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Nov 9, Cold Weather Concrete- What happens to fresh concrete when it freezes?

Cold weather concrete talks about pouring concrete when temperatures are at or below freezing. How to prepare and protect the concrete.

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What happens to concrete when temperatures are below freezing?

I experience cold weather concrete for 5 out of 12 months a year. Being from Maine our cold weather concreting season is from late October until sometime in March.

Having to make a living pouring concrete floors during Maine winters since the 1980’s, I’ve learned a lot about what happens to fresh concrete if it’s exposed to cold and freezing temperatures.

One thing I know for sure, if you let newly poured concrete freeze, you will have issues with the surface scaling, pop-outs, cracking, and overall weaker concrete.

cold weather concreteIt was 20 degrees F when we started this pour
cold weather concreteThe temp. reached a high of 33 degrees F and the concrete dried just fine

We covered the slab above with insulating blankets, a layer of hay, and a tarp over everything after we were done troweling.

The air temperatures for the next four days were all below freezing but the slab temperature under the blankets four days after the pour was 70 degrees F.

I highly recommend the insulating blankets like the one’s we’re using below to protect your concrete slabs, floors, and foundation wall pours.

You can buy them 6′ x 25′ or 12′ x 25′. I can vouch for them, THEY WORK!

You can get them right on Amazon and have them shipped right to you.

Buy your insulating blankets here.

I’ve had concrete floors where the entire surface has peeled off (top 1/8″) because the general contractor refused to protect and insulate the concrete after we troweled it and the temperature dropped into the 20’s overnight.





How to keep the concrete from freezing

FIRST LET’S STATE THE OBVIOUS

NEVER pour on frozen ground, Never! Sorry, just wanted to make that clear.

In cold weather, especially temperatures below freezing, the concrete mix should be batched with warm or hot water.

Generally speaking, water temps between 120 – 140 degrees F will give you a concrete temperature around 60 – 70 degrees after it’s mixed in the concrete truck.

I’m speaking from my own experience, actually checking the temperature of concrete mixtures when the concrete truck shows up on my job-site.

Forms, rebar, and embedded bond-outs should all be clear of snow and ice before pouring or you’ll have voids in those places.

After the concrete is placed, building enclosures, portable heaters, and insulated blankets should be ready to maintain the concrete temperature.

If the air temperatures are in the 30’s F or below and the ready-mix company isn’t using warm/hot water to batch the concrete, I would seriously think twice about pouring concrete that day.

Did you know this about cold weather concrete?

  1. Fresh or Plastic concrete will freeze if the temperature falls below 25 degrees F (-4C).
  2. Concrete gains very little early strength at low temperatures.
  3. Freshly mixed concrete must be protected against freezing until it reaches a compressive strength of 500 psi.
  4. At normal temperatures (70 degrees F) concrete usually reaches 500 psi in the first 24 hours.
  5. At 40 degrees F concrete could take up to 3 days to reach 500 psi.
  6. Significant overall reductions in strength gain, up to 50%, can occur if concrete is frozen before it reaches 500 psi.
  7. Concrete that goes through just one freeze cycle before reaching 500 psi may be restored to nearly normal strength if proper insulating/curing is done.
  8. Fresh concrete that freezes will not be as weather resistant or water-tight as concrete that hasn’t been frozen.
  9. Air-entrained concrete is less susceptible to early freezing than non-air-entrained concrete.
  10. Low temperatures greatly slow the rate at which hydration of cement occurs which ultimately slows the hardening and strength gain of the concrete.

CONCRETE GENERATES HEAT DURING HARDENING

Once the dry ingredients (cement, sand, aggregate) are mixed with water a chemical process takes place between the cement and water where they form a paste.

The heat generated from this process is called heat of hydration.

The amount of heat generated is affected by:

  • the type of cement used
  • amount of cement in the mix
  • thickness of the concrete
  • air temperature
  • initial concrete temperature
  • water-cement ratio
  • how fine or course the cement is made
  • any admixtures used

Heat of hydration is very important when pouring concrete in the winter.

Often the heat from hydration along with covering the concrete with curing or insulating blankets is enough to cure the concrete and keep it from freezing.

TO USE OR NOT TO USE AIR-ENTRAINED CONCRETE

In most cases, exterior cold weather concreting should include an air-entraining admixture.

Entrained air is most important when concrete is placed in freezing weather.

Why, because air entrainment provides concrete the capacity to absorb stresses due to ice formation within the mix.

Here’s my simple explanation of air-entrainment in concrete!

Picture what Dawn dish detergent does when you put it in the water to wash dishes. It bubbles up like crazy, right.

Those bubbles are kind of what air-entrainment is in concrete.

Thousands of microscopic air bubbles in the mix that allow concrete to absorb water and give the water room to expand when it freezes.

Since there’s voids for the water to expand, there’s usually little or no damage done to the concrete.

You know there’s a pretty good chance new concrete placed in the winter will see some rain, snow, or ice. Without any air entrainment, if the concrete freezes after being saturated with some form of water, it will lose strength.

The results might not be seen until the concrete thaws, but will likely
lead to some form of scaling or pitting on the surface.

POURING CONCRETE ON THE GROUND IN COLD WEATHER

Whether your pouring concrete footings, floors, or slabs, the ground can’t be frozen.

You’ll have to protect the sub-grade with insulating blankets, hay, or tent the area and heat it before the pour.

A cold sub-grade will suck the heat right out of the concrete, retarding the set time dramatically.

If you tent and heat the area with a direct-fired heater like a kerosene torpedo heater, you must vent the heater to the outside air. This type of heater produces CO2 (carbon dioxide) that will combine with calcium hydroxide on the surface of fresh concrete to form a weak layer of calcium carbonate that interferes with cement hydration.

In short, just make sure fresh air is coming in through the back of the heater.

Plan, well in advance, on how you’re going to protect the concrete after the pour. Have everything you’ll need, blankets, hay, tarps, heaters on site and ready as soon as you need to cover the concrete.

The sooner you protect the concrete from freezing the more heat from hydration you’ll save.

POURING CONCRETE ABOVE GROUND IN COLD OR FREEZING TEMPERATURES

When pouring on some type of decking it’s a good idea to enclose the area below the pour and heat the underside of the metal or wood decking.

Heat the underside area at least a day in advance to warm the decking and melt any frost, snow, or ice on the deck above.

After the concrete is finish troweled, lay some insulating blankets on top of the slab to keep it from freezing. Make sure to weigh the blankets down so the wind doesn’t blow them off, 2×4’s or rebar works good. 

Take a look at my 9 things to consider before pouring concrete in cold weather.

These are the same insulating blankets we use to keep our concrete floors, slabs, and walls from freezing in cold weather.

They’re available right from Amazon or if you have a local concrete supply store near you, they should have them also.

Disclaimer: I am an affiliate of Amazon, if you purchase them through my link, I will receive a small commission. Thank you.

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Source: https://www.everything-about-concrete.com/cold-weather-concrete.html

Concrete

Protecting Your Concrete Before Winter

With fall in full swing and the Louisiana heat finally starting to simmer down, it’s officially time to finish those yard enhancements that you’ve been putting off all summer. When preparing your yard for the freezes to come this winter, it’s important to include concrete in your checklist. All outdoor concrete surfaces need to be
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The post Protecting Your Concrete Before Winter appeared first on Port Aggregates.

Republished by Plato

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With fall in full swing and the Louisiana heat finally starting to simmer down, it’s officially time to finish those yard enhancements that you’ve been putting off all summer. When preparing your yard for the freezes to come this winter, it’s important to include concrete in your checklist.

All outdoor concrete surfaces need to be protected before winter hits. As temperatures begin to drop below freezing, repeated freeze/thaw cycles will cause your concrete to expand and contract, resulting in unsightly cracks when spring begins.

How to prevent winter cracks

One of the best (and most appealing) ways to protect your concrete this winter is with a decorative finish. 

A decorative concrete finish gives your surface an extra layer of protection and durability without replacing the entire slab. You can also customize its appearance with an endless array of colors and patterns. 

These finishes act as a concrete treatment and can protect against erosion from heavy rains, repeated freeze/thaw cycles, unsightly stains caused by decomposing leaves, and grout deterioration. 

If you’re satisfied with the appearance of your concrete and are looking for a cheaper option, concrete sealer is another great way to protect your existing slab during the winter. This will help protect your concrete without changing its appearance. 

Additional benefits of a decorative concrete overlay

Decorative concrete overlays can cover any imperfections, including discoloration and cracks, and transform your slab into a beautiful and protective slab. 

Whether you choose stamped concrete, stained concrete, or imitation stone to restore your outdoor area, you can rest assured that it will stay protected for years to come. Even in the rapidly changing Louisiana climate. 

With a decorative concrete overlay, you can create the appearance of flagstone, slate, hardwood, or cobblestone without spending an arm and a leg on real stone. Because the overlay is sealed, it will be resistant to chipping, peeling, staining, and weathering.

Don’t wait another day to protect your concrete from this year’s winter. With the Louisiana weather being as crazy as it has been in 2020, there’s no telling what this winter will bring. Start taking steps to protect your driveway now and contact Port Aggregates for assistance. We look forward to helping you keep your concrete safe this winter!

Source: https://www.portaggregates.com/protecting-concrete-in-winter/

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Concrete

Rebuilding the Future of Concrete Construction with Smart Technology

While local preference in building materials varies from region to region, high-rise construction in the Greater Toronto Area, especially in the residential subcategory, is exclusively done with concrete. Despite concrete having been available since the days of Ancient Rome, 20th- and 21st-century technological advancements have made it the medium of choice for an expanding range of uses.  In a region […]

Republished by Plato

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While local preference in building materials varies from region to region, high-rise construction in the Greater Toronto Area, especially in the residential subcategory, is exclusively done with concrete. Despite concrete having been available since the days of Ancient Rome, 20th- and 21st-century technological advancements have made it the medium of choice for an expanding range of uses. 

In a region like the GTA, with a variety of microclimates and underlying geological conditions, specialized types of concrete are being employed with increasing regularity. Customized formulations of concrete mixes now cater to foundations and caisson walls for sites with high water tables that need to be watertight, or road and water infrastructure that need particularly hardened varieties, and various other applications like industrial floors where standard concrete mixes aren’t necessarily up to the task.

One admixture manufacturer helping the construction industry create new varieties of concrete mixes is Kryton International Inc. For over four decades, Kryton has produced admixtures using Smart Concrete technology, which has allowed concrete producers and builders to give their concrete the necessary waterproofing and durability qualities. 

When Kryton first produced an admixture in the early 1980s, they developed a unique waterproofing admixture with a type of Smart Concrete technology known as Krystol® technology. With this feature, builders no longer needed to use waterproofing membranes. Instead, they could add Kryton’s admixture to their concrete mix, which would turn the concrete itself into a waterproof barrier. At any sign of water ingress then, the concrete would react, forming numerous needle-shaped crystals that fill up capillary pores and micro-cracks to prevent water from entering. 

Applications like this are especially important where construction of deep foundations spans a range of geological conditions. Our region’s glacial history and the resulting networks of ravines and waterways create challenging groundwater conditions for underground construction, while the need in dense areas and the desire in others to hide unsightly parking below ground are forcing builders to put their foundations deeper underground.

One such example is Terraces on the Park, a seven-storey building located in the Humber River valley in the Toronto suburb of Woodbridge. The site’s riverside location’s high water table and significant hydrostatic pressure means that waterproofing was critical for all underground concrete components. As a result, the foundation walls, slab-on-grade area, two levels of below grade parking, and the building’s exterior terraces were treated with Kryton’s Krystol Internal Membrane™ (KIM®) waterproofing admixture, while joints and tieholes were waterproofed with Kryton’s Krystol® Waterstop System. With Downtown Toronto situated on a former glacial lakebed and a proliferation of tall towers being built on reclaimed land on the waterfront, these waterproofing solutions have plenty of other potential applications in foundation construction around the city.

KIM technology was also incorporated into the concrete at the 2014-built Gibson Square Condominiums in North York City Centre, a project that may be more familiar to UrbanToronto readers. With construction already well underway at the time, Kryton’s products were used as a solution to waterproof a south foundation wall. With a constrained site footprint and no room for a trench to accommodate a traditional external waterproofing membrane, Kryton’s KIM admixture was added directly to the concrete mix for a faster, more cost-effective solution to the site-specific challenge. The benefits were immediately noted by the project team, who subsequently selected KIM for the waterproofing of the complex’s elevator pits.

A popular water feature in Toronto’s East Bayfront, Sherbourne Common, utilizes the same KIM waterproofing admixture for its lengthy concrete water channel, allowing the concrete to serve as an architectural finish without the need for additional water-sealing layers that could impact the aesthetic.

A more recent development in concrete admixtures produced by Kryton is being used in projects where increased abrasion resistance and durability are requirements. Projects like roads, hydro spillways, industrial flooring, agriculture, power generation, and marine structures are being built with the integral hardening admixture known as Hard-Cem®.

One local application of Hard-Cem was at the TTC’s new McNicoll Bus Garage, now late in its construction in Scarborough. The project’s construction team added Hard-Cem to the concrete used to form the building, increasing the hardness of the concrete paste and reducing wear loss and aggregate exposure due to abrasion. The result was a durable concrete structure capable of withstanding the constant surface abrasion and salt exposure associated with frequent bus movements.

This resistance to surface abrasion and salt exposure also makes this durable concrete a good candidate for warehouses and facilities that deal with harsh wear and tear throughout Ontario and the rest of Canada. There are plenty of examples of this, but a particularly significant one can be seen at Markham’s Earl Turcott Waste Management Facility. Considered to be the largest of its kind in Canada, this facility processes around 2,600 metric tons of waste and accommodates at least 350 vehicles. Despite the ongoing surface abrasion and erosive forces that result from this activity, the facility has stayed in working shape for over a decade with the help of Hard-Cem-treated concrete. 

Keeping in the spirit of Smart Concrete, Kryton’s latest big move came last year with the acquisition of a 30% interest in and North American distribution rights for a Denmark-based company producing advanced sensor technology known as Maturix®. This innovation attaches type K thermocouple cables to reinforcing steel, which will get immersed in concrete, and connects those cables to the sensors. That way, contractors only have to replace the cheap cables and can reuse these sensors for multiple projects. In return, the sensors monitor and log temperature data every 10 minutes and wirelessly transmit that data to Sigfox, a cloud-based platform. The platform then takes that data and time data to determine what strength the concrete currently has. Both temperature data and strength development data are then sent wirelessly to any connected device a contractor and their team chooses. All of which makes it easy to monitor concrete from anywhere at any time, giving the contractor, engineer, and any other team members the information they need to make critical decisions in a time-effective manner.

Overall, these updates to concrete construction will ensure that concrete remains the top material for thousands more years of civilization-shaping projects.

Excerpted From Urban Toronto

Source: https://www.kryton.com/in-the-news/2020/10/05/rebuilding-the-future-of-concrete-construction-with-smart-technology/

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Concrete

Oct 4, Diy Concrete Driveway Cost – The Real Cost Of Doing It Yourself!

A concrete driveway costs between $6 – $8 dollars per square foot for plain gray concrete and $10 – $20 dollars per square foot for decorative concrete.

Republished by Plato

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A concrete driveway costs from $6 to $8 dollars per square foot to install for plain gray concrete and from $10 to $20 dollars per square foot for a colored and stamped concrete driveway.

If you’re going to “do it yourself”, you will save some money on the labor costs. Labor costs of a concrete driveway usually range from 50% to 60% of the total costs of installation.





the average costs of a concrete driveway

The average concrete driveway costs between $2400.00 and $4800.00 to install based on a 400 square foot to 600 square foot driveway size. That’s based on a thickness of 4 inches with a 2 foot mat of rebar for reinforcement.

The gravel sub-base preparation could add  $1000.00 to $4000.00 to the total cost depending on how much gravel you need and if you have to demo and haul off an existing driveway.

Doing the work yourself you could save half of the costs above. Material costs for concrete and rebar for a 16′ x 25′ x 4″ concrete driveway will cost between $1000 and $1200 dollars.  

how much it costs to pour a 12′ x 40′ concrete driveway

Design and Gravel Prep
Forming and Reinforcement
Pouring the concrete
Finished concrete driveway

The costs breakdown for a 12′ by 40′ concrete driveway like the one we did above are below:

  1. Remove existing driveway and gravel prep – Labor 600.00 – Materials $600.00
  2. Forming & install reinforcement – Labor $750 – Materials $150
  3. Pouring & Finishing the concrete – Labor $1500 – Concrete $1100 (5″ thick)

Total cost of the concrete driveway: $4700.00

Deduct labor costs if you do it yourself: $4700 – $2850 = $1850.00 diy concrete driveway cost.

NOTE: These are my costs of labor and materials in my area, your actual costs for both of these may vary greatly depending on your situation.

basic tools for pouring a concrete driveway

Here’s a list of tools we use to pour and finish a basic plain gray broom finished concrete driveway:

Please note, these are affiliate links and I may make a small commission if you click through to Amazon and purchase these tools.

can i pour my own concrete driveway?

The basic steps for pouring a new concrete driveway are:

  1. Remove or demo the existing driveway (if needed)
  2. Design & Permits – Check with local building codes for permits & design specifications
  3. Excavation and gravel prep – install and compact gravel for the sub-base (the amount of gravel needed will vary depending on your conditions and climate.) 1 foot minimum gravel base.
  4. Install forms based on your design. Use 2×4’s or 2×6’s for straight forms and PVC boards for curves.
  5. Lay your reinforcement – Use 3/8″ or 1/2″ rebar and tie a mat 2 foot on center throughout the driveway then place bricks under it to hold it up in the middle of the concrete. Or use wire mesh.
  6. Calculate and order your concrete from the local ready mix concrete plant. (give them at least a weeks notice.)
  7. Pour the concrete level with the top of your forms, screed and bull float it smooth.
  8. Finishing the concrete – wait for the concrete to set up and use an edger to round the edges, mag float the surface, then drag a fine broom across the concrete to give it it’s final finish/texture.
  9. Saw contraction joints in the concrete the next day to help prevent cracking.
  10. Seal the concrete to protect it.

To learn how to work with concrete and the basic skills needed to install your own concrete driveway, check out  my concrete training academy The Concrete Underground.

other factors that add to the cost of installing a driveway

  • Your landscape – Is the area flat, slightly sloped, or steep. A steep sloped concrete driveway is more difficult to prep, pour, and finish which could add to the cost of installation.
  • The Driveway Size – A large driveway or a very long driveway would greatly add to the final cost. Concrete is a very expensive building material and adds about $150 per 65 sq. ft. of driveway.
  • How thick your concrete is – Driveway thickness contributes a large percentage  to the cost of a driveway. Concrete costs about $150 per yard – At 4″ thick that will cover 80 sq. ft. At 5″ thick that covers 65 sq. ft. At 6″ thick that covers 50 sq. ft.
  • Driveway design – Curved, circular, half moon shaped, or irregular angles may increase the material (and labor) costs. 
  • Adding color to the mix – Adding 1 bag of color per yard of concrete can add up to $80 per yard of concrete.
  • Stamping the concrete – Stamped concrete averages about $15 – $20 dollars per sq. ft. for labor and materials. 

how to build and pour a concrete driveway

The video below by Odell’s Complete Concrete will show you the basic steps it takes to build and install your own concrete driveway.

It shows you the demo and prep work, forming, pouring, and finishing process.


Conclusion: 

The diy concrete driveway costs above are figures I use when I give estimates for my customers in my area. 

These costs may change considerably depending on the cost of materials and labor in your area.

Please use these costs as a guide to help you consider whether or not you want to attempt to do your own concrete driveway or not.


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Source: https://www.everything-about-concrete.com/diy-concrete-driveway-cost.html

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