Construction World August 2016

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PRODUCTS AND SERVICES

Need for DETAILED KNOWLEDGE about concrete 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

John Roxburgh, lecturer at The Concrete Institute's School of Concrete Technology.

layout are essential, as is the specification for the concrete to ensure appropriate perfor- mance,” 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 opti- mise 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 important for concrete strength but can also prevent defects such as cracks, surface

Roxburgh says detailed specifica- tions for structural concrete work and industrial floors on the ground are essential to prevent prob-

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. 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 prob- lems stem from a lack of knowledge about concrete design, detailing and construction. “It is therefore essential for both engi- neers and contractors to fully understand the properties of concrete and construction requirements of different structures to produce appropriately detailed specifica- tions for concrete works. These subjects are dealt with in the two one-day courses the School of Concrete Technology is offering. ‘SCT36 Properties of concrete for the struc- tural 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. Companies can arrange for the School to present the courses on specific dates and venues and use this option as a marketing tool by inviting clients and associates to attend,” Roxburgh stated.

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lems 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: it must meet the strength require- ments 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

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FAST-CURING UNIVERSAL ANCHORING ADHESIVE Sika has extended its offering in the Anchoring range. This NEW two-part, general-purpose, anchoring adhesive is based on styrenated polyester and is intended for mechanical, electrical and plumbing works, as well as metal or structural work. Sika AnchorFix ® -S covers the requirements for standard applications of low to medium loads.

• Non-Sagging: Sika AnchorFix ® -S displays non-sagging behavior for both horizontal and vertical applications. Thanks to the easy-to-handle and highly efficient packaging and mixing mechanism, unnecessary waste of product is avoided. • Versatile: Sika AnchorFix ® -S can be utilised for fixing of sanitary equipment and the installation of kitchen fittings, aerials and satellites. Among the common applications in metalwork are general supports, window and doorframes, window protection cages, blinds, sunshades and handrails. Used extensively for rebars/reinforcing steel, threaded rods, bolts and special fastening systems. • Sika AnchorFix ® -S is suitable for use in concrete, hollow and solid blockworks and bricks as well as in hard natural stone and solid rock. Both outdoor and indoor applications are possible. It can be used for fixing both structural elements (such as balcony extensions) and non-structural elements (e.g. stair and balcony railings or sun blinds). • Sika AnchorFix ® -S is the ideal solution for applications using hollow blocks. Where mechanical anchors are ineffective as they loosen, the Sika AnchorFix ® -S system is combined with a perforated sleeve to ensure it stays fixed.

Advantages of Sika AnchorFix ® -S: • Chemical anchoring is much more effective than mechanical anchors: • No expansion – no cracking of substrates • Outstanding load bearing capacity • Corrosion prevention • Easy application: With an open time of three to four minutes, the applicator ensures a flexible working time. Due to the styrene in this product, a long application time is provided while fast curing speed is maintained - useful especially in high temperatures and tropical climates.

CONSTRUCTION WORLD AUGUST 2016 I