Properties of high strength concrete under uniaxial states of stress were studied. Main emphasis was given to tensile, compressive, and fracture properties of concrete with compressive strengths ranging from 6000 to 12000 PSI. Complete stress-deformation curves under uniaxial tension were obtained using a closed-loop servo-hydraulic testing system. Important mechanical and fracture properties such as moduli of elasticity, fracture energy, and the critical crack tip opening displacements, were evaluated from the experimental results. Fracture energies were evaluated from the descending branch of stress-crack separation curves using the direct tension test results. For the range of high-strength concretes studied, experimental results indicate that the relationship between tensile and compressive strengths are different from those of normal strength concretes. Comparison of stress-deformation curves in tension reveals a significant decrease in post peak compliance of the higher strength concretes.

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.

This paper provides a summary of part of the results of SHRP project C-205 on the Fresh and Hardened Properties of High Early Strength Fiber Reinforced Concrete (HESFRC). HESFRC was defined as achieving a minimum target compressive strength of 5 ksi (35 MPa) in 24 hours. Fresh HESFRC properties included air content, inverted slump test, temperature, and plastic unit weight. Tests on the mechanical properties included compressive strength, elastic modulus, flexural strength, splitting tensile strength, and fatigue life. Seventeen different combinations of parameters were investigated for each type of test. The main parameters included: (1) three different matrix mixtures (one control, one with silica fume, and one with latex), (2) two different volume fractions of fibers (1 percent) and (2 percent), (3) two fiber materials (steel and polypropylene), (4) two steel fiber lengths corresponding to aspect ratios of 60 and 100 respectively, and (5) hybrid mixes containing either an equal amount of steel and polypropylene fibers, or an equal amount of steel fibers of different lengths. The compression and the bending tests also included a time variable; the compressive properties were measured at ages 1, 3, 7, and 28 days, and the bending properties at ages 1, 7, and 28 days respectively. Information from the compression tests comprised the compressive strength, the elastic modulus, and the strain capacity. Information from the bending tests included the modulus of rupture and the toughness indices as per ASTM standards. Optimum mixtures that satisfied the minimum compressive strength criterion, and showed excellent values of modulus of rupture, toughness indices in bending, and fatigue life in the cracked state are identified. Potential applications in repair, rehabilitation, or construction of transportation structures are suggested. In this paper a description is given of key results of the bending tests only.

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.

High-performance concretes (HPC) characterized by a low water/binder ratio and generally high binder content which may include supplementary cementing materials, are used increasingly in the worldwide construction industry for technical or economical reasons as well as for their improved durability. The development and the use of such a high performance material necessitate some drastic readjustments within the construction industry. Concrete should not be envisaged as a commodity material that has to be produced with the cheapest materials and placed and cured in the cheapest ways. Concrete should rather be considered as an elaborate material for which constituents are carefully selected in order to achieve the desired performance. Of special importance are the selection of a compatible cement/superplasticizer combination and clean, strong, and well shaped aggregates. The use of cementitious materials should be considered not only because they can reduce the production cost of high performance concretes but also because they can be technically advantageous. Making and using HPC necessitate the implementation of a strong and efficient quality control program on the materials used to make the concrete, on the properties of the fresh and hardened concrete, and on the placing and curing techniques in order to be sure of obtaining a high performance final product. Testing high performance concrete necessitates great care and special attention.