ABOUT THE 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.

International Concrete Abstracts Portal

Showing 1-5 of 720 Abstracts search results

Document: 

SP-340-05

Date: 

April 1, 2020

Author(s):

Nakin Suksawang and Hani Nassif

Publication:

Symposium Papers

Volume:

340

Abstract:

For many decades, latex-modified concrete (LMC) overlays have been successfully used in the United States, inclusive of providing protection for many bridge decks and their steel reinforcements. LMC remains one of the most desirable rehabilitation materials for concrete bridge decks because it is easier to place and requires minimal curing. Nevertheless, as is the case with any cement-based material, LMC overlays are susceptible to plastic shrinkage and delamination. These problems are often solved by proper curing and better surface preparation. Yet, despite these solutions, many questions have been raised regarding the best practices for placing LMC overlays and the proper curing and placement conditions. The current curing practice for LMC in most states simply follows the latex manufacturer’s recommendation because very little information on the proper curing methods is available. There is a need to establish detailed technical specifications regarding curing and placement conditions that will provide more durable LMC overlays. This paper provides an in-depth laboratory-based experimental study of the effect of curing methods and duration on the mechanical properties and durability aspects of LMC. Four different curing methods were examined: (1) dry curing, (2) 3 days of moist curing, (3) 7 days of moist curing, and (4) compound curing. Based on the results from the laboratory tests, technical specifications were developed for field implementation of LMC. Various types of sensors were installed to monitor the behavior of the LMC overlays on bridge deck. Results show that extending the moist-curing duration to a minimum of 3 days (and a maximum of 7 days) significantly improves both the mechanical properties and durability of LMC.


Document: 

SP-340-06

Date: 

April 1, 2020

Author(s):

Maria Kaszynska and Adam Zielinski

Publication:

Symposium Papers

Volume:

340

Abstract:

The research paper presents an analysis of autogenous shrinkage development in self-consolidating concrete (SCC). The first stage of the study involved an evaluation of concrete susceptibility to cracking caused by shrinkage of SCC with natural and lightweight aggregate. The shrinkage was tested on concrete rings according to ASTM C 1581/C 1581M- 09a. The influence of aggregate composition, the water content in lightweight aggregate, and SRA admixture on the reduction of concrete susceptibility to cracking, due to the early-age shrinkage deformation was determined. In the second stage of the research, the innovative method measurement of autogenous shrinkage was developed and implemented. The tests were performed on concrete block samples, dimensions 35x150x1150 mm, that had the same concrete volume as ring specimen in the ASTM method. Linear deformation of the concrete samples was measured in constant periods of 500 s using dial gauges with digital data loggers. The investigation allowed evaluating of the influence of water/cement (w/c) ratio of 0.28, 0.34, 0.42, and of aggregate composition on the development of autogenous shrinkage in different stages of curing SCC. The results were compared to existing material models proposed by other researchers. The conducted study indicated a significant influence of the w/c ratio and composition of aggregate on the concrete susceptibility to crack caused by the autogenous shrinkage deformation.


Document: 

SP-338_02

Date: 

March 1, 2020

Author(s):

Kenneth C. Hover

Publication:

Symposium Papers

Volume:

338

Abstract:

PCA researchers interested in the problem of evaporation of bleed water from concrete surfaces borrowed an equation developed by hydrologists to predict evaporation from Lake Hefner in Oklahoma. PCA’s graphical representation of that equation, subsequently modified to its present form by NRMCA, was later incorporated into multiple ACI documents, and is known by concrete technologists world-wide as the “Evaporation Rate Nomograph.” The most appropriate use of this formulation in concrete construction is to estimate the evaporative potential of atmospheric conditions (known as “evaporativity”). Since the difference between actual and estimated evaporation rate can be in the range of ± 40% of the estimate, best use of the equation as routinely applied is as a semi-quantitative guide to estimate risk of early drying and inform decisions about timing and conduct of concrete placing and finishing operations. Use of the “Nomograph” and related “Apps” in specifications is more problematic, however, given: 1.) the inherent uncertainty in its underlying equation, 2.) the difficulty in obtaining input data that appropriately characterize jobsite microclimate, and 3.) establishing a mixture-specific criterion for tolerable evaporation rate.


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-338_05

Date: 

March 1, 2020

Author(s):

Ronald Kozikowski and Kevin Rowswell

Publication:

Symposium Papers

Volume:

338

Abstract:

Several documents have indicated that applying curing water cooler than the concrete surface by more than 20⁰ F (11⁰ C) can produce a strain of about 100 millionths, exceeding the concrete’s strain capacity, and resulting in cracking. Earlier work by the senior author and others has questioned the origin and applicability of the 100 millionths strain capacity for early-age concrete. Tests on small-scale specimens demonstrated that using curing water as much as 55⁰ F (34⁰ C) cooler than the concrete surface did not result in crazing or cracking. This paper describes a study in which cold curing water was used on a large concrete slab under field conditions. Experimental results suggest that at least a 50°F (32°C) temperature difference between curing water and a concrete slab can be withstood without causing surface crazing or cracking.


12345...>>

Results Per Page 




Please enter this 5 digit unlock code on the web page.