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International Concrete Abstracts Portal

Showing 1-5 of 33 Abstracts search results

Document: 

SP-338_06

Date: 

March 1, 2020

Author(s):

Oscar R. Antommattei

Publication:

Symposium Papers

Volume:

338

Abstract:

During hot weather concreting, contractors have several options for dealing with slump loss and rapid drying of concrete surfaces. Limiting slump loss requires cooperation between the concrete producer and contractor, especially with respect to reducing truck waiting time. Several options for minimizing surface drying are compared, based on effectiveness and cost. Finally, providing for adequate initial curing of concrete test cylinders can reduce the possibility of schedule delays and increased costs related to low strength-test results.


Document: 

SP-332_08

Date: 

July 1, 2019

Author(s):

Ashok Kakade

Publication:

Symposium Papers

Volume:

332

Abstract:

When preparing ready-mix concrete for private applications, it is typically recommended that owners and contractors collaborate with suppliers and concrete specialists to understand the possibilities and limitations of concrete in their applications. Here, we describe a situation in which a homeowner took direct control over the exact specifications of concrete and admixtures, and ultimately resulted in an unsatisfactory concrete slab. The owner subsequently sued and settled with the concrete supplier outside of the court, which raises important questions regarding who maintains responsibility for concrete mixtures, their installation, and the final slab results. Suggestions are provided to help mitigate this problem.


Document: 

SP275-62

Date: 

March 1, 2011

Author(s):

Amr El-Ragaby and Ehab F. El-Salakawy

Publication:

Symposium Papers

Volume:

275

Abstract:

The bridge deck slab is a prime example where FRP bars are used as main concrete reinforcement. In Canada, bridge deck slabs are usually subjected to a variation of cold and hot weathering while directly sustain the traffic loads. Both fatigue and thermal loading are expected to adversely affect the overall performance of such structural elements. In this research, a total of 4 large-scale bridge deck slabs totally reinforced with glass FRP bars were constructed and tested under simulated long-term loading and environmental conditions. The slabs were subjected to 3,000,000 cycles of sinusoidal waveform fatigue loading combined with either 100 freeze-thaw cycles or continuous cold temperature for one month. The test parameters included the environmental conditioning and the reinforcement ratio. It was concluded that the overall behavior of GFRP-reinforced bridge deck slabs after being subjected to simulated long-term fatigue load cycles and freeze-thaw or cold temperature is satisfactory according to the current design codes.

DOI:

10.14359/51682472


Document: 

SP253-19

Date: 

July 31, 2008

Author(s):

E. Moreno, R. Solís-Carcaño, and C. Serrano-Zebadua

Publication:

Symposium Papers

Volume:

253

Abstract:

The weather of the Yucatan Peninsula is classifi ed as hot sub-humid, with minor differences of relative humidity and temperature during the year. Local builders, in their search for process optimization and cost reduction, usually do not cure concrete beyond wetting the concrete surface immediately after removing the formwork. Teaching of concrete technology has been based on classic reports, where it is affi rmed that the strength gain is enhanced when moist curing is applied. Preliminary studies in the Yucatan region have not shown that moist curing helped to improve strength gain. Based on the meteorological conditions of the Yucatan region, it is possible that natural curing occurred with no need for additional curing for most of the cases. The objective of this study was to obtain the strength-gain curves as a function of the moist curing time from 0 to 90 days. Preliminary results confirm the hypothesis about the suffi ciency of the natural curing under the weather conditions of the Yucatan region. The use of porous aggregate may have contributed to curing during storage in air.

DOI:

10.14359/20181


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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