FAQs

Ready Mix Concrete can be transported in Drum mixer's, the big concrete trucks with the spinning drum on that we all see travelling around is probably the most common method, lets not forget concrete pumps, skip & buckets ,dumper trucks and the lowly wheel barrow which are all used to transport ready mix concrete.

The aim of placing Ready Mix concrete is to get the ready mix into position as quickly as possible, delay will cause the concrete to stiffen and thus making it unworkable. The ready mix concrete should be placed carefully in equal layers, avoiding large heaps or slopes as this will encourage segregation. Ready Mix concrete that is not placed properly will not compact properly. You must never add water to the Ready Mix concrete that is setting.

To compact Ready Mix Concrete, energy is applied so the mix becomes more fluid, Air trapped in the Ready Mix concrete will then rise to the top and escape, resulting in the Ready Mix concrete becoming consolidated and enabling it to develop it's full strength. Ready Mix concrete that is fully compacted will maximise the concretes strength, permeability and durability. Normal methods of ready mix concrete compacting are vibrating or tamping

Curing is the final and yet one of the important stages of concreting. Ready Mix Concrete that has been properly cured is stronger, more resistant to chemical attack, more hard wearing and more water tight. It will also be much tougher and last longer. When cement is mixed with water a chemical reaction known as hydration takes place. This is what causes the cement to harden, which develops it's strength and durability. Hydration can only take place if the concrete is kept moist and at a favourable temperature in its early life. If the concrete is allowed to dry out the hydration process will stop. The earlier this happens the weaker the concrete will eventually become popular ways of keeping concrete is to spray with water or cover the concrete in polythene sheeting.

Special care is needed when working in cold weather. If new concrete is allowed to cool too quickly, it will be damaged. Concrete should never be allowed to drop below 0° C, doing so will freeze the water in the mix, making it unfit for use. Heated concrete is used during the winter season, Ready mix concrete suppliers such as MixIt are capable of delivering heated ready mix concrete up to 10° c.

Ready Mix Cement when damp releases Alkalis which can be harmful to the skin, the effect depends on the length of contact, any abrasion, the individual and the part of the body involved. Suitable protective clothing should be washed out immediately and medical attention sought. A COSHH and Health & Safety sheet must be used at the construction site.

There are several effects that hot weather may have on the properties of Concrete these include;

Consistence – The workability, that is slump/flow of concrete reduces more rapidly. Adding water to improve the consistence will reduce the concretes compressive strength, and as such should be avoided.

Setting time – As concrete temperatures increase the setting time becomes shorter as dose the amount of time the user has to place, compact and finish the concrete

Plastic Shrinkage Cracking – Hot weather will accelerate the loss of moisture from the surface and may increase the risk of plastic shrinkage cracking.

Thermal Cracking – Changes in temperature of the concrete may potentially  result in cracking particularly where concrete is placed on a hot day followed by a cool night.

Surface Finish – With the increased rate of hydration due to higher ambient temperatures or direct sunlight the surface of the concrete may ‘dry’ quicker, this may lead to premature finishing e.g. floating the surface “early” may trap an amount of bleed water, this bleed water may result in debonding of the top surface and subsequent flaking/de-lamination.

We can design mixes to assist with these issues as follows;

• Use Super Plasticizers  to reduce the overall cement content hence reducing the heat of hydration
• Use higher levels of cement replacement (GGBS or PFA) to reduce heat of hydration and bleeding
• Increase dose of a lignosulfonate based plasticiser to use as a set retarder
• Use specialist admixture to ensure consistence retention of concrete