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  January 2015  
 
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Concrete International January 2015 No. 1 Complete Issue
Concrete International January 2015 No. 1 Complete Issue

SCC Under Pressure Research Program
Various pressure models for self-consolidating concrete have been developed independently by researchers from Europe, the United States, and Canada. To help reconcile these models, RILEM Technical Committee 233-FPC, Form Pressure Generated by Fresh Concrete, was formed 5 years ago. The committee conducted full-scale wall tests two years ago in Stockholm, Sweden. As a continuation of this research, another testing program was carried out on tall column forms in Toronto, Canada, in 2014. This article provides a brief summary of the event.

The Sky’s the Limit
Due to the development of powerful high-range water-reducing admixtures and viscosity modifying admixtures, it is now possible to very efficiently and economically build high-rise concrete structures. These admixtures allow concrete to be pumped from the first to the highest floor, so it is no longer necessary to use cranes to transport and place concrete. This article shows how the construction of high-rise buildings has evolved from entirely structural steel structures to almost exclusively reinforced concrete structures, by discussing the construction of some landmark structures built from 1968 to the present.

Assessing the Impact of the New ACI 318-14 Chapter on Construction
The recently released ACI 318-14, "Building Code Requirements for Structural Concrete," contains specific technical changes that will impact and benefit the work of contractors and the construction industry. Some of these changes are summarized, including a new chapter on "Construction Documents and Inspection," which specifically outlines what the Licensed Design Professional is required to provide to the contractor through the construction documents.

PCA’s 2014 Concrete Bridge Awards
Nine winners were named in Portland Cement Association's (PCA) Fourteenth Biennial Bridge Awards Competition.

Tilt-Up Concrete Association’s Achievement Awards
The Tilt-Up Concrete Association (TCA) announced the recipients of the 24th Annual Tilt-Up Achievement Awards.

Lap Splices in Unconfined Boundary Elements
Lap splices are not used near critical sections of frames that are required to resist earthquakes' demands because they are believed to limit frame toughness. The current building code nevertheless allows lap splices at the bases of structural walls, where large inelastic deformations are expected to take place during strong ground motions. The article presents tests conducted on six test beams and two scaled walls that were designed to represent 8 in. (200 mm) thick structural walls with lap splices in unconfined boundary elements.

Monitoring Temperatures in Concrete Construction Using IR Thermometers
Handheld infrared (IR) thermometers have been found to work well in the relatively narrow temperature range commonly seen in concrete construction: 0 to 120°F (-20 to -45°C). Although IR thermometers are not sufficiently accurate for some quality assurance tests, they do make it possible to estimate concrete temperatures and evaluate casting surface temperatures without interfering with the concrete placements. The article provides user guidance and lists possible applications for IR thermometers in concrete construction.

Products & Practice Spotlight: Smarter, Faster, Safer
A remote control demolition robot, Brokk 50, was used on a project that involved demolition and repair of concrete balconies on an 18-story apartment building in Toronto, Canada. The machine was a perfect choice for a mast climbing work platform. Thanks to the robot and 11 workers, the project was completed in just six months. The machine not only provided efficiency and speed but also improved safety of the crew.

Concrete Q&A: Vapor Retarders and Durability for Slabs-on-Ground
Q: Are vapor retarders required for a slab-on-ground? Also, what are the durability requirements for a slab-on-ground?

 


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