Commonly asked questions regarding concrete
Whether this is your first time sourcing concrete for a project, or you’re an experienced tradesperson, we understand you may have concrete questions that need answering.
To try and provide some clarity on the subject of concrete, below we’ve briefly answered some of the most common questions we are asked regarding concrete.
Concrete advice and orders
For help with choosing the right concrete mix design or to place an order, please call our friendly team 01202 579579 option 3.
A volumetric concrete mixer (also known as volumetric mobile mixer) is a mixer on a truck or trailer that contains concrete ingredient materials and water to be mixed at the job site to produce the exact amount of concrete needed.
A volumetric concrete mixer produces concrete by proportioning the materials out over time by volume and relating that volume back to the materials specific weight. These materials are then dispensed into a mixing auger where they are completely mixed together and all the cement is able to come in contact with water to begin hydration as well as encapsulate the complete surfaces of any other material being added into the mix. The material is being added into the mix auger as if it were in handfuls at a time so the there is more than enough energy in the mix auger to ensure a complete and uniform mix by the time it comes out of the discharge end of the auger, which is typically only about 5-10 seconds.
On average, the farthest distance concrete can be placed using a chute is 12 feet, depending on mix consistency, measured from the truck’s tyres to the point of discharge. The wheels of the ready-mix truck must be kept 1 foot away from below-grade walls and 1 foot away from excavations and trenches.
By using volumetric trucks, AMS Concrete can ‘mix onsite’ and dispatch a complete range of concrete mixes, with the most common variations including:
- PAV 2
- C35 Pump mix
Our ‘mix onsite’ trucks can dispatch between 1m3 – 9m3 of concrete per trip.
Temperature extremes make it difficult to properly cure concrete. On hot days, too much water is lost by evaporation from newly placed concrete. If the temperature drops too close to freezing, hydration slows to nearly a standstill. Under these conditions, concrete ceases to gain strength and other desirable properties. In general, the temperature of new concrete should not be allowed to fall below 50 Fahrenheit (10 Celsius) during the curing period.
There are a lot of reasons that concrete could crack. Initially, it could be because the concrete dries too quickly, there’s too much water in the mix or expansion joints weren’t installed properly.
That’s why it’s important to hire an experienced concrete contractor who knows just the right amount of water for the type of concrete being mixed and how to pour the concrete to avoid cracking.
Over time, tree roots could grow under the concrete and push up, resulting in stress on the concrete and eventual cracking. Settling in the ground underneath the concrete also can result in cracks if the concrete settles unevenly.
Under normal conditions, concrete has a useable life of about 1½ hours. However, in summer it will lose workability more rapidly. Ideally, it should be placed and completely finished within 1 hour of discharge from the truck. Usually, the concrete will need to be laid and levelled within two hours before the setting of the concrete makes things more difficult.
A cubic meter of concrete weighs about 2.5 tonne (2500 kgs) and it takes about 25 builders barrows to move 1.0 metres of concrete. Each barrow weighing 100 kgs approx.
When concrete is supplied by our volumetric trucks, it is discharged in to a pump’s hopper where agitators keep it moving. The concrete is then pumped through the pipelines to the pour location.
One cylinder pushes the concrete into the pipeline on the forward stroke, while the other cylinder draws concrete from the hopper on the return stroke. The pistons in both cylinders move in opposite directions to keep the pressure consistent and the concrete flowing freely.
The European standard for concrete EN 206, and its complimentary British Standard BS 8500, requires that concrete must be supplied at a minimum temperature of 5°C at the point of discharge and this temperature must be maintained on site using insulation. Therefore if concrete is batched below the minimum temperature the ticket is stamped and the strength of the concrete cannot be guaranteed.
Need more advice on concrete?
Our friendly and knowledgeable team would be happy to help you with your concrete queries or to place an order for you. You can speak to them today by calling 01202 579579 option3.