Jul 2020 Recycling Concrete
As climate change and the reduction in carbon gas emissions becomes a global concern across multiple industry sectors, Sephaku Cement discusses alternative waste management processes and how recycling concrete into aggregate alternatives present the building sector with more sustainable green solutions. Reduce, reuse and recycle, these are the three most important R’s in the waste management trifecta in finding a sustainable solution to the ongoing threat that climate change poses to global ecological communities.
From plastics to paper, tin cans and glass, there are many strategies in place for households and businesses to cut down on the amount of waste thrown away on a daily basis. As the need for more sustainable waste solutions becomes paramount, the construction and civil engineering sectors are also playing their part in repurposing and upcycling waste and rubble resulting from various civil engineering projects.
From concrete driveways that need to be replaced, to precast pathways, pavements or refurbishing concrete fittings, aged, damaged or compromised concrete installations can be effectively recycled into an affordable and eco-conscious aggregate. A critical component in reinforcing concrete applications, aggregates create the volume and added durability that Portland cement binds to resulting in the compressive strength of various concrete installations. Natural aggregates such as stone, sand and crushed gravel, are both costly and a non-renewable resource derived from natural sources, however, when upcycling aged concrete fittings that are being replaced or refurbished, recycled concrete offers an eco-conscious and sustainable solution as a natural aggregate alternative effective in reinforcing new concrete applications.
Although not a totally new concept, many concrete installations are 100% recyclable with this process put into practice in Europe since the 1940s. Recycled concrete aggregate (RCA) offers both cost saving as well as various environmentally sustainable benefits that include;
- Conservation of natural aggregate resources
- Sustainable building waste and rubble management
- Reduction in landfill consumption Energy and
- greenhouse gas emission reductions
The production process of recycled concrete aggregate includes breaking up the old concrete installation which is then collected and hauled to a crushing plant. The demolished concrete is then crushed into specified sizes and quality grades and then sorted and further refined into batches of consistently sized aggregate material. In most cases, recycled concrete aggregate is produced to meet both the quality and grading requirements that can be used in a diverse selection of new concrete applications. In other instances, an alternate recycled concrete aggregate can be created when demolished concrete is blended with other building waste materials such as wood. This material is produced to result in a totally new aggregate material that offers a more pliable or bendable strength put to use in more specific concrete projects.
“RCA particles – which tend to be extremely angular – consist of reclaimed virgin aggregate, reclaimed mortar or both. Reclaimed mortar generally has higher absorption, lower strength and lower abrasion resistance than most virgin aggregates. RCA therefore generally has lower specific gravity and higher absorption than virgin aggregate.”
“The properties of a specific recycled concrete aggregate depend upon many factors, including the properties of the original concrete and the processes used to produce the RCA, particularly the crushing operations. With proper process control, RCA can be produced to meet quality and grading requirements for almost any application and should be considered an engineered material for which the properties must be determined at the outset so that appropriate mix design or construction adjustments can be made.
“When RCA is used in the production of new concrete mixtures, its effect on the properties of those mixtures can range from minimal to significant, depending upon the nature, composition and gradation of the RCA. For example, when little reclaimed mortar is present in coarse RCA and virgin fine aggregate is used, the handling characteristics and engineering properties of the new concrete properties will be practically the same as if all virgin aggregate had been used. But if the new mixture contains only coarse and fine RCA, these characteristics and properties will be substantially different from traditional concrete mixtures when all other mixture design factors remain constant.”
With the hopes to reduce construction costs and the added benefit of reducing carbon emissions, as the cement and construction sector continues to pursue more “green” building practices, the production of recycled concrete aggregates offers a number of added benefits. While addressing the growing concerns of climate change and waste management solutions, recycled concrete not only addresses a more environmentally sustainable alternative to natural sand and stone aggregates, but also stimulates a circular economy that offers society wide benefits and job creation.