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Showing 1-10 of 92 Abstracts search results

Document: 

SP228

Date: 

June 30, 2005

Author(s):

Editor: Henry G. Russell

Publication:

Special Publication

Volume:

228

Abstract:

SP-228CD This CD-ROM of Special Publication 228 contains the papers presented at the Seventh International Symposium on the Utilization of High-Strength/High- Performance Concrete that was held in Washington, D.C., USA, June 20-24, 2005. The symposium continued the success of previous symposia held in Stavanger, Norway, (1987); Berkeley, California (1990); Lillehammer, Norway, (1993); Paris, France, (1996); Sandefjord, Norway, (1999); and Leipzig, Germany, (2002). The symposium brought together engineers and material scientists from around the world to discuss topics ranging from the latest applications to the most recent research on high-strength and high-performance concrete. In the years since the first symposium was held in Stavanger, there has been worldwide growth in the use of both high-strength and high-performance concrete. In addition to more research and applications of traditional types of high-performance concrete, the use of self-consolidating concrete and ultra-high-performance concrete has moved from the laboratory to practical applications. This publication offers the opportunity to learn the latest about these developments.

10.14359/16471


Document: 

SP228-96

Date: 

June 1, 2005

Author(s):

C. Magureanu, B. Heghes, and B. Rosca

Publication:

Special Publication

Volume:

228

Abstract:

Chemical attack poses a serious problem for concrete structures in severe environments. This investigation deals with exposure of high strength/high performance concrete to sulfate attack in a controlled environment. Experimental tests consisted of measuring the compressive strength, tensile strength and modulus of elasticity after 3 years of exposure to corrosive conditions consisting of chemical solutions containing 1%(NH4)2SO4 and 2%(NH4)2SO4.

10.14359/14551


Document: 

SP228-95

Date: 

June 1, 2005

Author(s):

A. Yonekura, H. Ito, S. Wakasugi, S. Goto, S. Numata, and H. Maeda

Publication:

Special Publication

Volume:

228

Abstract:

This study deals first with the deterioration of glass fiber in mortar due to the alkali of cement and how to improve the deterioration of the glass fiber in mortar using special admixture of blast furnace fume (BFF). The deterioration is estimated by an accelerated test for flexural strength of mortar stored in water at 80 °C for 3 weeks. Secondly, the deterioration of mortar due to sulfuric acid attack using blast furnace fume(BFF) is investigated. Dust collected from the top of Chinese small-sized iron blast furnaces is called BFF in Japan , and is used as admixture for high strength concrete in China. BFF is composed of very fine particles with spherical shape. Its average grain size is several micrometers in diameter. Test results of this first study shows that the deterioration of glass fiber in mortar due to alkali is not improved by using BFF alone but is significantly improved by using both BFF and blast furnace slag (BFS) or silica fume (SF). Concerning acid attack, it is found that the deterioration of mortar in dilute sulfuric acid is significantly decreased by using both of BFF and BFS or SF.

10.14359/14550


Document: 

SP228-93

Date: 

June 1, 2005

Author(s):

A. Sharma and R. Rambalack

Publication:

Special Publication

Volume:

228

Abstract:

The porosity of cement mortars can be reduced by decreasing the water cement ratio with corresponding addition of superplasticizer to maintain workability. Further, the pore structure itself can be modified by the incorporation of pozzolanic admixtures such as Silica Fume, and Ground Granulated Blast Furnace Slag (GGBFS) powder. The reduced water cement ratio combined with refined pore structure increases the compressive strength in addition to enhancement in durability characteristics. Such cement mortars are termed as High Performance Mortars. The paper highlights the findings of a project which investigated the sorptivity characteristics of mortar mixes using (a) different percentages of GGBFS partially replacing OPC (b) reduced water cement ratios using superplasticizer admixture to improve the workability of mixes and (c) combination of superplasticizer admixtures and GGBFS. It is concluded that High Performance Mortars can be obtained by modifying a conventional high strength mortar mix by reducing the water/binder ratio and adding pozzolanic admixtures and superplasticizers.

10.14359/14548


Document: 

SP228-92

Date: 

June 1, 2005

Author(s):

E.H. Hewayde, E.N. Allouche, and G. Nakhla

Publication:

Special Publication

Volume:

228

Abstract:

Corrosion of concrete sewer pipes by sulfuric acid attack is a problem of global scope. The current paper aims at evaluating two supplementary cementing materials metakaolin and geopolymer cement as partial cement replacements for improving the ability of concrete to resist severe sulfuric acid attack. Both, metakaolin and geopolymer cement were found to significantly improve the resistance of concrete made of Type 10 and 50E cements to 3% and 7% sulfuric acid solutions (pH of 0.6 and 0.3, respectively). Maximum weight loss reduction with respect to the control for specimens made of modified Type 50E cement ranged between 20% and 37%, depending on the additive and the concentration of the acid. Maximum weight loss reduction for specimens made of modified Type 10 cement range between 10% and 42%, depending on the additive and the concentration of the acid. For this test Type 10 cement was found to perform best in the presence of geopolymer cement while the performance of the Type 50E cement was best when metakaolin was used as partial replacement for cement. The results emphasize the important role that the nature and composition of hydration products and the completeness of the hydration process play in improving concrete resistance to acid attack.

10.14359/14547


Document: 

SP228-91

Date: 

June 1, 2005

Author(s):

B. Lin and Y. Cai

Publication:

Special Publication

Volume:

228

Abstract:

This paper presents an overview on durability of reinforced concrete in marine environment in China and relevant test methods based on comparison of results from laboratory and exposure tests. The test results of the reinforced concrete specimens, including ordinary concrete and high-performance concrete containing silica fume and other anticorrosion measures are comprehensively analyzed. The test data of the specimens exposed 3, 9, and 20 years in-situ in the South Sea and 3, 8, and 16 years in Huanghai Sea of China are reviewed. A comparison of test results between the laboratory and long-term exposure is made for evaluating their common characteristics and differences. Based on the Fick’s Law, the chloride ion penetration and diffusion characteristics in the concrete specimens exposed 16-20 years in marine environment are used to estimate the service life of reinforced concrete structures in marine environment. Recommendations for ensuring and improving the durability of the reinforced concrete in marine environment are provided.

10.14359/14546


Document: 

SP228-90

Date: 

June 1, 2005

Author(s):

T. Hassan and P. Zia

Publication:

Special Publication

Volume:

228

Abstract:

Low permeability is an important characteristic of durable concrete. Concrete of low permeability minimizes the entry of moisture and aggressive chemicals. It provides better corrosion protection of steel reinforcement and limits freezing/thawing damage of concrete. A variety of test methods using gas or liquid have been developed to measure the permeability of concrete, but most of them are costly and suitable for use only in the laboratory. A simple device and test method developed by Zia and Guth at North Carolina State University measures air permeability of concrete. The Zia-Guth device, consisting of two concentric cylindrical chambers, is adhered to the concrete surface by vacuum and measures the rate of pressure increase in the inner chamber as air flows from the outer chamber through the concrete and into the inner chamber. The device is economical, and its compactness and quick response time make it suitable for nondestructive testing of in-place concrete in the field. Permeability of concrete depends not only on the microstructure of the concrete but also on the moisture content in the concrete. This paper presents the results of an experimental study undertaken to evaluate the effect of moisture content on the air permeability of concrete using the Zia-Guth testing device. Three different types of concrete varying in w/cm ratio and admixture content were tested. The influence of moisture content of the concrete on airflow was examined by testing slab specimens (400 x 400 x 75 mm) for each type of concrete under different moisture contents and at different concrete ages. Test results showed that the measured permeability index could vary by 10 to 300 percent depending on the moisture content and the type of concrete. Based on test results, a general methodology is proposed to account for the effect of the moisture content of concrete on the air permeability of different types of concrete.

10.14359/14545


Document: 

SP228-89

Date: 

June 1, 2005

Author(s):

N. Suksawang, H. Nassif, and A. Mohammed

Publication:

Special Publication

Volume:

228

Abstract:

This paper presents results of a study conducted to identify the drying shrinkage and compressive creep of high performance/high strength concrete (HP/HSC).The study included an experimental program and a comparison of available analyticalmodels for predicting creep and shrinkage. Results from creep and shrinkage tests performed on different mixes (with compressive strengths up to 90 MPa) were compared with those from prediction models available in the literature. The effects of pozzolanicmaterials the creep and shrinkage were also investigated. Results show that while fly ash increases the compressive creep of concrete, silica fume decreases it. Furthermore, thedrying shrinkage of silica fume concrete is higher than fly ash concrete. Adding fly ash could reduce the drying shrinkage of silica fume concrete. Moreover, current creep and shrinkage prediction models need to be revised for the HP/HSC mixture.

10.14359/14544


Document: 

SP228-88

Date: 

June 1, 2005

Author(s):

M. Tanimura, M. Suzuki, I. Maruyama, and R. Sato

Publication:

Special Publication

Volume:

228

Abstract:

This study investigates the effectiveness of low shrinkage-high strength concrete (LS-HSC) using expansive additive and shrinkage-reducing agent with regards to the time-dependent structural performance of reinforced HSC flexural members. Design equation for evaluating the flexural crack width and deformation of RC beams considering the effect of shrinkage/expansion before loading are proposed on the basis of JSCE (Japan Society of Civil Engineers) Design Code of 2002. The results show that autogenous shrinkage of conventional HSC with no additives can significantly affect the time-dependent serviceability performance of the RC beams, while LS-HSC can markedly improve its serviceability performance. In addition, time-dependent flexural crack widths of reinforced LS-/conventional HSC beam, can be evaluated by the JSCE Code Equation, which takes into account the strain change in the reinforcement bars from the state where the stress in concrete at the depth of tension reinforcements is zero. Also, time-dependent as well as instantaneous curvatures of reinforced LS-/conventional HSC beam can be accurately calculated by the proposed equation. This equation takes into account the effect of the change in curvature due to the release of restrained-shrinkage/expansion stress at cracked section.

10.14359/14543


Document: 

SP228-87

Date: 

June 1, 2005

Author(s):

D. Cusson, T. Hoogeveen, and L. Mitchell

Publication:

Special Publication

Volume:

228

Abstract:

A comprehensive research program at the National Research Council Canada is underway to develop low-shrinkage high-performance concrete for the design of cost-effective and sustainable concrete structures. This paper presents the structural laboratory testing of large prismatic high-performance concrete (HPC) specimens under restrained shrinkage and tensile creep. A systematic testing approach is presented, including a description of the theoretical background and the experimental apparatus used. The structural behaviour of two different HPC mix designs are compared and documented. The control concrete had a water-cement ratio of 0.34 and a cement-sand-aggregate ratio of 1:2:2. A slight variation of this mix design included 6% sand replacement by pre-soaked porous expanded shale lightweight aggregate. One of the objectives of this study is to determine whether the addition of this type of aggregate could effectively reduce autogenous shrinkage due to internal drying in HPC. Test results show that 6% sand replacement by pre-soaked porous lightweight aggregate reduces autogenous shrinkage moderately. This moderate shrinkage reduction was accompanied by a moderate increase in tensile creep. The results also reveal that most internal drying and autogenous shrinkage developed shortly after setting in both concrete mixes. This observation suggests that solutions to preventing autogenous shrinkage cracking in HPC will involve techniques that should be effective shortly after setting.

10.14359/14542


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