Quarry Southern Africa May 2019 - Page 34

BENEFICIATION Preparing for a days production. slabs, bridges, grand stands, and reservoirs because we do it every day. However, with work being scarce at the moment we have to take what we can get and build in contingencies for that learning curve,” he says. Each delivery from the on-site batch mix is put through a slump test or more recently, it has gone for the flow test on every mix, where a margin of 750 is accepted. “We do get rejects even though we have a sophisticated system, as most of the glitches are water related. However, with experience, our workers can increasingly adapt to variances and still work with a margin above 750 rather than reject it. The concrete we mix is a durable concrete — we use a SCC mix that gives us 90Mpa on a beam that is actually designed for 35Mpa. It is our choice, and is more expensive — but we do it for a superior end product.” The batch mix produces roughly 2 000t a month of concrete, or 850m3, at the moment, which is not full capacity. De Bruin emphasises that the tonnage produced is a factor of the type of product being manufactured at a moment in time, with some containing high volume and others much less. Of greater relevance is the rand value being produced. 32_QUARRY SA | MAY/JUNE 2019 “We manufacture bridge beams 15m long, weighing five tonnes each, but in the past, we’ve done 15m bridge beams weighing 20t each. That’s what pushes up tonnage because it takes the same time to shutter, handle, and cure — the only difference is the pouring time. The batch plant is currently running a single nine-hour shift, down from two shifts, because there is not enough work. We have in the past run the batching plant 24 hours a day, but not now.” Marketing potential of precast De Bruin says that during the past decade, precast products have grown considerably in popularity among civil engineering contractors and consultants. “Ten years ago it was difficult to persuade engineers: where five years ago we had to convince consultants to use precast, today they make their building designs with precast in mind, often because the client wants to speed up delivery — with no convincing necessary today from our side. “The major advantage of precast is decreased construction time and the high quality of the product, because it is manufactured under controlled conditions “There are standard moulds for certain products, as stadia and reservoirs for instance typically have the same specced products, and the moulds can consequently be repeatedly reused.” in a factory. It’s already quality controlled and known to meet specifications, and they get it when they want it. When they are ready for the beams, they receive it on that day,” explains De Bruin. Where South African construction is headed is perhaps revealed by trends overseas, where precast is more commonly used. De Bruin says South Africa is fast catching up to that level of usage, “faster than we would have ever anticipated”. De Bruin says precast manufacturing is competitive. CoreSlab competes against many smaller rib-and-block suppliers in Limpopo that supply both the residential www.quarryonline.co.za