Application Of High Performance Concrete Research Articles

Effect of Curing Methods on Durability of High-Performance Concrete

Many state departments of transportation are currently either using high-performance concrete (HPC) or developing new mix proportions for the application of HPC to transportation structures, with emphasis on bridge decks. However, many state engineers have observed that curing methods and conditions in the field affect the behavior of HPC structures. Moreover, little is known about the effect of curing on the long-term durability of HPC. Therefore, it is necessary to understand the behavior of HPC under various curing conditions and durations and the effect of pozzolanic material such as fly ash and silica fume on rapid chloride permeability (RCP). These factors were studied as part of a project for the New Jersey Department of Transportation to develop and implement mix design and technical specifications for HPC transportation structures such as pavements and bridges. Several mixes were tested, and the best mix was selected on the basis of strength and shrinkage test performance. The long-term durability was assessed by tests for RCP, creep, and freeze–thaw behavior. Moreover, the effect on HPC of four curing methods—moist curing, air-dry curing, burlap wrap, and curing compound—was investigated. Moist-cured cylinders performed better than those cured with other methods, and a minimum of 14 days of cure was required for HPC to attain its full strength.

Practical Issues for the Application of High-Performance Concrete to Highway Structures

The advantages of high-performance concrete (HPC) have been well documented in recent years. These include enhanced design flexibility and improved durability performance resulting in reduced maintenance costs and an increased service life. In spite of these obvious benefits, implementation of HPC has been very slow. This can be attributed to several factors including the uncertainty related to current design codes and a lack of familiarity of designers and contractors with proper design and construction practices and requirements for HPC structures. This paper introduces and discusses some fundamental issues that affect the implementatation of HPC and impact the practitioner. These include those related to quality control/quality assurance, specifications, material performance, and structural behavior. Within the scope of this discussion, the fundamental differences and similarities between HPC and conventional concrete are discussed. The aim is to provide the practicing engineer with a conceptual understanding of the practical issues that affect the design and use of HPC for highway structures with the desire to further stimulate the implementation of HPC.

Application of High-Performance Concrete to High-Rise Building in Taiwan

The research and development of high-performance concrete (HPC) that can give both high flow characteristics and high strength have attracted wide interest in Taiwan. The construction of the 101-storey Taipei Financial Center and the 85-storey Tungtxt & Chingtai (T&C) Tower requires the slump to be in the range of 230 – 270 mm, the initial slump flow in the range of 580 – 620 mm and slump more than 230 mm after 45 minutes, as well as a 56-day compressive strength of over 56 MPa. The HPC mix is designed using a densified mixture design algorithm which aims to achieve the lowest cement content. With the addition of pozzolanic materials such as fly ash, the workability is much improved because the shape of fly ash is spherical. After one-year of strict quality control, the HPC achieve consistent workability and excellent strength. This indicates that the appropriate use of local industrial by-product materials can produce HPC of the required design strength.

Structural Design of High-Performance Concrete Bridge Beams

Recently high-performance concrete (HPC) has been used in highway bridges and has gained popularity for its short-term and prospective long-term performances. Benefits of using HPC include fewer girder lines required, longer span capacity of girders, reduced creep and shrinkage deformation, less prestress losses, longer life cycle, and less maintenance of bridges. Research has been conducted on several issues of structural design of HPC bridge beams. The topics discussed include the effects of section properties of prestressed concrete girders, allowable tensile and compressive stresses, creep and shrinkage deformations of HPC, and prediction of prestress losses with HPC. The results from a parametric study have shown that a section that can have a large number of strands placed in its bottom flange is more suitable for HPC applications. The use of 15-mm-diameter prestressing strands allows the higher prestressing force applied on sections and can provide more efficiency in HPC bridges. The research results also indicate that the allowable compressive strength of HPC has a major effect on the structural design of bridges, whereas the allowable tensile stress has a minor effect on the design. Equations for predicting prestress losses based on the experimental and analytical results are recommended. The recommended equations consider the effects of lower creep and shrinkage deformations of HPC.

Developments and applications of high-performance concrete

In High Performance Concrete structures, both the increased strength as well as the improved microstructure can be utilized. Both effects are achieved using an optimized concrete technology, namely an extremely low w/c-ratio and the addition of silica fume. In the case of High Performance Concrete, reinforcement can be minimized and/or the dimensions of the structural members can be reduced. This type of concrete is mainly used for columns, walls, etc. within high-rise buildings, as an alternative to steel structures. However, in comparison with normal reinforced concrete structures, some additional measures are necessary to obtain an adequate fire resistance. Some interesting applications for high-rise buildings in Germany are presented. The dense microstructure of HPC is mainly used in case where, because of chemical attack or abrasion, additional protective measures are necessary in normal concrete structures. These measures can be avoided by using such a concrete.