Products & Services

Frequently Asked Questions about Concrete


Can I obtain advice on the correct type of concrete to be used?
Yes, providing there is no structural requirement we can advise on the types of mixes to be used for most jobs. - See more at: http://www.cemex.co.uk/readymix-concrete-faqs.aspx#sthash.T51FlxPQ.dpuf
What is concrete?
Concrete consists of a mix of ingredients, including Portland cement, pozzolans, water, coarse aggregates, fine aggregates, and additives. Concrete may also contain mineral colors, granulated blast-furnace slag, and blended cements. When fresh, concrete can be molded hours after it is produced. Once the initial set time is reached, the concrete continues to gain strength.
Are there quality standards for concrete?
Yes. CEMEX Concrete is produced to British & European Standards
My concrete has oil/grease stains. How can I get rid of them?
Commercial products are available in paint/hardware home centers. Sprinkle with tri-sodium phosphate. Allow to stand for 30 minutes, then scrub with a stiff brush and hot water. Rinse with clean water. Scrub stain with concentrated detergent using a stiff brush. Rinse well with water. Dry and repeat if necessary. Sprinkle dishwasher detergent on wet concrete. Let it stand a few minutes, then pour boiling water on the area. Scrub and rinse. Dissolve a cup tri-sodium phosphate in 1 gallon of hot water. Pour over stained concrete surface and allow soaking for 25 minutes. Scrub with stiff brush or broom. Rinse with clean water. Repeat if necessary.
What is fly ash?
Fly ash is a by product of coal combustion. Most commonly the material is produced by coal fired electrical generating facilities. Fly ash is a cementitious material, meaning it has certain properties that cause it to harden upon exposure to water. Typically, fly ash does not develop much compressive strength on its own. However, in the presence of Portland Cement, fly ash can develop strength characteristics very similar to cement. The fly ash reacts with a chemical by-product of the cement hydration reaction called calcium hydroxide -CaOH-. CaOH can cause deleterious effects in concrete such as increased porosity and efflorescence -the formation of calcium carbonate crystals on the concrete or mortar surface-. Because fly ash reacts with the calcium hydroxide to form more calcium silicate hydrate -the binder derivative of cement- fly ash actually adds strength to the concrete and helps to remove an agent that may be harmful. Fly ash is also particularly beneficial for use in hot weather as it tends to slow the generation of heat in the concrete. » See More
How is concrete measured?
Concrete is measured by the cubic metre. One cubic metre of normal concrete will weigh about 2.4T/m3.
What is the difference between cement and concrete?
It's simple. Concrete is used for the finished products, such as structures, foundations, and the surface of many roads. Concrete contains sand, gravel and cement. Cement is the special hardening ingredient (the gray powder) that makes concrete harden. Cement is usually made of 60% lime (limestone), 25% silica, 5% alumina, and 10% other materials, such as gypsum and iron oxide. (Content provided by the Mineral Information Institute, © 2002 www.mii.org)
What strength concrete is normally used for the slab under a house?
Typical mixes are around 8 - 20n/mm2 , depending on the geography of the country and the quality of the raw materials. Sometimes we are asked if a different weight should be used for the garage area. This is not really necessary. Usually the biggest load on a slab is the heaving from the sub grade and not the structure on top of it (or the car).
How long will the truck-mixer wait at site?
Because of the scheduling of deliveries, it is helpful to release the truck as quickly as possible. The normal time allowed is ten minutes plus five minutes for each cubic metre. Therefore a full load of 6m3 could be at site for forty minutes before an additional charge is applied.
My concrete is cracking after only a short period. Is there something wrong with it and can it be repaired?
All concrete cracks. It has to crack because it contracts during the drying, curing, hardening process, and the bond between the cement paste and the aggregates is not strong enough to withstand that stress. The best way to prevent unsightly cracking is to put joints in your concrete at regular intervals. A good formula is to measure the depth of your structure and multiply the number by three. Use this number to determine the approximate number of feet between joints. (For example, a 100mm slab of concrete should have joints every 3 to 3.5 metres.) Uneven shifting of the substructure or sub grade can also cause cracking. This is a structural failure, as opposed to improper curing or jointing as mentioned above. Before repairing any concrete cracking, determine the source of the cracking and remedy that first. Epoxy grout is an excellent crack repair agent. For more information call our Product Support Helpline 0800 667 827
What types of concrete does CEMEX offer?
CEMEX offers a wide variety of high quality products such as Performance Concrete, Durable Concrete, High Strength Concrete, Pavement Concrete, Light Weight and Heavy Weight Concrete, Grouts, Architectural Concrete, and Customized Concrete. See our "Special Products"
How do I stain/paint my concrete floor?
Any paint store will have concrete stain or paint. Discuss how you want the floor to look and what function it will perform with the paint store manager, and he/she should be able to recommend the appropriate stain/paint.
Can an order be cancelled, for example if it rains?
Yes, provided that the load has not already been dispatched.
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