Admixtures designed for problematic sands

The use of crusher or manufactured sand in concrete mixes has become common practice as a costeffective alternative to natural sand. There have, however, been issues with grading, which often prompts contractors to supplement with natural sand from sources such as rivers and dunes.

“This is where the challenges lie, with less availability of natural sands – which increases costs – as well as the presence of clays, which means that less of this material can be used or it has to be excluded completely,” explains Patrick Flannigan, technical manager: Concrete Business Unit, Chryso Southern Africa.

As Flannigan points out, sands that contain swelling clays tend to absorb newer-generation plasticisers, preventing them from delivering benefits such as water reduction or slump retention –areas addressed by the development of Chryso Quad Clear (Clay Enabling Admixture Response).

Chryso Southern Africa also offers the quick and innovative Chryso Clear Test to identify where these swelling clays could present a problem for concrete users. Where they are identified in the source material, Chryso Quad Clear can then be added as a liquid to the relevant plasticiser.

Fines issues

Another important development for the construction and concrete manufacturing sectors is Chryso Quad Graft (Gap Gradation Fixing Technology). This can solve the problem of an excess or lack of fines in source material, which often occurs in crusher sand.

“The industry is seeing the environmental benefit of moving away from natural sand and more toward crusher sand, but this product often has varying levels of fines. In the past, this could have compromised the performance of concrete, but Chryso Quad Graft now solves this challenge,” Flannigan concludes.

Because sands are unique, Chryso offers tailor-made solutions for both an excess and lack of fines