Like any liquid, fresh concrete forms and conforms to the structure it is poured into and fills. However, unlike most liquids, concrete gradually solidifies, hardens, and shrinks.
During this process, concrete is vulnerable to cracking, and these cracks can often appear in undesirable positions and appear unsightly.
Rather than let all your hard work go to waste, control joints can be used to force these cracks to appear along the cut, rather than in some other obvious spot.
For this reason, anyone working with larger concrete pours needs a petrol concrete saw to introduce cuts into poured concrete before it’s fully cured. Let’s look at the process in more detail.
Cut Control Joints vs Expansion Joints
Control joints are sometimes confused with expansion joints, but they are quite different. Control joints are cuts made in recently poured concrete, whereas expansion joints are predetermined gaps between each slab. Both help counteract cracking, but only control joints help determine where cracks will appear. A control joint can be summarised as an intentional point of weakness within the slab to control where the cracks will form.
When is Best to Cut Control Joints
The most common question asked about control joints is “when is best to cut?” If you are using a concrete saw, then the best timeframe is within 6 to 18 hours after pouring. Any later than 18 hours and you run the risk of randomised cracks appearing anywhere on your concrete slab.
How Deep Should Control Joints Be in Concrete?
Control joints are not cut the entire way through concrete but about one-quarter the way down. This helps create enough of a weak joint that the cut attracts the cracks where you want them to be, without splitting the slab in half.
It is also important to spread the control joints evenly apart, neither too far nor too close. Too far apart and you will get randomised cracking. Too close and you will have more cuts than you actually need.
What Type of Concrete Saw Should Be Used?
In order to not damage your uncured concrete unnecessarily, you need a good quality saw machine for the job of control joint cutting.
MEIWA Concrete saws come in three weight categories, 3L-6L fuel tanks, and 10’’-18’’ blade diameters.
MCP120 has a manual drive.
MCP140 has a self-propelled, screw type drive that makes concrete cutting easier and less physically demanding.
MCP180E is an electric start model that has a self-propelled, screw type drive that makes it accurate and easy to operate.
MEIWA concrete saws are equipped with Honda GX engines, which are regarded as the best in the world of construction equipment. They deliver smooth torque and low fuel consumption, while being EPA Phase 2 and CARB Tier II compliant.
You should also look for a concrete saw that is equipped with a water tank. Meiwa water tanks range from 16L to 45L and are designed to keep the blade cool and lubricated for a seamless cut. A water tank also reduces the amount of debris and dust particles that are inhaled by your workers, so it really is an essential feature.
Contact MEIWA NZ for All Your Concrete Cutting Needs
At MEIWA, we manufacture the world’s most reliable concrete and compaction equipment for the construction industry. Precise, durable, and ergonomic, MEIWA concrete saws are a sought-after solution. Contact us today for more information.