Materials Science and the Use of Waste Products

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Tuesday, July 21st, 2015
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Australia has been witness to some ground breaking innovation and some spectacular if unfortunate failures in building technology. Without the risk of failure, no progress in technology or in materials science is possible.

One example of a technology which was a little before its time can be seen in Dante Bini’s domed concrete structures. Bini, who is now highly regarded for his work with domed structures, designed a system for reinforcing his concrete works. A series of radiating spring loaded and interlocking steel reinforcements were placed over a large dome shaped bladder. Ferro cement concrete was shot onto the surface of the deflated bladder and simultaneously the bladder was inflated. As the bladder reached full inflation as a temporary form for the concrete dome, the shot concrete filled in the voids between the reinforcing.

The resulting dome could cover a large floor plan and be used for a showroom, a hall or any other requirement for space unimpeded by columns or other supports. Some of Bini’s original innovative domes remain standing, but the concrete technology and formulations were not up to the same standard as the innovative structural technique, and after a collapse of a partially inflated dome, his technique was temporarily discredited.

Bini retains much of his intellectual property. He continued his research into domed structures and is now revered as a pioneer in the innovative use of geometry, steel reinforcing and concrete technology.

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 Many innovations in building technology have occurred through the use of industrial and agricultural waste as a building product.

One recent example is the use of recycled crushed glass as an aggregate in lightweight precast elements. Glass is made from sand, which typically has a high silicon content. Naturally there are thousands of formulations, but glass generally is stable and can be an excellent aggregate in many concretes. Crushed glass is also used in road base and to improve the grip and wear characteristics of bitumen.

Another popular use of a waste by product is with plastics. Many types of petroleum-based plastics can be are reheated and then used to make specific products. Reconstituted plastic planks with ingredients to render them UV light resistant can be excellent building materials. They do not rot, can not be eaten by termites, are not affected by chlorine or salt around swimming pools, can be treated not to easily ignite, and are lightweight. A variety of extrusions are now in use with innovative Australian technology.

A by-product of burning coal for electricity generation and for smelting metals is fly ash. Long used in concrete blocks called Clinker blocks in the US, many modern ready-mixed concretes use a higher proportion of fly ash, making this formerly unused waste a highly sought after material.

The aluminium industry uses caustic soda to extract aluminium from bauxite. Generally, the leftover sludge is an environmental hazard and is left in large sediment ponds to evaporate. There have been several leaks and spillages of the sludge in recent years which have contaminated the environment. An innovative Australian company has found a way to turn the leftover unwanted sludge into a high quality ceramic or concrete building material.

One of the initial recycled building products came as a by-product of the sugar refining industry. The cane pulp was compressed and turned into a cheap and utilitarian building board and ceiling panels.

The huge volume of paper and cardboard waste in landfills is often a product which can be recycled into pulp for cardboard and paper. Cardboard has been used as the wrap for plasterboard, and a high recycling rate for paper and cardboard reduces the number of trees required to meet these demands.

Sawdust is used in a variety of building materials, so much so that it has become a highly sought after material. It is used in some formulas of lightweight concrete blocks.

Research in Australia has been conducted into the use of organic fibre as a cellulose structure for building board or extruded products. Cellulose may come from the leftover husk from grain production. The industrial hemp association has researched many uses for this organic fibre, including high-strength plasters and fibre-reinforced polymers and concretes. These composites can be formulated to be durable, fireproof, lightweight and easy to build with. Hemp production can be a rotational crop, and as such does not greatly impede primary production.

Plywood has been an extremely effective building material for building board making. Creating plywood from chips and shaved timber has a long and successful history in building, yacht making and even aircraft manufacture. The “Mosquito” aircraft fuselage and body was made entirely of laminated plywood, the laminations creating very strong and flexible aircraft wings.

Aluminium and steel recycled from waste products is a major component in all new steel and aluminium.

Organic waste can be composted to create non-toxic high quality soil conditioners and fertilisers. Our sewerage and liquid waste can also be recycled into high quality fertilisers.

Where there is highly toxic waste such as heavy metals, materials science has been able to render these inert by encapsulating them in impervious high strength composite concretes.

There are now very few waste products which cannot be recycled into high quality building products, and where there are large volumes of a waste product, many novel uses are being created in building materials science. Another example is the recycling of vehicle tyres. Chipped rubber can be used as a valuable sport surface, as a filler in some road bases, or converted to be used again as a petroleum material.

Highly toxic materials such as heavy metals and cyanide radioactive waste can be encapsulated in glass or encased in high strength concrete and rendered inert for long term storage.

It may be surprising to learn that some of the most innovative companies in these fields have come from Australian-based discoveries and inventions.

Wherever waste materials can be collected, a use may be found in the building industry, and where a waste product is too toxic and present a danger to future generations, these may be encapsulated so as to render them inert and safe for storage.

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