Ancient concrete mixes made use of various materials like horse hair, urine, beer, and tree bark, as well as sugar, to elevate the strength of this long-lasting building material.
The Roman aqueducts, Mayan temples, which date back a thousand years, and even the Great Wall of China, which is 2,200 years old, were constructed by way of using a combination of limestone, other natural materials, as well as locally sourced ingredients.
At present, there is ongoing testing and also the utilization of fly ash, steel fibres, glass, as well as recycled plastic when it comes to concrete mixes for the modern era.
Rishi Gupta, a professor of civil engineering at the University of Victoria, says that they are indeed gaining valuable insights from the previous experiences and currently have modern versions that are available.
It is noteworthy that Gupta has dedicated more than two decades to researching methods so as to enhance the strength of concrete and frequently studying historical approaches. Today, he is bent towards two distinct methods: fibre-reinforced concrete and rammed earth- RE.
Builders happen to be knowledgeable about the challenges that happen to be associated with 20th-century concrete, which mainly has a lifespan ranging between 50 and 100 years.
In the mid-19th century, the steel rebar introduction as a reinforcement for concrete was a major development. But when salt is added to this equation, there is a likelihood of deterioration taking place rapidly in settings such as parking garages and roads.
Notably, animal hair, especially horse hair, was often used within concrete before metal was introduced. As per Gupta, the hair happens to function like a fiber and elevates the quality of concrete by making a bridge across cracks, just like what the staples do.
In the modern era, there is a growing trend of making use of natural as well as synthetic materials as an alternative choice to animal hair.
Gupta, along with his team at the University of Victoria, have been pretty much engaged in the Idea to Innovation company. One of the projects has in it collecting plastic waste from recyclers, especially milk jugs, and changing it into plastic fibres. The fibres are then incorporated into the concrete. It is well to be noted that this concrete has already been successfully used for a section of the sidewalk outside Victoria’s Crystal Pool.Apart from this, concrete with carbon fibres has also been utilized by BC Transit and the University of Victoria.
Traditionally, steel has been used in applications like sidewalks, but recent research suggests that it may not be an ideal choice.
As per Gupta, the inclusion of fibres that happen to be made of plastic is broadly recognized for its significant reduction when it comes to cracking.
Steel fibres happen to be used, apart from synthetic fibres like polypropylene, polyethylene, and HDPE. That said, the steel used these days is not the same as the rebar that happens to be used in the past. Presently, small strands with diameters that are similar to tin wire as well as pieces that are two inches long are commonly used.
Apart from this, cellulose, which happens to be derived from wood bark, pulp as well as paper waste, and also wood ash from Prince George’s forest industry and fly ash from coal burning, is made use of and incorporated into concrete mixes.
Just like cooking, the process of making concrete has seen a major transition from being a simple batch to rather becoming a carefully blended mixture now. Gupta opines to add a pinch of fibre to every bucket of concrete, but then there do lie certain limitations.
In the case of a 50-storey building, steel would not need to be removed. Fiber happens to be excellent when it comes to flat work, says Gupta.
He says that a study conducted by the National Research Council went on to reveal that concrete that has steel can explode when exposed to temperatures of more than 400°C because there is no outlet for the moisture to escape.
On the other hand, synthetic fibre helps moisture disperse effectively and efficiently.
Gupta happens to specialize in RE construction, which is led by compacting earth into formwork, which is indeed essential for maintaining the structural integrity of the RE wall in the drying process that involves repeatedly compacting earth by making use of a manual or pneumatic rammer until the desired wall height gets achieved. The RE happens to be typically arranged in layers.
It is well to be noted that the composition of the earth can vary depending on its location, but it should not contain any organic material. Adequate binder is indeed the need of the hour to hold together the grains of silt, sand, and gravel as small stones, and in order to further enhance strength, lime or cement can be added.
The practice of construction happens to have a long history; evidence suggests of its use in China dates back to somewhere around 3000 BC. It gained major popularity in Europe in the 18th and 19th centuries, whereas in North America, construction techniques happened to be first employed in 1556 in Florida, wherein a mixture of soil as well as seashells was compacted by way of using heavy formwork.
Today, Gupta explains that modern RE happens to have incorporated the use of cement so as to enhance stability, and this cement percentage varies depending on the attributes of the local soil. As per Gupta, the ideal approach will be to involve excavating the soil so as to construct the foundation and also utilizing it for the walls. He goes on to compare the development of RE to the concept of the 100-mile diet, wherein local ingredients in a 100-mile radius are used so as to create a final product.
Since the RE happens to be manually removed from the form every time, each section looks unique.
Notably, the University of Victoria is home to the renowned First Peoples House, which happens to feature RE walls.
Interestingly, the Van Dusen Visitor Centre, Vancouver showcases two RE walls, which happen to be constructed by making use of soil, chalk, lime, and pigment, which get combined skilfully to build elegantly curved walls in earthy tones.
Gupta says that there are other locations in British Columbia as well where structures are being built by ramming earth, like a pump station and washroom on the Gorge Waterway in Victoria, and also more than a dozen homes across Salt Spring Island.
The Nk’Mip Desert Cultural Centre, which happens to be located at the Osoyoos Indian Band Reservation, boasts the title of being the largest insulated RE wall in the world, spans an impressive length of 80 meters, stands at a height of 5.5 meters, and happens to have a thickness of 600 millimeters. The thermal resistance, which is denoted as R33, indicates that there is effective insulation in place and that there are only a few control joints as well as minimal non-structural cracking present.
As per Gupta, reconstruction would be very suitable for remote Indigenous communities, and it could potentially be a superior choice to the current housing options that are available. He adds that the use of rammed earth results in the creation of incredible architectural marvels.