Concrete Vibrating Techniques
As a vital part of a successful concrete pour, concrete vibrating techniques have been widely used to ensure the compaction of concrete structures all over the globe. Though little recognition is given to the important process, concrete vibration is considered to be a mainstay in the industry of construction as it serves multiple long-term benefits in establishing a high-quality finish for the concrete itself.
Concrete Vibration and Its Role in Concrete Compaction
Cement Concrete and Aggregates Australia, also known as CCAA, describes compaction as the process which expels entrapped air from freshly placed concrete and packs the aggregate particles together so as to increase the density of concrete. This means that upon pouring the cement mixture onto the surface or into a mould, tightly packed particles will ensure a denser concrete outcome which results to a stronger, durable, and long-lasting structure.
To achieve optimum concrete compaction, concrete vibration is done to eliminate air bubbles through vigorously shaking the freshly poured concrete. As their are different concrete surfaces, different built structures, and different construction challenges, tools used for concrete vibration come in varying forms and sizes which can greatly fit the needs of contractors and builders.
Commonly referred to as “poker” or “needle” vibrators due to its tubular shape, immersion vibrators rotate with an eccentric weight which causes the vibrations to ripple from the casing and throughout the concrete to which it is immersed to. The vibration’s radius produced depends on the diameter of the casing, the tool being used, and the setting of its frequency and amplitude. In the current market, immersion vibrations come in different action radiuses and are powered either by fuel, electricity or compressed air motors. When it comes to the actual process of concrete vibration, the Compaction of Concrete Guide published by CCAA recommends 15 to 20 seconds stationary insertion of the immersion vibrator until air bubbles cease to surface. The vibrator is said to penetrate through the top layer and up to 150 millimetres into the previous layer to consistently meld both layers together when laying vertical or deep concrete pours.
Ideal for compacting concrete slabs, roads, and industrial floors, surface vibrators offer a different approach in concrete vibration compared to immersion vibrators. This type of concrete vibrator applies an external downward force onto the concrete, making it easier to work on larger areas of flat concrete pours. However, it only reaches a limited depth and the degree of compaction is not as consistent across the width of the beam. Thus, immersion vibrators are used to complement surface vibrators, especially for slabs of more than 200 millimetres to even ensure that the particles are thoroughly and equally compacted. Depending on the desired use and the size of the concrete surface, a wide variety of surface vibrators are available in the current market, which includes: single or double vibrating beam screeds, vibrating roller screeds, and pan-type vibrators, which are mainly used on specialised road paving equipment.
For concrete structures with high-density reinforcement, form vibrators, also known as external vibrators, are clamped to specially designed formwork. Through consistently vibrating the formwork, concrete compaction is achieved once there are no more air bubbles visibly released to the surface of the concrete pour. It is ideally used for concrete floors and ceiling, beams, and one-sided blind walls.
Concrete Vibrating Tips
● Do not over vibrate the concrete as it lets the mixture break and separate. Also, do not under vibrate the concrete because air might still be trapped in the lower layers of the cement pour, which leads to a weak concrete structure that easily breaks with minimum pressure.
● Eliminate the process of concrete vibration by opting to use self-consolidating concrete instead.
● To prevent cold joints from occurring to concrete layers as these are poured over with a new layer of cement mixture, make sure to penetrate the pour thoroughly with a vibrator and mixing in the previously poured layer with then newly placed one.
● For maximum efficiency, use only vertical movements when vibrating to have an even mixture of aggregate and concrete. Horizontal motion can lead to uneven distribution and increases the possibility of the vibrator tangling in the rebar or reinforcing steel.
● Avoid using the vibrator as a concrete placement tool because it will not produce a consistent surface and it might even provide more problems in structural strength and form.
● Use the appropriate type of concrete vibrator depending on the structure being built or the size of the working area. Consider using a compact lightweight concrete vibrator for smaller jobs for manageability and efficiency.
● Always keep a back-up concrete vibrator on hand to have a second replacement tool instantly once the first one encounters any problems while on the job. Having the first vibrator to break right in the middle of the concrete pour as is simply a contractor’s worst nightmare.
To get to know more about concrete vibrators and other concrete construction tools, visit Safari Group online or drop us a call today at 08-94551144.