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International Concrete Abstracts Portal

Showing 1-10 of 14 Abstracts search results

Document: 

SP140-14

Date: 

September 1, 1993

Author(s):

J. M. Shilstone, Sr., and J. M. ShilstoneI, Jr.

Publication:

Special Publication

Volume:

140

Abstract:

The paper provides guidelines for the development of concrete mixtures that will function in an aggressive environment. Performance will be based upon durability and not high strength. In few cases will strength greater than 5000 psi (34.4 MPa) be of structural value. Some concrete has performed well in severe environments for more than 100 years while some newer concretes exposed to similar environments have deteriorated prematurely. Attention to basic concrete technology during the early years contributed to long-term durability. in the authors' opinions, emphasis on strength without regard to special needs for durability contributed to the current performance problems. Graphical means are suggested whereby the need for high performance concrete for durability can be identified by project type and environment. The requirements for various durability requirements are listed and summarized in a cross reference table that can aid in translating qualitative measures into quantitative terms.

10.14359/3915


Document: 

SP140-13

Date: 

September 1, 1993

Author(s):

W. F. Kepler and K. F. Von Fay

Publication:

Special Publication

Volume:

140

Abstract:

Theodore Roosevelt Dam is a rubble-masonry dam, located on the Salt River, 76 miles northeast of Phoenix, AZ. The dam will be modified by adding a mass concrete gravity section to the downstream face of the dam. Over 350,000 yd 3 of mass concrete will be placed. A high-performance mass concrete mixture was developed that met conflicting low heat and strength development requirements. The mixture needed to meet thermal requirements of no more than 45 F total adiabatic temperature rise in 20 days, and less than 5 F adiabatic temperature rise after 20 days. In contract, the mixture needed to meet early-age compressive strength requirements of 1000 psi between 3 and 7 days and have sufficient paste to insure bond between the new concrete and the original masonry structure. The Bureau of Reclamation developed a concrete mixture with a 4-in. maximum-sized-aggregate (MSA), containing 270 lb of cementitious material per pubic yard that met design requirements. The cementitious material consisted of 80 percent cement and 20 percent fly ash. A low-heat, Type II cement was used, with a heat of hydration of 65 calories per gram at 7 days. The fly ash is an ASTM class F ash. The concrete has a water-to-cementitious materials ration of 0.53. The mixture is very workable, and reaches a compressive strength of 1100 lb/in.¦ in 7 days. It has a total adiabatic temperature rise of 43.4 F, with only 2 F temperature rise after 20 days.

10.14359/3914


Document: 

SP140-12

Date: 

September 1, 1993

Author(s):

L. D. Wakeley, T. S. Poole, J. J. Ernzen, and B. D. Neeley

Publication:

Special Publication

Volume:

140

Abstract:

Concrete is an essential component of the seal system planned for geologic repository under development for disposal of defense-generated radioactive wastes in the U.S. Performance requirements for concrete at this facility are unique: mass-concrete seals will be placed underground in a region where all the groundwaters are rich in chloride, and some also are highly concentrated in magnesium and sulfate ions. Sodium chloride in brines presents less of a problem than do other ions. In experiments simulating the worst-case of brine composition and availability, the nature and extent of deleterious chemical reactions were determined for materials being considered for use in mass concrete for a repository. Chemical degradation of cement pastes related to this concrete included loss of calcium and precipitation of magnesium compounds, and formation of other sulfate- and chloride-bearing phases. Calcium was lost first from calcium hydroxide and then from C-S-H. Strength loss is attributed principally to loss of these phases, and not to substitution of magnesium for calcium in hydration products.

10.14359/3913


Document: 

SP140-11

Date: 

September 1, 1993

Author(s):

G. J. B. Ithurralde and J. L. Costaz

Publication:

Special Publication

Volume:

140

Abstract:

To insure the tightness function of nuclear reactor containments, a special high-performance concrete (HPC) having a high silica fume content (30 kg/m 3) and a low cement content (270 kg/m 3) has been developed. The aim of this concrete formulation, which has a 28-day compressive strength of about 75 MPa and very good workability, is both to control the risk of cracking of the concrete in the structure and to reduce creep. This paper describes the feedback from experience acquired in the construction of the first HPC containment built in Civaux, France. The advantages and the difficulties encountered and overcome in the use of this material are presented, together with the results of tightness tests of the structure. The industrial mastery now achieved of this special HPC formulation also made it possible to take the performance of this concrete into account in the engineering of the work. This led to a new containment design, presented in this paper, combining HPC and very strong prestressing using 55 T 15 cables. This new design substantially improves the safety of nuclear reactors for severe accidents (core melting and hydrogen deflagration): the structure is guaranteed gas-tight up to an internal pressure of about 1 MPa.

10.14359/3912


Document: 

SP140-10

Date: 

September 1, 1993

Author(s):

J. Moreno and G. Detwiler

Publication:

Special Publication

Volume:

140

Abstract:

On April 13, 1992, the engineer of the Merchandise Mart, one of Chicago's downtown buildings, reported flooding of the building basement. A few hours later flooding was found to be related to an eddy observed at the Chicago River. The flooding was occurring through a system of service tunnels built at the beginning of the century and abandoned in the late 1940s. The failure of the tunnel was caused by wood pilings installed at the end of 1991 to protect the bridge abutment in the Chicago River. The flooding of these tunnels affected more than 100 downtown Chicago businesses, which had to be evacuated for several weeks. The repair of the tunnel was conducted in two stages using high-performance concrete (HPC). First, an interim plug was placed using a high-performance, underwater concrete. The severe environment caused by the current in the tunnel required concrete to be highly fluid, have anti-washout properties, set quickly, and gain strength rapidly Second, a permanent plug was placed using HPC concrete designed to reduce heat of hydration and minimize potential for thermal cracking. Actual temperature of the permanent plug was monitored by thermocouples and compared to a computer-generated model. The use of this system to predict performance of special concretes allowed the concrete supplier to start a new generation of high-performance concretes.

10.14359/3911


Document: 

SP140-09

Date: 

September 1, 1993

Author(s):

N. Hasan, E. Faerman, and D. Berner

Publication:

Special Publication

Volume:

140

Abstract:

Underwater repairs to, and rehabilitation of, existing reinforced concrete velocity caps of the circulating water intake structure at St. Lucie Powerplant, Fort Pierce, Florida were made utilizing high-performance in a marine environment. Use of this repair technique avoided the necessity of constructing a cofferdam for repair work in the dry, and thus minimized interruption to plan operation, and resulted in considerable savings. Mix proportions for the high-performance concrete included cement, fly ash, silica fume, and antiwashout admixtures as well as high-range water-reducing and set-retarding admixtures. The mix proportions were tested extensively in the laboratory and field conditions to optimize the slump and the initial setting time of concrete while assuring early compressive strength requirements for conformance with the specified requirements. Large scale mock-up tests, utilizing both tremie and pumping methods, were conducted to simulate under water placement in the surf zone and to select the actual concrete placing method, rate of placement, and to identify surface preparation and protection requirements. Construction procedures for the new reinforced concrete slabs involving approximately 3000 yd 3 precast and tremie concrete utilizing a barge-mounted concrete batch plant; quality control and post-placement inspection measures are also discussed.

10.14359/3910


Document: 

SP140-08

Date: 

September 1, 1993

Author(s):

N. Miura, N. Takeda, R. Chikamatsu, and S. Sogo

Publication:

Special Publication

Volume:

140

Abstract:

In Japan, a new super-workable concrete, which has higher flowability and filling capacity, has attracted attention as being effective in rationalization of concrete execution. It can be applied for simplifying placing work while securing high quality of reinforced concrete structures. Especially in case of heavily reinforced structures, it is highly applicable because of its excellent filling capacity or lower consolidation effort. For several years, the authors have studied improvements of workability of some special concretes, such as anti-washout underwater concrete, expansive grouting concrete for inverted placement, and ultra high-strength in-site concrete, and have consequently succeeded in developing super-workable concrete, suitable for rapid placing or perfect filling without consolidation. The authors also have established a new evaluating method for segregation resistance of mortar and aggregate, that is useful to design mix proportion, or keep high quality of super-workable concrete in site. Recently, opportunities to apply super-workable concrete to several actual structures with difficult construction conditions have arisen. One is the LNG (liquefied nitrogen gas) in-ground storage tank, which has much complicated reinforcement at the junction of base mat and side wall, another is a tall, thin reinforced concrete wall, which must be placed from upper point, 6 to 8 m in height. This paper describes the basic properties of super-workable concrete, the new method of quality control, and a summary of applications to reinforced concrete structures mentioned.

10.14359/3787


Document: 

SP140-07

Date: 

September 1, 1993

Author(s):

S. Kuroiwa, Y. Matsuoka, M. Hayakawa, and T. Shindoh

Publication:

Special Publication

Volume:

140

Abstract:

A super-workable concrete, which has excellent deformability and resistance to segregation and can be filled into heavily reinforced formwork without vibrators, was developed. This new type of concrete is made not only with the general materials for concrete such as ordinary portland cement, aggregates, water, and air-entraining water-reducing agent, but also with blast-furnace slag, fly ash, superplasticizer, and a newly developed viscosity agent. When the slump of this super-workable concrete is tested, diameter of the flow is more than 60 cm. Since the super-workable concrete has excellent durability as well as superior filling ability, it should be a proper concrete for projects under severe conditions. The super-workable concrete was employed in the construction work of a 20-story building. It was placed in the center-core from the basement to the third floor. The building was designed as a hybrid structure, in which the reinforced concrete core was surrounded by the steel structures. The specified design strength of the concrete was 480 kgf/cm 3 (47.1MPa). The greatest nominal diameter of deformed bars was 51 mm, and they were very congested. The super-workable concrete was produced in ready mixed concrete plants near the construction site, and 1500 m of the super-workable concrete was placed successfully. Through this project it was confirmed that the super-workable concrete can be supplied from general ready mixed concrete plants with practical care of quality control in materials.

10.14359/3909


Document: 

SP140-06

Date: 

September 1, 1993

Author(s):

M. R. Hansen, M. L. Leming, P. Zia, and S. Ahmad

Publication:

Special Publication

Volume:

140

Abstract:

Three types of High Performance Concrete (HPC) for highway applications were investigated: Very Early Strength (VES), High Early Strength (HES) and Very High Strength (VHS). Two of the objectives of the research were to measure the chloride permeability of these concretes and explore an alternate method using AC impedance. Many of the concretes had coulomb values of 4000 and higher, placing them in the "high permeability" category as specified by AASHTO T 277 - Rapid Chloride Permeability Test (RCPT). Coulomb values were also found to decrease with concrete age and with increased silica fume content. Coulomb values were found not to vary significantly with dosage of calcium nitrite used as accelerator, up to 6 gal/yd 3 (29.7 l/m 3). The AC impedance test results (ohms) were found to correlate well with the RCPT results (coulombs) and were sufficiently accurate to place the concretes in the proper chloride permeability category. The advantages of the AC impedance test are that it is faster and less expensive than the RCPT and it avoids the potential heating problem sometimes encountered in the RCPT. AC impedance was found to increase with concrete age and with increased silica fume content and decrease with increased calcium nitrite dosage.

10.14359/3908


Document: 

SP140-05

Date: 

September 1, 1993

Author(s):

J. J. Schemmel and M. L. Leming

Publication:

Special Publication

Volume:

140

Abstract:

In 1989, the Strategic Highway Research Program contracted with North Carolina State University to investigate the use of High Performance Concrete in highway applications. A major goal of this research project was to determine if HPC mixtures could be successfully produced in the field. In addition, an evaluation was to be made of the long-term performance of this material under field service conditions. Five field installations were constructed around the country for this purpose. The fresh and hardened properties of the concrete were found to be generally acceptable at each site. Some cracking has developed in a few sections. A set of recommendations with regard to the use of HPC in the field was developed as a result of the field work.

10.14359/3907


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