Reuse Of Construction Materials: Concrete And Timber

No matter what we do, our construction sites will always create some waste. That's why it’s up to us as contractors and homeowners to make educated decisions in how we build, and what techniques we use, to reduce the materials that go into our landfills every year. According to National Post, over half of the waste from the building industry — which amounts to over 100 million tons a year — comes from renovations and demolitions. The sad part is, only a small percentage of that — less than a quarter — is properly recycled. As I mentioned earlier, all the construction branch fellows are sort of entering a new building era, in which building's effect on environment and its eventual disposal is a great responsibility. That's why it is very important to find a solution to this issue also in our project. So what can be done?

First of all, while choosing the building technique and materials, we need to throw away everything that supports condensation and eventually leads to mold or fungal rot. For obvious reasons - such materials cannot be reused, and it is our environmental responsibility to deal with construction waste in a way that recycles as many materials as possible. Of course, while trying to provide as many materials as possible from a building being demolished, it is a necessity to sort waste. In my opinion, the best way to do it is simply deconstructing the building instead of demolishing it. Essentially, it works like "unbuilding" - it makes sorting through materials to see what’s salvageable much simpler. Now, what about material?

Both concrete and timber are perfectly fine to recycle, given that they present proper properties. In case of concrete, its type is crucial (i. e. in-situ, precast), wise like amount of preprocessing and amount of contamination from materials such as glass, metal or soil. In the case of timber, we have given types that are acceptable in various markets (for example, treated, native, and untreated), contamination from nails, paint or concrete is also a thing to check here. Applying this knowledge to our project, we can already tell two good things for recycling:

1) the construction site is going to leave relatively small amount of waste, as we use prefabricates.

2) wooden prefabricated elements are easy to deconstruct, as they are precisely put together and come with project plans that can help in classification of viable waste and eventual deconstruction.

Yet it is worth to consider in which case the recyclement would be more efficient, concrete or wooden prefabricates? First, let's take a closer look at the processes of recyclement. Wood waste from deconstruction activities is typically delivered to wood waste recycling operations for processing, although a small market exists for salvaged timbers, boards or other components. Most construction recycling related wood is received at mixed reuse processing facilities, where it is inducted into the wood grinding system. After quality check required for a particular fiber requirement, the product is available for sale. The markets for recycled wood include landscaping mulch, bedding material, boiler fuel, as well as fiber for composite board products, including press wood pallets, and pellets. As for the concrete, its aggregate is put through a crushing machine. Crushing facilities accept only uncontaminated concrete, more specifically without trash, wood, paper and other such materials. After crushing is done, other particulates are filtered out using various techniques like hand-picking or water flotation. The best option seems to be crushing the concrete at the actual site, using portable crushers, as it allows to save a lot of money and contamination by eliminating transportation from quarry. Large portable plants can crash concrete and asphalt rubble with efficiency of 600 tons per hour or more. Compact, self-contained mini-crushers are also available. They can handle up to 150 tons per hour and fit into tighter areas. With the advent of crusher attachments - those connected to various construction equipment, such as excavators - the trend towards recycling on-site with smaller volumes of material is growing rapidly. These attachments encompass volumes of 100 tons/hour and less. Such recycled concrete is reused in various ways, depending on its size. Smaller pieces are used as gravel. Concrete pavements can be broken in place, and through a process called rubbization, they are used for an asphalt pavement, which is very efficient for rebuilding roads. Larger pieces are used as riprap revetments. With proper quality control at the crushing facility, well graded and aesthetically pleasing materials can be provided as a substitute for landscaping stone or mulch. "Use of aggregates from recycled construction and demolition waste in concrete", recycled aggregate doesn't have good durability like the natural coarse aggregate but the durability can be improved by mixing it with special materials such as flying ash to produce high strength and durable concrete. Furthermore, recent statistics show that the demand of construction aggregate raises 5. 2 percent annually, and will eventually reach 51. 7 billion metric tons in 2019.

World's forestation is getting larger with every year, thanks to big focus of many countries on artificial plantation through various campaigns. Therefore the productivity is steadily rising, but is the case the same with demand? This is the most recent statistic I could find, and according to this, the increase in demand is not as steep as forestation levels, therefore the demand is definitely fulfilled. Reclaimed lumber, for the other hand, is demanded for different reasons: the wood's unique appearance, its contribution to green building, the history of the wood's origins, and the wood's physical characteristics such as strength, stability and durability. The increased strength of reclaimed wood is often attributed to the wood often having been harvested from virgin growth timber, which generally grew more slowly, producing a denser grain. Reclaimed beams can often be sawn into wider planks than newly harvested lumber, and many companies claim their products are more stable than newly-cut wood because reclaimed wood has been exposed to changes in humidity for far longer. However, the market for recycled timber is still a niche, as with those massive areas of planted forests, there is no real endangerment or any other reason for recycled timber to be highly in demand. Moreover, the timber recycling is more time-consuming and comes with a greater cost.

To sum up, the conclusion here is that while looking for the highest recycling-potential in a building, concrete is definitely the best candidate material, providing simple and low cost reprocessing and finding much more options for reuse. Furthermore, its global demand is incomparably higher than the one for timber. However, when we take into consideration other factors of the material, such as functioning properties or toxicity, wood takes the main spot.