**2. Waste classification**

For many years a lot of wastes have been accumulated in the entire world and they influenced the environment and people life. The necessity of eliminating or at least, reduction of huge quantities of wastes is a priority of researches. Their use in the building material and con‐ struction industry is a one of the possibilities which can help to keep the environment clean.

In the building material industry there are used a lot of types of wastes, which can be classified as follows:

**• By-product waste** is the waste produced by industry which includes any material that is rendered useless during a manufacturing process from plants, mills and mines. Usually they are storaged in landfills, which are placed on agricultural fields or around big cities. Some examples of industrial waste are silica fume, slag, sludge, fly ash, sand paper, metals, glass, etc. [1].

The by-products which are used in construction are:

**• Silica fume** is resulted from the processes of obtaining ferrosilicon industry, as a very fine powder which is recuperated by filters from furnaces. The quantity of dust involved by burnt gases from the furnace represents about 35% from the quantity of the end product. Silica fume generally contains more than 85% SiO2, and also other components in smaller quantities, such as: Fe2O3 (1.3 - 4%), Al2O3 (0.85 - 2.5%), CaO (0.4 - 0.8%), Mg (0.6 - 1.5%), C (1.1 - 2.5%). Silica fume has the shape of particles spherical and the specific surface is between 13000 and 23000 m2 /kg. Its spreading in the atmosphere has as effect the environment pollution [2].

atmosphere). For reducing the aggregate and cement consumption, the replacing materials

Because the cement industry is responsible for 5-7% of worldwide emission of CO2, (which means 1.6 billion tons of carbon dioxide into the atmosphere), in preparing concrete, the cement dosage can be reduced by using mineral additions, strategy that also can contribute to environment protection by preserving the energy and consume the huge quantities of wastes.

Near cement concrete other building materials are obtained by using wastes, such as: high strength concrete, which has in the mix different additions (silica fume, fly ash, etc.), asphalt

Some building materials are totally obtained from wastes, such as "green" materials. The new concept of green buildings offers more energy-and resource efficiency. This concept means the greening of building industry by using only green materials. The technologies of obtaining

The building material and construction industry is one of the principal users of wastes in the processes for obtaining materials or products, for constructing bridges or highways, in soil stabilization, in hydraulic construction, etc. From environmental considerations an extensive waste utilization in construction is recommended, although particular wastes may be too risky

For many years a lot of wastes have been accumulated in the entire world and they influenced the environment and people life. The necessity of eliminating or at least, reduction of huge quantities of wastes is a priority of researches. Their use in the building material and con‐ struction industry is a one of the possibilities which can help to keep the environment clean.

In the building material industry there are used a lot of types of wastes, which can be classified

**• By-product waste** is the waste produced by industry which includes any material that is rendered useless during a manufacturing process from plants, mills and mines. Usually they are storaged in landfills, which are placed on agricultural fields or around big cities. Some examples of industrial waste are silica fume, slag, sludge, fly ash, sand paper, metals, glass,

**• Silica fume** is resulted from the processes of obtaining ferrosilicon industry, as a very fine powder which is recuperated by filters from furnaces. The quantity of dust involved by burnt gases from the furnace represents about 35% from the quantity of the end product. Silica fume generally contains more than 85% SiO2, and also other components in smaller quantities, such as: Fe2O3 (1.3 - 4%), Al2O3 (0.85 - 2.5%), CaO (0.4 - 0.8%), Mg (0.6 - 1.5%), C

concrete, bricks, pavements, roof tiles, prefabricated units, claddings, etc.

green materials are available, but their use in construction industry is limited.

obtained from wastes were studied.

to use.

82 Agroecology

as follows:

etc. [1].

The by-products which are used in construction are:

**2. Waste classification**


Another source of sludge and slag is from steel industry and they are generated as waste material or byproduct. They contain considerable quantities of valuable metals and materials. Different technologies are used for recovering the metallic parts, such as: classification, magnetic separation, leaching, roasting, etc. The wastes are then transformed in different sorts of waste, such as powder, conglomerate, etc. function the necessity of applied technology for a better use of natural resources and environment protection.

The paper industry that uses recycled paper as raw materials has as by-product paper sludge, which has a high content of calcium carbonate, organic materials and other minerals. Because its pozzolanic activity, the paper sludge can be used as cementitious materials in building industry.

**• Fly ash** is a residue from power plants or from different processes of incineration of solid materials. The fly ash is disposal on the landfill [6].

In Romania annually great fly ash (FA) quantities resulted: in 1980 resulted 15 million tons of FA, in 1985 obtained 30 million tons, and after 1990 the FA quantities decreased because the electricity consumes reduced. In our area annually resulted around 21740 tons of ashes (fly and bottom ashes). In the last twenty years resulted approximately 500 million tons of fly ash, from that a small part is capitalized. The FA unused is disposal on the landfill [7].

Toxic substances in the waste - including arsenic, mercury, chromium, and cadmium - can contaminate drinking water supplies and damage vital human organs and the nervous system. Ecosystems are also been damaged by the disposal of coal plant waste.

Fly ash produces environmental damage by causing air and water pollution on a large scale while the cost of storage of this waste is very high. The most serious problem is the hazard to atmosphere and underground water quality which would be a potential risk to the health and property of citizens and cause a huge stress to the economic and environmental system [7].

Another source of fly ash waste is from the solid waste incineration technology which is used in big cities of the world because its effectiveness in volume reduction, weight reduction and toxicity reduction, and also in energy and resource conservation. However, this technology produces fine fly ash residue which is equivalent to 2-5% of the original waste according to the Chinese researchers [8]. The municipal solid waste incineration (MSWI) fly ash can be used as raw material in sintering and preparing calcium sulphoaluminate cement (CSA), which had similar properties as the control cement [8].

**• Organic wastes** are generally biodegradable materials which are accumulated rapidly and for their storage it must design and realize great disposal landfills.

Biodegradable waste can be decomposed in a short period of time, under the natural conditions into the basic compounds, usually micro-organisms, bacteria, etc. This type of waste is found in municipal solid waste and is resulting from food, paper, biodegradable materials, etc. The wastes which are decomposed in the absence of oxygen are also considered as biodegradable waste and here are included wastes from manure, sewage, animal fat, palm fruit bunch, sugar bagasse, banana leaves, etc [1].

At the Iasi municipal sewage water treatment station, one of the greatest from Romania, a flow of 4.2 m3 /s has been processed daily, the sludge resulted by processing reaching an amount of about 3,600 t/day.

The fermentated sludge of the Iasi municipal treatment station had a neutral reaction and content in organic carbon of 29 - 34 %. The concentration of nitric nitrogen is low (0.16 - 0.42 ppm) and that of ammoniacal nitrogen between 24 and 830 ppm. The total content in macro‐ nutrients (N, P, K, Ca, Mg) from fermented sludge is 1.37 % N total, 1.19 % P total, 4.45 % K total, the calcium content is higher (3.12 %) and organic S and Mg have normal values comparable to those from soils.

The total content in heavy metals (Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn) of fermentated sludge is low, comparable to the one from soils, and under values of maximum admitted values in sludges, in order to be used as fertilizers for soils. Bacterial and fungic microflora of sludges has similar values to the ones of composts, size and composition of microorganism populations were very close to the ones of soils. The lack of bacteria from Salmonella group and a low number of coliform bacteria made a fertilizing material without contamination danger caused by pathogenic microflora from the fermentated sludge. Because the soils from the Moldavian area, most of them placed on slope lands, are poor in organic matter and nutrients, these sludge, adequately used, could be a substitute for a great part of expensive technological consumptions (mineral nutrients) and contribute to the improvement in organic matter content from soil.

**• Mineral wastes** are resulted from the industry processes where the natural resources are transformed in products. In construction industry a lot of natural raw materials are used in natural state. Mining, from the exploration to the closing stage, has a severe impact on the environment. Environmental impact can be direct through the activities: prospecting; exploration; site improvement; extraction; mineral preparations; mineral storage and preparation for delivery; transportation to beneficiary [9].

All technical stages in the minerals exploitation have an important impact on the environment and community life; the dust waste is very aggressive in the atmosphere, in water and soil because of the fine particle and toxic elements. The huge noise from technological processes is also an inconvenient for the community.

toxicity reduction, and also in energy and resource conservation. However, this technology produces fine fly ash residue which is equivalent to 2-5% of the original waste according to the Chinese researchers [8]. The municipal solid waste incineration (MSWI) fly ash can be used as raw material in sintering and preparing calcium sulphoaluminate cement (CSA), which had

**• Organic wastes** are generally biodegradable materials which are accumulated rapidly and

Biodegradable waste can be decomposed in a short period of time, under the natural conditions into the basic compounds, usually micro-organisms, bacteria, etc. This type of waste is found in municipal solid waste and is resulting from food, paper, biodegradable materials, etc. The wastes which are decomposed in the absence of oxygen are also considered as biodegradable waste and here are included wastes from manure, sewage, animal fat, palm fruit bunch, sugar

At the Iasi municipal sewage water treatment station, one of the greatest from Romania, a flow

The fermentated sludge of the Iasi municipal treatment station had a neutral reaction and content in organic carbon of 29 - 34 %. The concentration of nitric nitrogen is low (0.16 - 0.42 ppm) and that of ammoniacal nitrogen between 24 and 830 ppm. The total content in macro‐ nutrients (N, P, K, Ca, Mg) from fermented sludge is 1.37 % N total, 1.19 % P total, 4.45 % K total, the calcium content is higher (3.12 %) and organic S and Mg have normal values

The total content in heavy metals (Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn) of fermentated sludge is low, comparable to the one from soils, and under values of maximum admitted values in sludges, in order to be used as fertilizers for soils. Bacterial and fungic microflora of sludges has similar values to the ones of composts, size and composition of microorganism populations were very close to the ones of soils. The lack of bacteria from Salmonella group and a low number of coliform bacteria made a fertilizing material without contamination danger caused by pathogenic microflora from the fermentated sludge. Because the soils from the Moldavian area, most of them placed on slope lands, are poor in organic matter and nutrients, these sludge, adequately used, could be a substitute for a great part of expensive technological consumptions (mineral nutrients) and contribute to the improvement in organic matter content from soil.

**• Mineral wastes** are resulted from the industry processes where the natural resources are transformed in products. In construction industry a lot of natural raw materials are used in natural state. Mining, from the exploration to the closing stage, has a severe impact on the environment. Environmental impact can be direct through the activities: prospecting; exploration; site improvement; extraction; mineral preparations; mineral storage and

All technical stages in the minerals exploitation have an important impact on the environment and community life; the dust waste is very aggressive in the atmosphere, in water and soil

preparation for delivery; transportation to beneficiary [9].

/s has been processed daily, the sludge resulted by processing reaching an amount of

for their storage it must design and realize great disposal landfills.

similar properties as the control cement [8].

bagasse, banana leaves, etc [1].

comparable to those from soils.

of 4.2 m3

84 Agroecology

about 3,600 t/day.

**• Inert waste** is waste which is neither chemically or biologically reactive and will not decompose in time. Examples of inert wastes are sand, drywall, and concrete. The inert waste typically requires lower disposal fees than biodegradable waste or hazardous waste.

In the industry of building materials the raw materials are used in natural state and as processed materials (case in which they are transformed in other materials (lime, cement, plaster, additives, etc). Among the raw materials there are: clay, calcareous, gypsum, dolomite, marble, mica, granite, etc. Natural aggregates are obtained from gravel from river or from quarry. Because the aggregates are used in different sorts as sizes, the natural aggregates are usually crushed for obtaining an imposed granulometry. A lot of powder waste remains after aggregate selection and their disposal affect the vegetation of the environment.


Construction wastes are obtained during the building process or after demolition. Different types of materials such as bricks, concrete, mortar, wood, steel rebar, insulation material, electrical wiring, plastic materials, glass, iron plate, tile, sanitary pieces, etc. which can be unused or damaged. According to specialty literature about 10% to 15% of materials are lost from the total building material, quantity which varies from site to site [4]. The uncontrolled disposal of this waste is very dangerous for the environment because building materials can contain toxic substances such as lead, asbestos, aluminum, etc.

The recycling demolished waste as aggregate in ordinary concrete offers a solution to the preservation of natural resources and the disposal of construction residues.

**• Transportation industry wastes** are represented by used tires, asphalt and concrete aggregate. Huge quantities of tires were used in artificial reefs, break waters, dock bumpers, soil erosion control mats, etc. [4].
