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Home > Publications > International Concrete Abstracts Portal
The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts.
Showing 1-5 of 49 Abstracts search results
September 26, 2002
J. M. V. Gomez-Soberon
This study presents the experimental results on properties of concrete with replacement of natural aggregate by recycled concrete aggregate (RCA). Experimental data on the creep behavior of concrete mixtures (basic and drying creep) was obtained. The replacement factor of natural aggregate by RCA were 0%, 15%,30%,60% and 10096, and the test conditions were 50% RH and 20°C. The results of these trials were used to provide a comparison with results of tests on the reference concrete, for ages up to 270 days. The creep coefficient data (instantaneous, basic and drying) presented, along with the maximum strain and the specific creep data. The results reveal considerable increase in creep when is increase replacement of natural aggregate with recycled concrete aggregate. The drying creep, especially shower more significant increase when compared to the reference concrete.
In this paper we present theexperimental analysis of samples of concrete where portion of the natural aggregate were replaced with recycled aggregate originating from concrete (RCA). Experimental analysis to obtain the shrinkage properties (basic and dried) of the concrete containing recycled concrete aggregate (CRCA) was performed. The percentages of replacement of natural aggregate with RCA were 0%, 15%,30%, 60% and 100% with test conditions of 50% RH and 20°C. The results of these trials are compared with reference concrete tests, at an age of 270 days. The results demonstrated an increase in the shrinkage of the CRCA that is proportional to the am- of RCA used as a replacement for the natural aggregate. When compared to the derence concrete, the drying shrinkage showing significant changes; however, their evolution over time is similar to standard concrete.
H. El-Chabib, M. Nehdi, and M. H. El Naggar
Cast-in-place deep foundations such as drilled shafts and piers are often subjected to two sources of problems. First, the integrity and uniformity of the cross-sectional area of these structural elements cannot be assured using normal concrete because of limited accessibility and visibility during construction. Cavities and soil encroachments leading to soil pockets can jeopardize their load-bearing capacity. Second, corrosion problems of steel reinforcement in deep foundations have been costly, requiring annual repair costs of more than $2 billion in the US alone. To address these two challenges, a novel technology for the construction of drilled shaft concrete piles is proposed in this study. Self-consolidating concrete, a material that compacts under its self-wight without vibration and without bleeding or segregation, is used to assure the structural integrity and uniformity of the cross-sectional area of deep foundations. The self-consolidating concrete is cast into FRP envelopes, which provide corrosion-resistant reinforcement. This paper presents results of a laboratory investigation on the mechanical performance of these novel piles including the effect of using expansive cement and shrinkage-reducing admixtures to enhance the FRP tube-concrete interfacial bond.
M. A. Starnes, N. J. Carino, and E. A. Kausel
The finite-element method is used to carry out parametric analyses on the thermal response of simulated defects in fiber-reinforced polymer (FRP) lami- nates applied to a concrete substrate. The aim is to assess the potential for qualtitative infrared thermography in not only detecting a flaw but also being able to describe its physical characteristics. Three parametric studies are presented, namely: 1) relationship between the thermal input, the maximum signal, and the maximum surface temprature; 2) effects of flaw depth and the number of FRP layers; and 3) effect of flaw width. From these simulations, procedures are established for selecting the thermal input and estimating the flaw depth and width.
Thermal cracking is a serious problem with modern portland-cement concrete structures, especially cast-in-place massive elements made with relatively high cement content and cured under hot-weather conditions. From theoretical considerations and field experience it is concluded that blended portland-cement concrete mixtures containing 50 percent or more ASTM Class F fly ash by mass of the total cementitious material perform much better under these conditions.
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