Solidifying The Future Emerging trends shape the world of precast concrete by Robin Brunet Advancements in precast concrete are completely changing the design and construction sectors. The use of precast concrete building elements have been proven to positively impact the bottom line. Precast systems help minimize cost with faster construction, lower maintenance and overall operating costs, and reduce the environmental impacts, while providing comfortable, safe buildings. Innovations dominate the precast realm too, thanks to developments such as computerized precision colour control, carbon fibre reinforcement (for ultralite panels) and prestressed open space trusses, which provide long spans but maintain the shallow floor depth of a flat plate system. Thus, companies such as The Prestressed Group that has made the process of strengthening concrete s natural weakness with tension one of its specialties can meet virtually any precast need, whether it is hollowcore plank and structural products (voided slabs, box beams, girders, double tees, beams, columns, walls and noise walls) or high-end architectural products. In fact, precast concrete is the material of choice for many developers who seek durability, construction efficiency and pleasing visual esthetics, says Brian Hall, managing director, Canadian Precast/ Prestressed Concrete Institute (CPCI). Our members are involved in some interesting projects, adds Hall. Take the recently opened ALT Hotel in Halifax for example; precast concrete mixed with imported black granite sand and charcoal was selected to pull off the building s sleek, dark exterior. Almost 3,000 square metres of architectural precast concrete was required for the 169-room hotel. The recent construction of the Toronto South Detention Centre highlighted one important competitive benefit that precast concrete has over other structural materials; the cost effectiveness of selecting a system that would provide an architectural precast concrete finish on both the load bearing and the non-load bearing panels were integral to the structural system. Once the structural parameters were established, the architect (Zeidler Partnership) developed the final design of the interior spaces, addressing structural details that ultimately defined the overall character of the building. In particular, due to the nature of the facility, the owner wanted connections between the precast elements hidden wherever possible. During the engineering design process, The Prestressed Group and Stephenson Engineering developed many concealed and hidden types of connections. Organizations such as the Cement Association of Canada (CAC) have publicly expressed disappointment that some governments have officially endorsed wood as the building material of choice for all government buildings, and that the proposed building code change would increase the maximum height of wood buildings to six storeys, from the current limit of four. The CAC s counter-argument to wood proponents is a familiar but compelling one. CAC contends that the construction of five- and six-storey wood-frame buildings could present many safety concerns for Canadians. If these taller wood-frame buildings are included in the Building Code, Canada could see an increase in fires, putting more Canadians at risk. Manufacturers and builders continue to innovate and take advantage of the latest systems in order to differentiate themselves from the competition. Plus, companies like Ontario-based Res Precast Inc., that has over ten years experience in the design, fabrication and erection of architectural precast concrete products, aggressively expand their expertise by involving themselves in the latest construction methods and techniques for the simple reason that quicker turnarounds, greater project scope responsibility, high-quality products and competitive prices are routinely demanded of subcontractors by developers and design-build specialists. Lafarge, a leader in product innovation, recently signed a partnership agreement with the U.S. startup Solidia Technologies to industrialize an innovative technology that could reduce the environmental footprint of concrete. The technology allows lower carbon dioxide (CO2) emissions in the cement production process and involves the capture of CO2 in precast Solidia concrete. Overall, CO2 emissions could be reduced by up to 70 per cent. The development of a new type of cement, Solidia, is significant because the manufacturing process uses conventional cement kilns and existing precast batching/mixing equipment, as well as conventional aggregates. The major difference is that CO2 replaces water in the setting and curing process, says Don Zakariasen, director of marketing at Lafarge Canada Inc. Water is used for mixing and placing Solidia concrete but is not consumed in a hydration process. Curing does not require autoclaves or other specialized equipment. Zakariasen adds that not only does this process result in a dramatic reduction in CO2 emissions compared to conventional mixes, but Solidia has a favourable cost of manufacturing because it s fired at a lower temperature. The finished product has a higher strength and permeability, and it sets in one day instead of 28 days. Plus, the colour is beige, not dark grey, which I m sure will be attractive to many architects. Solidia Concrete, which was the brainchild of New Jersey-based scientists, is being manufactured for the first time in block, pipe and precast plant production in Alberta. We need to ensure that it works on a commercial basis, but I have a strong feeling it will blow the socks off the industry overall, says Zakariasen. Embedded fibre optics in the wall panels of the Simons Retail Store Anjou in Quebec create the sparkling effect. Made possible by Béton Préfabriqué du Lac (BPDL) precast concrete. Photo courtesy CPCI. Precast Concrete april 2014 /13
Solidia Concrete products: The technology allows lower CO2 emissions in the cement production process and involves the capture of CO2 in precast concrete manufacturing. Photos courtesy YUI+Company, Inc. Brad Forder, sales representative of precast solutions for Armtec, cites an interesting project that involved Armtec Brooklyn (the leader in rooftop pavers in Ontario) and Ripley's Aquarium of Canada in Toronto. The Aquarium is a 12,500-square-metre attraction with more than 5.7-million litres of water showcasing marine and freshwater habitats. Flynn Canada Ltd., a key customer of Armtec Brooklin, was contracted by Ripley s to supply the rooftop pavers for the building. The architect s vision was to provide the benefits of rooftop pavers and a strong visual effect: that of two sharks swimming. Forder says, The rooftop pavers were a combination of our white solar and charcoal paver slabs in a matte finish. Different tones of our charcoal rooftop pavers were manufactured and provided for review. The darkest of the charcoal samples were approved, and we received an order for over 60,000 f2 of custom 2.5-inch rooftop pavers. The project was started in late 2012 and completed in the spring of 2013, and Forder notes that getting the order for the project was a result of our strong brand and ability to provide customized product to meet customer needs. From job specification, manufacturing, delivery and coordination, the Ripley s project was a success. South of the border, concrete giant U.S. Concrete Inc. and its business units (such as Central Concrete Supply Co. Inc.) have been particularly busy of late collecting awards for exceptional work and winning contracts for multibillion-dollar projects. In November, Central Concrete (a leader in delivering low-co2 concrete to the San Francisco Bay Area) received the Northern California & Western Nevada Chapter American Concrete Institute (ACI) Award for Outstanding Construction, Structural Category. The award recognized the work performed for Stanford University's Bing Concert Hall. One of the key objectives was to accommodate unamplified musical performances in the Hall, and to achieve this Ennead Architects designed a tilted oval ceiling canopy suspended 47 feet above the centrally located stage, creating a lower reverberation and richer, fuller sound. In addition, concrete sails with their convex shapes were installed to disperse the sound, enabling the audience to hear sounds coming from more than one direction. Central Concrete supplied 7,500 cubic yards of concrete for the project, and the low-co2 mixes selected reduced the overall carbon footprint for the construction project by just over one million pounds. That same month, Eastern Concrete Materials, Inc., a business unit of U.S. Concrete, began delivering land-supplied ready-mix concrete and precast concrete products for the three-mile-long New Tappan Zee Bridge. The new bridge crosses New York s Hudson River at one of its widest points and will replace the deteriorating Governor Malcolm Wilson Tappan Zee Bridge. The new $3.1-billion bridge will be constructed of low maintenance "100-year-life concrete" with precast concrete decking and, when it is finished in 2017, will be the widest bridge of its length in the world with eight traffic lanes, a bike and pedestrian walkway, and provisions for a rail transit installation. As the demand for precast work steadily increases, smaller precast companies are expanding the product range and improving plant processes. Such is the case for the owner of Edmonton-based Concrete Inc., Rui Veiga, who last year invested in a new batch plant that 14/ april 2014 Precast Concrete
Tappan Zee Bridge, courtesy New York State Thruway Authority. is automated for improved speed and accuracy. CPCI s Hall adds that the precast concrete industry is working hard to meet the demand for sustainable design. CPCI is utilizing its completed Life Cycle Assessment study for the development of Product Category Rules (PCR) for precast concrete of North America. The PCR will allow the industry to develop Environmental Product Declarations (EPDs) for precast concrete. North American precast Concrete associations are working together with ASTM International and the Athena Sustainable Materials Institute to achieve third-party verified EPDs to provide comprehensive, uniform and transparent details about a product s composition and environmental impact throughout its life cycle. The EPDs release will be available in fall. n Precast Concrete April 2014 /17