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Dictionary

Construction Materials

Sustainable development requires waste to be minimised, and energy consumption to fall. How successful is the construction industry in meeting their obligations towards the sustainable economy?

Asbestos is a fibrous mineral that is found naturally in different forms: chrysotile (serpentine group, white asbestos), crocidolite (Magnesio Riebeckite), hornblend (blue asbestos), grunerite (brown asbestos), anthophyllite, and actinolite. Chrysotile is the most widest-used type of asbestos for technical applications, and as a building material in the form of asbestos cement, asbestos board, and spray asbestos.

Asbestos was a very widely used mineral until the 1980s. Since 1989 in Switzerland, and 1993 in Germany, the production and use of asbestos has been subject to a broad, though not total, ban. Since 2005 the EU has banned the production, use and export of asbestos. Unfortunately, it still finds large production volumes in certain countries, despite strong criticism and evidence of the link between the inhalation of asbestos fibres and later development of cancer (asbestosis and mesothelioma).

Chrysotile or white asbestos is the most commonly used form of asbestos, accounting for over 90% of asbestos removed during renovations. It is a fibrous silicate mineral in the serpentine subgroup of phyllosilicates. Chemical formula: (Mg,Fe,Ni)3Si2O5(OH)4. It is banned in most countries because it can cause cancer when inhaled.

Asbestos was discovered soon after the turn of the 20th century to be a valuable admixture to many building materials, since it possesses exceptional fire resistance and insulation properties. Its use around the world has been very widespread, and is found in more than 3000 products and applications.

By the 1930s, fears were arising that the dust from asbestos was linked to increased risk of occupational cancer, particularly amongst workers who mined and worked asbestos. In 1938, the German physician, Martin Nordmann, described two cases of ‘Occupational Cancer of Asbestos Workers’. This led the workers’ accident insurance fund in Germany in 1943 to include lung cancer linked with asbestosis in the list of occupational illnesses. Switzerland followed suit and in 1953 entered asbestosis in its list of occupational diseases.

Profits before health

However, despite the suspected link between the substance and disease, asbestos enjoyed unlimited use till its peak in the 1970s, when many countries began moves to restrict it. In the 1980s, industry resisted the banning of its treasured substance, and formed unions in many countries, including Switzerland, to lobby against universal bans, ceding step by step restrictions on specific applications, insisting that proper use made asbestos a safe substance.

Gradually, as the level of concern with the number of confirmed deaths and sufferers, and scientific evidence of a direct link between asbestos and mesothelioma, bans and limitations began to become stricter. In 1970, Germany officially recognised asbestos fibres as carcinogenic, and banned spray-on asbestos in 1979, and placed a general ban on asbestos as a construction material in 1993.

SUVA sets a MAK (maximum workplace concentration) threshold level for Switzerland of 0.01 asbestos fibres/ml. This is defined for fibre lengths >5 um, diameter < 3 um, and a ratio length: diameter < 3:1.

World production increasing

While most industrialized countries are united in the belief that asbestos should be banned, asbestos is unfortunately increasingly used in the developing and newly industrializing countries. This is because asbestos is cheaper than substitutes, and hazards for workers are put on a low priority level.

Mesothelioma
Claims accepted for mesothelioma due to asbestos
    World Production (2011 '000 tonnes p.a.)
  1. Russia: 1,000
  2. China 440
  3. Brazil 302
  4. Kazakhstan 223
  5. Canada 50
  6. India 19

Asbestos is a 'controlled waste' under Annex I of the Basel Convention on the Control of Transboundary Movements of Hazardous Wastes and their Disposal (1992). Article 13 prohibits the export of waste containing asbestos dust or fibres to Parties which have then prohibited their import (notification procedure).

Annex III

The Rotterdam Convention does not provide an outright ban, but rather the obligation on exporters to inform importers of the restrictions and bans which exist for their products (PIC prior informed consent procedure for certain hazardous chemicals and pesticides in international trade). It enables countries to control their borders through the informed consent process, although they may still grant permission for the import.

At the 2011 COP (Conference of the Parties), Canada refused to allow the addition of chrysotile asbestos fibres to Annex III of the Rotterdam Convention. Canada is the only G8 country objecting to the listing. Other objectors were similarly self-interested producers: Kyrgyzstan, Kazakhstan, Ukraine and Vietnam. India withdrew its objection prior to the 2011 conference. In 2012 Canada withdrew its opposition, following the election of a more enlightened government.

The Chemical Review Committee of the Rotterdam Convention recommended to the 7th COP meeting held 4 May to 15 May 2015 in Geneva, Switzerland, that chrysotile asbestos be added to Annex III of the convention. The Russian asbestos industry on this occasion prevented chrysotile asbestos from being included in the list of dangerous products.

In total, 7 countries raised objections to the inclusion of chrysotile asbestos at the 2015 COP: Russia, Kazakhstan, India, Kyrgyzstan, Pakistan, Cuba, Zimbabwe.

The United states, not a member of the Convention but present as observer, was uncharacteristically supportive of the general good, and supported the inclusion of chrysotile in Annex III.

Asbestos is carcinogenic and its use in construction has been banned in Switzerland since 1989. Switzerland also ratified the ILO Asbestos Convention concerning Safety in the Use of Asbestos, in force as of 1993. The Swiss Construction Ordinance, Article 3, sets out what must be done prior to the execution of construction work. In addition, as a hazardous substance, the working with, removal and disposal of asbestos from contaminated buildings is subject to restrictions.

In Article 3, Planning of Construction Work, from Chapter 2 of the Ordinance for Safety and Protection of Health or workers during building work, is stated:

"If it is suspected that particularly hazardous substances such as asbestos or polychlorinated biphenyls (PCBs) may occur, the employer must determine the risks in detail and assess the associated risks. Any measures which are necessary shall be incorporated in the planning. If a particularly hazardous substance in the course of building work be encountered unexpectedly, the work concerned shall be interrupted and the client notified."

Responsible Authorities

The authorities concerned with asbestos are:

BAG (Bundesamt für Gesundheit, Federal Office for Health) resp. for classifying cancer-causing agents under the Toxic Substances Act. Releases public info about indoor limits.

BAFU (Federal Office for the Environment) oversees the implementation of the Hazardous Materials Ordinance. It oversees bans on the use, sale and import of asbestos and products that contain asbestos, as well as the disposal of asbestos.

SUVA (Schweizersiche Unfallversicherung, Swiss Accident Insurance Fund): occupational safety and corresponding employer obligations. Responsible for preventing occupational illnesses from asbestos in the workplace. Defines TLVs (threshold limit values) for substances dangerous to human health.

Cantons and municipalities: construction codes which affect asbestos removal.

Cantonal Occupational Inspector's Office (KAI Kanonale Arbeitsinspektorate) and SECO (Staatssekretariat für Wirtschaft, State Secretariat for Economic Affairs): authorities for implementing occupational health protection.

FACH

To simplify the procedures, the the Swiss Coordination Committee Forum for Asbestos (FACH) (Koordinationsgruppe Forum Asbest der Schweiz) was founded in 2002. This committee coordinates control measures.

The Ordinance on Air Pollution Control (CH) classifies chrysotile and other asbestos forms as carcinogenic substances, class 1. These substances must be restricted as much as technically and operationally feasible and economically acceptable, but not more than 0,1 mg m3 at a mass flow rate of 0.5 g/h.

There are no regulatory limit for contaminants in ambient air in private housing, although it emphasises that concentrations above 1,000 m-3 should not be tolerated.

MAK (maximale Arbeitsplatzkonzentation, maximum workplace concentrations) = 0.01 respirable asbestos fibres RAF / ml of air (= 10k RAF / m3 of air).

EU Regulatory status of asbestos in the EU

The placing on the market and use of chrysotile fibres and products containing these fibres added intentionally are prohibited (Directive 1999/77 /E.C. of 26.7.1999). Exception for diaphragms for existing electrolysis installations till end of service life, or substitutes become available. Construction materials containing asbestos are classified as hazardous waste as of 01.01.02 (Commission Decision 2000/532/EC. Council directive 2003/18/EC sets limit of workers exposure to an airborne concentration of asbestos to 0.1 fibres per cm3 as an 8h time-weighted average (TWA).

Strong and weakly-bonded asbestos

In Switzerland, it is estimated that between 60-80% of buildings, particularly those built between 1950 - 1980, are contaminated with asbestos. Under Swiss law, these need to be assessed, and the categories of asbestos, primarily weakly or strongly bonded, identified, and entered in the BUWAL (Federal Office for the Environment) Spray-Asbestos Register. Spray asbestos, cement asbestos and asbestos board are the most common of asbestos-containing materials used.

Strongly-bonded asbestos materials are less urgent than weakly-bonded, since there is little likelihood of fibres being released under normal conditions and building use. Only in the cases of physical work being conducted on the materials, such as during renovation or demolition, are protective measures required, and hazardous substance disposal regulations apply.

Weakly-bonded asbestos, such as in spray applications and board, present a greater hazard, since its fibres are typically found to be present in enclosed spaces through normal use and conditions. This asbestos needs to be removed quickly and a time period of one year is set as the maximum.

Respirable asbestos fibres RAF

RAF are asbestos fibres which can penetrate through to the alveoli, where they become trapped, creating a long-term condition conducive to mortal diseases like asbestosis and mesothelioma.

Cement and concrete are major construction materials, produced at exponentially growing rates (19 Gt in 2010). China alone produces more than half of all the world's concrete for its massive civil engineering projects.

Limestone

Limestone is a sedimentary rock commonly used as a building stone, for its aesthetic qualities. Limestone is particularly susceptible to erosion from acid rain.

Limestone is formed from the sedimentary deposits of marine organism shells and skeletons, containing calcium in the forms of aragonite and calcite. Corals are composed mainly of the material which is destined to become limestone.

Limestone can take different forms (crystalline, clastic, granular or non-granular), and its base form is white, but impurities can give it colouring. Limestone can recrystallise to form marble during metamorphism.

Pozzolan

Pozzolan is an ingredient in the concrete recipe. It reacts chemically with CaOH (calcium hydroxide) and water to add bonding and structural strength to concrete.

Pozzolana is volcanic ash, and was used by the Romans in their concrete. The name derives from Pozzuoli, Naples, where the volcanic pumices and tuffs from Mt. Vesuvius were quarried by the Romans.

The Roman concrete making techniques were lost until the 15th century, when Vitruvius' description of lime-pozzolan binders was discovered in his De architectura. By the 18th century, Portland cement, with its more readily available limestone base, became the dominant form.

Belite

Belite is a mineral used in Portland cement, and is responsible for its 'late strength' during curing. The main component of belite is dicalcium silicate, Ca2SiO4.

Alite

Alite is the common usage name for tricalcium silicate, Ca3SiO5. Alite is the mineral in Portland cement which provides the early strength during setting.

Clinker

Clinker is a mixture of calcium silicates, usually alite (Ca3SiO5) and belite (Ca3SiO4), and is the the product of sintering limestone and alumino-silicate minerals during the manufacture of cement.

Fly Ash

Fly ash is the residue of coal combustion which escapes the furnace with the exhaust gases, as opposed to bottom ash, which falls to the bottom of the boiler chamber.

Fly ash is easily removed from exhaust gases by electrostatic precipitators, which charge the particles, which are then attracted to charged plates.

Fly ash can be used in concrete production, as a partial substitute for Portland cement. It contains varying amounts of silicon dioxide, and oxides of aluminium and calcium.

The US EPA does not classify coal fly ash as hazardous waste (Ruling Dec 2014 of the RCRA, Resource Conservation and Recovery Act). However, fly and bottom ash from other incinerator fuel sources, such as waste, may be classified as HazMat.

Concrete has in the past been the source of air pollution, primarily NOx and CO2. New mixtures and design characteristics allow concrete to adsorb these pollutants from the air, thereby providing a cleansing benefit.

Adsorption is defined by the IUPAC (International Union of Pure and Applied Chemistry) as the "Increase in the concentration of a substance at the interface of a condensed and a liquid or gaseous layer owing to the operation of surface forces."

Activated carbon, or bio-char, is carbon that is very porous, and has a very large surface area.

Switzerland's Gotthard road tunnel experienced a deadly fire in October, 2001. Two trucks collided, and the resulting inferno killed 11 people, and injured scores more. Most of the deaths were caused by the build-up of toxic fumes from the burning fuel. The structural integrity of the tunnel was seriously damaged, causing collapse as the concrete lining failed.

The accident prompted investigations into how concrete can be improved, to make it safer and more fire-resistant. It has always been assumed, however, that admixtures which change characteristics, such as fire retardation and adsorption/absorption, would be paid for by a loss in strength, hardness or elasticity.

A team of researchers in southern Switzerland began experimenting with the innovative idea of including activated carbon in concrete. To their delight, it not only worked to improve fire resistance, but led to a stunning discovery: activated carbon in concrete can also suck pollutants out of the air!

In fact, their concrete can sequester so much CO2 and NOx, it provides a net sink for the pollutants. Employing concrete of this type not only reverses the environmental impacts of the manufacture of the cement itself, but can continue to cleanse the air of NOx and CO2 from other sources for decades. And the new concrete shows no loss in strength, durability or longevity.

The combination of these remarkable properties with its enhanced fire protection makes this new concrete particularly suitable for use in road tunnels, where the accumulation of vehicle exhausts, combined with fire danger, is an ever present hazard.

The gases which are of most concern for environmentalists are the group of compounds produced by the burning of fossil fuels. These emissions include various combinations of nitrogen and oxygen, known collectively as NOx. The most common NOx resulting from car exhausts are NO and NO2. The latter is a photosynthetic gas, and reacts with sunlight to produce ozone, another major urban pollutant. It will also combine with water in clouds to form acid rain.

A second pollutant which is causing concern is carbon dixoide, the infamous greenhouse gas which countries around the world have made commitments to reduce. Commitments which innovations like green concrete could help to achieve.

"Finding a cheap, standardised method of producing resilient, safe and clean concrete, with the added bonus of being a net CO2 sink, would have a tremendous impact on the global warming problem as well," says the concrete specialist Di Tommaso enthusiastically.

When organic matter is heated in the absence of oxygen, a process known as pyrolysis, it produces a substance which is around 70% pure carbon, but in a structure which is very porous, with an enormous surface area. Such a substance has the ability to draw molecules from the air and lock them more or less permanently onto its surface. This is is known as adsorption. The activated carbon, or biochar, produced through pyrolysis has long been used in filters to remove pollutants from liquid and gas streams. However, no-one knew that when it is included in porous concrete, the air which comes into contact with it will be cleansed of its dangerous pollutants.

Switzerland uses a lot of concrete in its enormous civil engineering projects, such as the new AlpTransit railway tunnel, the longest in the world, completed this year. But Europe's consumption is dwarfed by China, currently consuming 53% of the world's annual concrete production. Something of the order of 5.5% to 6.5%1 of anthropogenic greenhouse gases are the result of cement production for concrete alone. Turning the over 4 billion tonnes of cement produced annually into a net sink, would save more than 3 billion tonnes of CO2.

"The bio-char seems to offer a chance to make concrete sustainable, but which has all the other qualities we need in concrete across a full range of applications," says Michel Di Tommaso. "The science has shown it works. All we need to do now is to convince the industry to change its ways - for the right reasons."

IMM SA is in corporate member of UmweltScience, and more details about its research may be read on its member page: Corporate Homepage: umwelt.science/IMM.

A profile about the researcher Michel Di Tommaso is also available: Profile: Michel Di Tommaso.

1 Cemnet.com: Harnessing CO2