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Waste light concrete (WLC) is a type of light weight concrete where the traditional construction aggregates are replaced by a mix of shredded waste materials [1] (thermoplastics, thermosetting plastics, glass, tires, incinerator bottom ash, solid agricultural waste etc.) and a special group of additives. Used in infrastructure and building construction.
Concrete products contain a different mix of cement + water + aggregates, depending on desired product quality. With the cost of aggregates and the waste awareness rising, a need to decrease aggregate usage and an alternative way to dispose solid waste arose. Extensive research and development around the early 1960s lead to the realization of the first samples of polystyrene based light concrete products, where the aggregates (rocks and sand mostly) had been largely or in 100% replaced by granulates of plastic materials, or plastic waste. The main problem of this concrete was its soft consistency.
By 1990 a group of engineers formulated (and later patented) the first industrially stable version of the polystyrene concrete by mixing in certain additives. The initially used additives were not health-friendly and cost too much for the product to be financially viable, but the product reached a 3-4 N/mm2 compressive strength, which was enough for wall insulation filling. It also proved that the process is possible.
In 2001, in an attempt to commercialize the technology they replaced the binding materials with a health-neutral polymer additive. Laboratory tests were completed on fire resistance and compressive tests. This light polystyrene concrete turned out to be structurally stable, light weight (from 100 to 300 kg/m3) and 100% fire retardant. A request from Argentine lead to the final formulation of the product, where they identified a big problem in pine tree leaf waste and they were interested if it could be used as aggregates. This led to the realisation in 2004 that it is not only polystyrene that could fulfill the purpose, but any small enough solid waste type, therefore any shredded mix of solid wastes.
The patent had been filed in 2015 [2] and awarded in 2017/2018 that covers any possible additive that enables the replacement (fully or partially) of natural aggregates by mixed shredded solid waste granules.
The resulting waste light concrete product covers a group of about 3000 possible final products. Including polystyrene concrete, heavy plastic concrete, incinerated bottom ash concrete, desert sand concrete and many more, which at the time of writing resulted in around 400 samples with different physical qualities. In general, the compressive strength of the final products is between 3 N/mm2 to 12 N/mm2 with a weight of 100 kg/m3 to 800 kg/m3. Traditional gravel-concrete can be 40 N/mm2 strong and weigh over 2.000 kg/m3.
The special additive is produced in a factory and shipped to the site of application in 5–25 kg bags. It is mixed together with cement (100–300 kg/m3), waste materials (1.1-1.2 m3) and water (100-300 liters), plus 5 kg/m3 of the additive powder.
Potential waste materials include: ocean waste, fire retardant plastics, thermosetting plastics, computer and phone motherboards, polyfoam, nylon bags, crops, glass and rubber products, incinerated bottom ash and other energy production waste, industrial processing byproducts, packaging materials and many more. Raw materials are shredded to less than 10 mm, do not have to be selected or washed. It is possible to use desert sand or low quality aggregates as main or filling materials.
On the working site, only the traditionally used concrete processing tools are needed for mixing, pumping or casting, which means no extra costs and a very high rate of market availability. The technology replacement cost is nearly zero.
The produced waste light concrete can be 100% recyclable at the end of the product life cycle (or in case of force majeure) by simply shredding the concrete on-site and remixing it into a new batch of waste light concrete for an indefinite number of times.
Laboratory results showed no leeching or other environment polluting effects of the process or the product.[ citation needed ]
Not applicable for: weight bearing structural concrete, high-friction contact surface.
For decades (unknown), asphalt producers include about 0.5% soft plastic [3] in the asphalt mix to increase durability of the road and to decrease at least very little the cost of building road surfaces. Probably the most well known 'plastic road' technology to date, it improves the quality of the top layer of the road. The input plastic types are very limited as they have to melt into the asphalt mix at 165 degree Celsius (thermoplastics), and the technology has a high initial investment and low expandability. As a comparison, plastic road claims to dispose 8–10 kg (or 4-6%) of selected and washed plastic waste in the road surface per tons of asphalt, [4] while waste light concrete can dispose around 800 kg / tons of road base concrete with only low energy consumption shredding and mixing at room temperature. However, these two technologies can be combined in the same stretch of road. It is possible to build plastic blocks as road building units from soft plastics, which is a complex process, and leads to a recyclable road material that has fire hazard risks as it is made from flammable plastic. [5]
Some thermoplastics can be melt and compressed together into solid plastic bricks. The raw materials are very limited, the machinery can be costly and the output speed is also limited by technology. It is possible to DIY hand-compress and oven-melt the bricks, which results in low cost and low output. [6] Another method to store soft household plastic is to compress it by hand into a plastic drink bottle and stack them as building blocks [7] as a no-cost building material.
Car tire granulates are used in road base as a stabilizing layer or in small quantities as a binding agent in asphalt. The concrete volume ratio is very small.
There is a large variety of research that has been and continues to be carried out to study the feasibility of waste plastic and other waste materials for usage in lightweight concrete. This only becomes more important as the demand for concrete increases, and continues to exacerbate the catastrophic effects of sand and gravel mining, along with the general carbon emissions that result from concrete production. [8]
The replacement of fine aggregates in concrete (e.g. sand) with plastic naturally will decrease the Young’s Modulus and compressive strength of the material, as plastics have lower strength than typical fine aggregates, and their hydrophobic properties decrease their adhesion to the concrete matrix at the interfacial transition zone. [9] This makes plastics suitable for use in lightweight concrete, where compressive strength is less important. [10]
Research has generally shown that a replacement of fine aggregates with plastic by about 10% is optimal for minimizing the strength reduction caused by adding plastic. [10] [11] Other benefits of adding plastic aggregates to concrete include reduction in heat conduction, reduction in density, and increase in fracture energy. [9]
Several studies have been conducted to address the issue of plastic’s adhesion with the concrete matrix. Studies show that treating plastic aggregate with gamma radiation before adding to the concrete improves compressive strength of the material. MIT students were able to produce concrete that is up to 20% stronger than conventional concrete with this method. [12] Similarly, microwave radiation pre-treatment of PET was shown to improve adhesion with cement paste. [13] Research is also being done to assess the use of air reducing agents to increase adhesion. [9]
Aside from plastic, other waste materials can be useful for replacing fine aggregates in concrete, depending on the requirements for specifications such as specific gravity, specific strength, and particle size distribution. Researchers have demonstrated the viability of materials including coconut shell, glass powder, oil palm shell, waste clay brick, and various types of ash for this purpose. [8]
Bitumen is a sticky, black, highly viscous liquid or semi-solid form of petroleum. In the U.S., it is commonly referred to as asphalt. It may be found in natural deposits or may be a refined product, and is classed as a pitch. Before the 20th century, the term asphaltum was also used. The word is derived from the ancient Greek ἄσφαλτος ásphaltos. The largest natural deposit of bitumen in the world, estimated to contain 10 million tons, is the Pitch Lake in southwest Trinidad.
Concrete is a composite material composed of fine and coarse aggregate bonded together with a fluid cement that hardens (cures) over time. Concrete is the second-most-used substance in the world after water, and is the most widely used building material. Its usage worldwide, ton for ton, is twice that of steel, wood, plastics, and aluminium combined. Globally, the ready-mix concrete industry, the largest segment of the concrete market, is projected to exceed $600 billion in revenue by 2025. This widespread use results in a number of environmental impacts. Most notably, the production process for cement produces large volumes of greenhouse gas emissions, leading to net 8% of global emissions. Other environmental concerns include widespread illegal sand mining, impacts on the surrounding environment such as increased surface runoff or urban heat island effect, and potential public health implications from toxic ingredients. Significant research and development is being done to try to reduce the emissions or make concrete a source of carbon sequestration, and increase recycled and secondary raw materials content into the mix to achieve a circular economy. Concrete is expected to be a key material for structures resilient to climate disasters, as well as a solution to mitigate the pollution of other industries, capturing wastes such as coal fly ash or bauxite tailings and residue.
Polystyrene (PS) is a synthetic polymer made from monomers of the aromatic hydrocarbon styrene. Polystyrene can be solid or foamed. General-purpose polystyrene is clear, hard, and brittle. It is an inexpensive resin per unit weight. It is a poor barrier to oxygen and water vapour and has a relatively low melting point. Polystyrene is one of the most widely used plastics, the scale of its production being several million tonnes per year. Polystyrene can be naturally transparent, but can be colored with colorants. Uses include protective packaging, containers, lids, bottles, trays, tumblers, disposable cutlery, in the making of models, and as an alternative material for phonograph records.
Acrylonitrile butadiene styrene (ABS) (chemical formula (C8H8)x·(C4H6)y·(C3H3N)z ) is a common thermoplastic polymer. Its glass transition temperature is approximately 105 °C (221 °F). ABS is amorphous and therefore has no true melting point.
A road surface, or pavement, is the durable surface material laid down on an area intended to sustain vehicular or foot traffic, such as a road or walkway. In the past, gravel road surfaces, macadam, hoggin, cobblestone and granite setts were extensively used, but these have mostly been replaced by asphalt or concrete laid on a compacted base course. Asphalt mixtures have been used in pavement construction since the beginning of the 20th century and are of two types: metalled (hard-surfaced) and unmetalled roads. Metalled roadways are made to sustain vehicular load and so are usually made on frequently used roads. Unmetalled roads, also known as gravel roads, are rough and can sustain less weight. Road surfaces are frequently marked to guide traffic.
Asphalt concrete is a composite material commonly used to surface roads, parking lots, airports, and the core of embankment dams. Asphalt mixtures have been used in pavement construction since the beginning of the twentieth century. It consists of mineral aggregate bound together with bitumen, laid in layers, and compacted. The process was refined and enhanced by Belgian-American inventor Edward De Smedt.
Building material is material used for construction. Many naturally occurring substances, such as clay, rocks, sand, wood, and even twigs and leaves, have been used to construct buildings. Apart from naturally occurring materials, many man-made products are in use, some more and some less synthetic. The manufacturing of building materials is an established industry in many countries and the use of these materials is typically segmented into specific specialty trades, such as carpentry, insulation, plumbing, and roofing work. They provide the make-up of habitats and structures including homes.
Polymer degradation is the reduction in the physical properties of a polymer, such as strength, caused by changes in its chemical composition. Polymers and particularly plastics are subject to degradation at all stages of their product life cycle, including during their initial processing, use, disposal into the environment and recycling. The rate of this degradation varies significantly; biodegradation can take decades, whereas some industrial processes can completely decompose a polymer in hours.
Wood-plastic composites (WPCs) are composite materials made of wood fiber/wood flour and thermoplastic(s) such as polythene (PE), polypropylene (PP), polyvinyl chloride (PVC), or polylactic acid (PLA).
Aggregate is the component of a composite material that resists compressive stress and provides bulk to the composite material. For efficient filling, aggregate should be much smaller than the finished item, but have a wide variety of sizes. For example, the particles of stone used to make concrete typically include both sand and gravel.
Plastic recycling is the processing of plastic waste into other products. Recycling can reduce dependence on landfill, conserve resources and protect the environment from plastic pollution and greenhouse gas emissions. Recycling rates lag those of other recoverable materials, such as aluminium, glass and paper. Through 2015, the world produced some 6.3 billion tonnes of plastic waste, only 9% of which has been recycled, and only ~1% has been recycled more than once. Additionally, 12% was incinerated and the remaining 79% sent to landfill or to the environment including the ocean.
Biodegradable plastics are plastics that can be decomposed by the action of living organisms, usually microbes, into water, carbon dioxide, and biomass. Biodegradable plastics are commonly produced with renewable raw materials, micro-organisms, petrochemicals, or combinations of all three.
Construction aggregate, or simply aggregate, is a broad category of coarse- to medium-grained particulate material used in construction, including sand, gravel, crushed stone, slag, recycled concrete and geosynthetic aggregates. Aggregates are the most mined materials in the world. Aggregates are a component of composite materials such as concrete and asphalt; the aggregate serves as reinforcement to add strength to the overall composite material. Due to the relatively high hydraulic conductivity value as compared to most soils, aggregates are widely used in drainage applications such as foundation and French drains, septic drain fields, retaining wall drains, and roadside edge drains. Aggregates are also used as base material under foundations, roads, and railroads. In other words, aggregates are used as a stable foundation or road/rail base with predictable, uniform properties, or as a low-cost extender that binds with more expensive cement or asphalt to form concrete. Although most kinds of aggregate require a form of binding agent, there are types of self-binding aggregate which do not require any form of binding agent.
Tire recycling, or rubber recycling, is the process of recycling waste tires that are no longer suitable for use on vehicles due to wear or irreparable damage. These tires are a challenging source of waste, due to the large volume produced, the durability of the tires, and the components in the tire that are ecologically problematic.
Filler materials are particles added to resin or binders that can improve specific properties, make the product cheaper, or a mixture of both. The two largest segments for filler material use is elastomers and plastics. Worldwide, more than 53 million tons of fillers are used every year in application areas such as paper, plastics, rubber, paints, coatings, adhesives, and sealants. As such, fillers, produced by more than 700 companies, rank among the world's major raw materials and are contained in a variety of goods for daily consumer needs. The top filler materials used are ground calcium carbonate (GCC), precipitated calcium carbonate (PCC), kaolin, talc, and carbon black. Filler materials can affect the tensile strength, toughness, heat resistance, color, clarity, etc. A good example of this is the addition of talc to polypropylene. Most of the filler materials used in plastics are mineral or glass based filler materials. Particulates and fibers are the main subgroups of filler materials. Particulates are small particles of filler that are mixed in the matrix where size and aspect ratio are important. Fibers are small circular strands that can be very long and have very high aspect ratios.
Concrete is produced in a variety of compositions, finishes and performance characteristics to meet a wide range of needs.
Plastics are a wide range of synthetic or semi-synthetic materials that use polymers as a main ingredient. Their plasticity makes it possible for plastics to be moulded, extruded or pressed into solid objects of various shapes. This adaptability, plus a wide range of other properties, such as being lightweight, durable, flexible, and inexpensive to produce, has led to its widespread use. Plastics typically are made through human industrial systems. Most modern plastics are derived from fossil fuel-based chemicals like natural gas or petroleum; however, recent industrial methods use variants made from renewable materials, such as corn or cotton derivatives.
Recycling can be carried out on various raw materials. Recycling is an important part of creating more sustainable economies, reducing the cost and environmental impact of raw materials. Not all materials are easily recycled, and processing recyclable into the correct waste stream requires considerable energy. Some particular manufactured goods are not easily separated, unless specially process therefore have unique product-based recycling processes.
Plastic roads are roads that are made partially or entirely from plastic or plastic composites with other materials. Plastic roads are different from standard roads in the respect that standard roads are made from asphalt concrete, which consists of a mineral aggregate and asphalt, while plastic roads are made of plastic. Most plastic roads make use of plastic waste as the aggregate within the asphalt. It is currently unknown how these aggregates will perform in the mid- to long-term, or what effect their degradation might have on surrounding ecosystems.
UBQ Materials is an Israeli cleantech company created to convert unsorted household waste into a thermoplastic composite. The company's primary product, UBQ, is a thermoplastic, sold in the form of pellets, that can be used to substitute for wood, concrete, or oil based plastics in the manufacturing of durable products. In 2018, UBQ Materials Ltd. became a Certified B Corporation.
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