Anyone involved with concrete finishing and protection—either through design, supply, or installation—is likely to have been affected by blistering and other moisture-related failures on floor finishes. A multi-million-dollar problem in North America, there are numerous reasons for such failures. However, a conversation being had more frequently today surrounds the relationship between alkali-silica reaction (ASR) and near-surface alkali reaction (NSAR) and finishing failures.
Canadian firms have been using tilt-up concrete for creative applications for many years, helping to push the construction method into new territory. Familiar as a building method for commercial and industrial facilities, tilt-up is increasingly being used in high-end buildings—and this turn of events is taking the material back to its starting point.
Constructing buildings requires the skills and knowledge to meet the demands of speed of construction, energy efficiency, resiliency to environmental conditions, cost efficiency, and long-term durability. The tilt-up concrete method, which speaks to all these attributes, has steadily grown since the 1940s due in large part to the development of the mobile crane and advancements in ready-mixed concrete.
Insulating concrete forms (ICFs) offered an energy-efficient mode of construction long before sustainability was widely pursued, or even understood, in the overall building industry. In the intervening years, competing building methods have seen improvements in thermal energy efficiency, but the properties of ICF have remained virtually constant, until recently.
In seemingly every sector, from government to real estate development to retail, project owners are looking to make their construction sites greener. The movement toward more sustainable construction practices is neither trend nor fad; it is a functional philosophy responding to both a heightened public consciousness of the impact of human activities on the planet and the added value of doing ‘the right thing.’
The Rotman School of Management at the University of Toronto (U of T) has grown substantially over the last 12 years. Consequently, this innovative business school has outgrown its downtown space, resulting in a $91.8-million expansion project that includes construction of a new 15,004-m2 (161,500-sf) building clad with a curtain wall system incorporating ultra-high-performance concrete (UHPC).
From towering skylines and massive dams to modern bridges and centuries-old temples, concrete structures are the basis for much of civilization’s infrastructure and its physical development. Concrete is used worldwide, more than any other manufactured product—twice as much of it is used throughout the world than all other building materials combined. Each year, approximately four tonnes are used for every one of the nearly seven billion people on Earth. (This information comes from the 2009 U.S. Geological Survey).
When a reinforced concrete bridge deck is subjected to freeze-thaw cycles and de-icing salts over a number of years, the ensuing deterioration drastically reduces the structure’s service life and results in costly maintenance or early replacement. In such severe environments, high-performance concrete (HPC) is often required because of its superior strength and low permeability. Unfortunately, HPC also has a tendency to crack prematurely if not properly cured.
Concrete pavements are known for their strength, durability, and longevity. In the past, they have also been associated with a high initial price. However, in a number of lifecycle cost studies, concrete pavements prevail due to the significantly lower maintenance and rehabilitation needs.
Annex D of Canadian Standards Association (CSA) A23.3-04, Design of Concrete Structures, introduces a new and comprehensive limit states design (LSD) procedure for determining factored tension and shear resistance of both cast-in-place (CIP) anchors and pre-qualified post-installed mechanical anchors installed in cracked and uncracked concrete.