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International Concrete Abstracts Portal

Showing 1-10 of 39 Abstracts search results

Document: 

SP121-38

Date: 

November 1, 1990

Author(s):

Kaare K. B. Dahl

Publication:

Special Publication

Volume:

121

Abstract:

Presents the results of an investigation undertaken at the Technical University of Denmark to determine the parameters that affect the ultimate load capacity of a concrete structure subjected to concentrated loads originating from reinforcement bars bent 90 deg. The following parameters have been found to have a decisive influence on the ultimate load capacity of the concrete bar: bar diameter, internal height of the specimen, side concrete cover, and concrete compressive strength. The results show that the relative load-carrying capacity of the concrete åc / fc decreases for increasing concrete compressive strength. However, the use of high-strength concrete (HSC) still results in an increase in the absolute load-carrying capacity of the concrete whencompared to normal strength concrete (NSC).

10.14359/2870


Document: 

SP121-37

Date: 

November 1, 1990

Author(s):

S. Helland

Publication:

Special Publication

Volume:

121

Abstract:

In Norway, almost every car is equipped with tires that have small steel studs to improve the traction between the tire and the road for driver control during the winter season. These studded tires have an enormous wearing effect on ordinary asphalt pavement. Roads with the heaviest traffic near the major towns need to be resurfaced at intervals of 1 to 2 years. To improve the abrasion resistance, application of high-strength concrete instead of asphalt has been started. The national Norwegian cement producer has performed a large-scale investigation to determine the relation between concrete composition and abrasion resistance. The results prove that a 100 MPa concrete might approach the same properties as massive granite. The paper describes a number of projects performed by an independent company, where this high-quality material has been utilized in practical construction.

10.14359/3793


Document: 

SP121-36

Date: 

November 1, 1990

Author(s):

A. Takahata, T. Iwashimizu, and U. IshibashiI

Publication:

Special Publication

Volume:

121

Abstract:

Results of studies on the application of a high-strength concrete, with compressive strength of 42 to 60 MPa, to a high-rise reinforced concrete residence are presented. First, experiments were performed in accordance with the construction procedure, applying full-scale test structure modeling on part of the actual building. As a result, workable high-strength concrete was achieved by using a high-range water-reducing agent at the plant where concrete is being manufactured, and by adding a superplasticizer and placing the concrete carefully on site. In addition, for the quality control method of a ready-mixed concrete, water-cement ratio measurement before placement was useful. It is desirable to control the structure strength of high-strength concrete by not only using a test specimen cured in water on site, but also by taking out core specimens. Secondly, requirements for a construction method were set, by reference to the test results, and construction of the actual building was undertaken. Results of all the tests satisfied the requirements necessary to demonstrate the stable manufacturing control of ready-mixed concrete.

10.14359/3448


Document: 

SP121-35

Date: 

November 1, 1990

Author(s):

Erhard G. F. Chorinsky

Publication:

Special Publication

Volume:

121

Abstract:

Concrete repair materials applied in thin layers often fail under severe weathering conditions and high loading due to sensitivity in the bonding area to water, alkalinity, and mechanical strain. High-strength concrete, with its dense cement matrix, makes it even more difficult to connect repair materials to the old concrete. More than 15 years of experience in development and use of different systems for repair of high-strength concrete has shown that cementitious mortars with modification by high amounts of superplasticizers perform best. Practical aspects of application are shown on a large project carried out on a high-strength concrete floor in an airplane hangar. Cementitious repair systems are suitable for any kind of high-strength concrete repair where adequate surface preparation and the application of a special cementitious bridging agent is provided, but have to be adopted to the individual job site conditions. Shrinkage compensation techniques and sophisticated curing methods have to be used to achieve improved results with respect to drying shrinkage cracking. The durability of high-strength floor repairs with new technologies, used on a large scale in Europe, has proved to be reliable even under severe service conditions.

10.14359/3444


Document: 

SP121-34

Date: 

November 1, 1990

Author(s):

M. Berra and G. Ferrerra

Publication:

Special Publication

Volume:

121

Abstract:

Reports on high-strength lightweight and normal weight concretes. Sintered fly ash lightweight aggregates, crushed limestones, and two types of cement with different contents were investigated. All the concretes contained silica fume and a high-range water-reducing admixture. To obtain high specific strengths (i.e., ratio of strength to relative density), lightweight concretes were prepared with only lightweight particles (coarse and fine), reaching strengths higher than 60 MPa with density of about 1700 kg/m3. The results of physical (permeability, thermal conductivity, thermal diffusivity, and thermal expansion coefficient) and mechanical (compression, direct tension, direct shear, modulus of elasticity, bond strength, fracture energy, and compression softening behavior) tests, carried out on specimens cured for different ages at two curing conditions (20 C and 95 and 50 percent relative humidity, respectively), are reported and discussed.

10.14359/2576


Document: 

SP121-33

Date: 

November 1, 1990

Author(s):

V. Novokshchenov and W. Whitcomb

Publication:

Special Publication

Volume:

121

Abstract:

Describes production and properties of lightweight concretes based on a recently developed expanded siliceous aggregate. With the unit weight below 20 lb/ft3, this aggregate is one of the lightest among aggregates obtained by processing natural materials, after expanded perlite and exfoliated vermiculite. It was expected that this aggregate would be most effective in manufacturing moderate strength concretes with the unit weight ranging from 50 to 85 lb/ft3 and compressive strengths below 2500 psi. Recent experiments show that, in addition to this traditional application, the expanded siliceous aggregate can also be used to manufacture structural and even high-strength concretes with compressive strengths 10,200 psi and greater.

10.14359/2571


Document: 

SP121-32

Date: 

November 1, 1990

Author(s):

Min-Hong Zhang and Odd E. GjorvI

Publication:

Special Publication

Volume:

121

Abstract:

Pore structure, density, and strenght may vary within a wide range for different types of lightweight aggregate. Hence, not all types of lightweight aggregate are suitable for production of high-strength concrete. In the present work, the significance of various lightweight aggregates on the concrete strenght and density was studied. Twenty-eight-day compressive strengths up to 102 MPa, corresponding to a density of 1865 kg/m3, were obtained. The type of lightweight aggregate appears to be the primary factor controlling both the density and the strength. For high-strength lightweight concrete, it is difficult to predict the 28-day strengths from early strengths because of the influence of the aggregate.

10.14359/3778


Document: 

SP121-31

Date: 

November 1, 1990

Author(s):

V. M. Malhotra

Publication:

Special Publication

Volume:

121

Abstract:

Reports results of a study undertaken to develop high-strength lightweight concrete having compressive strength of about 700 MPa and a density of less than 2000 kg/m3. The materials used consisted of an expanded shale lightweight aggregate of Canadian origin, ASTM Type III cement, low-calcium fly ash, and condensed silica fume. A series of 7 concrete mixtures involving 14 concrete batches were made. The cement or cementitious material content of the mixtures ranged from 300 to 600 kg/m3. All mixtures were air entrained and superplasticized. A large number of test cylinders and prisms were cast for the determination of mechanical properties and drying shrinkage of concrete. From the results of this investigation, it is concluded that concrete with a compressive strength of about 70 MPa at 365 days and density of less than 2000 kg/m3 can be made incorporating supplementary cementing materials. The highest compressive strength achieved was 69.3 MPa at 365 days for a mixture with a cementitious material content of 600 kg/m3 of concrete; the highest flexural strength obtained was 8.7 MPa at 28 days.

10.14359/2567


Document: 

SP121-30

Date: 

November 1, 1990

Author(s):

George c. Hoff

Publication:

Special Publication

Volume:

121

Abstract:

Briefly reviews five joint industry-research programs pertaining to offshore concrete structures. These programs were sponsored by the oil and gas industry and related construction industries. These studies, conducted in both North America and Norway, included the use of high-strength, lightweight aggregate concretes in both material and structural evaluations. Selected characteristics of the high-strength, lightweight aggregate concretes used in these studies (such as ductility in reinforced concrete elements, punching shear behavior, and fatigue characteristics) are summarized. Future research needs are discussed.

10.14359/3768


Document: 

SP121-29

Date: 

November 1, 1990

Author(s):

Norio Marushima, Kenji Kuroha, and Kuniyiki Tomatsuri

Publication:

Special Publication

Volume:

121

Abstract:

High-strength concrete tends to mean small water-cement rations, implying poor workability. This tendency becomes more pronounced when much higher strength is required, and conventional concreting processes cannot sufficiently guarantee high-quality work. In current construction work, therefore, maximum use has been made of precast concrete (guaranteeing quality and minimizing the need for concrete cast in situ) and a new high-performance, air-entraining, and plasticizing admixture has been used for the necessary in situ concrete. The concrete prepared in this way exhibited a mix strength of 55 MPa at best. This value, in itself, is by no means high, but meaningful efforts to establish methods of concreting that insure still greater strength have been made. This construction work has demonstrated that combining the reinforced concrete (RC) layer method (which uses a large proportion of precast members) with high-strength concrete obtained from mixing with the new high-performance, air-entraining, plasticizing admixture is an extremely effective way to secure quality structures. Since this admixture is a novel product, the physical properties of the resulting concrete have been thoroughly checked to supplement the results of laboratory experiments and preliminary field tests.

10.14359/3758


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