Water Treatment Plant

THE CHALLENGE

The Klipdrift Water Treatment Works Extension Project near Hammerskraal, South Africa was getting further behind schedule as the weeks progressed. The job called for large amounts of concrete for filter blocks, pump stations, and reservoirs that had to be totally impervious to the 42 million litres of potable water that would be produced each day. The team originally opted for traditional concrete delivery methods using batch plants and drum trucks, but on top of scheduling difficulties, the plant’s distance from the nearest batch plant made for long wait times—often loads could not be used because the quality of the concrete had deteriorated on the way.

THE SOLUTION

In switching to a contractor that operates ProAll Mixers, the team was able to bring the project back on schedule and under budget in only six weeks. Nico Swanepoel, site manager for the project, identifies quality control, speed and reducing waste as key benefits, saying, “Our main reason for now using ProAll Mixers is all the added value of having a mixing plant on site, available at a minute’s notice”. In switching to volumetric mixers, Swanepoel also noticed a decrease in cost, saying, “I was amazed with the price, regarding competitiveness to anyone we had supplying us up to that date. It was significantly cheaper than what we’re used to.”

COMPLEX MIX DESIGN & CUSTOM MIX DESIGN

J.J. Fivaz, who served as concrete specialist on the project, explains the elements of the mix design: “we are using dolomite, which doesn’t corrode as easily as normal stones, or, let’s say, granite. We are using a 90mm stone, and supersand that has a fine content of more than 10%. With these three components we can pretty easily mix water-tight concrete for a water-tight structure. Right now we’re getting 35 MPA concrete, but we are always over-strength. We are getting around 10 MPA over strength, so we are looking at about 45 MPA. And we also work with a specific water-to-cement ratio, which is 0.55 for water retaining structures.”

6WK