International Concrete Abstracts Portal

International Concrete Abstracts Portal

Showing 1-5 of 14 Abstracts search results

Document: 

CI4303Nelson

Date: 

March 1, 2021

Author(s):

Yvonne Nelson

Publication:

Concrete International

Volume:

43

Issue:

3

Abstract:

The REACH is a 72,000 ft2 (6700 m2) expansion of the John F. Kennedy Center for the Performing Arts in Washington, DC, USA. It comprises three prominent pavilions connected by studios, classrooms, and a parking structure below an interwoven green roof. It was constructed using a variety of exposed concrete finishes and structural and architectural components. The article provides insights into the execution of some of the project’s outstanding features.


Document: 

SP-343_22

Date: 

October 1, 2020

Author(s):

Zani, G.; Colombo, M.; Failla, C.; di Prisco, M.

Publication:

Symposium Papers

Volume:

343

Abstract:

A new partially prefabricated elevated slab has been recently introduced in two different industrial buildings, to propose a viable alternative to the classical double tee deck with the addition of an in-situ RC topping. The solution is characterized by an adjustable spacing in the orthogonal direction, 40 mm thick FRC plates used as predalles and a cast-in-place FRC finishing, designed according to a continuous slab resting on the simply-supported beams. The proposed deck is a structural solution that tries to fit different issues like construction speed, transport and cost reduction, structural optimization, high fire resistance (R120) and quality performance. All elements are made of SFRC, characterized by different mix designs. This paper presents a design investigation on this kind of floor element, aimed at optimizing the global structural solution by minimizing the whole floor weight. Longitudinal and transverse bending, as well as vibration limit state, were considered in the design. The optimization strategy will be here presented, through the discussion of the parameters considered in the design, the variables taken into account and the constraints adopted within the procedure. A Model Code 2010 design approach was followed.


Document: 

CI3607Belkowitz

Date: 

July 1, 2014

Author(s):

Jon S. Belkowitz, Whitney B. Belkowitz, Matthew A. Best, and Frank T. Fisher

Publication:

Concrete International

Volume:

36

Issue:

7

Abstract:

Colloidal silica (CS) is generally used as a finishing aid and densifier for concrete floors. Recently, tests were undertaken to evaluate CS as an admixture to mitigate alkali-silica reactivity (ASR) in dosages that would not retard early concrete strength development. The article presents development and evaluation of concrete mixtures with CS admixture in the laboratory and on a commercial job site. Field and laboratory tests showed that CS provided increased early strength of Class F fly ash mixtures while reducing ASR expansion.


Document: 

SP249-08

Date: 

March 1, 2008

Author(s):

C.A. Menzel

Publication:

Symposium Papers

Volume:

249

Abstract:

class="red">Due to copyright issues, this paper is only available by purchasing the SP-249.

Cracks often develop in the surface of fresh concrete soon after it has been placed or finished and while it is still in the plastic state. The development of such cracks, commonly referred to as plastic cracking, can be practically eliminated if appropriate measures to minimize the causes are taken at the right time. The development, location and extent of cracks in fresh concrete may be readily observed if they occur in the exposed top surface. However, cracks may also develop, though much less frequently, in the vertical surface of fresh concrete slabs in horizontal forms. Cracks in vertical surfaces are seldom due to drying shrinkage, which is the most frequent cause of top-surface cracks.

DOI:

10.14359/20129


Document: 

SP241-04

Date: 

April 1, 2007

Author(s):

V.T. Cost and G. Knight

Publication:

Symposium Papers

Volume:

241

Abstract:

Abnormal early hydration resulting from "incompatibilities" of common concrete materials can result in erratic set and strength gain behavior and associated finishing, curing, and cracking issues. Contributing influences include high temperatures, cement sulfate levels, Class C fly ash content, chemical admixture use, and design approaches for retardation of hot-weather concrete. Simple, expedient test methods are needed to identify potentially incompatible materials and conditions and to verify appropriate modifications to concrete proportions. Thermal measurements of the early heat development of materials mixtures in the laboratory (semi-adiabatic calorimetry) have been shown very useful toward this end. Abnormal set and strength development of field concrete was reproduced in laboratory paste and mortar mixtures and studied using thermal measurements, verified by parallel mortar cube strengths. Sensitivities of various contributing influences were documented in extensive testing. Changing one or more of the key material or mixture characteristics was usually successful in restoring normal behavior. Recommendations are presented for avoiding related field issues and for the use of calorimetry testing programs for diagnosis of such problems.

DOI:

10.14359/18650


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