Gulf Construction Online - CDE sand washing tech boosts concrete quality

Quarrying

CDE Combo ... specifically designed for the quarry waste fines challenge.

CDE sand washing tech boosts concrete quality

01 June 2020

CDE, a leading wet processing equipment company for sand and aggregates, mining, construction and demolition waste recycling and industrial sands, is giving a new lease of life to waste material left over from crushed rock by offering its innovative systems that help produce manufactured sand.

Since 1992, the company has been designing and manufacturing wet processing systems for mines and quarries that enable customers to maximise the quality and quantity of the materials they produce whilst saving on energy and water consumption.

Ruchin Garg, CDE Regional Manager for the Middle East and North Africa, tells Gulf Construction: “CDE has extended its footprint across the world at speed and has since become a household name in the Gulf’s construction materials industry, with an unrivalled reputation for product performance, reliability and customer service excellence.

“The Gulf region is, indeed, a natural focus for business development for CDE, where it has successfully developed its presence in the past 10 years, grounded with a full-fledged local customer service team based out of Dubai.”

Traditional systems

Concrete, a product of a carefully measured mix design of cement, sand, gravel and water, is the most used man-made material on Earth, with per capita consumption, according to the UEPG (European Aggregates Association) annual review (2017-2018) being five tonnes annually.

The use of unwashed crusher fines – a waste material left over from crushed rock – for concrete production is limited to specific construction operations with unsophisticated needs. Crusher fines are, therefore, often disregarded and stockpiled as an unwanted by-product, says the company.

This is where CDE patented washing technology comes in.

Ruchin elaborates: “Traditional materials processing systems, including bucket wheels, are still widely used in the Gulf. This technology had its place in its prime when sand resources were abundant, and the price of construction materials was high. However, it is now being replaced by more advanced technology to address shortcomings such as the difficulty to control the volumes of water required for accurate material classification, high levels of moisture in the final product that increase drying times and therefore productivity, and loss of valuable fines to large settling ponds that require expensive maintenance.”

Previously, crusher fines could not be turned into an in-spec product, as existing processes did not offer the cut point accuracy required to achieve reliable and consistent manufactured sand (M-Sand).

CDE is changing all of that by applying its expertise in wet processing systems to this challenge. With more than 25 years expertise in developing materials washing technology, the company produces cyclone-based washing solutions that are specifically adapted to the production of high-quality, in-spec manufactured sand products that are used to optimise the performance and minimise the cost of concrete mixes.

“With the successes met in the Gulf with the CDE EvoWash sand washing plant and the AquaCycle thickener in past projects such as in Oman by Kunooz Mining for M-Sand applications, more operators are now looking for a user-friendly solution that incorporates both,” Ruchin explains.

The Combo

This technology is encapsulated in CDE’s compact washing solution plant – the Combo – which fully addresses the twin challenges of the ever-growing demand for in-spec construction aggregates, and ever-diminishing natural aggregate resources.

Using CDE M-Sand in the mix design lowers the production of carbon dioxide (CO2) by optimising the concrete mix with less cement required to obtain the same compressive strengths. Similarly, operators are able to reduce CO2 through the reduced need for transport as Combo technology can turn sand into product where it is needed straight from the belts.

The CDE Combo is relocatable and is specifically designed for the quarry waste fines challenge. It can process a stockpile in one location and then be moved to process another elsewhere. The Combo’s on-board water supply and recycling are also significant advantages, reducing water consumption by up to 90 per cent.

Further benefits of CDE M-Sand are that it does not contain organic and soluble impurities such as clay, dust and silt that affect the setting time and properties of cement. The required strength of the concrete can, therefore, be maximised.

CDE M-Sand can also be optimised to achieve specific gradations of fines – for instance, by optimising its size and shape – creating a highly suitable sand for construction, thereby achieving higher compressive strength through reduced segregation and bleeding.

Not all M-Sand is the same, of course. Each has different qualities depending on the original crushed rock it was created from. For example, M-Sand produced from granite rock helps the concrete structures to withstand extreme environmental conditions and prevents the corrosion of reinforcement steel by reducing permeability, moisture ingress, and the freeze-thaw effect, all of which increases the durability of concrete structures.

Size and shape of the sand play an important role in the workability of concrete. With more sand surface area, there is an increased need for cement and water in order to bond the sand with coarse aggregates. Using CDE M-Sand with less surface area means that the concrete can be equally workable using less water, and consequently less cement too.

Consistency is also an important factor when producing concrete. Inconsistent sand qualities typically lead to higher safety margins, which in turn means a higher amount of cement. Cement is the most expensive aspect of the concrete mix, representing around 50 to 60 per cent of the cost at less than 20 per cent of the volume. This further emphasises why consistency of CDE M-Sands is so important. Cleaner, in specification CDE M-Sand requires less water, a key requirement of higher strength concrete.

“Combo technology delivers consistent in-spec sand which reduces cement consumption. A cost-effective and energy-efficient solution, it also reduces CO2 and boosts profitability,” Ruchin concludes.

To maintain their competitive edge in the construction sector that is demanding increasingly high standards, construction companies are under pressure to use concrete that is strong in specification, versatile and of course value for money. CDE’s systems help achieve sand – a key component – of the right quality.