May 19, 2021
Concrete is an extremely versatile material; there are so many uses for it. You see concrete in a wide variety of applications – the obvious of which are curbs, sidewalks, columns and walls – but there are roads, paving stones, precast (pipe, culverts, maintenance holes, etc.), cement board, masonry, roller compacted concrete, dams, cement treated soils, counter tops…the list is endless. Even the new high rise wood buildings have a large portion of concrete in them.
When it comes to paving, concrete sometimes gets a bad rap because it is viewed as an expensive solution when compared to asphalt. On the other hand, it is also known to last longer. The reality is: they both have their place.
Mick Prieur, Director of Operations, Geotechnical and Materials Engineering, southwestern Ontario and Lindsay Freckleton, Director of Operations, Southern Alberta, are two of Englobe’s masters of concrete innovation. They recently spared some time demystifying the above assumptions of this sustainable construction material.
When you think of innovation in concrete science, what comes to mind?
LF: Recent innovations in concrete science have been intently focused on improving the sustainability of concrete by either utilizing raw materials that lower the initial carbon footprint or by improving the long-term durability of the concrete produced. Techniques to increase the replacement of traditional cement with ground limestone, fly ash, blast furnace slag, pumice and other waste or low carbon materials without compromising concrete performance have been extensively researched and are now commonly used. In addition, admixture technology has advanced to allow targeted improvement of specific desired properties such as shrinkage and permeability which can lead to increased service life of concrete structures.
MP: I think of admixtures as well. The chemicals that go into concrete these days can do so much: when I started my career 26 years ago, 35 MPa* concrete was considered high strength. Now, concrete producers regularly make 50 MPa concrete and even up to 100 MPa! Without the innovation of concrete admixtures, this would not be possible. Also, the cements are ground more finely now and are much more reactive; we use greater quantities of supplementary cementing materials; the chemicals we add are very different as well. With the goal of reducing carbon emissions produced by cement manufacturers, we will see even bigger changes in the coming years.
*MPa (or a megapascal) is a unit of measurement to denote pressure, stress, and ultimate tensile strength. It is a measure of force per unit area.
Tell us about the coolest project you worked on using concrete?
LF: In the spring of 2008, I had the pleasure of coordinating Englobe’s (then, McIntosh Lalani Engineering) portion of the Calgary Bow Tower raft slab pour. It was the largest continuous concrete pour for a commercial building foundation in Canada for a 58-storey office tower in downtown Calgary, Alberta. The pour started at around 8 p.m. on Friday night, and ended around lunch time on Sunday, taking just under 14,000 cubic metres of concrete! Our concrete team certified all the plants used to provide concrete, fully instrumented and monitored the internal temperature of the raft and performed the quality assurance testing with rotating teams of technicians, supervisors and materials engineers.
How has the invention of concrete improved society?
MP: If you live in an area susceptible to hurricanes, you would want to live in a concrete house. Whenever you see large natural disasters occur, you’ll often see that concrete buildings are the only ones left standing when all others crumble.
Another benefit of concrete is the light grey colour. The albedo (light reflectance) of the concrete is high, which means it reflects more light. When you compare that to a dark asphalt pavement, there is a significant difference in surface temperature on a hot day.
Just as whitewashed buildings are the norm in some warmer climates, using more concrete in place of asphalt would reduce heat island effect, making cities cooler.
Mick Prieur, Director of Operations, Geotechnical and Materials Engineering, southwestern Ontario
How does concrete affect the environment?
MP: Concrete is the second most used material in the world next to water, therefore, it will necessarily have a big impact on the environment. Statistics show that the making of cement represents 8% of the world’s CO2 production. The cement industry is trying very hard to change that and reduce its impact by using supplementary cementing materials, GUL cement, admixtures, different fuels for heating the kiln, carbon capture, and more. These techniques all help reduce impact.
Overall, concrete has a lot of benefits. When you make something that lasts 50+ years without major repairs and compare that to materials that only last 15-30 years before having to be recycled, I would expect the longer lasting solution to be more sustainable. Concrete is 100% recyclable, at the end of its life, it can be crushed and then reused. When crushed, the exposed surfaces of the crushed concrete also absorb CO2.
Concrete has the potential to outlive many other building materials. To meet its full potential, proper upfront design and collaboration between the project team members is critical.
Lindsay Freckleton, Director of Operations, Southern Alberta
LF: When materials engineers are brought in to consult early in the construction process, concrete mixes, admixtures, and placement techniques can be specifically tailored to meet both the short-term concerns of the contractor and the long-term goals of the owner. Englobe has the expertise across the country to facilitate these discussions which lead to sustainable and durable concrete structures.
A concrete advantage:
In general, concrete is slightly more expensive initially, but in many applications, it can be very competitive. A typical asphalt pavement is designed for 20-25 years whereas a concrete pavement is normally designed for 30-50 years, so concrete should last longer. If we designed concrete for 20-25 years, it would be more cost effective, but by increasing the cost by 10% you can double the life of your pavement. A great return on investment!
The price of concrete is not tied to the world oil market prices, which makes it more stable and predictable a construction material than asphalt, for example. The world oil market directly affects the price of asphalt and clients do not have to include provisions in their specifications for the price of oil jumping up from time of tender to when the project actually starts. In today’s economy, this is an important distinction.