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  July 2014  
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Concrete International July 2014 No. 7 Complete Issue
Floors and Foundations

2014 CFA Awards
The Concrete Foundations Association (CFA) has announced the winning entries for the 2014 Projects of the Year.

Mitigating Thermal Cracking in Massive SCC Slab Foundations for a Wastewater Pumping Station
The North Jeddah Wastewater Pumping Station and Treatment Plant, Jeddah, Saudi Arabia, is one of the deepest and largest in the world. Three reinforced concrete mat foundations for the pumping station are 42.6 to 44.0 m (140 to 144 ft) in diameter and 5.5 m (18 ft) thick, and positioned 70 m (230 ft) below the ground level. The article discusses the mixture design development for those slab foundations, temperature rise modeling, test mock-up, and full-scale continuous casting of about 24,000 m3 (31,400 yd3) of self-consolidating concrete for this project.

Multiple Deterioration Mechanisms in Coastal Concrete Piles
The article presents a forensic investigation of precast prestressed concrete piles removed from the I-95 Turtle River Bridge, near Brunswick, GA. The piles exhibited extensive damage that led to the discovery of unexpected threats to bridge substructures in marine environments. The results of the study emphasize the need to consider the presence of multiple modes of deterioration in concrete structures and their potential synergistic interaction.

The Code Cycle’s Inherent Value
The Chair of ACI Committee 318, Structural Concrete Building Code, shares his opinion on the ACI code development and revision process. The article emphasizes the contributions of time and expertise by committee members and other interested parties, as well as the need for regular updates to reflect new knowledge and developments. The author also outlines the ACI business model, revenue sources, and their importance to the quality and timeliness of code development.

ACI Foundation’s Student Fellowships and Scholarships Awarded
For the 2014-2015 academic year, the ACI Foundation has awarded seven Student Fellowships and eight Graduate Scholarships.

ACI Spring 2014 Convention Highlights
Making concrete structures last longer, the benefits and rationale of the reorganized ACI 318-14, and concrete for challenging applications were just some of the topics covered during the technical sessions of the ACI Spring 2014 Convention.

Pressure of Self-Consolidating Concrete on Formwork
Designing and fabricating formwork for vertical elements are significant parts of the construction process for reinforced concrete structures. Formwork reliability can have financial and safety implications, so formwork designers need accurate methods for predicting lateral pressures. The article describes the rheological (flow) behavior of self-consolidating concrete (SCC), identifies differences in some of the existing form pressure models, and presents recommendations for determination of the lateral pressure of formwork exerted by SCC.

Colloidal Silica Admixture
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.

Concrete Q & A: Vapor Retarder Placement
Figure 3.1 in the 2004 edition of ACI 302.11 and Fig. 7.1 in ACI 302.2R-062 (refer to Fig. 1) provide a decision flowchart for determining the need for and location of a subslab vapor retarder. It’s very clear that if a project has a vapor-sensitive floor covering or a humidity-controlled area, a vapor barrier is required.


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