The Ten Commandments for concrete construction

With the Covid-19 pandemic having created a survival mode for many smaller and emerging building contractors, it is now more important than ever for site staff to have at least a basic knowledge of concrete behaviour and performance in construction, says John Roxburgh, senior lecturer at the School of Concrete Technology.

Here Roxburgh deals with the importance of 10 topics covered in the school’s popular online training course, SCT10 “Introduction to Concrete”: 1. The properties of concrete: For any successful concrete project, understanding both the plastic and hardened properties of concrete is essential. With the correct plastic properties, staff will be able to transport, place, compact and fi nish off the concrete correctly so that it has the correct hardened properties, which includes strength and durability with minimum shrinkage.

“It is now more important than ever for site staff to have at least a basic knowledge of concrete behaviour and performance in construction.”

2. Materials for concrete: Knowing the function of each material in the concrete mix – and the consequences these materials have on both the plastic and hardened properties of concrete – is essential in obtaining concrete that will perform well over its design life.

3. Receiving and storing materials:

The overall quality of concrete depends on many factors. Often, the receiving, storage and handling of the original materials are overlooked. Contracting staff must know how to prevent contamination of stored materials and have methods in place to ensure they are receiving and using the correct materials.

4. Batching, mixing, and testing

concrete: There are specific requirements for accurately batching and mixing concrete. Control of water content is probably the most important because the 6. Finishing and surface preparastrength of concrete is strongly related tion: Finishing and surface preparation to the water content. Concrete quality require a unique set of skills, coupled with must be assured throughout practical experience. For and this requires a good proper finishing, staff must working knowledge of the have a detailed knowledge of various tests that need to be concrete technology to apply performed on both the plastic their skills on the surface of and hardened concrete. the concrete in good time.

5. Transporting, placing 7. Protection and curing:

and compacting: There Often all other aspects of the is only a limited amount of concrete works are completed time to transport, place and acceptably – and then the compact plastic concrete and curing is botched. For good, contractors’ staff inevitably durable concrete, proper have to work against the (Above): John Roxburgh of the curing is essential. It cannot, clock to ensure that the full School of Concrete Technology. for example, simply be potential of the concrete is interrupted and then resumed reached. They need to know how to achieve many hours later. a dense non-segregated concrete – and to 8. Formwork and reinforcement: do so timeously. Formwork is crucial for moulding the concrete to the correct shape, but is also very influential in the final off-shutter finish. Knowledge of shutter materials and different types of release agents allows contractors’ staff to make the correct decision when it comes to achieving the desired off-shutter finish. 9. Sand-cement mixes: Sand-cement mixes are typically problematic. When there is an excessively high water content, the concrete tends to shrink substantially and is very weak. It is therefore important to know how and where sand-cement mixes should be applied. Often the mixes are used inappropriately and a contractor should be able to advise a client before this happens. 10. Durability: Sustainability is an important consideration in the world today and materials with a low carbon footprint are given preference. Cost-effective concrete is sustainable and has a low carbon footprint, as it does not need excessive maintenance or repair over its service life. It is therefore essential for small, medium and micro-enterprises, as well as junior technical and sales staff in the building and construction industry, to receive training on the matters listed above, as they are all intrinsically linked to concrete durability.

“Sustainability is an important consideration in the For further information about the “Introduction to Concrete” and other online courses presented world today and materials with a low carbon footprint by the School of Concrete Technology, tel: (011) are given preference.” 315 0300, e-mail: sct@cemcon-sa.org.za or visit: www.cemcon-sa.org.za.