Author: Eloisa Holiday

Lots of people fear using concrete. If it goes wrong, it can be difficult to fix, but for smaller domestic jobs it’s actually a lot easier than many people think. With this guide, we’ll go over the different ways to mix concrete so you can decide what’s best for you when attempting your DIY project.

Concrete Proportions

Concrete has 3 main ingredients. Cement, aggregate, and sand. These ingredients are mixed with water, which when dried out, binds into a solid, very hard material. Depending on what you’re using the concrete for, these can be mixed in different proportions to give you different finishes and strengths.

It’s very important to get these proportions correct. With too much sand, your concrete won’t be hard enough to withstand the test of time. However, too much aggregate and you’ll be rushing to find a way to cover it up and pretend that it isn’t there.

Mixing Methods

In a domestic setting, there are several different approaches you can take to mix your concrete. If you’re happy giving the different proportions a go, you can either do this by hand or by using a mixer. For small scale jobs, mixing by hand can be ideal as it’s easy to keep track of the consistency and see how it’s going. This can often be a good thing to do as a practice if this is your first time. For larger jobs, a concrete mixer can save you hours of time and strength mixing larger amounts of concrete together.

When it comes to domestic concrete, it’s often overlooked that there are some other options also available to you, especially for slightly larger jobs such as concrete bases for sheds, summerhouses and other garden accessories. The main differences between domestic and commercial worksites are space. Often with a commercial worksite, the work will be planned to make these processes as efficient as possible, allowing the concrete mixers to reverse right up to where they’re going. However, this doesn’t mean you can’t utilise similar methods.

Types of Concrete Mixers

There are two main different types of concrete mixer. There are ordinary concrete mixers and also volumetric concrete mixers and both of these have different uses. You’ll likely have seen ordinary concrete mixers or mini mixers driving around quite frequently. These have the advantage of being able to transport one of many different mixes of concrete. Extra ingredients can be added to the concrete at the factory in order to provide different properties such as waterproofing or extra fibres for additional strength. However, this isn’t often needed when it comes to domestic concrete.

The other type of concrete mixer is a volumetric concrete mixer. These are ideal for domestic concrete as you don’t need to worry about having too little or too much. ‘Mix as you go’ concrete mixers contain the raw ingredients needed and as you pour out the concrete will mix it straight away. They also have the added advantage over traditional concrete mixers of being able to supply multiple different mixes of concrete to the same job without having to pay the additional cost of bringing in a second load.

Concrete mixers and volumetric concrete mixers are also a great choice for people taking on DIY projects that don’t want to take the risk of getting the mix wrong. All you’ve got to worry about is where it goes with the extra guarantee of knowing that it will stand the test of time. Thank you for reading this blog post. Should you have any enquiries, feel free to call us on 07812 182778 or visit our contact page for more information.

The post How to Mix Concrete by Hand or in a Mixer first appeared on Base Concrete.

When it comes to getting a durable concrete slab, a critical part of it involves keeping the concrete resistant to abrasion. Without that resistance, construction professionals will often encounter ruts, dips, potholes, or worse in the surface of their concrete. All of which can lead to safety hazards and operational inefficiencies.

Professionals usually try to counter this with conventional surface-applied concrete hardening solutions. But these aren’t reliably effective and come with a number of setbacks.

To look into why that is, we’ve decided to explore the bad, the good, and the better parts about concrete abrasion resistance. Helping us in this discovery are two of our Smart Concrete experts: Jeff Bowman, one of our technical directors, and John Andersen, our territory manager for Western Canada. To start, let’s dive into some of the negative aspects surrounding concrete abrasion resistance.

Thank you for joining us on the first part of this interview series. Let’s start by discussing what abrasion actually is and why it is an issue for concrete in the first place.

Jeff: Abrasion describes the steady loss of material from the concrete through some sort of mechanical action. It’s generally more of a surface phenomenon. So forces that are acting on the abrasion of concrete are usually going to be some sort of object that’s either rolling or sliding over the concrete. And this may also be combined with foreign particles trapped between those two phases that are also gouging and sliding through the concrete.

John: When we talk about the significance of that wear and tear on concrete, we typically think about just the cost of taking the building out of service and replacing the concrete. But there’s also a cost regarding safety. And it’s not just about the people tripping and falling and encountering all other hazards because of it. There’s also an issue of breathing in the concrete dust, the cost associated with keeping the facility and machinery clean, the cost to the equipment, and the reduced productivity due to the worn out concrete.

How exactly do construction professionals usually try to resolve this issue?

Jeff: Dry shake hardeners are quite a common product for this. I’m sure many people reading this now probably use or specify them.

But for anybody who’s not familiar with them, a dry shake hardener is some sort of blend of cement and possibly some other additives and an abrasion-resistant aggregate particle, such as aluminum oxide (also called emery). And these products get broadcast in a dry form overtop fresh concrete and then worked into the surface during the final finish.

Now, certainly, these products can work and can give you a good abrasion-resistant finish if they’re installed well. The challenge that the industry has is they’re very difficult to install.

Dry shake hardeners are applied in two portions, and there’s some work that needs to be done in-between. And one of the significant challenges of this application is that it all takes place in a very time-critical period. All the steps are time-critical, and it can be very easy to miss that perfect window of opportunity.

There are just so many variables that could be happening with the concrete and with the weather. And if workers start to have trouble with it, sometimes they just can’t get a full specified amount of the dry shake applied to the concrete.

John: That’s exactly the challenge that the contractor Graham Construction faced when they were building a new pea protein plant in Manitoba. This is a massive facility with large slab pours, and they were trying to get that shake-on hardener down in that little window of opportunity. And they lost the first slab.

They eventually changed to Hard-Cem to get away from the challenge of that little window of opportunity for properly applying the shake-on.

re there other challenges that come with using dry shake hardeners?

Jeff: Another challenge that we see is that this work normally comes up fairly late in the day when workers have been at it for many hours and they’re just getting fatigued. This is a lot to put on them at the end of the day.

Another challenge that we see is that the dry shakes are very sensitive to bleed water. If there’s too much bleed water coming out when you apply the dry shake and you work that water back in, the surface will become weaker and is likely to delaminate. If you have a low-bleeding concrete, perhaps something with a lot of fly ash, there’s just not enough water there to really work it in properly. The concrete sets up too quickly.

There can also be challenges with wind. And of course, it’s very important not to use dry shakes with air-entrained concrete because the power troweling needed to really work them in properly leaves a high risk of delaminating the concrete surface. So there are many challenges to dry shake products that people might face.

There are also some products that professionals apply post-construction, right? What about those?

John: Yes, I think if you’re in Western Canada, where I live, many of these products use silicate as the base for their formulas.

Jeff: Right. When we’re describing liquid hardeners (which are sometimes called liquid densifiers), these are all some sort of silicate-based product. They work by penetrating into the concrete and reacting with the calcium hydroxide there, which is a by-product of cement hydration. That reaction turns into what is called calcium silicate hydrate gel, which is the normal hydration product of cement. It’s what gives the cement paste its strength and what gives concrete its properties. So this reaction pathway is really quite similar to the reactions you get from fly ash or slag or other supplementary cementitious materials.

That introduces some challenges in and of itself. Some suppliers of these products recommend limiting the amount of fly ash or slag you’re using in your concrete. That’s not always possible or desirable for many other reasons. Or they may recommend delaying the application for at least 28 days to allow the concrete to come up to its specified strength first so that the silicate is not competing with the other cementing materials.

Does their application work effectively?

Jeff: While they are often used or specified specifically to increase the abrasion resistance of the concrete as placed, that’s not really what they’re intended to do.

They function by slightly increasing the amount of cement paste on the surface. But cement paste is the weakest and most vulnerable phase to abrasion. Having a little bit more doesn’t significantly move the dial on the abrasion resistance of that concrete.

Now, liquid hardeners do serve an important purpose. If a contractor does have a slab that has had some challenges when they’re placing it, the surface might be poorly hydrated or weak or might have dried out too early. These products can help strengthen that surface as a remediation measure.

But they’re not really an appropriate material to specify as an abrasion-resistant material for concrete that’s been otherwise properly placed and finished.

re there other solutions that have been used to increase concrete abrasion resistance?

Jeff: Another common solution is high-strength concrete.

And why not just use stronger concrete? You get better abrasion resistance. And normally, this approach would be just using a mix that has more cement. You could use more fly ash or slag or maybe silica fume to really get that strength up and keep that water-cement ratio down real low. The concrete gets stronger, and the abrasion resistance is better. And this generally does work.

But there are some limitations.

Now, the research shows that when you double the compressive strength of concrete, you can roughly double the concrete’s abrasion resistance. And there is research and literature on this.

But there can also be some consequences. Any time you are using a stronger mix, especially with anything that has more cement paste, you’re getting more hydration. That generates more heat in your concrete. More paste means more shrinkage. More shrinkage normally means more cracking. And if you’re pouring a slab, you also now get more curling, so your floors just don’t stay as flat. And curling can result in a lot of damage and wear at the joints.

All of these things are actually really bad. They target some of the core properties that a facility owner expects of their floor. An owner wants more than just good abrasion resistance. They want their floor to perform in many other ways.

And as an added bonus, using high-paste strong mixes comes with a cost premium. Because you are using so much more cement in the concrete, the carbon footprint of that concrete can go up quite significantly.

So most popular concrete abrasion-increasing efforts don’t seem to work as well as expected. Is there a better way to get that abrasion resistance?

John: Adding Hard-Cem into concrete at the batch plant! Hard-Cem lives in that concrete paste, and that’s how it works. It increases the resistance to abrasion and erosion that way. It’s easy to apply. There are no negative effects on your plastic or your hardened concrete. It’s fully compatible and used often with air-entrained concrete, so no longer do you have to specify products like this just for indoor use. You can now use it outdoors. And it can be used in horizontal and vertical slabs, behind formwork, in precast, and in shotcrete. There’s a huge opportunity for this product to be used often in mining applications as well.

And Jeff very clearly articulated the difficulty in applying the shake-on hardeners. So no longer do the jobsites have to take all this into consideration. Basically, they can just order Hard-Cem when they order their concrete. And there’s no harmful dust exposure.

Hard-Cem’s been used for 18 years now for over 7 million m2 (80 million ft2) in all kinds of applications. And many of the top-producing concrete companies have branded their own durability concrete using the Hard-Cem admixture.

Once concrete finishers get to use this, they start to ask for it by name because it just makes their job that much easier.

It sounds like Hard-Cem could be a much more effective solution. But how well does it perform? We’ll look into that in more detail in Part 2 of this interview series.

The post Concrete Abrasion Resistance: The Bad, the Good, and the Better (Interview Part 1) appeared first on Kryton.

Lately, there’s been an increase in interest over the well-being of coral reefs. These marine habitats represent an estimated $2.7 trillion in ecosystem service value and support around 25% of all marine life after all. But we have already lost 50% of the world’s reefs at this point. And there appears to have been no specific global funding to help develop the protection and restoration of these reefs in the past.

Recognizing this, a coalition of partners from the 75th session of the United Nations General Assembly created the Global Fund for Coral Reefs. With this fund, they hope to raise and invest $500 million (USD) to support programs that will increase the resilience of coral reefs.

That means you may soon see more construction requests for artificial reefs. These sorts of reefs are manufactured constructs designed to promote the growth of coral reefs and provide marine life with shelter. It’s a great way to secure a profitable tender and give back to the environment all at the same time.

But if you do decide to take on an artificial reef project, what can you expect?

You May See a Wide Variety of Structural Requests

Over the years, the innovation for building artificial reefs has only increased. People from all over the world have their own ideas on how to build reefs effectively. So when you do encounter such a project, you might find some unique structural requests. Here are just some of the more well-known ones you might end up with.

They May Be Complex Like a Habitat Skirt

If you win a bid for an artificial reef construction project from a governmental authority, your work may be fairly large and complex.

For instance, back in 2008, the Vancouver Convention Centre used governmental funds to include a habitat skirt worth $8.3 million. The first of its kind at the time, this project used 362 precast concrete slats. They were fit into 76 frames and arranged to look like a large five-tiered staircase. That extended the center’s shoreline by 477 m (1,564.96 ft) and added 6,122 m2 (65,896.66 ft2) of marine habitat surface area.

That is no easy feat for a project that had never been done before! As one of the University of British Columbia’s blogs notes, this amount of space is equivalent to “the length of five Canadian football fields and the floor space of the entire White House.”

It’s also not the only government project thinking big. Further south, down in the United States of America (USA), in San Diego, the port there has started to install a sea wall. Designed to protect the edges of Harbor Island, the wall is expected to help restore the island’s marine ecosystem.

It makes use of a structure that consists of the Coastalock system, which interlocks hollow concrete units to create habitats for oysters, sea stars, algae, and a variety of other marine wildlife.

The port hopes to use 72 of the 3.5-tonne modules of this system to replace the island’s current riprap.

With those two projects in mind, you can see that certain artificial reef projects will involve a decent amount of construction material, some intricate design input, and a keen contractor eye to keep everything working smoothly.

Or They May Be a Smaller Affair Using Reef Balls or Cubes

Not every artificial reef project is so extensive of course. There are plenty of people around the world who go to the Reef Ball Foundation and ARC Marine to install concrete structures in waters. These structures may be circular or more cube-like in shape, and they can range in size. Some may be as small as 0.3 m (1 ft) or so or as big as 1.5 m (5 ft) or more. In either case, the structures come with holes and various surface textures to offer marine wildlife places to rest and hide from predators that still look and feel like natural reefs.

They aren’t always interlocked and don’t need any additional design work. So it’s easier for people to order these structures from the organizations making them or from contractors for these organizations and have either group deploy the structures into the water.

It also makes it a less complex project on your end if you win a contracting tender for an organization that already handles this sort of work.

It May Even Involve Just Deploying Structures or Materials in a Specific Part of a Marine Area

Sometimes building artificial reefs is all about the structures or materials and nothing else.

In some cases, that might mean placing defunct ships, oil rigs, or some other old, large structure into open waters.

In other cases, it might mean doing the same but with defunct subway cars! Running with that last idea, the State of Delaware in the USA has been pushing old New York City Redbird subway train cars into the open waters off the coast of Slaughter Beach since 1996. However, to make sure these cars are marine-friendly, they strip them of any glass, seats, signs, wheels, and petroleum products before dumping them. That way, water can flow in and out of the old vehicles, allowing larvae from sea invertebrates to safely drift in and gain shelter, which in turn, lets them flourish and feed other marine animals.

An even simpler version of this project that you might encounter could be a request to place concrete pipes or steel beams on the ocean floor. For instance, further south from Delaware, in Pinellas County, Florida, such projects have helped to create around 42 reefs.

These Requests Can’t Just Be Fulfilled with Any Material, However

While some projects will already have a specific material in mind like those using the reef balls or reef cubes, there will be others with more leeway. And when that happens, you’ll need to carefully consider what material you use.

Think of it as building a home of sorts. You wouldn’t just use or reuse any old material for a person’s home. It could end up being structurally unsound or even toxic for the person who chooses to live there.

The same can be said for building artificial reefs. If you choose to build reefs by reusing waste like old tires or polyvinyl chloride, you’ll soon discover that neither material is the right kind for marine wildlife to call home. They’re usually too small, for one. So organisms needed to create reefs can’t grow on them. And they’re also very unstable. The waves can carry them to any part of the ocean floor easily, which is not appealing to marine wildlife as reefs are meant to be naturally anchored to the seabed. What’s worse though is that they can both release toxic chemicals, transforming their potential to be homes into a danger zone for any aquatic creature nearby.

So, what can you use instead?

Concrete Is Often the Preferred Material for Building Artificial Reefs

You might have guessed it already considering how often previous projects have used it already. But concrete really is one of the more preferred materials for building artificial reefs. And there are a number of reasons why that’s the case.

According to the New Heaven Reef Conservation Program, some of those reasons have everything to do with the composition and versatility of concrete.

Much like reefs, the composition of concrete makes use of the chemical compound calcium carbonate. Reefs get it naturally through coralline red algae, which form a calcareous skeleton that supports coral reefs by cementing them together. Meanwhile, concrete often gets the compound through common building materials like limestone. But regardless of how they get the compound, that makes concrete at least seem more natural to marine wildlife.

That’s not all that gives its composition such an appeal. Concrete is also innately strong and heavy enough to remain anchored at the bottom of any waters it’s placed in and lasts for a long time, giving marine wildlife a secure shelter for protection or habitation.

But what about concrete versatility?

Well, because concrete can be constructed into almost any shape and size, it gives you an opportunity to give an artificial reef any number of nooks and crannies that fishes and other aquatic wildlife like to hide in.

However, There Are a Few Other Materials You Could Work With

With that said, concrete isn’t the only material that people have gone for when building artificial reefs. They have also gone with the following materials using unique methods:

Electrified steelUsing biorock technology, ecologists in Indonesia have been able to form artificial reefs with electrically charged steel structures. Using a low-voltage current to charge the steel, the ecologists create an interaction between the electricity and the minerals in the seawater. That reaction causes limestone to grow on the charged steel. That growth eventually solidifies, forming reefs much quicker than they naturally would otherwise. This method has also shown to heal injured coral up to 20 times faster than other methods.

Steel spiders Even without electricity, steel remains a good material for building artificial reefs. For instance, people off the coast of an Indonesian island have been attaching parts of coral reefs to rust-protected reinforcing steel structures known as steel spiders. Over time, this process increased the amount of coral on the steel spiders by over 60%. At least 42 different coral species were growing on the steel spiders because of this. And in the rubble surrounding the steel spiders, people found at least 58 species.

Glass bottles in concrete While this method still uses concrete, the main focus is the glass bottles embedded in the concrete. As the concrete keeps the glass bottles anchored securely, the bottles themselves act as a way to transplant broken or nursery corals to attract marine life to the area and eventually create a reef and feeding hub for fish.

If You Do Go with Concrete, Consider Increasing Its Durability

As you know by now, concrete has a lot going for it as a material for artificial reefs. So if you do choose to use it, you know you’re in good hands.

But like with anything, you want to make sure you’re using your chosen material as effectively as possible. Part of that means making sure the concrete for your reef lasts for as long as possible. After all, artificial reefs are meant to be a lasting solution to the loss of so many natural reefs worldwide. And they won’t last if they don’t remain a permanent fixture in the water.

There are plenty of solutions out there that can help you strengthen the life span of your artificial reef, however. So which should you go with?

Here are some good choices that you might want to consider first:

Con-Fume One major artificial reef organization in the USA, the Reef Ball Foundation, requires silica fume in the specs for their artificial reefs. So if you want to follow their design as a blueprint for your own artificial reef, you may want to apply our Con-Fume solution. It is a silica fume product made from pozzolanic material to produce high-performance concrete. It comes in ready-mix bags and meets ASTM and CSA standards for silica fume.

Hard-Cem If you happen to be placing your artificial reef project in waters with swift currents, you may want to add Hard-Cem to your concrete mix. With fast-flowing water, there’s a higher chance for debris to bump up against your reef structure, gradually eroding away its surface and even potentially causing cracks. That surface will likely weaken after some time, leaving it vulnerable to losing aggregate and cement binders to the fast-moving water. But with Hard-Cem, this possibility becomes less likely. As an integral hardener, Hard-Cem increases the abrasion and erosion resistance of concrete and doubles concrete wear life even under harsh conditions. So it is capable of giving your artificial reef the durability it needs to withstand the abrasive and erosive forces in the water.

Krystol Internal Membrane

(KIM Another issue that can threaten your artificial reef’s longevity is a sulfate attack. Sometimes caused by industrial water pollution or seawater, a sulfate attack can chemically change the reef’s cement, weakening its bond with the surrounding aggregate. That can then cause extensive cracking and wear, ruining the structural integrity of your reef. Luckily, KIM can safeguard your reef from such a situation. Using Krystol technology, it enables your concrete to react chemically to water, forming needle-shaped crystals that fill up its capillaries and micro-cracks. That ensures the sulfate in the water cannot get through your concrete and damage its structure. KIM was also one of the top-performing products at preventing the corrosion of steel reinforcement during a 10-year study in a marine environment by the University of Hawaii. Moreover, KIM is also NSF-certified as safe for potable water and has the Singapore Green Label, proving that it is non-toxic.

You’ll Soon Have an Artificial Reef Perfect for Clients and Marine Life

Knowing what to expect and what tools to consider now, you’ll be ready to create a marine-friendly artificial reef of your own in the future. Just keep in mind the potential scope, materials, and obstacles you might encounter, and you’ll have an artificial reef up in no time.

The post Building Artificial Reefs: What to Expect appeared first on Kryton.