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Sika admixtures for local low-cost housing project

The Highflats low cost housing project was initiated in November 2012, with a goal of constructing 2000 houses within a 24-month period. Even with challenging rainy conditions, this goal was successfully achieved. Highflats is located 50km inland from Scottburgh in KwaZulu-Natal. Main contractors, Multicrop Construction sub-contracted Kencrete Readymix to supply the concrete and, following a highly successful former project using Sikaplast V210, Kencrete specified Sika’s high performance admixtures, Sikaplast V210 and SikaTard 930 for the project.

Kencrete set up a batch plant at the project location, thus easing delivery of the batched concrete to site. Multicrop Construction prepared the formwork by cutting out the base from the ground/bank and the ready batched concrete was delivered by truck and discharged into the base to form the house foundation. About 40% of the labour onsite was from the local community.

Sikaplast V210, a multi-purpose water reducer and superplasticizer, was added to the concrete used to construct the concrete slabs/ foundation of the houses. The superplasticizing action of SikaPlast V210 provides high-slump, flowing concrete that maintains excellent workability and may be placed with minimal vibration. It also provides controlled and extended slump life for periods of 45 to 90 minutes (depending on dosage) with increased set times without significant loss in early strength development. A 0.6% dosage is used in the concrete mix and around seven cubes of concrete are used per house.

SikaTard-930, was recommended for the mortar, as it is a lot coarser than the combination of plaster sand, river sand and cement. This admixture was developed for the control of cement hydration; it stabilises concrete mixes without setting for extended periods and without negatively influencing their quality. A 0.3% dosage was used which allows for the mortar to be workable for up to nine hours, and preventing the need for water to be added on site. If water is added on site, it causes a drop in mortar strength. Around three and a half cubes of mortar were used per house.

Because the project began in the rainy season, it affected construction as contractors battled to gain access to the sites via dirt roads. Due to the isolated location of the project, the houses are vastly spread out which resulted in the need for construction of access roads off the main dirt road.

Kencrete is based in Izotsha and supplies many types of laboratory-accredited mixes. Careful attention to the manufacturing process enables them to guarantee their concrete is always up to its specified strength. With a well-trained staff complement, Kencrete is able to offer professional service delivery. Implementing a new batch plant in the project location has allowed Kencrete to expand its operations. 

For further information on Sika products and systems, visit www.sika.co.za

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