Although highly suited to primary aggregate production in quarries and sand and gravel plants, modern mobile material processing and handling equipment have found a real niche in processing materials arising from construction operations.
Possessing exceptional productivity but at the same time being fuel efficient, the crushers, screens and stockpilers are now at work throughout the world processing a variety of materials, turning what was once considered to be waste into a valuable resource. Screencore director Ciarán Ryan outlines why mobile screening, crushing and material handling solutions are playing a major role in dealing with construction materials.
Recycling of construction materials involves processing concrete, metal, wood, bricks, metals and glass, amongst others, to reduce landfill use, conserve resources, and promote sustainability. This material, once viewed as ‘waste’, is generated from construction and demolition activities, with the increasing volume posing significant environmental challenges, making effective recycling and management essential for sustainable development.
Many building components can be recycled where markets exist. Asphalt, concrete, and rubble are often recycled into aggregate or new asphalt and concrete products. Wood can be recycled into engineered wood products like furniture, as well as mulch, compost, and other products. Metals, including steel, copper, and brass, are also valuable commodities to recycle.
In addition, it is estimated that globally hundreds of millions of tons of carbon dioxide could be removed from the atmosphere by recycling and reclamation. This significant reduction in emissions highlights the environmental benefits of recycling construction materials.
Estimates of the C&D material generation indicate mass quantities of the generated materials have traditionally been sent to landfills. Besides environmental concerns, doing this ignores valuable construction materials that through crushing and screening can be turned into a valuable resource. Modern material processing and handling equipment are also equipped with magnetic separators which enable metals to be separated and recycled to be put back into use.
The actual figures are daunting: it is estimated that globally the construction industry generates 1,3-billion tonnes annually. A detailed report in 2018 titled, ‘Characterisation of Building-Related Construction and Demolition Debris in the United States’, identified that 600-million tonnes of C&D debris were generated in the United States, which is more than twice the amount of generated municipal solid waste.
Demolition represents more than 90% of total C&D debris generation, with just over 455-million tonnes of C&D debris being directed for reprocessing with just under 145-million tonnes being sent to landfills. Similar figures are reported throughout Europe and other parts of the world, with India in particular now looking to reduce the amount of material being sent to landfill.
Advanced technologies and their application are key to recycling and reuse. Although facilities exist that employ automated sorting systems, magnetic separators, and other technologies to efficiently recover recyclable materials, being able to deal with material at source is often more cost effective, and minimizes transport costs, road emissions and avoids ‘double handling’.
Companies working in the demolition and recycling industries have been quick to see how mobile material processing and handling equipment can aid their business operations. Playing a major part has been the development of compact tracked jaw crushers, scalper-screens, trommels and radial stockpilers, all being used to recycle construction and demolition materials. In addition, mobile pugmills have proved to be the ideal piece of equipment for dealing with asphalt, channelling what was waste back into highway construction.
These solutions are designed to benefit users, helping them to turn what was once a burdensome and difficult to deal with material into high quality aggregates and other valuable products, with processing and handling solutions developed in order to meet the needs of the modern contractor and recycling operation.
Manufacturers have set out to build equipment to the highest standards that helps people in the field be more profitable, efficient and effective in what they do. Environmental efficiency has in most cases been incorporated into product development to minimize customers’ carbon footprint and turning construction waste into reusable and/or resaleable products.
A typical application will see in the first instance, a compact – for ease of transport to and from site – tracked jaw crusher being fed the demolished or excavated material, usually by an excavator or loading shovel. Many modern compact jaw crushers are designed with a low environmental footprint, making them an ideal solution to meet the needs of a recycling contractor, rental fleet or inner-city demolition/recycling site.
They often weigh around 60 to 65 tonnes (such as Screencore’s XJ Dual-Power Crusher with other manufacturers compact crushers being of similar dimensions and weight) which means that they can be easily relocated without the need for permits. They are also designed to be both environmentally and acoustically friendly while delivering impressive throughput even on concrete with rebar.
Following crushing to -100 mm, for example, the material is then fed into scalper/screener, often to produce 25 mm, 50 mm and +50 mm products. In addition, any ferrous metals such as rebar or wire, are easily removed for resale/recycling by the overband magnet on the discharge conveyor before being fed into a mobile screen. In many applications the 25 mm material is generally used for pipe bedding; 50 mm and +50 mm directly as road subbase or as feed material for secondary crushing for concrete production, whilst the +50 mm is used as drainage stone.
Due to the easily transportable and modern nature of the equipment, contractors and rental fleets have found that the crusher and screen combination can be readily transported to where the material is. This means that the material can be processed where it originated, and generally where it is needed, resulting in no unnecessary emissions, material handling or transport costs.
In addition, the local environment is not subject to unnecessary traffic disturbances, and the overall carbon footprint of the contract is dramatically reduced. Quick set up times, easily adjusted closed side settings, fuel efficiency and ease of transport are just some of the reasons that has seen contractors and recyclers adopt such mobile equipment.
Despite the excellence of the individual product ranges, to combine the attributes of precision screening and scalping with large material stockpiles, two pieces of equipment are required: a screener and a stockpiler. To overcome this, Screencore has introduced a development which combines stockpiling and scalping-screening, the Hi-Stak 125. The new solution comes from contractors having a requirement to produce high quality accurately sized aggregates and at the same time produce large material stockpiles. Mounted on tracks, the screener-stockpiler is able to go where the material is and follow the tracked crushers and screens.
For some operations, however, mobility is not essential. This has led to the development of ranges of bespoke stationary solutions, often based around a trommel screen working alongside stockpilers and scalpers. Many manufacturers offer a variety of customised stationary solutions tailored to suit individual applications with in-house design teams collaborating with customers to develop an efficient and long-lasting material handling system.
These are often used in conjunction with air separation systems for use in both stationery and mobile plant. Engineered for plastic or ‘lights’ contamination removal from C&D, compost and mulch, they are available in diesel or electric power to suit customer requirements.
An increasing trend in these days of high fuel costs has been the focus given to both stationery and mobile equipment to be supplied with power solutions to suit requirements. Stationary, and increasingly mobile plants, are electrically powered which makes efficient and cost-effective use of mains electricity to provide a low cost and low emission solution.
Mains electricity has proved to be an ideal power source delivering a cost effective and environmentally efficient solution. Through the use of this power source, precision processing of materials is accomplished without producing the emissions that would be of concern, and at the same time, at a low cost.
