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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 10 Abstracts search results
Document:
SP241-05
Date:
April 1, 2007
Author(s):
J.L. Poole, K.A. Riding, K.J. Folliard, M.C.G. Juenger, and A.K. Schindler
Publication:
Symposium Papers
Volume:
241
Abstract:
Accurate characterization of the temperature rise in a concrete element requires an estimate of the adiabatic temperature rise of the concrete mixture. Semi-adiabatic calorimetry is commonly used to provide an estimate of the heat generation characteristics of a concrete mixture because of the relative simplicity of the test. This study examines the sources of variability in semi-adiabatic calorimetry, and an estimate of the confidence limits of the test is calculated. Then, twenty concrete mixtures are investigated using semi-adiabatic calorimetry. Activation energy values are calculated for each mixture using isothermal calorimetry. The adiabatic temperature rise is then calculated. The following mixture properties are investigated: cement type, cementitious content, water/cementitious material ratio, coarse aggregate type (siliceous river gravel and limestone), mixture placement temperature, and the effects of selected supplementary cementing materials. The following factors were the most important to reduce the adiabatic temperature rise: reduced cement content, use of a lower-heat cement, such as a Type V cement type, reduced aggregate specific heat, and substitution of cement with Class F fly ash.
DOI:
10.14359/18651
SP241-01
P. Taylor and J. Gajda
There is a growing interest in monitoring the temperature of cement paste, mortar and concrete, particularly at early ages. However, there also seems to be confusion about what is being achieved by this activity, and what to do with the information once it is recorded. This paper outlines the tools and techniques in use, and discusses their applications, benefits and limitations. The discussion will cover concepts such as heat of hydration, maturity, isothermal calorimetry and semi-adiabatic temperature monitoring for assessing setting times, and potential incompatibility between the reactive ingredients (cements, supplementary cementitious materials, and chemical admixtures) in a mixture.
10.14359/18647
SP241-03
K.A. Riding, J.L. Poole, M.C.G. Juenger, A.K. Schindler, and K.J. Folliard
An accurate and practical method of determining the heat development of concrete mixtures under real mixing, cooling, hauling, placement, and curing conditions would greatly benefit contractors and engineers in helping predict in-place concrete member temperatures. Semi-adiabatic calorimetry was performed at several construction sites in temperature controlled rooms using concrete sampled from concrete placements. Semi-adiabatic calorimetry was also performed for comparison with concrete made under laboratory conditions from materials sampled at the respective batch plants. An energy balance-based finite difference method is presented for calculating the concrete non-linear heat generation using the measured heat of hydration determined from semi-adiabatic calorimetry. This method was used in a program which allows the direct input of values from semi-adiabatic calorimetry testing and estimates the development of in-place temperatures in mass concrete members of various geometries. Estimated concrete member temperatures are compared to the values measured on-site. Best practice suggestions are also given for performing semi-adiabatic calorimetry using concrete sampled on-site.
10.14359/18649
SP241
Editors: Kejin Wang and Anton K. Schindler
SP-241CD This CD-ROM contains nine papers presented at a technical session on Heat Development: Monitoring, Prediction, and Management, held in Atlanta, GA, in April 2007. Topics include innovative technology for concrete heat monitoring; use of the heat measurements to characterize concrete mixtures, evaluate the mixture performance, and detect potential incompatibilities of concrete materials; heat management in precast concrete; and modeling and prediction of in-place concrete temperature development, among others.
10.14359/18614
SP241-04
V.T. Cost and G. Knight
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.
10.14359/18650
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