Completed technical committees
The global warming problem is becoming the world's political issues and expected to become the most important agenda in the G8 Hokkaido Toyako Summit, Japan, which will be held an July 2008. Concrete sector is consuming a tremendous amount of resources and energy. The drastic increase of the amount is expected because of the infrastructure development of many developing countries. The concrete sector will not be exempted from reducing the environmental impacts in near future.
In order for promoting better understandings on the overseas state of construction material technologies, this TC organizes the International symposium ( ConMat '09 ) and investigates foreign standards and requirements relating to concrete and concrete materials. ConMat'09 attempts to build on the successes of the first three conferences which were co-organized by JSCE and CSCE in Ottawa, Canada(1997), San Jose, USA (2001) and Vancouver, Canada (2005) and the primary purpose of the symposium is to bring experts in materials and structures on a common platform with the objective of exchanging cross-disciplinary ideas and learning from recent advances in respective fields. The research on standards and requirements will be conducted based on the a questionnaire survey under the cooperation of international board and committee members of the symposium and the research accomplishments will be presented at the synposium.
From the viewpoint of environmental impacts, utilization of industrial byproducts such as ground granulated blast furnace slag or fly ash is inevitable. However, when these materials are used in concrete, some examples of troubles such as cracking at early ages are reported. Besides, the performances of concrete where several kinds of mineral admixtures are used or functional chemical admixture and/or expansive additives are combined have not been clarified in some cases. Therefore, in this technical committee, in order to promote the wide usage of concrete using these admixtures, the technology regarding the general performance improvement of blended cement is discussed including the countermeasures to reduce the cracking.
The purpose of this committee is to clarify the present state, technical issues and future perspective of the recent performance-oriented seismic rehabilitation technology for concrete structures such as "seismic isolation", "seismic control" and "seismic strengthening utilizing exberior structures". Existing data of research, design and application of such technology will be collected and surveyed. As a result, technical guides for researchers and practicing engineers will be provided. Results of the activity of this committee will be presented at an international event to be held in Japan in autumn 2010.
In the 21st century, sustainability has become one of the most important paradigms for the further development of the society. The building industry is required to construct durable social overhead capital with improved quality while preserving energy and natural resources. Precast concrete (PCa) products can provide consistent quality and a shorter construction period and thus enable to construct concrete structures with durability at lower cost. Use of PCa in Japan, however, remains at about 13% which is considerably low compared with those in Europe and the United States of America. Technical innovations in recent years enabled to develop PCa products with much higher intensity and durability. Promotions of recycled materials in conjunction with concrete have been thriving so far and utilization of PCa products may further expand in various fields in future. This committee is established to identify the issues related to PCa products and to provide technical resources in order to promote PCa products.
Generally, pilotis structures are not safe against strong earthquake as people may suppose. In fact, so many pilotis structures are damaged and collapsed at the great earthquake of "Hyogoken Nanbu Earthquake". However due to the merit of usability and convenience ,the demand or necessity of this kind of structures are so high in not only buildings but also civil structures. ,shere are effective new techniques to make pilotis type structures safe enough against strong earthquake.
The mission of the technical committee is to develop and report information on prestressing techniques used not only for improving vertical load carrying capacity but for other purposes such as enhancing seismic performance and designing environmentally-friendly "decomposable"structures by unbonded tendons.
Concrete must be constructed by an appropriate placing method and have the required performances (strength, durability, etc.) so that a concrete structure may have necessary performances. Therefore, the mixture proportion of concrete is determined on the test results done in the room beforehand. At the stage of the execution, the slump test etc. is done in order to confirm whether the concrete can be accepted or not. However, it is not suitable to judge the performance of fresh concrete, which has several properties, by slump test. The construction performance of concrete with the same slump is not always constant due to the different viscosity. The evaluation method to judge whether the fresh concrete has excellent construction performance is needed. The committee will propose the simple method to represent the performance of fresh concrete. The construction at oversea is increasing. It is profitable to understand overseas circumstances. The technique for improving the reliability of construction management is established while analyzing and evaluating the oversea information. Sometimes, maximum size of aggregate in the test piece is different from that in concrete structures. However, the characteristic such as concrete strength is required in the design. In the committee, the adjusting factor to represent the correlation between concrete test and concrete performance in construction is going to be discussed. The factor discussed in this committee will contribute to the reliability of concrete structures designed according to present design method.
There are many ideas on autogenous-healing phenomena in cementitious materials, such as rehydration of unhydrated cement at cracks, artificial systems using sensors to detect damage of concrete and actuators to repair it.) Although autogenous-healing phenomena have been recognized in cementitious materials, there is few application using the function passively. One of the reasons might be the difficulty of its quantitative evaluation. Particularly, recovering performance, conditions to obtain autogenous-healing phenomena and evaluation methods have not been clarified.
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JCI-TC081A Technical Committee on Minimization of Global Warming Substrances and Wastes in Concrete Sector
Environmental problems are now being considered and recognized as the most important issues in our socioeconomic activities. This is because it is becoming more likely that the dramatic increase in resource and energy consumption in recent years and its consequential problems may even threaten the survival of the mankind. At present, efforts to reduce environmental impacts are being made in various industries, and the concrete field is no exception.
Objective of this committee is to establish recommendation of prediction and modification methods of time dependent of cement-based material, such as autogenous shrinkage, drying shrinkage, creep, and so on.
Damages caused by alkali aggregate reaction, ASR, are widespread in Japan. There are extremely severe damages such as breakings of rebars. On the other hand, majority of damaged structure is assumed appropriate to be watched for the progress. Recently structural safety and the retrofit methods of deteriorated structures have been discussed at a sub-committee on the countermeasures for the damage due to alkali silica reaction. However, regarding to the aspect of material science of ASR, there has been no committee activities after two research committees of JCI during 1980's and there is no guideline for ASR diagnosis.
The purpose of this committee is to clarify the present state, technical issues and future perspective of high-strength/high-performance/high-ductility concrete structures. Existing data of performance, analysis and design of members and structures of such concrete will be collected and surveyed. As a result, technical guides to be used for developing and spreading the technology of such concrete will be provided. Results of the activity of this committee will be presented first at the international symposium to be held in Japan in autumn 2008.
Nowadays nonlinear analysis methods are becoming common tool at design and performance verification. To make full use of the methods and to obtain reliable computed results, the knowledge on appropriate combination technique of various constitutive laws, problems related to material softening and so on are required. So far, the validity and reliability of the results were confirmed by some engineers who have accumulated a certain amount of experience. What we have to think about under the condition that the nonlinear analysis methods are becoming common tool in a world of concrete structure design is to develop general procedure on preparatory measures and operation for analysis and then assessment of the results. This can contribute improvement of the credibility of the nonlinear analysis methods and, what is more, promotion of utilization of the method. Consequently, the committee will study the following items with the aim of improvement of reliability of the nonlinear finite element method. In the committee, two working group called WG1 and WG2 will be set up. WG1 will prepare a guideline which contains analysis procedure and points to remember. On the other hand, WG2 will survey the state of the art and carry out some parametric analyses which are required for preparation of the guideline.
Frost damage is one of the most common deterioration of concrete structures. Though huge amount of relevant researches have been made so far, we still have many deteriorated structures suffering from cracking and/or scaling due to freezing-thawing action. Furthermore, it is not clear how much structural influence those deteriorations bring to structures.
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