South African engineers and contractors need detailed knowledge about the properties and construction requirements of concrete to prevent incorrect specifications for building projects, says John Roxburgh, lecturer at The Concrete Institute's School of Concrete Technology, which has developed  two one-day training courses specifically dealing with this subject.

Roxburgh says detailed specifications for structural concrete work and industrial floors on the ground are essential to prevent problems during the construction and lifespan of a concrete structure.  In the design and construction of concrete structures, both the plastic and hardened state properties should be considered.
"A contractor is inclined to be more concerned about the plastic state of concrete which, if designed with construction methods in mind,  will simplify the job and achieve better results when the shutters are removed.   An engineer, on the other hand,  often places more emphasis on the hardened properties of concrete: for him or her it must meet the strength requirements and be durable and free from defects. 

"But the contractor, engineering consultant and clients can all win if the specifications - whether prescriptive or performance-based - are correct, detailed enough and, importantly, cover not only the performance of the finished product but also concrete mix design, transport, construction methods and the plastic state of the concrete. In the case of industrial floors, in particular, detailed specifications for joint types and layout are essential, as is the specification for the concrete to ensure appropriate performance," Roxburgh stated.
"Fundamental to obtaining the correct performance out of any concrete structure is the concrete mix design.  However, even with the correct mix design, there are many things that can go wrong between batching and completion of the hardened product.  The plastic properties of the concrete must suit both the transport and construction methods employed as well as the finish required when it comes to industrial floors. 

The construction process, in particular, should be carefully thought through to optimise the performance of the concrete.   A large percentage of strength and durability problems start in the plastic phase of the concrete but with good specifications and site practice these can be avoided.

"Protection and curing are aspects that are often under-specified,especially in the case of industrial floors and pavements which have large surface areas relative to concrete volume and are therefore prone to drying, especially during finishing.  Curing is not only important for concrete strength but can also prevent defects such as cracks, surface wearing and quality.  Durability is also greatly enhanced with proper curing.  Sadly,  too often curing and surface protection are inadequate because of a lack of suitable specifications. This is why by far the greatest number of enquiries received, and consultations carried out, by The Concrete Institute deal with problems with industrial floors and pavements. These problems stem from a lack of knowledge about concrete design, detailing and construction.

"It is therefore essential for both engineers and contractors to fully understand the properties of concrete and construction requirements of different structures to produce appropriately detailed specifications for concrete works.  These subjects are dealt with in detail in the two one-day courses the School of Concrete Technology is offering. ‘SCT36 Properties of concrete for the structural designer and constructor’ and ‘SCT21 Concrete industrial floors on the ground’ are available on pre-set days according to the School of Concrete Technology's annual training programme or companies can arrange for the School to present the courses on specific dates and venues. Companies often use this option as a marketing tool by inviting clients and associates to attend," Roxburgh stated.

More information about the two courses is available from John Roxburgh on tel 011 3150300 or email johnr@theconcreteinstitute.org