Housing in Southern Africa March 2015

Cement & Concrete

C hryso and Concrete Testing Services provided technical support to the principal con- tractor, Aveng Grinaker-LTA onwater- proofed plaster. “The most common defect experienced by contractors on A wide variety of products supplied by Chryso Southern A f r i ca we r e us ed f o r t he construction of the Vodacom Business Data Centre inMidrand. It has been built in line with Vodacom’s greenphilosophy and designed tohaveminimal impact on the environment. Waterproof plaster

duce bleeding, there ismorewater available for the hydration process which improvesbondingwithin the cement matrix. The product also improves the long-term durabil- ity and surface properties of the concrete. • Chryso CIM helped in the bonding of the plaster to the wall surfaces. The bonding agent increases mor- tar plasticity, cohesion and adher- ence, and also improves tensile strength, abrasion resistance, and impact strength and acts as a cur- ing aid. • Chryso Fuge B was used for the high standards of waterproofing specifiedby the client. The product blocks the pores in the plaster and ensures that mortar and concrete are highly resistant to capillary ac- tion. • Chryso Stab was used for enhanc- ing theworkability retention of the plaster. The admixture has a built- in stabiliser that allows retardation of up to eight hours. • Chryso Cure Acrylic water-based emulsion concrete curing com- pound was used by Aveng Gri- naker-LTA to achieve economical, efficient plaster curing. The 3 000 m² energy efficient data centre houses virtual private servers, dedicated servers, managing hosting, and data back-up among its host of facilities, and amassive cooling plant. Theprofessional teamplayedapivotal role in designing, co-ordinating and constructing a building that can fit the vast amount of mechanical and elec- trical work into a confined space and still make the building aesthetically pleasing,” concludes Muirhead. ■

site is usually the plaster. Vodacom requested a waterproof plaster in order to prevent the possibility of tiles falling off the façade due towater ingress. For consistency and quality purposes, Aveng Grinaker-LTA chose to use waterproofed plaster for the entirebuilding including the façades,” says Rob Muirhead, Contracts Man- ager at Aveng Grinaker-LTA. According to Muirhead, locating the correct sand for the plaster mix was vitally important. “After a few trials and a lot of research, it was de- cided to use washed Vaal River sand. “The cleaner the sand, the better the plaster; the Vaal River sand contained less clay and had a sufficient amount of fines to assist in preventing plastic shrinkage cracks.” The plaster was mechanically mixed to ensure the better dispersion of the Chryso admixtures and fibres as well as the sand. The following products were used: • A Chryso Plastisicer was part of the mix for all concretework, including plasters and mortars. The admix- ture strongly disperses the fine particles in concrete to produce fluid, cohesive concrete with a low water-to-cement ratio. • Chryso Mortar Plasticiser, a chlo- ride-free admixturewhich entrains air to enhance durability, and im- proves cohesion andworkability of the concrete mix. It makes the mix easy to plaster. • Chryso Fibre Pluswas added to the mix used for plaster work to help reduce early age plastic shrinkage and settlement cracking. It also prevents the segregation of fine cement and sand particles which causes bleeding. By helping to re-

March 2015