Wang Ling informed the committee members that Group B collected 46 test methods and standards related to concrete durability before the first plenary meeting in Beijing last year, mainly Chinese standards (GB) and European standards. After that, more than 10 ASTM standards and CEN standards were collected. Participants of group B provided a lot of test methods used in their countries to test concrete durability under one single environmental factor, such as freeze-thaw cycles, carbonation, AAR, leaching or chloride penetration. It was found that even test methods of concrete durability under the same environmental actions differ a lot. The draft compilation of standardized test methods prepared for this meeting consists of 7 test procedures for carbonation, 5 for frost damage and 7 for chloride penetration. But there are no standards and recommendations for testing durability of concrete under combined actions so far. Some members summarized their own test methods used in research projects to study the behavior of concrete durability under combined actions, such as mechanical load, freeze-thaw cycles, carbonation, and chloride penetration. Experts all over the world carried out tests under different load combinations. Many projects were focused on the influence of stress level on the concrete durability, but the critical stress threshold btained varied a lot due to the differences of test devices, concentration of chloride solution and dimension of specimens. So, there is a real need to establish a unified test method, which will allw us to determine durability of concrete under combined actions in order to be able to predict the corresponding service life of reinforced concrete structures in aggressive environment..

It turned out that the selection of the most suitable test methods for studying the effect of combinations of environmental actions and mechanical load is really very difficult. During the Cape Town meeting, we came to the conclusion that TC-TDC should focus on the following two types of combinations: (a) axial compression and tension combined with chloride penetration and (b) axial compression and tension combined with carbonation. Test rigs for these four types of combinations were designed and a prototype was manufactured. Prof. Wang Ling hopes that the TC members will agree on these proposals and then the first round of comparative test series can start as soon as possible. The test rigs were co-designed by Prof. Yao Yan, Prof. F. H. Wittmann, and Dr. Wang Zhendi. Prof. Erik Schlangen provided valuable suggestions for details of the design.

Prof. Wang Ling introduced the basic principles of the test rigs: (1) The most important requirement for a standard test, which ought to be run in as many laboratories as possible, is simplicity of the test. Many standard laboratories from different parts of the worlds should be able to run such a test following a RILEM recommendation. (2) The test results should be applicable directly to quantify the influence of a given applied load on service life of reinforced concrete structures under given environmental conditions.

For more detailed description of the test rigs, please see Attachment 2.

After an intensive discussion, the following modifications of the test rig for compressive load were suggested:

1) The dimension of the specimens should be fixed to be 100 x 100 x 400 mm.

2) Screw nut should be used rather than hydraulic equipment for loading.

3) Adding a movable ball bearing on the top.

4) Using 4 steel bars (as thin as possible) instead of 2, pasting 4 strain gauges on the 4 tensile bars.

1) Adding a cover to the two end sides of the mould to prevent fresh concrete come into the box.

2) The dumbbell shaped specimens shall have a square section in the centre, and the dimensions of the part with square section shall be: 100 x 100 x 200 mm³.

3) 4 screw bolts of one pull head should not be put in line, It is suggested to place them at each corner (better distribution of stresses).

4) Using ball hinges instead of hinge units.

5) Dr. Dong Zhijun will calculate the maximum stress in the steel bars and provide us with the results within 3 weeks to see if there is a need for further modifications.

6) Five strain gauges are needed for 4 compressive bars and a tensile bar above the hinge. It is decided that the indication of tensile strain gauge is the reference value.

See Attachment 3.

First, Mr. Cao Yin, a PhD student in CBMA, introduced the State Key Laboratory of Green Building Materials of CBMA. Next, some of the delegates from other labs introduced their labs and showed their interest to participate in the comparative test series. Finally, the result of the inquiry among the TC members present in Qingdao on the availability of diffeerent labortories is shown in the following Table I:

 

No.	Member	Affiliation	Carbonation + load	Chloride + load
1	YAO Yan	CBMA	Y	Y
2	ZHAO Tiejun	Qingdao Tech. Univ.	Y	Y
3	XING Feng	Shenzhen University	Y	Y
4	LI Weihua	Institute of Oceanology, Chinese Academy of Science	N	Y
5	DE BELIE Nele	Ghent Univ.	Y	Y
6	SCHLANGEN Erik	Delft Univ. of Technology	Y	Y

 

Prof. Glinicki sent an email to express his interest to participate in the forthcoming comparative tests on May 25. In addition, several colleagues were recommended because of their existing research experience and test facilities. The secretary will invite several TC members officially to join the comparative test program, such as Prof. Tamon UEDA from Hokkaido Univ., Prof. Carmen ANDRADE from the National Research Council of Spain, Prof. Christoph GEHLEN from Munich University of Technology. Hopefully even more laboatories will join the comparative test series. If more laboratories participate the results may become more reliable.

The mix proportion of concrete for the calibration test series (zero series) before the first round of comparative test series was decided to be as shown in Table II:

 

Cement kg/m3	w/c	Water kg/m3	Fine aggregate kg/m3	Coarse aggregate kg/m3	Superplasticizer kg/m3	Slump cm
368	0.45	165.5	840	1027.5	5.1	12~15

 

The meeting was closed at 16:00 p.m. on May 24^th in the afternoon. In the wrap-up presentation, Prof. Yao Yan expressed her sincere thanks to Prof. Folker H. Wittmann, who has volunteered to be the Chairman of Group A and has given TC-TDC a lot of guidance, and to Prof. Wang Ling for her continuing engagement to make this meeting meaningful and successful, and to Prof. Erik Schlangen who provided valuable ideas for a promising design of the test rigs. Then she offered her sincere thanks to Prof. Zhao Tiejun for hosting and supporting this meeting. She also thanked all the experts who attended the meeting for their personal efforts and their support for the RILEM TC-TDC, and those who were unable to attend the meeting but helped a lot in sending TC-TDC their publications and regionally applied test methods. She looked forward to the future co-operation with all our TC members.

At last, she suggested having a short informal meeting of RILEM TC-TDC in Paris during the first week of September 2013. That would be a good chance to discuss results of the zero test series, which ought to be run before the first official round of comparative tests and share the experiences and achievements with other RILEM members who could not come to Qingdao.

Before the meeting was closed, she expressed her hope that everyone would enjoy himself or herself in Qingdao after this meeting. She also invited everyone to visit CBMA before or after the International Symposium on Cement and Concrete (ICCC2013) held in Nanjing this September.

She concluded that herself and all members present were confident that the ambitious aim of TC-TDC will be achieved finally.

 

After the meeting, Prof. Jiang Fuxiang and Wang Penggang, both from QTECH, presented in an ad hoc seminar their research work on concrete durability under combined actions. All TC –TDC members had the opportunity to discuss the state-of-the-art in this field. All participants visited later the laboratories of QTECH in which relevant tests are run.