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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 9 Abstracts search results
Document:
19-355
Date:
September 1, 2020
Author(s):
Diogo Henrique de Bem and Ronaldo A. Medeiros-Junior
Publication:
Materials Journal
Volume:
117
Issue:
5
Abstract:
No widely accepted method is available to assess the efflorescence in small-scale mortar specimens. Thus, the analysis and determination of parameters that actually have an influence on the occurrence of efflorescence in cementitious materials become difficult to be accomplished, especially considering that its appearance in natural field conditions can take months or even years to happen. This paper has the objective to compare eight small-scale accelerated test methods for the assessment of efflorescence in lime-cement mortars and then to evaluate their sensibility to variations in the mixture composition. The results show that the method in which a water column introduces pressure produced the highest amount of efflorescence in the smallest time. The method was able to clearly identify the impact of silica fume towards the refinement of the porous microstructure and the efflorescence reduction. This study demonstrates that 28 days is enough time to finalize the accelerated testing proposed.
DOI:
10.14359/51724627
14-301
November 1, 2015
Don MacMaster and Oscar Tavares
112
6
Early-age carbonation curing of concrete products results in improved strength, increased surface hardness, and reduced surface permeability to water, as well as the reduction of efflorescence. Carbonation reactions between carbon dioxide and calcium compounds result in permanent fixture of the carbon dioxide in thermodynamic stable calcium carbonate. The moisture content, relative humidity, and temperature profile of the hydrated system have considerable and important influence on the rate and ultimate extent of carbonation. During carbonation, CO2 penetrates the surface of concrete and reacts with cement hydration products—namely, calcium hydroxide and calcium silicate hydrates—to form carbonates. This study quantifies carbon sequestration levels in concrete masonry units using various curing methodologies. The test results of a dynamic pressurized CO2 curing chamber and normal ambient CO2 pressure at various concentrations levels are compared to traditional kiln curing procedures. Early compressive strength profiles for 30% CO2 cured concrete masonry units (CMUs) are equivalent to 100% CO2 cured CMUs and exceed the traditional kiln-cured compressive strengths. Carbon sequestration reduced water requirements by 20% for optimum strength performance and provided water conservation opportunities.
10.14359/51688069
JL62-53
August 1, 1965
ACI Committee 516
Journal Proceedings
62
8
High pressure steam curing (autoclaving) is employed in the production of concrete masonry units, sand-lime brick, asbestoscement pipe, hydrous calcium silicate-asbestos heat insulation products, and lightweight cellular concrete. While all are covered, this report emphasizes concrete masonry units because they represent the greatest use of autoclaving in the United States and Canada, and most of the information available is in this field. The chief advantages offered by autoclaving are high early strength, reduced moisture volume change, increased chemical resistance, and reduced susceptibility to efflorescence. Many properties of concretes are improved by autoclaving, however, some, such as permeability and brittleness are not. The report presents a summary of modern practice and makes general comparisons of physical properties of autoclaved products.
10.14359/7728
JL62-35
May 1, 1965
R. A. Kennerley
The formation of a deposit of ettringite in a submerged dam gallery is described. It occurred in an area where a fly ash-cement mixture had been used for the placement of pre-packed concrete. Where fly ash was used to replace a portion of the cement in conventionally placed concrete nearby, no such deposit was observed. No evidence of deterioration of the concrete could be found. It is believed that water seeping along permeable planes in the concrete dissolved some of the sulfate and alumina-containing phases formed during cement hydration and, on reaching the gallery, ettringit tew asprecipitated from the solution. The deposit was found adjacent to a stop-work plane in the grouting of the aggregates, and it is thought that the concrete at this point could have become enriched in lighter hydration products (e.g., calcium sulfoaluminate, calcium hydroxide) and grout admixtures. The formation of ettringite as a stable product of cement hydration would have been assisted by additional sulfate derived from the fly ash.
10.14359/7710
JL58-35
December 1, 1961
Donald F. Griffin and Robert L. Henry
58
12
Presents basic data about water vapor permeability of plain concrete and the effects on permeability of certain admixtures such as oleic acid and sodium chloride. Other variables included in the study are: (I) specific location of specimen disk as cut from a concrete cylinder; (2) maximum size of aggregate and (3) environment of specimen whether in 7 3 .4 F , 20 or 50 percent relative humidity. Part of the total study includes the results of a quarter replicate statistical experiment for two levels of each of six factors to permit an analysis of variance of different variables in the permeability study. Salt whisker crystal growth on specimens with sodium chloride as an admixture is discussed. Test results revealed that water vapor transmission values were found to be significantly higher for the higher water-cement-ratio concretes, the absence of sodium chloride, and the presence of smaller aggregate. Origin of concrete disk within cylinder, presence of oleic acid, and relative humidity were factors found to have no statistically significant effect.
10.14359/8006
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