Austin-based pavement engineering firm The Transtec Group delivered an expert review and lifecycle recommendations for the pursuit phase of the Southwest Calgary Ring Road public-private-partnership project (P3) in Calgary, Alberta.
The Calgary Ring Road Project consists of a full 101-kilometer circle around Calgary, which the Government of Alberta and the City of Calgary have been planning since the 1970s. The Southwest section of the project, which broke ground in the summer of 2016, is one of the last segments to complete the ring, and is expected to be open for traffic in 2021.
“The Southwest section of the Calgary Ring is a critical link to facilitate mobility within and around Calgary,” said Dr. Robert Rasmussen, Vice President & Chief Engineer for The Transtec Group.
The Transtec Group provided a comprehensive analysis and independent opinion for pavement-related aspects of the project, with a heavy emphasis on construction methods and their impact on long-term pavement performance. As part of Transtec’s unique and thorough assessment, a field review of existing pavements was performed as well as a study on the methods used to produce that pavement.
“The cold climate in Calgary can cause pavements to crack if not designed properly, which is why we spend a lot of time assessing the methods used and the ability of materials to withstand extreme temperature changes,” said Dr. Rasmussen. “The value of our expertise lies in our independent evaluation, providing guidance for the developers to ensure a quality, long-lasting pavement.”
The firm has previous expertise with a similar P3 project in Winnipeg, Manitoba, when it delivered a plan for pavement design and life cycle advisement for the Southwest Transitway project with the Plenary Group.
The Southwest Calgary Ring Road Project was awarded to Mountain View Partners, for whom KGL Constructors is performing the design and construction. KGL is a consortium made up of Kiewit Management Co., Graham Infrastructure and Ledcor Group of Companies. Mountain View Partners will also provide oversight during the Operations and Maintenance period, which has been subcontracted to Alberta Highway Services Ltd. (AHSL), a subsidiary of Colas Group.
About The Transtec Group
The Transtec Group is a pavement engineering firm that delivers exceptional engineering in pavement design, design/build, P3, construction, research, pavement surface testing, pavement software development, and technology implementation. Transtec engineers pavements that reduce cost, accelerate schedules, and protect clients from risk. The firm has completed over 700 projects worth more than $50 billion on five continents and is a minority-owned small business based in Austin, Texas.
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Lauren Concrete was selected to provide ready mix for ABC’s award winning show, Extreme Makeover: Home Edition when the show traveled to Bastrop, Texas to build a home for a family that lost all in the Labor Day fire of 2011 in Texas.
Mizzy and Chris Zdroj and their three children were the recipients of the new home as EFC Custom Homes of Bastrop and “Extreme Makeover: Home Edition” harnassed the power of more than 3,000 volunteers. Mizzy is an unpaid volunteer firefighter who battled the Bastrop wildfire while her own house burned. Her fellow firefighters nominated her for the home makeover.
The builder, EFC Custom Homes of Bastrop, selected Lauren Concrete for this precision timetabled build. “We are working under an amazing schedule and Lauren Concrete has the state of the art dispatching and technical systems to coordinate the pour with precise deliveries” said one worker on location at the site. “Lauren Concrete has built a reputation as the go to company when you need the finest materials and a disciplined team. That’s why they were selected from all the ready mix companies in Central Texas”.
There was an added surprise for the Bastrop community, Extreme Makeover: Home Edition” remodeled the Heart of the Pines Volunteer Fire Department building located next to the Zdroj home and other companies also donated firefighter uniforms and additional equipment.
If you have any questions you can always visit the Concrete Forum and post your questions. Here’s an example of the great information shared for one person who had a question about why their concrete was cracking after only four months.
I am in the late stages of an addition to my home which includes a master bath and covered patio. The slab was poured in late November 2010 all at the same time (bath slab and patio). We had a major storm roll thru the afternoon/evening the concrete was poured but the concrete did sit for 4-6 hours before it started raining. As the addition progressed, I started noticing cracks in the concrete. The tile guy found nine hairline cracks across the bath area alone. Last month I noticed a crack all the way across the patio, which is about 16′ x 30′. I refuse to believe that this is “normal” like the contractor says. I had a detached garage and driveway extension built summer of 2009 and that concrete doesn’t have any cracks at all…..even with the recent trucks driving over it for the current addition. I believe the concrete supplier didn’t mix the concrete properly. Is there any way to test a sample of the concrete or have it inspected by an expert? What are my options if I find out the concrete is substandard?
Some of the helpful replies:
It’s extremely common for concrete to crack. it’s far more uncommon for it NOT to crack. There are several reasons for cracks. The two most likely are:
1) The concrete was poured much too wet, leading to excessive shrinkage as it cured. Many times, contractors add a lot of water to the mix to make it easier to pour it out of the truck. When the concrete cures, it loses water and shrinks a bit. Too much added water leads to a high water to cement ratio and therefore a lot of cracking, and typically within a couple of days of the pour!
2) There were not enough crack control joints, or they were improperly installed. These are the joints that are either tooled in while the concrete is wet, or sawed in as soon as possible after the concrete sets up. They are designed to control random cracking. There are specific ways they need to be installed. Probably the least likely scenario is that the concrete was defective. It’s more typically contractor error. Did the same contractor pour both of the slabs you mentioned? I wrote an article about concrete cracks. It can be found at www.4greatconcrete.com under the artcles and publications link. It goes into much more detail as to other causes of cracking as well. Good luck.
Although you were not there when they actually filled the truck with the appropriate materials, once the truck comes to the job site, the contractor or the man in charge of the concrete usually takes a look at the concrete by pouring a little into the shute. So the driver of the concrete truck gives this blank look and looks at the contractor or the man in charge and sometimes the man in charge will have the driver add water so he can work the concrete easier. At that point the question would be, who is responcable for the mixture of the concrete? As it is not feasable to hire a state licensed testing company to be there during the pour on a small job, that would have been possibly the only way to protect yourself. So the options are tear it out or live with it, sorry to be blunt.
If concrete is of perfect mixture and of perfect placement and perfect subgrade(of course there is nothing perfect in concrete)over a period of time will crack every 15 feet. The control joints just try to get the crack to happen at the control joint. So the object is to make the control joints asthetically pleasing to the eye with the surrounding architecture. The more control joints the better chances you have of hiding the cracks. Climate – soil conditions – placement voids – where the rebar is inside the concrete and mix all will have a contributing factor in a crack.
Question sent from a reader: I have a large concrete driveway that has obviously been enlarged over the years and pieced up with mortar at various points. Consequently it’s a mismatch of colours. I was thinking about painting or staining the driveway with exterior paint or concrete stain, assuming I can find any here in the UK, and sealing it the same day using a concrete seal?
Would such a process be effective or would I be wasting time and money?
Here’s our expert’s answer:
It won’t be miraculous buy it will be effective.
We have a waterbased stain that will color everything including your sneakers. Very potent.
Acid stain may not be as effective with different surfaces and patched areas.
How long should I cure (keep the plastic, straw, blankets, water, etc) on my concrete (driveway, sidewalk, slab, etc.)?
This question can only be answered by the professionals associated with the project. Concrete cures at different rates depending on the constituent ingredients and the ambient conditions it is exposed to. Your contractor (concrete supplier) should know what sort of curing is required for the particular mix being used. Also, by following their recommendation, you maintain whatever warranty that might be associated with the work performed. If there is a problem that occurs later on, they can’t blame you for not curing it properly if you did it according to their instructions.
How do I level (screed) the concrete over an area that is wider than my screed board.
You can tackle this several ways. The professionals will drive grade stakes inside the forms at convenient intervals (less than the width of the screed board). The grade stakes will have the proper level marked on the stake, usually a nail in a wooden stake. You can place some concrete in the forms and using the grade stakes as a guide, begin screeding the concrete. As you get the proper grade on the concrete, you can pull the grade stakes. As you can tell, this requires a little experience to get it just right, but beginners can do it with less accuracy.
Another method is to get a probe, such as a stick or steel stake, mark it with the depth you want the concrete to be, then place the concrete in the forms. Screed the concrete and probe to ensure the proper depth. This is not as efficient as the first method, but it will get the job done with a little more effort. You can set construction joints (1×4’s, metal keyway forms, etc) inside the forms at intervals of 25-30 times the depth of the slab. You can use these as screed guides.
Finally, you can set screed guides inside the forms using 2×4’s and stakes so that the bottom of the 2×4’s are at the top of where you want the concrete to be. Nail ears on the end and top of your screed board so that when you set the screed board on the screed guides, the bottom of your screed board is even with the bottom of the screed guide, thus level with the top of where your concrete will be. Once you get your concrete down and screeded, you can pull these screed guides and fill in the stake holes and re-level by eye.
What standard specifications should I know or understand regarding information received from a contractor in anticipation of signing a contract to have my concrete driveway replaced? What is better rebar, reinforcement mesh (both?) , fiberglass reinforced cement? Depth of the driveway poured, 2inches 4 or more? How far should expansion joints be put in to handle heat and cold.
Reinforcement steel in flatwork is strictly for crack control. The best crack control is affected by putting the steel in the upper half of the slab. If your contractor can guarantee he will keep the wire mesh in the upper half of the concrete, that will do as well as rebar. Make sure he gives at least 3/4″ cover to whatever reinforcement he uses. The standard driveway depth is 4″, but that doesn’t mean that depth is right for you. It really depends on the soil conditions and the load you will be putting on the concrete. Thickened edges (beams) are highly recommended for the outsides of the driveway. This will enable the edges to take that occasional load on the edge or coming onto or off of the edge. Normal
Portland cement concrete likes to crack every 10-12′, so jointing in all directions no more than 10′, with the joints being a minimum of 1/4 the slab depth, should help the expansion/contraction problem. There are two types of joints: contraction and construction. Contraction joints are usually installed with a concrete saw after the concrete gets hard or a jointing tool while the concrete is still fresh. Construction joints are preinstalled dividers such as redwood strips, aluminum keyways, or other physical barriers. Either type of joint will allow for expansion/contraction, so if you don’t want redwood every 10′, you don’t have to have it. Make your joints as square as you can. Try to avoid rectangular jointing sections. Make sure the contractor orders concrete that has 4-6% entrained air, since you live in conditions that probably require salting of roads. The air will enhance the concrete’s freeze/ thaw durability and make it less susceptible to salt damage. I could spend at least 8 hours going over things to look out for and things to avoid. The main thing is sitting down with the contractor before you sign a contract, and tell him how you want the thing to look when he gets finished. Discuss whether visible cracks are acceptable or not. Discuss a warranty. Tell them what you want in the end, put it in your contract, then get out of his way and let him give you what you want. If he doesn’t give you what he says he would in the contract, you have legal standing for a remedy. Also, let him buy the concrete so
he can’t blame you for buying an inferior product that he couldn’t work with.
Periodically, as a service for our readers, we’ll feature a select job posting with a top concrete industry company. This month we are proud to present a posting for a Ready Mix Dispatcher.
Candidates must have experience with Command Alcon software.
This is not an entry level position. Professional experience as a ready mix dispatcher is a prerequisite. The geographic location for this job is the Austin, Texas area.
How to apply: please email resume and requests to: email@example.com
*No phone calls, please – email correspondence only – send resume in PDF or doc format
So, you want to put in a patio, driveway or sidewalk, and you are going to use concrete. A very wise choice, we can all agree. One thing to know before you put in your concrete all concrete cracks. You say, “Wait a minute, I’ve seen concrete that doesn’t have any cracks. How can you say all concrete cracks?” Concrete typically consists of cement, rock, sand and water. In the fresh, or plastic stage, concrete is fluid.
By Kenneth Wayne Meyer
As it hardens, the cement and water begin to shrink, and the stresses created by this shrinking cannot be overcome by the small amount of strength developed by the young concrete. If you place the concrete on a windy day, the top may start to harden before the bottom, which will cause the concrete to shrink unevenly (plastic shrinkage cracks.) Also, if the ground underneath the concrete is not level, there will be an unequal dragging force while the concrete shrinks, also causing stresses the new concrete cannot withstand. So, how do you get concrete with no VISIBLE cracks in it? By following a few simple steps before and after you place the concrete, you will have a very nice looking structure that will require very little maintenance, and give you years of enjoyment.
Before you place the concrete, make sure your subgrade (ground beneath the concrete) is thoroughly compacted and level. The absolute best thing to do is get a garden tiller, till the soil to a depth of 6 inches, then rent a hand operated compactor and compact the soil vigorously. This will help ensure there are no soft spots. You can apply a layer of cushion sand if you want. This will help achieve a totally level surface and allow a consistent friction to the shrinking concrete. Four inches of washed sand ought to be plenty for the cushion. If you use a wire mesh for reinforcement, use panels and not rolls. The rolled wire mesh is extremely difficult to keep in the top half of the concrete, where it HAS to be in order to do its job. You can also use reinforcement bars (rebar) tied together with steel wire, but spacing and size requirements vary based on load and soil conditions, so it is hard to recommend a standard set up for that. If you do use rebar, it is essential that you keep it in the top half of the concrete. You can use stones, broken brick or you can buy plastic chairs that the steel will sit on to keep it in the proper position when you place the concrete. You can also have the ready mix concrete company supply fibers to the mix. These fibers are usually nylon or polypropylene. They help keep the cracking of the concrete on a micro level instead of a macro level (where you can see the cracks with your naked eye.) Steel reinforcement also helps keep cracking in check, but if cracking does occur, the steel, when properly placed in the concrete, will hold the concrete together, whereas fibers will not do that.
Okay, you’ve got your subgrade ready, you have placed a plastic vapor barrier on the subgrade for slabs that will support dwellings, your steel is sitting nicely on your plastic chairs in the proper position, and you now have 14 of your closest friends on their way over to help you place the concrete you have coming. When the concrete arrives, if you don’t have a vapor barrier, wet the subgrade without puddling the water so that the water in the concrete will not be absorbed by the dry subgrade, thus causing uneven drying and the dreaded plastic shrinkage cracks. Once the concrete is placed, make sure to protect it from high winds and direct sunlight so the concrete will dry evenly from top to bottom. You are now ready to perform the most important step in preventing noticeable cracking. Contraction joints are the secret to no cracking! By placing contraction joints that are at least 1/4th the depth of the concrete and on intervals of 25 to 30 times the depth of the concrete (usually easiest with a jointing trowel or tool while the concrete is still fresh), you will almost ensure there will be no visible cracking in your concrete. If your slab is 4 inches thick, the joints must be at least 1 inch deep and placed every 100 to 120 inches. If you cannot use a jointing tool to put the joints in, you can hire a concrete sawing contractor to do this for you. Make sure he cuts the joints a minimum of 1/4th the slab depth. This jointing method helps the concrete crack at the weakest point. This is why it is so important for the joints to be deep enough. Variations in subgrade levels could cause greater stress in the concrete in an area where the joint isn’t deep enough, and the concrete will crack outside the joint. Once your joints are in place, and the concrete has cured for about two weeks, you are ready to seal the joints. This will prevent water from migrating into the subgrade and expanding and contracting, or getting into the joints and freezing, causing the water to expand and breaking out the concrete around the joints. You now have a concrete structure that will serve you well.