Concrete mix solutions for improved sustainability

CHRYSO’s Quad range of concrete admixtures is designed to promote sustainable practice in the use of challenging sands.

CHRYSO Southern Africa technical manager: concrete business unit Patrick Flannigan says the use of crusher, or manufactured, sand in construction has been prevalent for many years as it is a cost effective and more readily available 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,” he explains. “This is where the challenges lie, with less availability of natural sands, which increases costs as well as the presence of clays, meaning that less of this material can be used or it has to be excluded completely.”

The CHRYSO Quad range aims to allow customers to reduce the use of natural sand while making better use of crusher sand, without compromising the quality of concrete mixes.

Flannigan highlights that using less natural sand lowers the impact on the environment, particularly on sources such as rivers. Where natural sand is still being used, CHRYSO Quad Clay Enabling Admixture Response, or CLEAR, allows for a wider choice of sources, including challenging sand that contains swelling clay. This can allow contractors to source from locations closer to site, reducing the carbon footprint and cost of transporting sand over a long distance.

“The challenge is that swelling clays absorb newer generation plasticisers, thereby preventing them from delivering benefits such as water reduction or slump retention,” he explains.

CHRYSO Southern Africa’s CLEAR Test is designed to identify where these swelling clays could present a problem for concrete users. Where identified in the source material, CHRYSO Quad CLEAR can be added as a liquid to the relevant plasticiser.

CHRYSO Quad Gap Gradation Fixing Technology (GRAFT) also aims to improve sustainability in the construction and concrete manufacturing sectors, by solving the challenge 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,” asserts Flannigan.