Construction World April 2023

CHRYSO Quad admixture solutions deliver the perfect response to using challenging sands and producing concrete meeting performance criteria.

ADMIXTURES

As the construction sector aims to achieve more demanding sustainability targets – including a lower carbon footprint – the CHRYSO®Quad range presents CHRYSO’S SUSTAINABILITY SOLUTIONS FOR SWELLING CLAY AND FINES

Patrick Flannigan, Technical Manager in the Concrete Business Unit at CHRYSO Southern Africa.

valuable opportunities for dealing with challenging sands.

T he shortage of natural sand is a growing environmental issue in countries like South Africa and indeed across the African continent as it is a non-renewable resource, explains Patrick Flannigan, Technical Manager in the Concrete Business Unit at CHRYSO Southern Africa. The trend is to use more manufactured sand, usually sourced from stone crushing operations – and hence also called crusher sand. When contractors have to truck sand to site over long distances, this extended value chain adds to the carbon footprint of the product and project. “For environmental and cost reasons, there is a shift towards trying to reduce the volume of natural sand in a concrete mix,” says Flannigan. “It is also usually preferable to procure sand from a source closer to site to reduce carbon emissions from transportation and to lower the cost.” The challenge, he points out, is that the clay content of readily available sand can cause complications in the mix – while the manufactured sand often includes a level of fines that is too high or too low to be optimal. This is where the CHRYSO®Quad range has provided a breakthrough, as the first comprehensive range of admixtures for all challenging sands. This is good news for companies who rely on quality results in their concrete including contractors, readymix suppliers and precast manufacturers. While not all clays are a problem in concrete, he explains

that swelling clays tend to absorb newer generation plasticisers which denies the user the intended benefits such as water reduction or slump retention. “Our CHRYSO® Quad range uses CLEAR® (Clay Enabling Admixture Response) technology allowing for efficient dispersion of hydraulic binders in concrete mix design,” he says. “CHRYSO® Quad CLEAR® therefore restores the benefits of plasticisers in conditions where the clay content is problematic.” To understand where such a solution will be required, there is also a CHRYSO® CLEAR Test – an innovative and quick service from CHRYSO Southern Africa to analyse sand. Due to the fact that swelling clays cannot be easily identified visually, it is important to conduct a special test for total clays on site before the local material is used in concrete. “An advantage of our Quad CLEAR® test is that it picks out only the swelling clays, so contractors can be alerted to the presence of those clays that will negatively affect the performance of the concrete,” he says. Where these swelling clays are detected, CHRYSO® Quad CLEAR® can be added as a liquid to the relevant customised solution. Where the use of CHRYSO® Quad CLEAR® worked well recently for a customer was in the heavy precast manufacturing sector. Flannigan explains that this particular precast manufacturer operates a number different sites and there were

28 CONSTRUCTION WORLD APRIL 2023