Concrete

Freeze-Thaw Cycles in Concrete

The effects of the freeze-thaw cycle in concrete and how you can prevent them.

The freeze-thaw cycle is one of the main catalysts of erosion. Yes, water and wind impact can also slowly wear down even the toughest rock over millions of years. But one of the fastest and most efficient ways to break stone, rock, asphalt, brick, and concrete, is the freeze-thaw cycle. In fact, water penetration/expansion is the primary cause of concrete and asphalt degradation.

What is this cycle?

The freeze-thaw cycle is something we have covered quite bit, and is the primary reason to get your asphalt seal coated. Basically, what happens is that water gets inside and below the surface of the asphalt. From there it naturally expands and contracts as the weather changes. Normally, this change in water volume damages concrete, but doesn’t totally destroy it. The weather change from night to day, or spring-fall is not too serious. It’s when the water that’s inside concrete starts to freeze that it becomes a serious problem.

When water gets into concrete at all, you are going to have a bad time. It will bleed into small cracks, and then get into smaller and smaller crevices, all the while creating more. Basically, water gets in through a crack system and then extends and deepens that same crack system. Imagine it like a network, or the shape of a spider web.

Once water that’s inside your concrete freezes, then you have an even bigger problem. Freezing water takes up significantly more volume than liquid water, whether the liquid water is hot or cold. This seriously expands the cracks, making existing ones much larger and creating new ones for the water to get deeper inside. Untreated, freezing and melting water can completely destroy concrete or asphalt paving in just a few years.

What to look for

Crack propagation

Unfortunately, freezing water may cause internal cracking, which is hard to notice. If you notice cracking that looks like it originated from its interior, or beneath it, then you may have damage from the freeze-thaw cycle. Here is a good guide for identifying various types of concrete cracks.

Surface spalling

This happens when chunks break off of the surface of the concrete. It is a problem that gets worse over time, because when the surface breaks off, the aggregate beneath is exposed. The concrete below the surface is not usually sealed against water, so once it is exposed, expect the damage to come in even faster. Spalling can even reveal the rebar/structure at the core of the concrete. If this happens, you may need a replacement if the concrete is structural.

Heaving

Heaving, often called frost heave, is when the ground below the concrete lifts many inches and the concrete can not move with it. This causes the concrete to lift and break. Frost heave is one of the main ways that concrete is damaged. It’s incredibly difficult to make sure that moisture stays out of the ground below concrete thanks to groundwater and seepage from underground pipes.

The problem may not be due to water though. Tree roots beneath the concrete can cause the same issue.

Preventing freeze-thaw damage to your concrete

Deicing

One of the best ways to ensure your concrete doesn’t get water in it is the use of deicing chemicals. These chemicals work by lowering the temperature needed by water to freeze. When these chemicals, like sodium chloride (you know, salt), are placed on the concrete surface, they mix with water that falls on that surface. When the water does penetrate the concrete, it is unable to freeze and will (mostly) harmlessly drain out. If you live in a place that gets snow, then keeping all moisture out of your concrete is a lost cause, and you need to adapt to what does get in. Here’s a great list of other deicing mixtures.

Applying a sealer

Just like asphalt, you can apply a sealer to the surface of concrete. A hydrophobic coating will help make the concrete resistant to water penetration. Apply a sealer only after the concrete has fully-cured, and before you use an deicing agent. It also needs to be used before a freeze-thaw cycle has occurred on the concrete, usually in warmer temperatures, so before autumn has set in.

Good construction practices

One of the best ways to ensure your concrete isn’t damaged in the first place is to make sure the construction is done right from the get-go.

Controlling environmental water

Before beginning a paving project, you should make sure that the area is well-irrigated. Gutters, drip edges, and slightly inclined concrete planes help ensure that water drains away from and off of concrete.

This goes for groundwater as well. Before concrete is placed, the earth around it should be well-drained. Earth around concrete should also slope away from it a little to prevent groundwater from flowing toward the concrete. Flashing can also be used to ensure water flows away from the wall structures.

Concrete slabs need to have some wiggle room

No matter your best efforts, water will sometimes get into and under concrete. This will cause expansion and if the concrete has nowhere to expand to, it will break. Make sure that concrete slabs are able to move a little bit with the earth below them. If they can do this, then heaving will cause significantly less fracturing and cracking of concrete than it would otherwise. You can place small barriers between slabs of concrete, using asphalt, wood, or rubber to give your concrete expansion joints. These joints provide some cushion so the concrete can expand without breaking.

Is your concrete damaged?

Do you have freeze-thaw damage on your concrete? Would you like to get it fixed or prevent future damage? If so, you’re at the right place. Reliable Paving, is a large, experienced paving contractor company with the skill and professionalism to get your paving fixed, or done right the first time. Our concrete services include (but are not limited to): repair and sealing. If you want to make sure you can resist the frost, then let us know today, and we can start weatherproofing your concrete.

How To Repair And Seal Cracks in Concrete

A guide for repairing concrete damage.

Cracks in concrete aren’t just an eyesore. They pose a hazard for tripping, and will result in more damage down the line. Cracks allow in water, water expands and contracts over the course of a day/year. This change in volume causes cracks to expand and causes all kinds of other types of damage. Broken out pieces, rutting, and uneven surfaces can all happen to concrete. Repairs will keep damage from spreading and getting worse. Fortunately, we’ve got a handy guide for repairing damage and cracks.

Required tools and materials

  • A tub/bucket for mixing the concrete sealant.
  • Two trowels/floats.
  • Paint brush.
  • A chisel.
  • Hammer/sledgehammer (depending on the size/depth of the crack).
  • Concrete product. This can be epoxy/latex or a mortar mix. These mixes can be called filler, sealer, and more. They vary differently according to the size and requirements of the repair job.

Mortar mix is made from:

  • Portland cement
  • Vinyl
  • Sand
  • Water


Optional:

  • Stiff fiber brush/ wire brush
  • Putty knife (for more delicate/detailed work).

Step 1

Choose your concrete repair product. There are many. You should NOT fill a concrete crack with more concrete. You will need something to fill the patch and something to seal it afterwards.

Products include:

  • Concrete sealant
  • Ready-mix concrete
  • Patching compound
  • Vinyl patch repair
  • Epoxy
  • Latex
  • Polymer structural concrete repair product
  • Self-leveling sealant

And much more. You can even by full-on kits that have just about everything you need. Choosing the right product is important, and based on a few considerations. A marine environment will require a heavy-duty seal that won’t be damaged by salt water. Structural repairs may require their own special mixtures. Light/surfaces scratches or cracks can sometimes get by with epoxy/resin mixtures. For this guide, we are assuming you are fixing outdoor concrete for general business/home use.

For general outdoor concrete repairs, you can use the following two fillers:

  • Epoxy/latex for cracks whose width is 1/8 an inch or less.
  • Mortar mix is best for larger imperfections. Big cracks and full-on holes will require mortar mix. The surface can be covered with a sealant after the main repair is complete.

Step 2

This may seem counterintuitive, but you will start by making the crack bigger. Use the chisel to make the crack wider at one side than at the other. The crack should be shaped like a carrot or daikon. The main area to be filled should be the widest. The narrow area helps to anchor the filler by providing more contact area per filler volume.

Widen the crack at the top by using your chisel and hammer. If the crack is shallow, chip away until it is about 1 inch below the surface of the plane of concrete. If the crack is especially deep, or the concrete is especially hard, you may need a sledge hammer instead. Lightly tap the chisel with the sledge hammer so you don’t accidentally do too much damage. You should also make sure to remove large loose rocks from the crack with your hammer/chisel. 

Step 3

Use your paintbrush to clean out the crack. Every small pebble and shard of loose concrete weakens the fillers grip on the inside of the crack. They take away from purchase area, and they weaken the sealer itself. Ideally your crack will have nothing but filler when it is repaired. You can use also use the stiff fiber/wire brush if the paint brush and your fingers aren’t enough for the job.

Step 4

Inexperienced people working on their homes, and sometimes even paving contractors who like to cut corners will treat this as step 1. Additionally, people will often simply use more concrete to fill the crack. This will not result in as secure and permanent a repair as using the proper product.

Using epoxy/resin in small cracks

For 1/8 an inch or less width cracks, use your epoxy/latex mix. Before use, you may have to mix the two substances. Be sure to follow the manufacturer’s guide on what ratio to use. Use the trowel to force the mix into the crack. You may prefer using a putty knife for this. After the crack has been filled, smooth it so it is level with the surrounding concrete. Afterwards, consult the directions on the packaging again so you know how long it will take to cure. It may need to be covered during the curing process.

Using a mortar mix in large Cracks

Mix your Portland cement, vinyl, and sand. Use as little water in the mix as possible. Blend 1 part Portland cement to 3 parts sand. A ready-mix will have the Portland cement and sand already combined. Mix 1 part water to 3 or 4 parts mix. Make sure the mortar mix is not too thick and not too runny. Stir for 5-10 minutes and let it rest 10 minutes before stirring again. The process should take at least 2 hours.

Now it’s time to fill the crack. Use the trowel to ensure the crack is completely filled. When filling with this substance, be sure to frequently press down on the area with the trowel to eliminate air bubbles. Once the crack is completely filled, make sure to level its surface with the trowel, so it is the consistent with the rest of the concrete. Let it sit for about 2 hours afterwards. Next, cover it with a plastic sheet to keep humidity levels high. Sprinkle water once per day over the next several days on the surface until it has fully hardened.

Does your asphalt or concrete need some love?

At Reliable Paving, cement, concrete, and asphalt is our bailiwick. We are consummate professionals when it comes to asphalt paving, concrete and asphalt repairs, striping, and seal coating. If you want your pavement fixed right the first time, come to us. Contact us today and we can get the job started — and finished, sooner.

Causes of Concrete Deterioration

Concrete has enjoyed a reputation as a “set it and forget it” building material since it became popular in the mid-twentieth century. However, concrete definitely is victim to plenty of external influences. Many of those influences can cause serious degradation. 

Builders today are realizing that existing concrete structures won’t last forever. Many buildings from the 20th century, and even some built in the last few decades, show significant damage. Let’s look at what these signs are, and the causes for concrete deterioration.

General signs of deterioration

Fortunately, concrete, as well as most paving work, wears its heart on its sleeve. It’s easy to see damage to concrete and find it. On the other hand, it’s rare for the damage to be totally hidden. So here’s what you should look for:

  • Cracking: This is the most common type of damage sustained by concrete. Fortunately, cracks are easily visible, and thus easy to treat once spotted. Be aware though, that hairline cracks can become massive over time, as they allow water inside. When that water expands and contracts, you get small cracks becoming bigger and radiating out more fractures.
  • Discoloration: A change in the color of the concrete is not a good sign. If the concrete is changing to a brown/reddish color, it means that there are other chemicals in it. Often the change in color is from corrosion from metals or exposure to other outside chemicals.
  • Erosion/Disintegration: These two (used interchangeably), are denoted by cracks and crumbling. They are often caused by the freeze thaw cycle, or heavy precipitation.

 

Specific signs of degradation

Sometimes very specific elements cause concrete to deteriorate. For example cracks can be caused by a huge variety of things, but the specific cracks that look like scales are caused by an alkali-silica reaction. Here is a list of specific types of damage often sustained by concrete. 

  • Spalling: Spalling is basically when the concrete flakes away. It can be unimportant or extremely serious. Spalling occurs when the concrete is installed poorly in the first place OR when it is under too much structural stress. 
  • Alkali-Silica reaction: This chemical reaction in the concrete causes a scale-like cracking pattern. The concrete swells outward and in doing so the surface cracks like the surface of a desert drying after the rain. Also called concrete cancer, it can read to serious degradation, and might even require demolition after being untreated for some time.
  • Delamination: Caused when the top surface of the concrete (the laminate) separates from the lower levels. It is found by tapping on the concrete, if a hollow sound is made, the concrete is delaminated.
  • Scaling: Scaling occurs when the mortar covering concrete begins to wear away. The mortar is an outside protective layer, so when it goes, the aggregate underneath the surface becomes exposed. 
  • Chemical diffusion: Also called chemical corrosion or penetration, this happens when a chemical is exposed to the concrete and works its way through the layers. This is a common occurrence with solvents and acids. Chemical diffusion causes cracks, divots, and pits. 

 

Causes of the degradation

Now that you know what to look for, let’s take a look at what causes the problems listed above. Looking through the specific causes of concrete degradation will help create some insights on how to avoid them.

Exposure to chemicals

Chemicals exposed to concrete can wreak all sorts of havoc. From erosion to chemical penetration, there are many threats posed by various chemicals to concrete. 

Some of the chemicals might come from routine maintenance:

  • Antifreeze agents put on pavement in the winter. These include liquid chemical compounds and salt.
  • Cleaning agents for concrete.

Many of the chemicals that damage concrete come from tangential outside sources.

  • Vehicles leaking oils/other fluids on pavement.
  • Concrete in industrial buildings becoming exposed to solvents or other agents used in manufacturing, agriculture, etc.
  • Paint or graffiti. 
  • Accidents and spills.
  • Natural solvents. Carbonic acid, acid rain, and other solvents from nature can seep into the ground and damage concrete. This is especially a threat to underground concrete (foundations). Concrete structures at the bases of hills and mountains may have similar exposure.
  • Degradation of the reinforcing steel. When the steel that supports concrete starts rusting or dissolving. 

Weather

Weather – most notably water is probably the number one destroyer of concrete. The freeze-thaw cycle erodes mountains over time. Concrete is not immune. When water freezes, it expands by 9%, according to a Cement.org study (look at page 4).  It’s not hard to imagine water getting into small cracks and freezing to break them open further. The problem is degenerative, once water is in your concrete, it can be impossible to get out.

The freeze thaw cycle also effects the ground. The ground sets differently in the warm months than when it is frozen. This setting can crack and break concrete foundations. Weather damage most often is in the form of cracking and potholes.

Structural stress

When the concrete begins to degrade, or the reinforcing steel begins to degrade, it can not take as much stress. This means that structural concrete may no longer be up to the job it was built for once the deterioration begins. 

Adding new levels to a building, placing heavy machinery, or building with heavy materials may induce too much stress on concrete, and cause serious damage. Stress can show up in many forms, spalling, scaling, and cracking.

Improper installation

Just about all of the problems and signs of bad concrete can be caused by one other thing as well: improper installation. If the concrete is mixed poorly, sets poorly, or installed poorly, a myriad of issues can arise. The rebar can dissolve, cracking can occur, delamination…the list goes on. 

Get your concrete installed right

If you want your asphalt paving, concrete, or cement inspected for issues, don’t hesitate to contact Reliable Paving. We are an experienced paving contractor who can check your concrete for damage, do repairs, and entire new installations. You want your concrete installation to be done right, the first time, so get a service that’s reliable.

Ancient Concrete and New Construction

In modern Italy, a unique question has only been answered in the last several years. Modern concrete constructions built at the seaside have degraded and crumbled after only a few years. The salty sea waves and ocean wind had destroyed creations of modern technology while ancient concrete has lasted thousands of years. Why do our modern buildings collapse while ancient concrete islands can withstand the elements for millennia? 

How the Romans did it

Ingredients

The ancient Romans started building concrete thousands of years ago. They used various ingredients, including some of which are hard to reproduce in modern labs. 

Opus caementicium, or concrete, was used commonly in ancient times. It was made in the same over all method that modern concrete is. It consists of an aggregate and a mortar. The aggregate was made from small rocks, pebbles, and hard pieces, just as it is now. The mortar functioned as the binding agent, keeping everything together as an extremely tough glue. However, a few different construction ingredients and methods keep ancient Roman constructions in good working order while our own fall apart. Opus caementicium used aggregate made from tuff. Tuff is a rock made from volcanic ash, ejected from vents during a volcano’s explosion. There are many types of tuff, but the tuff was not the most important ingredient.  

What really keeps the Roman buildings together is how the binder and aggregate interacts. Gypsum and quicklime were used, as well as pozzolana. Pozzolana is a volcanic ash that is resistant to sea salt – more so than modern concrete. The pozzolana was used in conjunction with the binders to create a cement that strengthened and became more resistant over time. 

Reactions with the outside world

Pozzolana and quicklime benefits from interacting with salt water over time. A rare crystal, tobermorite, formed over time as these three materials were exposed to one another. As seawater washed between the natural cracks in the concrete, it reacted with materials found in the volcanic rock. 

As the seawater flowed in the concrete, it would wash away the volcanic ash. It might seem that washing away part of the ingredients of the concrete would weaken the concrete, but it actually had the opposite effect. As the ash washed away, it allowed new formations. In particular, crystals could form and make interlocking “plates” that strengthen the concrete over time. Phillipsite, naturally found in volcanic rock, and seawater builds up a special type of tobermorite crystals. These crystals are called aluminous tobermorite crystals. Aluminous refers to the element aluminum. Aluminum is a light metal that is known for it’s low weight and tensile strength. These new crystals form over time, filling in tiny fissures and making the building stronger over time. 

Thanks to the unique reactions of the Roman concrete with seawater, it has the reputation of being the strongest, longest lasting concrete.

Other elements of construction also aided Roman buildings. The dome-shaped tops of many Roman buildings and their foundations aided longevity as well. The tops of many Roman structures were made of a less-dense, lighter weight concrete. The foundations were made of denser, harder, tougher concrete. The heavy foundations and light tops kept the buildings in place and stable. This type of construction is especially useful in the earthquake-prone Italian peninsula. 

What we can learn from ancient concrete

After reading the first half of this article, what we have to tell you now might seem like a surprise. Roman concrete has some amazing properties, but it is not actually better over all than modern concrete. There are quite a few reasons why this is true, and we will take a look at them. 

Benefits of Roman concrete

  • It gets stronger over time with reaction to sea water.
  • It is more natural, and has a lower environmental footprint.

Why it’s not quite as good as we think it may be

To most people, the idea of concrete that strengthens over time seems amazing. However, to any paving contractor or mineralogist, the idea of a concrete strengthening with crystals is pretty normal. Crystals form on all kinds of surfaces. The combination of materials that makes up cement makes the appearance of crystals pretty common. 

This article covers the following points, and some of the articles you might find about Roman seawall cement quite well.

There are a few other factors that really do effect how fast deterioration of modern cement occurs.

  • Roman cement did not have reinforcing steel. Rebar, or steel beams in the cement changes the chemical structure. Embedded steel actually corrodes the concrete when exposed to seawater. Modern cement has this steel, and thus is more inclined to degrade. Simply not using rebar extends the life of modern cement.
  • The southern Italian peninsula has a very temperate weather cycle. Unlike many other places where sea cement building might be compared, there is no freeze/thaw cycle. One of the main reasons for the breakdown of cement is water freezing in it’s small pores. 
  • Survivor bias is the idea that old things are better than new things. We believe this, because the old things that last are still there, and we don’t see the old things that no longer exist. This goes for buildings, societies, appliances, and vehicles. 

Looking for the best cement work?

Here at Reliable Paving, we follow the newest and most accurate data regarding cement and asphalt paving. Our over 35 years of experience and 200 plus person team means that no paving job is too big or difficult. We can make our paving ideal for the location and climate of your choice. If you have any questions, or would like a consultation about your paving job, don’t hesitate to contact us today.