The fracture surface in HSC is smooth. The fracture surface in NSC is rough. Aitcin recommends using fine aggregates with higher fineness modulus around 3. It is also required that the cement is compatible with chemical admixtures to obtain the high-strength.
High-strength concrete mixtures already have large amounts of small particles of cement and pozzolan, therefore fine particles of aggregate will not improve the workability of the mix; The use of coarser fine aggregates requires less water to obtain the same workability; and During the mixing process, the coarser fine aggregates will generate higher shearing stresses that can help prevent flocculation of the cement paste.
Guidelines for the selection of materials For the higher target compressive strength of concrete, the maximum size of concrete selected should be small, so that the concrete can become more dense and compact and less void ratio.
Fewer aggregate particles are broken.
Up to 70 MPa compressive strength can be produced with a good coarse aggregate of a maximum size ranging from 20 to 28 mm. While silica fume is usually not really necessary for compressive strengths under 70 MPa, most concrete mixtures contain it when higher strengths are specified.
The low-water to cement ratio used in high-strength concrete makes the concrete denser and the aggregate may become the weak link in the development of the mechanical strength. The particle size distribution of the fine aggregates plays an important role in the high strength concrete.
To produce MPa compressive strength aggregate with a maximum size of 10 to 20 mm should be used. Consequently, there is a reduction of the thickness of the interfacial transition zone in high-strength concrete.
To date, concretes with compressive strengths of over MPa have been produced, with 10 to 14 mm maximum size coarse aggregate. The particle size distribution of fine aggregate that meets the ASTM specifications is adequate for high-strength concrete mixtures. Using supplementary cementitious materials, such as blast-furnace slag, fly ash and natural pozzolans, not only reduces the production cost of concrete, but also addresses the slump loss problem.
Experience has shown that low-C3A cements generally produce concrete with improved rheology. The fracture develops along the transition zone between the matrix and aggregates. Materials for High Strength Concrete Cement Cement composition and fineness play an important role in achieving high strength of concrete.
The densification of the interfacial transition zone allows for efficient load transfer between the cement mortar and the coarse aggregate, contributing to the strength of the concrete. His reasoning is as follows: Aggregate Selection of right aggregates plays an important role for the design of high-strength concrete mix.
Extreme care is necessary, therefore, in the selection of aggregate to be used in very high-strength concrete. For very high-strength concrete where the matrix is extremely dense, a weak aggregate may become the weak link in concrete strength. The cracks move without discontinuities between the matrix and aggregates.
The optimum substitution level is often determined by the loss in or hour strength that is considered acceptable, given climatic conditions or the minimum strength required.While high strength concrete is defined purely on the basis of its compressive strength, Mehta and Aitcin defined the high-performance concrete (HPC) as concrete mixtures possessing high workability, high durability and high ultimate strength.
High performance concrete (HPC) is a specialized series of concrete designed to provide several benefits in the construction of concrete structures that cannot always be achieved routinely using conventional ingredients, normal mixing and curing practices.
High-performance concrete (HPC) is concrete that has been designed to be more durable and, if necessary, stronger than conventional concrete.
High-performance concrete is a term used to describe concrete with special properties not attributed to normal concrete. High-performance means that the concrete has one or more of the following properties: low shrinkage, low permeability, a high modulus of elasticity, or high strength.
ACI. Oct 22, · The main objective of this High Performance Concrete (HPC) Structural Designers’ Guide, referred to as the “Designers’ Guide” throughout, is to provide a source of information to structural designers for the design and construction of highway bridges and related structures.
High Performance Concrete.
HPC concretes are usually designed using materials other than cement alone to achieve these requirements, such as flyash (from the coal burning process), ground blast furnace slag (from the steel making process, or microsilica fume (from the reduction of high quality quartz in an electric arc furnace).Download