Exposed Aggregate Concrete

Matching Exposed Aggregates

As with most entries I make on this website in regards to concrete and contracting, they generally come about through my day to day experiences with projects and clients expectations.

One topic that comes up more often than not, are clients wanting to match their existing exposed aggregate concrete that they already have placed, with the new exposed aggregate concrete being placed.

It is correct to consider exposed aggregate stones in the same relative category as decorative resurfacing colours and colours for your colour through concrete. It is a natural product that is not calculated to precise measurements during mixing at the plant. Quite literally, the aggregates are mixed with the concrete by machinery and conveyor belts typically by weight, meaning, that no two loads of exposed aggregate will be exactly the same.

In saying this, you can trust (on most occasions), that when pouring a driveway for instance, where two or more truck loads of concrete are required, that the multiple loads supplied on that same day will be close enough to a match together that it is unnoticeable to both client and contractor. However, I have come across the rare occasion where we have poured a selected exposed aggregate, only to return a week later to pour the remaining part of the job, (with of course the same selection of stone), and have it look different enough that it was noticeable. The project itself still looked fantastic as a whole, but the blending of stone was different.

Now this is all well and good when we are talking about a singular project that we are completing at a given time. Even with a difference coming through, because the two parts of concrete are poured within a given time frame, along with being supplied by the same company, there isn’t a problem at all.

From here though is where we enter the problematic area. Lets say for instance you as the client, have had your exposed aggregate poured previously, for sake of conversation lets say it was 12 months ago. Now you are after some new exposed aggregate to be poured adjoining the existing slab. You’ve done the right thing, remembered who the company was supplying the stone and exactly what it is called, even with these measures in place, there is absolutely not guarantee that your new stone will be the same blended mix as the one that was poured a year ago.

Also you need to take into consideration the after a few months, concrete starts to build up dirt and mold in the actual cement, which typically starts to darken you cement within the concrete (seen between the stones). Then when we place the new exposed aggregate concrete, as normal, when cured it comes out a very white, bright colour. This will make the two sections of concrete appear different overall when looking at them together. This aspect of course will get better over time as the new concrete starts to get dirty and mold as well, so time is your friend in this case.

Now we get to the really tricky part. You’ve had your concrete poured a year ago and you’ve forgotten what company supplied it and what it’s name was…..This side of things is considered a bridge too far with matching. Yes, you can have your contractor look over your concrete and advise you what he/she thinks is the “best match”, you can also have a sales rep come out to site to also advise you on their thoughts, but at the end of the day it is a calculated guess and more often than not will be a wrong guess.

Our exposed aggregate concrete we supply comes in sections separated sometimes by 10%. For example, “Dalmation” (Salt and Pepper), concrete starts at 10% white stone and goes up in 10% intervals right up to 90%. So if we’re trying to match your existing “Dalmation” concrete and you can’t remember what percentage it was, we are basically then taking a guess at the problem. It might not sound much only being out by 20% of the white stone mix, but this will make the difference stand out dramatically when the two concrete’s are next to each other.

With all this said, I guess at the end of the day if you follow a few simple guidelines you can at least be assured that the best efforts are made to match your concrete…..

  1. Write down the name of the concrete exactly when you have it poured
  2. Write down the supplying company of your concrete
  3. If possible, try and complete all exposed aggregate at the same time

If you haven’t or couldn’t do these three steps…..

  1. Contact sales rep and contractor for their advice with samples
  2. Understand that the two concretes will look different
  3. Or….Choose a different aggregate to try and contrast rather than matching

Be reasonable with your expectations. We are dealing with natural products that are not mixed like paint through a computer, there is always room for error when matching these natural products and as with all colour and stone options, typically, the contractor should not have to take any responsibility for variations in these products.

Concrete Resurfacing Pimpama

Driveway Decorative Resurfacing Pimpama

Project Description

Location: Pimpama
Project Size: 70sqm

Having previously installed this plain concrete driveway a few weeks back, we returned to complete the Covacrete Resurfacing to finish it off. After a heavy acid clean and pressure wash to remove any unwanted particles and dirt, we base coated the surface with Light Bluestone Covacrete. Taping down an 800mm diamond pattern, we then proceeded to spray 2 coats of Bluestone Covacrete, followed by 2 off setting fleck colours and 2 coats of acrylic sealer. A beautiful finish matching the roof of the house and contrasting the other surrounding colours.

Exposed Aggregate

Exposed Aggregate Driveway Reedy Creek

Project Description

Location: Reedy Creek
Project Size: 70sqm

With our client requiring an exposed aggregate driveway for his newly built home, we set about the task at hand. Cutting and removal of the council kerbing and council footpaths was completed, followed by doweling of said areas and the garage door entrance. SL72 reinforcing mesh was placed throughout during the concrete pour allowing access for the truck up the tricky off angled incline. Unfortunately, (due to a miscalculation by the boss), we fell short on concrete by about 0.2mcub and had to order a plus of Dalmation 50 exposed aggregate. All in a days work though and the driveway was hosed off nicely to expose the ever popular “Salt & Pepper” variety of stone.

Concrete Resurfacing

Driveway Resurfacing Monterey Keys

Project Description

Location: Monterey Keys
Project Size: 120sqm

We began this driveway project with an existing tiled driveway would have been fantastic when it was laid, but over time and use had began to crack the tiles and lift them off. Initially we took to the tiles with a jackhammer with a dingo bobcat to back us up, helping lift the tiles and place them on the truck for removal. Following this a complete floor grind was completed removing approximately 120kg of tile glue and bad surface preparing us for the new surface to be applied. Our client and I decided to go with a custom look using sharp angled triangles over large areas with multiple colours contrasting very well against each other and matching the existing colours of the home. A couple of flecks and 2 coats of sealer finished off this project for a massive improvement on the tiles that were originally there.

Concrete Strength

Strengthening Your Concrete

A lot of clients I speak to ask about strengthening their concrete installation by making their concrete thicker throughout, but this method isn’t always the best option for making your concrete stronger.

There are more things you need to consider rather than just thickening the depth of concrete.

Now this isn’t to say that your concrete won’t be stronger by thickening it, but you need to consider the weight of the concrete upon the ground that it is sitting on. Concrete is extremely strong in compression and relatively weak in tension. Compression obviously being the sheer weight pressing straight down on the concrete, as opposed to tension being allowing the concrete to flex along it’s axis.

If you are considering making your concrete thicker simply because you need to drive heavy vehicles over it, then the difference between say 100mm of concrete and 125mm of concrete is negligible, as typically 100mm of concrete will handle the same weight in compression as 125mm will handle.

The main areas to attack firstly in strengthening your concrete I will explain now in better detail below. The trick is to initially strengthen the concrete in tension, then worry about the compression factor lastly.

Increasing Thickness of Steel
Steel Reinforcing acts as the backbone for the concrete under tension. It is used primarily to control cracking if/when it occurs by not allowing the cracks to pull apart and become structural. On a standard driveway installation for example, you can expect a contractor to install 6.2mm steel mesh throughout (hopefully chaired into the concrete). A good first step to improving the strength of your concrete under tension, is by installing a thicker version of reinforcing anywhere from 7.2mm to 9.2mm. A house slab for instance will usually have 8.2mm reinforcing installed. Thicker steel has less “bend” if you will throughout it’s horizontal line, which helps holding the concrete from being allowed to move along it’s horizontal line as much, therefor limiting the tension.

Concrete Steel

Thickening Beams / Footings
As you can probably imagine by looking at a slab of concrete, it is along the edges that the concrete is most at risk from moving up and down along the horizon (tension). Concrete, as a general rule of thumb as well, tends to want to tension crack roughly every 2-6m of laid concrete. It used to be if you’re using 6.2mm mesh that you need controls every 2.4m, 7.2mm mesh you need controls every 3.0m, 8.2mm mesh with controls every 4.0m then 9.2mm mesh controls every 6.0m. This I put into memory a very long time ago as per Australian Standards, so don’t check me up on this as they’ve most likely changed since then, although they are still a good reference point to work from. When I talk about “controls” they can either be saw or tool cut control joints, but also a thickening beam or footing can do the job just as effectively. By installing thickening beams or footings along your perimeter, as well as throughout the middle of your slab, you are effectively adding more strength in base compression whilst restricting the concrete from being able to “tension”.

Concrete Beams

Maintaining Course Aggregate Size
The course (or large) aggregate within your concrete is kind of the backbone of your concrete. It acts as the main property of your concrete that all the other properties (cement, fine aggregates etc), bond to to form your concrete. Standard concrete is installed with 20mm course aggregate, this is considered to be the strongest standard for the size of the aggregate. From here, contractors can install smaller aggregate of 10mm depending on the installation, usually though when this happens, the MPA rating is also increased to assist with de-strengthening your concrete. There is also an option getting around of “reduced line” concrete, which has approximately 30% less aggregate through your concrete, plus also a maximum size of 7-10mm course aggregate….if you ever have a contractor looking to install reduced line concrete, sack him/her immediately and find someone who is serious about supplying you a proper installation.

Concrete Aggregate

Ground Compaction / Subgrade
Typically the most common reason for your concrete cracking under tension is by the ground underneath the concrete moving under the weight of the installation. Upon request, an contractor can bring in a better sub-grade material than what is already on your site, typically being good fill sand, crusher dust or even 20mm road base depending on the depth of fill that is needed. Then from there, have this sub-grade compactor with a plate compactor making sure the ground is as solid as it can be to assist with holding that new concrete in one place.

Concrete Compactor

Further, typically when a professional contractor is out to install your project, there are base standards for your new concrete installation. The contractor is usually seeing what the underlying ground is like and endeavoring to install your new concrete to a good, solid standard for strength. Concrete has been around since the Romans, and for instance, having your concrete installed by Walker Concreting & Resurfacing, you will receive what is considered “the norm” for a good installation.

The factors I have listed above are considered above and beyond the standard requirements and are for clients who require that little bit of extra piece of mind with their concrete installation.

After the above factors have been met, you can then start talking about thickening your concrete installation, to assist with “compression” of the concrete. A good rule of thumb when thinking about “compression”, is taking a look at Hoover Dam in America, it was specifically designed in an arc against the force of the Colorado River because the compression strength with the water constantly pressing against it is when it’s at it’s strongest.

As always, by using these guidelines to strengthen your concrete, you can be assured of a structurally solid installation. This is not a guarantee against cracking, as cracking and concrete go hand in hand. But, these processes’s will assist in making sure your installation is there to last a lifetime.

Plain Concrete Pimpama

Plain Concrete Pimpama

Project Description

Location: Pimpama
Project Size: 175sqm

Installation of new plain grey concrete surrounds at Pimpama on the Gold Coast. Cutting and removal of the council kerbing. Machine excavation and sub-grade to desired levels. SL62 reinforcing mesh chaired throughout and N12 re-entry and starter bars. 100mm of 25MPA plain grey concrete placed throughout with soft broom finish ready to be Covacrete Resurfaced in a few weeks time. Project came up fantastic and we can’t wait to get back for some fancy spraying.

Concrete Resurfacing

Covacrete Resurfacing Process

Here I’m going to go through the nuts and bolts of a typical Decorative Concrete Resurfacing Project (Covacrete). The following articles consists of what I consider to be base standard with your application of the process when you choose Walker Concreting & Resurfacing to complete you project.

First things first. Typically, when we get to your concrete that you require to be resurfaced, lets be honest, it’s usually in pretty bad shape. It’s either a dirty old moulded surface, or has been previously sealed or painted in it’s history and all these things will hinder the bonding of our new Covacrete application.

Majority of the time we will complete either a heavy or light surface grind of your concrete to remove all these foreign properties and make sure that our new Covacrete product is bonding directly to the natural concrete surface. This is completed with a walk behind floor grinder and also a 9″ hand grinder for the tight to reach corners.

Surface Grinding

Concrete Floor Grinding

Next up is giving your concrete surface a nice, heavy bath in hydrochloric acid.

Using approximately 3-4 Liters in a 10 Liter watering can, your concrete surface is covered thoroughly with the acid and it is allowed to soak right into the concrete and all the pigments on the surface.

This helps to break up any remaining unwanted particles on the surface, but also lets us eat into the surface finding a more appealing structure to adhere our Covacrete to when applying it.

Acid Bath

Acid

After the hydrochloric acid has been applied and allowed to soak in for several minutes, we then attack the surface with a high powered gurnei to further remove anything we don’t want on that surface.

The combination of acid and pressure washing loosens up the surface particles even more so and again helps us get down to the bare bones of the concrete for a better Covacrete application.

Pressure Washing

Pressure Washing

Next we take care of the cracks. Cracks repair varies depending on what type of cracking it is, I’ve explained all this in another article, I really should link it here, but you’ll just have to do some research yourself :).

For standard hairline cracks that are non structural, then we simply go about grinding out these cracks thoroughly, then applying our “secret sauce” crack repair product to them. The idea behind this is that your concrete has already tensioned and cracked along it’s weak point and the crack is being held together by the steel. So if we expand that crack through grinding, then fill the area, then technically the crack should not pull apart any farther and not come back through.

This of course is not a fool proof system, although we do our best, and most of the time succeed, these little buggers do sometimes come back through again, but, typically only a hairline crack will show.

If you have structural cracking, then realistically your only option is to remove sections of your concrete where the problem is, and replace that section with new concrete before applying any Covacrete.

Crack Repairing

Crack Repair

Covacrete Application

Base Coating
After priming your newly cleaned surface, our next step for your sexy new concrete surface is applying our base coating. This stage of the application will allow us to level all of your surface smooth and give us a good initial coating of our products. Covacrete comes standard in “Ivory” colour, but there is the option of adding in a colour to your base coating. Your base coat will be visible as the “grout lines” if you will in your taped patterning. Colouring the base coat works really well when applying a lighter colour top coating of Covacrete and using a dark base to make those lines contrast well.

Taped Patterning
From here we apply our taped patterning to your hearts desire. You might decide you want diamond or tiled patterns, maybe borders, tile inserts or full showpiece compass’s installed. The world is your oyster here and we love getting a little creative with our patterns.

Top Coatings
After all our patterns have been completed, we then proceed with the fun stuff. Air compressor pumped up and hopper oiled, we begin spraying on your top coatings of Covacrete in the colour / colours that you have chosen. The top coatings are applied with a minimum of 2 coatings, with the initial run being more of a “covering” application and the later coatings for the even application and good looks.

Decorative Patterning
To finish up the spraying we then apply your decorative aspect to add contrast and depth to your installation. You might choose to simply apply a few different colour flecks to the surface or go all out with Sandstone Swirls and hand done patching. Obviously pricing matches the level of detailing we go into, but as always, we’re here to give our clients what they require and consider ourselves top of the game in the artistic side of things.

Finishing Up
From here, after all the spraying has been completed, we then rip off all the taping that we applied earlier, remove all the tape from your walls, blow off the surface, then proceed to apply 2 applications of high grade acrylic sealer to protect your new surface and give it a lovely shine in the process.

If you’re interested in our services for concrete resurfacing, give us a call soon about your next project. You’ll love what we have to offer and our professionalism and service is beyond reproach.

Exposed Aggregate Concrete

Exposed Concrete Options

Exposed Aggregate Concrete is a very popular residential concrete application on the Gold Coast. With many different options for stone colours, there is always a choice that suits your natural surroundings of your house. However, Exposed Aggregate Concrete doesn’t always have to be just a standard plain grey concrete with different coloured aggregates. It can be mixed up in a few different ways to really create something unique for your property.

Standard Installation

Installation of exposed aggregate is usually quite a simple process for a contractor with enough experience in it’s application. Exposed is all about timing by your contractor, it takes skill and experience to know the timings of each stage of it’s placement. Typically after placing and screeding off your Exposed Concrete, it is then floated and the surface is continually worked to bed and flatten the stone correctly. When the timing is right, the surface is then retarded by with Raw Sugar or a chemical compound specific to this requirement, then again, when the timing is correct, the surface will be washed off revealing the coloured stones underneath.

Variation 1: Inserts / Borders

One way of mixing things up is with inserts and borders. As you can see in the image installation of plain coloured concrete with exposed aggregate has been installed for the middle section, followed by the same aggregate being installed surrounding it with a simple colour through the concrete to change it up. You can also do this with borders, plain concrete with a colour and also inserting tiles and pavers directly into the concrete.

Exposed Aggregate Concrete

Variation 2: Colour Through Concrete

One of the simplest ways to change things up is to add a colour oxide through your concrete during the mixing stage. The Oxide mixes through the entire concrete body and once we wash off the surface, with the right choice in colour, contrasts against the stone choice of our clients. There area many different options for colouring your concrete, please check out our Colour Charts under Customer Relations to have a look.

Exposed Aggregate Concrete

Variation 3: Polishing to Expose

Our final way of finishing your Exposed Aggregate Concrete is to place the concrete as per normal, but instead of washing off the surface during placement, we will wait for the concrete to set and cure, then return with our grinding and polishing equipment to remove the surface revealing the stones, along with flattening the stones along the surface for a very sleek, modern finish. At times this finish can be slippery when wet, however we can add texture to the surface within the sealer to assist with this.

Polished Exposed Aggregate

If you’re thinking about putting in Exposed Aggregate Concrete for you new driveway or other installation, have a chat with us and think outside the box. With these few, simple process’s we can create something unique that not everyone in your neighbourhood already has installed.

Concrete Resurfacing Toowoomba

Concrete Resurfacing Toowoomba

Project Description

Location: Toowoomba
Project Size: 160sqm

Our client had an old existing concrete patio, parking area and surrounds at their property and were requiring decorative resurfacing to make the areas match and repair cracking. Work commenced with floor grinding of the painted areas along with a quick skim over the entire surface to bring the concrete to a workable level for resurfacing. We then proceeded to acid clean and pressure wash all areas. Crack repairing was completed then finally base coating of our Covacrete products was applied. We decided to go with sharply taped line throughout with a Slate Grey main coating, followed by Cuban Coffee and Bluegum flecking, finished off with 2 coats of high grade acrylic sealer. Overall the project was a success as you can see from the before and after photos below and we’re happy to be walking away from another happy client.

Concrete pour

Properties of Concrete

Ever wonder about the basic materials that are mixed to make your concrete? In this article I’ll be going through each of the main materials and what part they play in your concrete.

Cement

Cement

Cement in your concrete is essentially a binding material that forms as a glue for the other materials in your concrete.
It is made by combining silicon, aluminium, iron, calcium, chalk, clay, slate and limestone with other chemicals in a controlled mixture. When combined and water is added, it reacts with the other materials to heat and harden, binding the fine and large aggregate together that make up your solid concrete structure.

Fine Aggregates

Concrete Sand

The fine aggregate (sand), is a very fine material which can assist concrete to solidify, giving the necessary strength required. Sand can fill up the pores or voids inside the concrete which is also a contributing factor for the strength of the concrete. Its considerable hardness and resistant to weathering makes it the perfect material for the mixture.

Course Aggregates

Aggregates

Course aggregates are the larger stones in your concrete mix. They are also considered somewhat of a filler material making your concrete mix stretch further, but they are also one of the main strengthening properties of your concrete. 20mm aggregate is considered the base size and has the best strength properties. Once you lower the size of the large aggregates to 10mm you are weakening the strength of your concrete, so typically to make up for this you MPA rating will be raised (amount of cement) to counter the loss in aggregate. There is also an option for “reduced line” aggregate, which is basically a reduced mixture of large aggregates that are used. Personally, I would never place reduced line concrete as it’s strength properties are far below anything I would be confident in placing and standing behind as a contractor.

Water

Concrete Water

Water in the mix makes the concrete workable during placement. During the setting process, the cement materials start to super heat, which in turn makes the water start to evaporate and be forced out of the concrete mix, making all the properties start to harden and bind together. As a general rule of thumb, it will take only a few hours for the water to evaporate enough for the concrete to begin to harden to the point it can be finished and by the next day, enough water has removed from the concrete to harden enough to walk on without damaging it. It can take up to a month for 100mm concrete to cure properly with all the water evaporating from within the concrete.

[/vc_row