Sand and gravel are the most mined materials in the world, accounting for up to 85% of all materials extracted globally each year.

However, the world’s concrete industry is still vulnerable to shortages in supply – particularly relevant in Asia-Pacific – where many economies are enjoying economic growth of around 7% helped by continuing infrastructure and commercial construction work.

One popular way to cope with natural sand shortages is to partially replace it with manufactured sand or quarry dust. On the other hand, the shape, grading and presence of clay in these aggregates has a negative effect on the quality of concrete produced. This in turn can lead to poor workability, variances in performance and less durability.

GCP’s Clarena solution

GCP Applied Technologies is now bringing its cost-effective Clarena portfolio of admixtures. This range of products specifically addresses issues such as rheology and flow of concrete, in addition to delivering a high quality product.

Designed with ready mix and aggregate producers in mind, the Clarena portfolio helps reduce the negative effects of poor quality aggregates on concrete performance. It also makes production easier to manage and more cost-effective.

There are five products in the range, allowing concrete producers or quarry owners to select the right one for them:

• Clarena MR Series: a mid-range water reducer for rheology improvement
• Clarena MC Series: a mid-range water reducer for both clay mitigation and rheology improvement
• Clarena HR Series: a high range water reducer for rheology improvement
• Clarena HC Series: a high range water reducer for rheology improvement and clay mitigation
• Clarena AC Series: additives for aggregate treatment for aggregate producers.

GCP Applied Technologies research fellow Dr. Lawrence Kuo says using Clarena can help users improve operational efficiency in a number of areas.

“For concrete producers, Clarena admixtures offer better flexibility in the choice of materials used in a concrete mix, leading to both better consistency in quality and lower costs,” Lawrence says.

“By extension, this also reduces waste, enhancing the sustainability of individual production plants. Similarly for quarry operators, using Clarena additives leads to less waste, increasing yield and productivity. Again, this enhances sustainability at individual facilities and improves profitability.”

Improved rheology

One particular benefit of Clarena additives is that they help concrete and aggregate producers address the rheology and flow of concrete to deliver optimal performance. The rheological properties of concrete are important because they determine the ease of placement, consolidation, durability and strength of the final product. Getting this balance wrong could mean that the concrete has to be replaced, increasing waste and raising production costs.

Clarena mid-range and high range water-reducing admixtures enable better workability and a smoother finish by delivering a smooth flowing concrete with improved placement properties. The additives are ideal for use within a wide range of concrete slumps and in addition they deliver a superior finish – an increasingly important aesthetic detail, particularly in commercial and residential developments.

Advanced clay mitigation method

In addition to improved rheology, Clarena additives mitigate the performance issues related to higher clay contents in aggregates. Their advanced design means they are able to selectively react with clay contaminants in both coarse and fine aggregates. The highly engineered, irreversible chemical reaction produced by Clarena additives eliminates the negative effect of clays and overcomes the technical limitations of traditional mechanical processing methods.

For example, with fine aggregates, beneficial fines and clay contaminates can be of similar size, yet mechanical separation cannot distinguish between them, creating unnecessary waste. Clarena additives not only minimise this waste and reduce quality control difficulties, they also make concrete production more profitable and sustainable.

The Clarena portfolio of mid-range and high range water-reducing admixtures includes the Clarena MC Series and HC Series, which specifically address the issue of clay mitigation.

Clay minerals often expand in water and can intercalate and absorb the polyalkylenes oxide component of PC-based admixtures, reducing cement dispersion and water reduction capabilities.

The MC series overcomes this by using proprietary sacrificial agents that are absorbed and intercalate with clays before the PC component of the admixture. This way, the admixture is able to retain robust water reduction as well as other desirable properties – all at low dosage rates. The result is consistent and predictable water reduction in the mix, excellent early and later age strength, near neutral set times and a superior surface finish.

Effective and efficient

The Clarena aggregate management solution is supplemented by GCP’s industry-leading technical consultation and field support – Blue 360SM Field Advantage. In addition, its suite of evaluation protocol tools can assess the quality of aggregates and their impact on concrete performance.