Aggregate - Lime Trade Turkey - AKAR Lime Trade Consultant and Analysis Company

AGGREGATE TYPES and SPECIFICATIONS

Natural Aggregate: Natural stone aggregate; is the crushed or uncrushed aggregate obtained from terraces, rivers, seas, lakes and quarries.

Artificial Aggregate: is the crushed or uncrushed aggregate which is industrial product such as blast furnace slag stone, smelter slag or blast furnace slag sand (also called as artificial stone or artificial sand.)

Cyclopean Aggregate: is the aggregate remaining on the square perforated sieve with 4 mm aperture.

Gravel: is the cyclopean aggregate composed of uncrushed granules.

Crushed Stone: is the cyclopean aggregate composed of crushed granules.

Sand: is the fine aggregate composed of uncrushed granules.

Crushed sand: is the fine aggregate composed of crushed granules. It is made by crushing the gravel. Mixed Aggregate: it is the mix of fine and cyclopean aggregate.

Natural Mixed Aggregate (All-in aggregate): is the mixed aggregate directly obtained from aggregate quarry, crusher or industry. The aggregates sifted to sort out large granules from maximum granule size are called natural mixed aggregate.

Ready Mixed Aggregate: is the aggregate composed by mixing fine and cyclopean aggregate or these aggregates sorted in several granule classes with each other in a way to provide certain granulometry during the concrete production.

Aggregates should meet the requirements of TS 706 standard in terms of granulometric composition, granule shape, granule strength, wear resistance, frost resistance and harmful substances according to the place and purpose of use. Also they should not soften under the effect of water, should not disperse, should not compose harmful composites with the components of the cement and should not endanger the protection of the reinforcement against corrosion.

Granulometry: granulometry of aggregate, granulometry curves (sieve curves) and the fineness modulus assigned when needed depending on these curves is indicated with specific surface and water demand coefficient. Granulometries of aggregates used in the concrete production should comply with the values given in Figure-1, Figure-2, Figure-3 and Figure-4.

Granule shape: Shape of aggregate granules should be nodular and cubic as possible. The granules of which the rate of the biggest size to the smallest size is bigger than 3, are called defective granules in shape. The rate of granules defective in shape (flat or long granules) should not weigh over 50% in aggregates bigger than 8 mm.

Granule strength: aggregate granules should be strong to be eligible for the production of a concrete with the intended features. This feature is enabled in naturally formed sand and grave or the aggregates obtained by crushing them with the natural selection they are exposed to.

The aggregate is accepted as sufficient if a loss less than 30 % for the aggregates to be used in the production of concrete and less than 45 % for the other aggregates is found.

Frost resistance: The frost resistance of an aggregate should be sufficient for the intended purpose of use. Naturally formed sand and gravel or aggregates obtained by crushing them include too few frost resistant granules due to the selection they are exposed to in the nature. This feature is not sought in the regions in which continuous frost and dissolution does not happen.

Harmful substances: are the substances that harm the setting and hardening of the concrete, decrease the resistance or composite of the concrete, cause the decomposition of concrete or endanger the protection of the reinforcement against corrosion. Harmful substances according to granulometries and amounts are the followings. Washable substances, organic origin substances, substances damaging hardening, some sulphuric compounds, softening, swelling and bulking substances, substances and micas causing corrosion such as chlorides.

Washable substances: Washable substances can be as finely dispersed or tussocky on the aggregate or as adhered to the aggregate granules. These substances are generally clay, silt or fine dust. Organic Origin Substances: Humic or other organic substances can damage the hardening of the concrete when they are finely dispersed. When they are granular, they can cause color change or outburst on the surface of the concrete by swelling.

Sulphuric compounds: Sulphuric compounds can cause harmful changes on the concrete depending on their types, amounts in the aggregate and the environmental conditions of the building. Type and dispersion of the sulphuric compound is important in this situation. For example, the sulphates oxidized (alkali sulphates, gypsum, anhydride etc) due to air flow and moisture in the concretes not fully compressed can be harmful. Sulphates react with lime and aluminum compounds in the concrete and form crystals getting bigger in time and cause the concrete crush.

Substances damaging Steel: In the aggregates to be used in reinforced concrete, salts endangering the protection of the reinforcement against corrosion such as nitrates, halides (except fluoride) should not be at a harmful level. In the aggregates to be used for pre-stressed concrete, the water soluble chlorides should not be more than 0,2 % in weight when calculated as chlorine. (TS706) Standard values defined above are given for the sands of the concrete and cyclopean aggregates in Table 1.

Factors Causing Alkali Aggregate Reactivity: aggregates with specific origin can include the components composed of reactive silica. These types of components make a strong chemical reaction with alkali hydroxide dissolving in the pore water of the concrete and compose the clear and high concentration at first and then the high viscosity alkali silicate solution. It depends on the type and amount, granule size and dispersion of the alkali sensitive components of the aggregate, the amount of alkali hydroxide in the solution in the pore of the concrete and environmental conditions of the hardened concrete. Thus the evaluation of alkali sensitive granules alone is not sufficient. The alkali reaction in the concrete causes the segregation or rupture of alkali sensitive aggregate granules, cracks on the concrete hardened in the normal conditions at first and in excessive amounts to the disintegration of the concrete.

Bulk Unit Weight (TS3529) Min 1350 kg/m3

Min 1350 kg/m3

Specific Weight (TS3529) Min 1350 kg/m3

Min 1350 kg/m3

Content of seashell is applied when composite is lower than 0,49

Organic substance (TS3673) Color of the sample kept in sodium hydroxide solution in 24 hours should be in the color of standard reference solution or lighter.

Color of the sample kept in sodium hydroxide solution in 24 hours should be in the color of standard reference solution or lighter.

Middy substance amount (TS3527) The amount of middy substance should be lower than 0,5 % in volume at the end of the sink test.

The amount of materials finer than 63..m such as clay, silt or fine dust should not exceed 1,5 % according to washout test

Water absorption rate (TS3526) Max. 2%

Frost Resistance Standard In the frost resistance test performed with Na2SO4 solution, weight loss should be maximum 15%.

Standard In the frost resistance test performed with Na2SO4 solution, weight loss should be maximum 15%.

If the alkali sensitive granules are bigger than 0,6 % the equal alkali oxide rate in the concrete, the alkali sensitive granules should be less than 0,5% in weight in the sand.

Amorphous granule amount (TS3814)

It should not exceed max. 40 %.

The loss of material determined at the end of the corrosion test performed on the ball drum should be max. 45 % at the end of 500 rev.

Also the coal in the aggregates should be max. 1% and the substances swelling and stratifying after water intake should be max. 0,25 5 in weight. The soft granules detected by test should be max.3% in weight. In the cyclopean aggregates to be used for prestressed concrete, the chlorides should be max. than 0,06 % in weight when calculated as chlorine

Granulometric dispersion for concrete sands: (TS3530)

The sands used in the concrete casting should have a certain gradation. So the material percentages sifted should comply with Table 2.

Aggregates are chipped stone granules. They are the products of natural disintegration and the granules found in nature are called as sand or gravel according to their grades. When the disintegration is done by human or machines, aggregate that is called crushed stone or just crushed is obtained. Some industrial products or wastes solid and tough enough such as brick and tile are also used as crushed instead of natural stone. In other words, aggregates are objects that are granules like crushed stone, cinder, gravel, sand and compose tough blocks such as concrete, mortar, asphalt or and the like when bound with a binder.

Aggregates are divided into two as fine and cyclopean aggregates according to their size smaller or bigger than 5 mm in average in spite of slight differences in the norms of different countries. It should be added that 5 mm is for the aggregate belonging to hydraulic binders. The aggregates that belong to hydro carbonated binders are included in fine or cyclopean class according to their size smaller or bigger than 3 mm.

While it is accepted to classify aggregates in terms of granulometry, classifying them according to their weights will be suitable by considering the mentality dominant on the current construction technique. Accordingly it is possible to classify the granules used in concretes and mortars as;

1. Heavy aggregates,

2. Light aggregates

HEAVY AGGREGATES

The production of concrete with a unit weight of over 3,2 kg/dm3 is necessary to protect against g and X rays that emerges in nuclear reactors and similar places and destroy organs. This type of concrete can only be produced with the use of heavy aggregates. Types, components and specific weights of aggregates used for this purpose are given below:

Baryte Ba SO4.............................. specific weight 4.2 kg/dm3

Magnetite Fe3O4......................... specific weight 4.6 kg/dm3

Limonite 2 Fe2O3H2O.................... specific weight 3.7 kg/dm3

Baryte is found in the region of Anamur (Antalya) in our country.

Sands and gravels that are known as natural aggregate are composed of the toughest and solid minerals as they are formed as a result of the drift and disintegration of rocks and stones with the effect of atmospheric factors and time. Most of the gravels and sands used in the mortars and concretes are the ones left by the water flows such as stream, river and gulley and mined from the sand beds piled by river sands. The other sources are chipped brittle sandstone (gre) and the sea sand in the beaches and coasts. Although sea sand is a valuable material as aggregate, its use in the architectural buildings and house constructions due to the solution and salts it keeps on it. They can be used in the mortar and concretes of the said buildings only after they are washed with abundant fresh water. Otherwise it is very hard to prevent moisture.

The difference between sand, gravel or Bollast is weakness and subjected to coarseness and smallness. Sand granules are minerals alone and generally consisted of quartz. In addition minerals such as feldspar, clay, mica flakes and black iron and sometimes the granules of hard coal are encountered.

Gravels are composed of various minerals and one gravel granule is often heterogenic in terms of this. As granite is a compound of gravels, sandstone and chalk is also found. It is possible to use the gravels as they are or crushed as concrete aggregate. Thus more angled and sharp aggregate is obtained. Even though this shape is preferred to gravel in terms of connection, working with the concretes prepared with this type of aggregate is difficult and requires more water. Under the same circumstances the resistance of the concrete made with crushed is a little superior.

Super fine sand that is called dune and found in some coasts, especially in deserts is not suitable for mortar due to the smallness of its granules and ceaselessness and it becomes mud when mixed with water. It is not correct to use it in especially sea constructions. It can be used in plaster mortars made with water.

Both in gravels and crushed stones, the presence of shear and similar objects are not appreciated due to their soft, fragile natures and low resistance against atmospheric factors.

The stones separated for use in concretes are generally from granite, dolerite, basalt, sandstone, chalk, diorite classes. These differences are not considered in practice and granite, basalt, diorite crushed ones are used under several names.

Blast furnace slag is a substance used as aggregate in common concrete and reinforced concrete in the countries of Europe and America. But it is necessary to meet some norm requirements. The slag should be resolute, stay as stable in volume and resistant against the atmospheric factors. The blast furnace slag that is used as crushed is also benefited as fine aggregate so as sand.

Brick and the like crushed ones that are in old buildings and composed of industrial wastes and discards and their fine granules in the size of sand are used as aggregate. The crushed ones of brick and tiles are weaker than gravels and natural crushed stones. The main danger is the presence of low hardened and therefore soft granules and granules that are not resistant enough against atmospheric factors and the possibility that they can contain plaster and other harmful compounds. On the other hand they have superiority in helping binding. As the brick and similar crushed ones have a high level of wicking, the water should be adjusted according to it.

AGGREGATES RESISTANT TO HIGH TEMPERATURE

Concrete that is used as structure material in some factories is always exposed to high temperature. In such situations the concrete should not crack and lose its characteristics. For the aggregate to have such characteristic depends on the aggregate used. If the concrete is kept under up to 300 ⁰C, the aggregates that have the aforementioned characteristics should be used. Chamotte particles that are fireclay should replace the aggregate between temperatures of 300-800⁰C. When the temperature exceeds 1300⁰C, the following aggregates that are known resistant to high temperature should be used.

- Siliminate (Al2SiO3), - Corundum (Al2O3), - Chromite (FeCr2O4)

In the latter situation, the concrete should be produced by using aluminous cement that is a binding agent resistant to high temperature.

Lightweight term means rather aggregates that have low unit weights due to its high pore content. It is possible to classify these types of aggregates into several groups by resources:

Aggregates that are obtained by natural disintegration in their original form (pumice and tufa),

Industrial product or wastes,

Aggregates prepared specially.

It is a type of vulcanite and a stone with an appearance of sponge as the abundant gas it wicks as molten leaves the mass in the cooling period. In other words it is composed of cold fluff foams originated from silicate. It contains volcanic ash (very fine granules), schist and some foreign compounds in its natural form. Washed and cleaned tufa is a suitable material for the production of light concrete.

Blast furnace slag can be disintegrated in various forms and sizes with the aid of water, steam and flow of air sent vertically to the surface when it is in liquid form. Therefore the substance called slag cotton or slag wool is obtained. Some types of them are called slag foam.

Some clays enlarge and swell when they are heated up to certain temperature. The volumes of some types of schists enlarge 3 to 7 times when they are heated up to a temperature that causes melting. Therefore the cyclopean parts obtained are crushed by machines that have approx. 1000⁰C-1200⁰C temperatures and the aggregates in the intended size are obtained. The appearance of schist prepared in this way rather reminds tufa.

The substance in question is formed by the partial melting of ashes resulted from the burning of the coal, so that from the forming of globs by adhesion in the softening temperature. The ashes of the stoves and cooks in the houses are not suitable for being used as aggregate as they are in form of powder. However the ashes and wastes of the big facilities, for example electricity factories in the aforementioned form are used as aggregates.

It is the coal waste in small granules produced by factories such as gas house etc. It is mostly composed of unburned coal in nature. In comparison to coal slag, coal dust or chips show more changes of volume and take in moisture. It is rarely used as aggregate, as it gas other fields of use. Some sand is also added when it is used as aggregate. In some situations coal dust is used as mixed with coal slag.

It is a substance that has important features as an aggregate and it has two types:

1. Asbestos – horn blend,

2. Asbestos - chrysotile

Asbestos- hornblend has a more loose structure, it has thin and long fibers and it is resistant to acid.

Asbestos – chrysotile is more suitable for being used as cement aggregate. It has short fibers and it is not resistant to acids. But it is resistant to tension. It agrees with cement well, composes a starchy and sticky mortar. Its basic characteristics include these; it has a fibrous structure, low conductivity of heat, it is resistant to fire, it swells with the effect of water and compresses the mass.

It is used as aggregate but it is inconvenient for it to intake high level of moisture. The mineralization of sawdust by mixing with some salts has been tested in order to prevent this. But in can only be used in inside works in which it will not contact with water, also in this form.

-It can be used in emulsive substances such as albumin, metallic aluminum dust and special soaps rather than as aggregate in concretes. Its basic feature is to provide a porous structure by forming foam in sand-cement mixture.