The utility of sand & aggregate washing in the modern construction industry
Much of the sand currently used in the construction industry within India is sourced from rivers but this trend is starting to decline for a number of reasons. Key on the list of negatives is the potential environmental impact of river dredging and many states have already banned the exploitation of river sand, forcing producers to seek alternatives. Environmental legislation is not the only driving force, as the constant drive to achieve World class quality within the construction sector has also had an impact on the types of materials producers are prepared to use.
As a natural substance, sand is highly variable in grade and quality depending upon the source location, method of extraction, and even the season. What concrete producers in particular strive for is consistency. This is why virtually all construction sand in highly developed markets including Europe is washed – to achieve consistency and to ensure full compliance with construction sand specifications which limit the percentages which should be represented across the size ranges. Of particular concern to quality concrete producers and building sand buyers is the percentage of undersize within the sand; most notably the fraction below 75µm which should be below 4-5%.
Production of dual sands suitable for both concrete and plastering work
Washing sand in an efficient system is the recognised way to control fluctuations in the feed grade and also ensures consistent adherence to material norms. Various technologies exist ranging from screw classifiers through to modern hydrocyclone based systems such as those offered by CDE, a leading UK manufacturer now based in India. Selection of the correct system is essential to ensure optimal efficiency, particularly in achieving the correct balance of waste removal versus fine particles retention. To this end, CDE offers a highly customised approach and are able to cater to a diverse range of capacities and processing requirements. One of the great advantages of the CDE sand washing plants is the production of dual sands, that is, the same equipment can give different grades of product for use in different applications. The scope of producing spray grade sand of 2mm along with construction sand of -5+2mm size , is one of the main features. The company is the largest supplier of sand & aggregate washing plants in the world. It can supply plants with a capacity of 50tph to as high as 2400tph. The range of feeds treated is wide and can accommodate all variations. With experience across many sectors, material types, and at an International level, CDE now offer their expertise directly to the Indian construction industry.
CDE's innovative systems allow fine control of the required separation which not only gives operators much greater control over their products but also opens the industry to a much greater range of potential raw materials. At the top of the list is crushed rock (manufactured sand) as a natural sand substitute. Minus 6mm crushed rock fines are a typical by-product of the crushing sector and generally have little market value. These fines are now seen as a useful commodity in many markets as in most cases they can be washed to produce sand ideal for concrete production. In many cases, the product is actually better than naturally occurring sands which are often too fine and lack body in the plus 300 micron range.
CDE washing systems are environment –friendly and are packaged with water recycling and waste management as an integral part of the project. Water recycling system provides for substantial reduction in water consumption whereas proper waste management ensures there is no pollution from the use of the technology.
CDE are the European leader in washing crushed rock fines, often referred to as 'manufactured sand.' CDE are now actively targeting producers in India to help them get real value from their manufactured rock fines. Washing crushed rock fines to produce quality concrete sand in place of natural sand is now a recognised practice in the UK and one of the main driving forces within many construction materials markets. The rapidly developing Indian construction sector and ready-mix manufacturers in particular, can only benefit through the use of the higher quality and more consistent raw materials which CDE equipment offers.