Decorative and architectural concrete can help a project transcend its simple utilitarian form. Some recent awards have honored projects that have taken that transcendent step.

The 2009 Pretoria Portland Cement (PPC) Young Concrete Sculptor Awards, held in partnership with the Association of Arts in Pretoria, showcased a variety of high-quality submissions.

Artist uses shotcrete to create sculptural pieces.

The three-story white concrete monolith of the Swiss National Park Visitor Center in Zernez, Switzerland, rests on a plinth. At each story, the façades are slightly offset to create wall projections. To help prevent crack formation, the building corners were erected first, followed by the middle pieces with the window cut-outs. The center was built exclusively with cast-in-place concrete. The composition of the lightweight concrete was initially refined in laboratory experiments and subsequently used for a series of mock-ups. An environmentally safe, anti-graffiti coating protects the building’s exterior surfaces.

“Xtreme” concrete highlighted in Chicago.

After years of service, the durability of FRP-concrete bond in structures strengthened using FRPs remains uncertain. To investigate the durability of FRP-concrete bond, four in-service bridges in Canada strengthened using externally bonded FRPs were studied. To measure the integrity of the bond, mechanical pull-off tests were performed. In some cases, infrared thermography was used to detect debonding. Results indicate that thermography is an excellent way of detecting debonding between FRP and concrete. Bond is noted to be strongly influenced by the placement technique, exposure severity, location on the bridge, and type of loading. Generally speaking, while the bond in most instances is fairly good, in some cases, a severe deterioration in bond has occurred. This is a cause for concern.

Reinforcing bar assemblies, known as standees, are normally required for support of top mats of reinforcing bars in thick concrete members, such as footings and slabs. Standees are readily available as a standardized product up to 18 in. (457 mm) in height, but various sizes and configurations of standees have also been used in thick mat footings. Four common types of standees are illustrated. Safety is of paramount importance when designing a bar support system for heavy top mats of reinforcing bars. Standee spacing must be carefully determined to support the dead loads, and bracing must be adequate to handle all lateral forces.

The LENTON® THERMO Balcony System is designed to help eliminate the energy loss and potential condensation and mold growth associated with thermal bridging at slab-to-balcony and slab-to-wall connections. Because of the system’s modular design, balcony elements can be shifted as required to clear obstructions, and the connecting reinforcing bars can be installed after the installation of the balcony elements. Although the modular elements are very thin, they have extremely low thermal conductivities because they incorporate glass fiber-reinforced polymer bars as load-carrying components and vacuum-insulated panels as insulation components.

1. We’re considering having the concrete supplier use crushed concrete as coarse aggregate, and perhaps fine aggregate, in the 3000 psi (21 MPa) concrete specified for a project we’re building. Does aggregate produced by crushing returned concrete meet the requirements for aggregates in building codes and commonly used specifications?

2. We do most of our work in Canada, and we’ve become accustomed to using entrained air in our concrete to help protect it from freezing-and-thawing cycles. Because air entrainment also provides improved workability and decreased bleeding, we use it in most concrete—not just concrete exposed to freezing and thawing. Recently, one of our larger clients has asked us to work on a project in the Caribbean. The project includes a swimming pool near the ocean, and we’re considering using air entrainment for the pool and surrounding slabs.We know that air entrainment isn’t commonly used where the project is located.