Concrete creativity

ACI announces the winners of its annual Excellence in Concrete Construction Awards.

In October, the American Concrete Institute (ACI) announced the winners of the 2018 Excellence in Concrete Construction Awards. The highest honor — the Overall Excellence Award — was presented to Viaduct Over River Almonte in Garrovillas de Alconétar, Cáceres, Extremadura, Spain, which also took first place in the Infrastructure category (see description below in the Infrastructure category). This award is given annually to one project that demonstrates excellence in concrete innovation and technology and stands out above all other entries.

The ACI Excellence in Concrete Construction Awards were created to honor the visions of the most creative projects in the concrete industry, while providing a platform to recognize concrete innovation, technology, and excellence across the globe. To be eligible for participation in the Excellence Awards, projects needed to be winners at a local ACI Chapter level and submitted by that Chapter or chosen by one of ACI’s International Partners.

An independent panel of industry professionals judged projects and selected winners based on architectural and engineering merit, creativity, innovative construction techniques or solutions, innovative use of materials, ingenuity, sustainability, resilience, and functionality.

In addition to the Overall Excellence Award winner, first and second place projects were selected from the following six categories:

Decorative Concrete

First Place — Roofing of the Montpellier-South of France TGV Station, Montpellier, Herault, France — Montpellier-South of France TGV Station is a major step on a critical European corridor and a key facility for tourism and economic growth of the “French sunbelt.” The roof over the 107,640-square-foot area of the new station is a perforated mineral latticework comprising 115 modular and self-supporting precast elements, known as “palmes,” made from white ultra-high-performance fiber-reinforced concrete (UHPFRC). The palmes cover five identical spans over the railway lines, while 20-foot cantilever canopy shells overhang from the edge to eaves on all four sides.

The double-cambered palmes, 8 feet wide, have an average thickness of 2 inches and span 57 feet. They mainly comprise a central longitudinal rib with a variable cross section and a post-tensioning tendon; a warped, perforated shell, in which the 16- by 6-inch spaces for treated glass inclusions are arranged; a thin, V-shaped diaphragm at midspan; and peripheral thin connecting walls and bearing joists. The design parameters included a serviceability limit on tensile stresses of 696 psi, and this required development of a new UHPFRC mixture with a high stainless-steel fiber content. All roofing elements were prefabricated within a five-month period. They were installed with tight geometrical requirements (± 0.08 inch for the bearing points) in only two weeks.

Project team members include SNCF Réseau (owner); Marc Mimram Architecture et Inégnierie (architectural firm); Lamoureux & Ricciotti Ingénierie (engineering firm); Fondeville (general contractor); Méditerranée Préfabrication (concrete contractor); and LafargeHolcim (concrete supplier).

Second Place —Water Garden, Santa Monica, Calif. — Water Garden is a transformation of a 1990s office campus into a 17-acre sustainable creative office experience located in the heart of Silicon Beach. Decorative concrete played a major role in the modernization, which included renovation of the landscape, hardscape paving, and lighting over the existing podium deck. Adding to the complexity, the entire project had to be constructed with minimal impact to a fully occupied office complex.

Due to the loading restrictions on the podium deck, the site was constructed over a waffle system comprising expanded polystyrene blocks. The paving design features a rectilinear paving pattern within a curvilinear outline with inlayed LED lights. The field is a natural gray light wash finish. Bands are graphite integral color with a light wash finish.

Project team members include Water Garden Realty Holding LLC & Water Garden Company L.L.C. (owner); HLW International (architectural firm); AMA Consulting Engineers (engineering firm); Morley Builders (general contractor); Shaw & Sons (concrete contractor); and Catalina Pacific Concrete (concrete supplier).

High-Rise Buildings

First Place — Reston Station OB1 Tower, Reston, Va. — The new office destination at Reston Station features an exposed concrete frame. The tower slopes outward from the base to a roof area of 300,000 square feet. The exterior columns are all angled and form giant “X” shapes as they rise from the platform slab on the east and west façades. Columns with limb-like forms are visible on the north side of the structure — these included structural steel cores and were constructed using about 400 cubic yards of a 10,000-psi, self-consolidating concrete mixture. Other exterior columns were constructed using a 10,000-psi mixture over the full height of the building. This mixture had normal consistency, so it was consolidated using internal and external vibrators to ensure a high-quality architectural concrete finish. Interior columns had a maximum concrete strength of 12,000 psi at the base, decreasing to 7,000 psi at the upper levels. Slab mixtures included high-early strength, 5,000-psi concrete, and 7,000-psi lightweight concrete.

Project team members include Constock Partners (owner); JAHN (architectural firm); Thornton-Tomasetti (engineering firm); Davis Construction (general contractor); Miller & Long (concrete contractor); and Vulcan Materials (concrete supplier).

Second Place — Nexus Shopping and Business, Setor Marista, Goiânia, Brazil — The Nexus Shopping and Business complex is one of the biggest urban projects in Brazil. It consists of three multipurpose towers, with the tallest at 518 feet. The total floor area is 1,400,000 square feet. To improve building performance, many structural optimizations were implemented. Excellent mechanical properties of the soil allowed for the use of footing foundations. Main foundation elements for one of the towers were cast in layers and the concrete temperature was monitored, allowing the elements to be constructed without the need for precooling of the concrete and minimizing the risk of thermal cracking. The superstructure concrete was designed to achieve a high modulus of elasticity of 794,000 pounds per square foot (lb/ft²) at 28 days for the first floors and 710,000 lb/ft² for other floors. A high mortar content in the initial mixtures led to the need for special measures to avoid high shrinkage and thermal stresses. Due to these requirements, improvements in concrete mixture, optimization of the concreting process, and structural design adjustments were made.

Project team members include Consciente JFG Incorporações e Participações Ltda (owner); Consciente Construtora e Incorporadora Ltda (engineering firm and general contractor); Votorantim Cimentos S/A (concrete contractor); and Realmix Concreto Ltda (concrete supplier).

Infrastructure

First Place — Viaduct Over River Almonte, Garrovillas de Alconétar, Cáceres, Extremadura, Spain — A new high-speed rail line is under construction between Madrid and the Extremadura, a western Spanish region bordering Portugal. The line will cross over the River Almonte on a 3,270-foot-long viaduct — a concrete arch bridge with a main span of 1,260 feet. Designed to carry 218-mph rail traffic, the viaduct had to meet rigorous dynamic, serviceability, and safety criteria; it required complex, staged calculations based on nonlinear material and nonlinear geometry behaviors. Nevertheless, it is aerodynamic and slender, largely due to key design features, including a four-legged arch configuration; 11,603-psi high-performance concrete; an efficient erection method, with temporary towers and stays; and an innovative monitoring system.

The viaduct’s 1,260-foot main span makes it the largest railway bridge in Spain and the world’s largest concrete arch bridge for high-speed rail service. Its design combines structural efficiency, out-of-plane stability (as required by deformation limits), improved response against cross wind effects (verified in boundary layer wind tunnel tests), and aesthetics. The design is also environmentally friendly, as the bridge comprises durable materials, has been designed for expedient maintenance, and will include a custom barrier that will force birds to soar upward and above the overhead mast line. The bridge arch comprises high-performance, self-consolidating concrete (C-80). The complex erection procedure required development of singular construction devices. The bridge was constructed using a groundbreaking instrumentation and monitoring system that provides information regarding the behavior of the structure during construction and service.

The arch was erected from both sides of the river as cantilevering arch segments supported by temporary cables. The arch was divided into 32 segments on each side, plus the key central segment. Construction required the use of specially designed form travelers that allowed every dimension of the section to be adapted to the variable arch shapes. Due to the geometry of these segments, as well as the complex and dense positioning of the reinforcing bars in them, the use of a self-consolidating concrete was needed to guarantee that all the segments were correctly filled without leaving voids.

Selected materials and main characteristics included Ultraval SR Special Cement, with low quantities of C3A to help avoid delayed ettringite formation caused by elevated temperatures during hydration; river sand to provide a concrete mixture that could be pumped 655 feet horizontally and 260 feet vertically, yet resist segregation; and fly ash and the latest generation of high-range water-reducing admixtures to provide 90-minute workability and ensure adequate consolidation.

Project team members include Adif Alta Velocidad (owner); ARENAS & ASOCIADOS – IDOM (architectural and engineering firm); FCC CONSTRUCCIÓN – CONDURIL (general and concrete contractor); and CG Hormigones (concrete supplier).

Second Place — Viroflay Underground Train Station, Meudon, Hauts-de-Seine, France — Located at a depth of 82 feet, the Viroflay-Rive Droite and Viroflay-Rive Gauche stations were built simultaneously to extend the T6 tram line. Each station has eight prominent, white, cast-in-place concrete arches that evoke the nineteenth century railway viaducts spanning the Viroflay valley. The arches are not only aesthetically pleasing but fulfill two distinct functions: buttressing of the stations’ concrete diaphragm walls and supporting the intermediate concrete slab for the technical rooms 12 inches thick with a 65-foot span. The arches are about 49 feet wide and are hollow at various levels to provide space for escalators. The diaphragm walls were constructed using a hydraulic bucket to excavate the softer surface layers and a compact hydrofraise to excavate the bases. The walls are 98 feet high and 3.3 feet thick, and they have a light beige color and appearance that recalls the stone that is characteristic to the Viroflay region.

Project team members include Public Transportation for Paris Area (owner); Atelier SCHALL (architectural firm); EGIS Group Branch Railway (engineering firm); Eiffage Travaux Publics & Soletanche Bachy (general and concrete contractor); and CEMEX (concrete supplier).

Low-Rise Buildings

First Place — University of Iowa Visual Arts Building, Iowa City, Iowa — The new four-story facility for the University of Iowa’s School of Art and Art History replaces the 1935 Art Building, which was heavily damaged during a flood of the campus in June 2008. The entire concrete structure is exposed and painted white for a clean industrial aesthetic, culminating in a sculptural central atrium for open display of artwork and studio activity of all art disciplines. The building envelope is clad with zinc and stainless-steel plate panels, channel glass wall systems, operable windows, and a green roof. The concrete frame construction is supported on drilled pier foundations. The building’s foundation employs a biaxial (bubble) voided slab, decreasing the amount of material used by 30 percent compared with a typical structural concrete slab. This allowed for long spans uninterrupted by columns for generous studio spaces, and it generated savings on materials, transportation, and labor. The structural concrete skeleton of the building consists of 10- and 12-inch cast-in-place walls, 12.5-inch structural slabs, and 16- to 24-inch columns, all formed with Class A surface tolerances. All structural slabs were topped with a bonded 3-inch structural topping slab.

Project team members include University of Iowa (owner); Steven Holl Associates (design architect) and BNIM (construction architect); Structural Engineering Associates, Inc. (engineering firm); Miron Construction Co., Inc. (general contractor); Ceco Concrete Construction (concrete contractor, flat slab/shoring) and Miron Construction (concrete contractor, vertical); and Croell Redi-Mix, Inc. (concrete supplier).

Second Place — Design & Build of South Marina Yacht Club at Lusail (BP15), Doha, Qatar. — Occupying a prominent position over the water of Lusail Marina District, the iconic two-story South Marina Yacht Club can be seen from the four directions of the district and the marina sea. Features of the building include post-tensioned slabs spanning 49 feet and providing an open indoor space, and a cantilever spanning 17 feet all around (tapered in the free end to reduce dead load) to provide distinctive panoramic wide terraces. Concrete for the substructure had a design strength of 10,800 psi. The building is supported on a 28-inch raft with piles founded in Simsima limestone. The perimeter wall was continuously placed to ensure integrity. Slag cement was incorporated into the concrete mixture for the ground slab and suspended pit slab to limit the temperature of hydration, thus minimizing cracking. Other durability-enhancing factors for these slabs included corrosion-inhibiting admixtures, increased concrete cover, and reduced water-cement ratios. To provide corrosion protection in the piles, they were constructed with a concrete mixture comprising 60 percent slag cement and 8 percent microsilica; the specified concrete cover was 3 inches.

Project team members include Qatari Diar, Lusail Real Estate (owner); Chapman Taylor Espain (architectural firm); MZ & Partners (civil and MEP engineering firm) and Octatube (steel structure engineering firm); JV of Ceinsa & Al Jaber Trading & Contracting (general contractor); and Al Wataniya (concrete contractor).

Mid-Rise Buildings

First Place — 1200 Intrepid Avenue, Philadelphia — The 1200 Intrepid project is a USGBC LEED Gold-certified four-story mid-rise building with 94,000 square feet of high-end office space. The predominant feature of the design is the building’s eastern elevation, which makes use of compound double-curved, load-bearing precast concrete façade panels fashioned to echo the circular geometry of an adjacent park. The curvilinear wall was designed with a 22-degree tilt out over the adjoining pedestrian walkway to create an exterior suggestive of a ship’s bow and pay homage to the site’s maritime history. BIM software was used to ensure proper alignment in each of the 421 architectural concrete panels. The precast exterior employs interlocking embeds within the concrete, eliminating the need for traditional precast spandrel panels. Each precast panel on the inclined façade has a unique slope and different angle of rotation. Computer-generated cut sheets delineated embed layout and formwork construction. Architectural self-consolidating concrete mixtures were used to produce panels with exceptionally tight tolerances and ensure uniform window frame alignment.

Project team members include Liberty Property Trust and the Philadelphia Development Corporation (owner); BIG – Bjarke Ingels Group (architectural firm); Environetics (engineering firm); Turner Construction Company (general contractor); and High Concrete Group LLC (concrete contractor and supplier).

Second Place — Royal Alberta Museum, Edmonton, Alberta, Canada — The Royal Alberta Museum is the new home of Alberta’s Natural History and Human History collections. The project boasted one of the most advanced uses of BIM ever realized in Canada. The shared model allowed for increased geometric complexity, observable clash detection, and 4D construction scheduling. The design-build procurement method allowed for experienced and prequalified subcontractors to be engaged early in the design process. Concrete was selected for a majority of the structure due to its inherent acoustic rating, vibration and fire resistance, aesthetics, thermal mass, and durability. Cast-in-place concrete flat plate slabs were used for most of the structure to resist the exceptionally heavy loads imposed by displays and back-of-house artifacts. A spiral cast-in-place concrete stair located in the main entrance lobby acts as the focal point of the space and provides access to the second-level galleries. The museum showcases exposed concrete surfaces, including columns, slab surfaces, edges, and soffits. Basement foundation walls were constructed using shotcrete, reducing the need for formwork and thus cutting the time and crane dependency required to erect formwork. Construction of the $260 million base facility was completed in the fall of 2016 and the new museum is now open.

Project team members include DIALOG (owner, architectural firm, and engineering firm); Ledcor Design Build (Alberta) Inc. (general contractor); Pagnotta Industries Inc. (concrete contractor); and Lafarge Canada Inc. (concrete supplier).

Repair & Restoration

First Place — Provo City Center Temple, Provo, Utah — After a major fire in 2010, the Provo Tabernacle was transformed into the Provo City Center Temple (PCCT). Stabilizing the existing unreinforced brick masonry walls was the first step in the restoration process. Existing brick walls were five wythes thick. Stabilization comprised removal and replacement of two interior wythes with shotcrete concrete walls. The remaining brick was attached or adhered to the new shotcrete walls with helical anchors. The temporarily shored shotcrete walls were then reinforced with new concrete foundation walls. These walls were hand set to work around the shoring system and were constructed below the building’s original shell. This made it possible to build two new basement floors. To resist the loads on the basement floors, reinforced concrete mat footings were constructed in each area and micropiles were driven into soils below the mat footings. A dampproofing membrane and waterstop system were placed around all subgrade structures. A dampproof admixture was also used on the subgrade concrete to create a back-up mechanism for the dampproofing system. Self-leveling fiber-reinforced concrete was used for slab-on-ground and around the temple’s underground foundation walls.

Project team members include The Church of Jesus Christ of Latter-day Saints (owner); FFKR Architects (architectural firm); Reaveley Engineers (engineering firm); Jacobsen Construction Company, Inc. (general and concrete contractor); and Jack B. Parson Companies (concrete supplier).

Second Place — Ford Theatres Off Season Improvements Phases 2 and 3, Hollywood, Calif. — The Historic John Anson Ford Theatres in the Hollywood Hills is tucked into steep canyon walls in the Cahuenga Pass. From 2013 to 2017, the Ford Theatres Foundation (with support from Los Angeles County) invested in a major renovation and addition to restore the historic board-formed castle-like structure and bring the stage, lighting and sound systems, electrical infrastructure, and back-of-house areas up to current standards.

Off-Season Improvements Phase 2 included reconstruction of the stage and an extensive basement expansion. The excavation was stabilized using shotcrete retaining structures while the permanent structure was built. The new tiered stage includes suspended slabs and slabs-on-ground, flanked on either end by the historic concrete stage towers. The existing stairs and walkways used to access the theater were out of code compliance. Concrete was used to create double steps that aid in bringing the stairs up to code as well as providing a way to conceal and protect the new egress lighting.

Off-Season Improvements Phase 3 includes addition of a new 30,000-square-foot building with a loading dock, administrative offices, and an outdoor dining terrace for guests. The front-facing walls of the new structure resemble the original with exposed concrete walls with a board-formed finish. The 12-inch shear/gravity walls are up to 70 feet tall and are heavily reinforced due to the high seismicity of the region.

Project team members include The Ford Theatres Foundation (owner); Levin & Associates (architectural firm); Structural Focus (engineering firm); Charles Pankow Builders, Ltd. (general and concrete contractor); and Cemex (concrete supplier).

Photos and details about all of the winning projects can be found at www.aciexcellence.org. Entries for the 2019 Excellence in Concrete Construction Awards are being accepted now through April 2, 2019.

Information provided by the American Concrete Institute (www.concrete.org).