International Concrete Abstracts Portal

Although the cement-paste matrix is intrinsically protective to steel, it also permits the ingress of deleterious agents that leads to its own progressive deterioration and consequent destabilisation of steel. Further, the development of a highly impermeable cement matrix, per se, may not ensure a high- performance concrete structure in practice, since the development of strength and pore structure are both time-dependent phenomena and aggressive elements somehow find a means of penetrating concrete and initiate a cumulative process of structural damage. This paper advocates an integrated design philosophy from concept to completion and during service life of a concrete structure. It is shown that by selecting concrete constituents that encourage synergic interactions, it is possible to develop a concrete matrix of high strength and excellent durability. However, concrete also needs to be protected from aggressive agents to enable it to attain its full potential and examples are given to show how such techniques can be adopted to ensure durable service life even in the most unfriendly environment. The application of this integrated design strategy is further illustrated with the design of columns exposed to alkali-silica reactivity and the production of cost-effective, fiber-reinforced thin sheets.

Flowable concrete has been used for a long time in Thailand and has been known as tremy concrete for bored pile construction. For this type of concrete, strength may be less important in early development, but workability must satisfy the performance in construction. In the second stage of development, research has concentrated on high strength concrete. Even though higher strengths have been achieved, workability of the concrete may be slightly poor. Several studies have emphasized utilization of concrete here high strength can be an advantage. The structural members were both reinforced concrete and prestressed concrete; and the emphasis was placed on flexure, shear, and compression. In recent development, both workability in the fresh state and strengths in the hardened states have been considered so as to satisfy the performance in workability, strengths, serviceability, and durability. Efforts have been concentrated on constituent materials for high performance concrete, mix proportions, and concrete properties. Satisfactory structural behaviors for compression, flexure, and shear in reinforced and prestressed concrete members have been reported. Various developments to suit particular applications such as bored pile, mass concrete, structural concrete, and durable concrete have been made for the construction industry. Demands of HPC are growing, further development and utilization are expected.

Taiwan, with a population of over 21 million and situated within only 36,000 sq km of land, has achieved miraculous economic growth in the last 20 years. This economic achievement has transformed the national image from one of underdeveloped work force to that of a global economic power. The mass volume of concrete construction which has occurred during the transition period has resulted in the near exhaustion of natural resources such as limestone, river gravel, and river sand. Diminishing supplies of limestone for the manufacture of cement and aggregate for making concrete have resulted in serious shortages over the last four years. In response to the crisis, the Architecture and Building Research Institute (ABRI) of the Ministry of Interior initiated a research program in 1991 to investigate all concrete-related industries in the private sector. A team of six professors and ten graduate students from five prominent universities were asked to examine these problems and to draft a national strategy to resolve the crisis at hand. The program was completed in June, 1992 and the final report is being used to guide the process of bolstering the domestic concrete industry. This aper presents an overview of current problems existing in the concrete related industries, methods used in investigations, and suggested topics for current and future research. The proposed research programs were subsequently divided into three term stages with the objective of avoiding possible delays with the on-going Six-Year National Construction Plan and laying down a sound foundation for the development of high performance concrete (HPC) technologies in Taiwan. With the support from governmental agencies, high performance concrete has been successfully used in the construction of a few major highway bridges and an 85- story high-rise building that is currently under construction in Kao-Hsiung, the second largest city in Taiwan.

Ferrocement is a type of thin-wall reinforced concrete with high performance characteristics such as high tensile strength to weight ratio, ductility, and impact resistance. Basic considerations of the materials used, fine galvanized wire mesh and a cement mortar coupled with its good crack controlling characteristics, indicated that ferrocement will provide better durability, ease of maintenance, and lower life cycle cost. It can be cost competitive through mechanized production and proper choice of reinforcement. The National University of Singapore has since the early 1970's made considerable efforts in popularizing ferrocement through research and development. Several studies have been conducted on the application and performance of prototype ferrocement structural elements. Some of the applications such as sunscreens, secondary roofing slabs, and water tanks for high-rise buildings are presented in this paper.

This paper reviews the developments of HPC in France for the past ten years in bridges, buildings, tunnels, offshore platforms, and nuclear containers. Different projects are presented wherein 55 to 80 MPa concretes were used. The motivation for using HPC are many. The future developments initiated by owners, public research institutes, consultants, and contractors are documented and innovative materials are introduced, as well as research program initiated by different laboratories.