WConstruction aggregate, or simply “aggregate”,
is a broad category of coarse particulate
material used in construction, including sand,
gravel, crushed stone, slag, recycled concrete
and geosynthetic aggregates.
We manufacture and supply all of your
Construction Aggregate Materials - loose
and packed - including sand, gravel, crushed
stone, slag, industrial products such as recycled
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supply high-quality aggregate materials for all
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Aggregate can be defined as a material that is used as filler for filling up
the voids during construction. It comprises of a broad category of coarse
material that is used in construction. Aggregates are the most mined
category of minerals in the world. They have been in use for thousands
of years with significant use taking place back during the Roman Empire.
The invention of concrete resulted in demand for aggregate since it is a
crucial material for preparation of concrete.
Aggregates impart strength by reinforcing the composite material, that is
to say, they fill up the voids to form a substance that has more compressive
strength. By filling up the space that is available, aggregate ensures that
the structure doesn’t fail when load is applied to the structure.
Working principle of aggregate
TYPES OF AGGREGATE
The word soil, when used in normal contents, just refers to that on which we all stand. However, engineers define
(in construction) soil as any earth material that can be moved
without blasting, while geologists define as rocks or sediments
altered by weathering. Practicing engineers classified soils in to
different types based on the grain (particle) size distribution of
soil. According to this classification, the main soil types are
boulders, gravel, sand, silt, and clay. Different ‘soil separate
size limits’ have been developed by different institutions and
organizations like Massachusetts Institute of Technology (MIT),
US Department of Agriculture (USDA), American Association
of State Highway and Transportation Officials (AASHO), Unified Soil Classification System, etc. However, currently the
classification of Unified Soil Classification System is widely used all over the world.
Sand is one of the oldest materials used in the world of construction. Individual particles or grain of soil can be
seen with our naked eye. Sand consist of coarse particles; according to unified soil classification system, particles
sizes ranging from 0.075mm to 4.75mm are categorized as sand. Sand is cohesion less aggregate of coarse, sharp,
angular particles. Sand is one of the raw materials of concrete (as fine aggregates). When sand is used as the
bedding material, it must be compacted before the commencement of construction, then the settlement will be low.
Natural sand and gravel deposits are diminishing, and the utilization is also restricted by legislation. At the same time,
demand for aggregates is increasing, but sources for fluvial sand are fewer and further away from the marketplace,
especially densely populated areas. High transportation costs often make its use an economically unfeasible option.
The solution for this has now become manufactured sand which has quality consistent quality. The more cubical,
rounded and consistent the sand is, the better is the performance in concrete and asphalt.
Key performance indicators in the concrete industry are workability, strength and production costs. High-quality
sand is the most significant component affecting these.
• 5-15% - Higher compressive strength with manufactured sand
• 5-10% - Savings in cement due to consistent sand quality
• 10-30% - More sellable product for aggregate producer
Even when natural sand is available, variations in its quality present a
challenge for concrete producers. Natural sand quality is often not
consistent in moisture nor in grading curve. This inconsistency is often
compensated for by increasing the amount of cement in a concrete mix.
Gravel is not only used for construction purposes, but also
for a variety of purposes like gardening, etc. Gravel is an
aggregate of rounded or angular fragment of rocks and
minerals. According to unified classification system, particle
sizes ranging from 4.75mm to 76.2mm are categorized
as gravel. Gravels have a large bearing capacity. Bearing
capacity means the safe load per unit area that the ground
can carry. Further, gravels can carry huge structures without
any sign of settlement. Settlement in construction means
the settlement of structures in to the ground. In some rural
areas, gravel is also used to surface the roads.
Though sand and gravels are construction materials, they
have some different characteristics embedded on them;
• Particle sizes of soil in gravel range from 4.75mm to
76.2mm, while particle sizes of soil in sand range from
0.075mm to 4.75mm. That means soil particles in gravel
are larger than that of sand.
• Bearing capacity of gravel is higher than that of soil.
• When huge structures are considered, foundation cost in gravel is lower than constructing foundation in sand.
• Settlement of structures in gravel is much smaller than settlements in sand, for a given large load.
• Porosity in sand is relatively higher than in gravel.
• Sand can be used as a raw material of concrete, while gravel is not used.
• Water retention capacity of gravel is higher than that of soil.
SLAG is a broad term covering all non metallic co products
resulting from the separation of a metal from its ore, Its
chemistry and morphology depends on the metal being
produced and the solidification process used. Slags can be
broadly categorized as ferrous (iron/steel) and non-ferrous
(copper, lead/zinc) depending on the industry from which
they come. Non ferrous slags make up only 12% of the total
annual production Described below are the main types and
uses of slag commercially available in Ferrous Slag products.
Slag is a byproduct of steel production and is similar in character to volcanic rocks such as basalt and granite. Slag
is primarily used in the cement and construction industries, and largely in road construction.
Slags are one of the most natural products of all. They are comparable to fluid magma from the earth’s core. Just
like natural rocks, slags contain trace elements, but these are completely bound up within the crystal lattice, and
therefore almost impossible to leach out. For instance, a study by the Fraunhofer Institute (German only) showed
that wear debris from LD slag used in road construction does not represent a danger to health. In addition, slags
have the advantage of a very homogenous structure. That means that their quality and characteristics are consistent
within individual charges. As a result of precise analysis and comprehensive process controls in iron and steel production, the detailed composition of every slag is known. And therefore, just as for the entire manufacturing
process, slag is permanently subject to process and quality controls.
Slags are principally divided into blast furnace slag and metallurgical slag. At voestalpine the two types of slag are
separately collected, prepared, and processed further into products. As the name suggests, the blast furnace slag
is generated in the blast furnace, during the production of liquid pig iron, and is mostly processed further into
granulated blast furnace slag which is a valuable additive in the cement industry The main type of metallurgical slag is LD slag, the byproduct of the Linz-Donawitz process. It is produced in the LD
converter as pig iron is processed into steel Iron Blast Furnace Slag (BFS)
This is the co-product from the reduction of iron ores to produce molten
iron and molten slag.
1. When allowed to cool slowly to a crystalline rod< form It becomes
a light gray vesicular rock known as Air-Cooled Blast Furnace Slag.
Principle uses include:
• Uncrushed - fill and embankments (particularly areas subject to severe loading such as mainline rail systems),
working platforms on difficult sites pavements, where binding fines are produced by rolling to break the slag
down to fill the voids.
• Graded road base - on its own or blended with other slags and/or with other natural rocks and sands.
• Crushed and graded - for concrete aggregates, concrete sand, glass insulation wool, filter medium, and use
under concrete slabs as a platform
2. By passing the molten slag through high volume high pressure water sprays, a glassy, sand-Type (granulated)
material Is formed, known as Granulated Blast Furnace SIag.The color of this product is very similar to normal
• The principal use is as Cement replacement (when ground), replacing 30-50% of Portland Cement in ‘normal’
concrete, but can replace up to 70% in specialist applications such as marine concrete.
• Other uses include, glass making, trace elements in agriculture, concrete block manufacture, sporting field
sub-base (for drainage), filtration medium, reinforced earth embankments, and mine backfilling and gritblasting
medium requiring fine etching.
Basic Oxygen Furnace Steel Slag (BOF or Steel Furnace Slag)
This slag Is formed when molten Iron, scrap metals and various fluxes, such as lime, are oxidized by injecting large
amounts of pure oxygen into the molten iron mix to create molten steel and molten slag. Slow cooling of the
molten slag produces a dense rock material. Principal uses include:
• Blending with many other products such as granulated slag, fly ash and lime to form pavement material
• Other uses Include, skid resistant asphalt aggregate, rail ballast asphaltic concrete aggregate, soil conditioner,
hard stand areas and unconfined construction fill.
Electric Arc Furnace Slag (EAF or steel furnace slag) Produced when scrap metal and fluxes are oxidized by the use
of an electric current. Molten slag is generally placed into ground bays for cooling. Both BOF and EAF slags are
somewhat heavier than Blast Furnace Slag and most quarried rock material. Uses include Slag – Ancient uses
During the Bronze Age of the Mediterranean there were a vast number of differential metallurgical processes in
use. A slag by-product of such workings was a colorful, glassy, vitreous material found on the surfaces of slag from
ancient copper foundries. It was primarily blue or green and was formerly chipped away and melted down to make
glassware products and jewelry. It was also ground into powder to add to glazes for use in ceramics. Some of the
earliest such uses for the by-products of slag have been found in ancient Egypt.
Historically, the re-smelting of iron ore slag was common
practice, as improved smelting techniques permitted greater
iron yields – in some case exceeding that which was originally
achieved. During the early 20th century, iron ore slag was
also ground to a powder and used to make agate glass, also
known as slag glass. Slags - Modern uses
Ground granulated slag is often used in concrete in
combination with Portland cement as part of blended
cement. Ground granulated slag reacts with water to
produce cementitious properties. Concrete containing
ground granulated slag develops strength over a longer
period, leading to reduced permeability and better
durability. Since the unit volume of Portland cement is
reduced, this concrete is less vulnerable to alkali-silica
and sulfate attack.
This previously unwanted recycled product is used in the
manufacture of high performance concretes, especially
those used in the construction of bridges and coastal
features, where its low permeability and greater resistance
to chlorides and sulfates can help to reduce corrosive
action and deterioration of the structure.] The slag can
also be used to create fibers used as an insulation material
called slag wool.
The primary purpose of aggregate is to add strength to the overall composite
material and to serve as reinforcement. Aggregate, in building and construction,
material used for mixing with cement, bitumen, lime, gypsum, or other adhesive
to form concrete or mortar. The aggregate gives volume, stability, resistance to
wear or erosion, and other desired physical properties to the finished product.
Commonly used aggregates include sand, crushed or broken stone, gravel
(pebbles), broken blast-furnace slag, boiler ashes (clinkers), burned shale, and
burned clay. Fine aggregate usually consists of sand, crushed stone, or crushed
slag screenings; coarse aggregate consists of gravel (pebbles), fragments of
broken stone, slag, and other coarse substances. Fine aggregate is used in
making thin concrete slabs or other structural members and where a smooth
surface is desired; coarse aggregate is used for more massive members.
According to size the aggregates are classified as:
• Fine Aggregate
• Coarse Aggregate
• All in Aggregate
It is the aggregate most of which passes 4.75 mm IS sieve and contains only so much coarser as is permitted by
specification. According to source fine aggregate may be described as:
• Natural Sand– it is the aggregate resulting from the natural disintegration of rock and which has been deposited
by streams or glacial agencies
• Crushed Stone Sand– it is the fine aggregate produced by crushing hard stone.
• Crushed Gravel Sand– it is the fine aggregate produced by crushing natural gravel.
According to size the fine aggregate may be described as coarse
sand, medium sand and fine sand. IS specifications classify the
fine aggregate into four types according to its grading as fine
aggregate of grading Zone-1 to grading Zone-4. The four grading
zones become progressively finer from grading Zone-1 to grading
Zone-4. 90% to 100% of the fine aggregate passes 4.75 mm IS
sieve and 0 to 15% passes 150 micron IS sieve depending upon its
It is the aggregate most of which is retained on 4.75 mm IS sieve and contains
only so much finer material as is permitted by specification. According to
source, coarse aggregate may be described as:
• Uncrushed Gravel or Stone– it results from natural disintegration of rock
• Crushed Gravel or Stone– it results from crushing of gravel or hard stone.
• Partially Crushed Gravel or Stone– it is a product of the blending of the
above two aggregate.
According to size coarse aggregate is described as graded aggregate of its
nominal size i.e. 40 mm, 20 mm, 16 mm and 12.5 mm etc. for example a
graded aggregate of nominal size 20 mm means an aggregate most of which
passes 20 mm IS sieve.
A coarse aggregate which has the sizes of particles mainly belonging to a
single sieve size is known as single size aggregate. For example 20 mm single
size aggregate mean an aggregate most of which passes 20 mm IS sieve and
its major portion is retained on 10 mm IS sieve.
All in Aggregate
It is the aggregate composed of both fine aggregate and coarse
aggregate. According to size All-in-aggregate is described as
all-in-aggregates of its nominal size, i.e. 40mm, 20mm etc. For
example, all in aggregate of nominal size of 20mm a mean an
aggregate most of which passes through 20 mm IS sieve and
contains fine aggregates also.
Sizes are described in terms of a lower limiting sieve size, “small” d, and an upper limiting sieve size, “big” D. Written
as d/D [note the slash is just a separator, it is not little d divided by big D]. The sizes of both small d and big D are
selected from a list of prescribed sieve sizes. For the UK, these sizes are: 1mm, 2mm, 4mm, 6.3mm, 8mm, 10mm,
12.5mm, 14mm, 16mm, 20mm, 31.5mm, 40mm, 63mm (taken from ‘Basic set plus set 2’). For convenience, 6.3mm
can be referred to as “6mm”, and 31.5mm as “32mm”.The ratio of D/d must not be less than 1.4.
Aggregates are then designated as being either GC (coarse), GF (fine), or GA (all-in). Aggregate is classed as coarse
if D is greater than 2mm, fine if D is less than 2mm, and all-in if D is less than 45mm and d is 0.
Next, the required minimum percentage passing D is given, followed (for coarse aggregates only) by the maximum
percentage allowed to pass d. Minimum percentage of D can be either 90% or 85%. For coarse aggregates, maximum percentage of d can be 10%, 15%, 20% or 35%. For all-in aggregates, d is always zero.
For example, coarse aggregate previously called 20mm single size, and suitable for pre-coated chippings, would be
Crushed stone - the most basic commodity of many construction,
chemical, manufacturing, and agricultural industries.
Crushed stone is not a “standard commodity.” It is made by
mining one of several types of rock such as limestone, granite,
trap rock, scoria, basalt, dolomite, or sandstone; crushing the
rock; and, then screening the crushed rock to sizes that are
suitable for the intended end use. Crushed stone, one of the
most accessible natural resources, is a major basic raw material
used by construction, agriculture, and other industries that
utilize complex chemical and metallurgical processes.
Crushed stone is the world’s most basic mineral commodity. It is abundant, widely available, and inexpensive. It is a
material that people are familiar with in almost all parts of the world.
Most crushed stone is used in highway construction and building construction. In the construction of a two-lane
asphalt highway, about 25,000 tons of crushed stone is used per mile. In building a small residential subdivision,
about 300 tons of crushed stone is used per home.
Types of Rock Used for Crushed Stone
Many different rock types are used to make crushed stone including limestone, granite, trap rock, sandstone,
quartzite, dolomite, volcanic cinder and scoria, marble, slate, shell, and calcareous marl.. Each of these rock types is
suitable for a number of uses and unsuitable for others. A brief description of the more important rocks for crushed
stone is provided below.
Limestone is a rock composed of calcium carbonate (CaC03). It is the rock type most commonly used to make
crushed stone in the United States. It holds this position because it is widely
available and suitable for a greater diversity of uses than any other type of
rock. Limestone can be used to make cement. It is the primary ingredient of
concrete. It is used as a base material for highways, rural roads, buildings,
and railroad construction. It is used to make agricultural lime and for acid
neutralization in the chemical industry. There are many products made from
or using limestone that consume a small volume of material. These include
poultry grit, terrazzo, glass, air pollution sorbents, mine safety dust, animal food supplements, cosmetics, dietary
supplements, and blast furnace flux, among others.
Granite and Trap Rock
Granite is the layman’s name used for any light-colored igneous rock that
is used in construction. Granite, granodiorite, diorite, and rhyolite are a
few of many light-colored igneous rocks that are called “granite” in the
construction industry. “Trap rock” is a layman’s name used for any darkcolored
igneous rock that is used in construction. Basalt, peridotite, diabase,
and gabbro are examples of trap rock.
Granite and trap rock are the second and third most commonly used types of rocks for producing crushed stone.
They are superior to limestone when used in acid waters or soils and when subjected to abrasion. They can substitute
for limestone as a concrete aggregate and when a durable aggregate is needed.
Dolomite and Dolomitic Limestone
Dolomite and limestone are very similar rocks. Dolomite is a calcium
magnesium carbonate (CaMg(CO3)2) while limestone is a calcium
carbonate (CaC03). Limestone is more effective for making cement and
for neutralizing acids. Dolomite has a Mohs hardness of 4 compared to
limestone with a Mohs hardness of 3. This hardness difference makes
dolomite distinctly more durable when the rock is subjected to abrasion.
Dolomite, dolomitic limestone, and limestone have similar appearances and often occur together in the rock units
mined at a single quarry; however, they are rarely mined as separate products. A significant amount of the material
reported as “limestone” in the pie chart in the right column of this page is actually dolomitic limestone and dolomite.
Most quarries sell their production as “limestone,” which is acceptable to customers in the construction industry if
the chemical composition of the rock is not important. Customers interested in rock for chemical, acid neutralization,
blast furnace flux or agricultural purposes will probably demand rock that has the chemical composition of a very
pure limestone or a very pure dolomite.
Sandstone and Quartzite
Sandstone and quartzite are composed primarily of quartz, a very durable mineral, but each has its drawbacks in the
construction industry that limits its use. Sandstone is generally composed
of sand grains cemented together by calcite, clay, or silicate minerals that
have precipitated between the sand grains. The cement usually does not
completely fill all of the voids between the sand grains, leaving a porosity
that typically ranges between 5 and 30%. This pore space allows the rock
to absorb water. That water will expand in volume by up to 9% every time
it freezes. Over the course of many freeze-thaw cycles, the forces of this
expansion has the ability to dislodge grains and break the rock. This is why sandstone is not popular for long-term
use in areas where freezing temperatures occur
Quartzite is a sandstone that has been metamorphosed. The process of metamorphism heats and compresses the
rock and often causes the sand grains to become welded together. This produces an extremely durable rock that
usually does not have the freeze-thaw concerns of sandstone. Quartzite can actually be so durable that it is difficult
to mine, handle, and transport to construction sites.
Quartzite has a Mohs hardness of 7. That makes it harder than crusher jaws, loader buckets, sizing screens, truck
beds, and other equipment used to handle and process the stone. As a result, it can quickly put very expensive wear
and tear on essential equipment. For that reason, some of the most durable rock in the United States is avoided for
Volcanic Cinder and Scoria
Volcanic cinder and scoria are vesicular rocks, meaning they contain
voids that formed when gas bubbles were trapped within the rock
as it solidified from a melt. These voids decrease the load-bearing
strength and freeze-thaw durability of the material. However, the
voids make the rock lighter. The surface roughness of the stone
helps it bind effectively when used as a concrete aggregate. These
properties often make volcanic cinder and scoria good rocks for
producing lightweight aggregate, lightweight concrete, and roofing
granules. The lower density of volcanic cinder and scoria makes them easier to handle when used in landscaping, planters,
gas grills, saunas, and other similar uses. The high surface area of these rocks makes them suitable for filter stone in
some sewage disposal and drainage applications. Their angular shape and low density makes them suitable for use
as a traction material that is spread on snow-covered highways.
Fine-grained marble and dolomitic marble can be crushed and used for most of the same purposes as limestone.
When coarsely crystalline, these rocks often break into pieces due to cleavage, which can reduce their durability.
Some white marbles are pure enough that they can be crushed, processed to remove impurities, and used as
chemical-grade stone, whiting, fillers, extenders, and even in cosmetics and dietary supplements for humans and
animals. These high-purity marbles make some of the most valuable crushed stone.
Crushed Stone vs. Gravel
To a geologist, “crushed stone” and “gravel” are two distinctly different materials. “Crushed stone” is a commercial
product made by mining rock and crushing it into angular pieces. “Gravel” is a natural material that consists of watertransported
particles of rock that are larger than two millimeters in diameter and usually have a rounded shape as
a result of their water transport. The shape of the grains and man’s role in producing them are the differences that
separate crushed stone from gravel.
The average person in the United States rarely uses the term “crushed stone.” Instead, the word “gravel” is used
generically for almost any type of rock material with a particle size over a few millimeters. Their “gravel” includes
both the crushed stone and the gravel of geologists.
• Make sure that segregation of aggregate does not occur.
• Depending upon its usage, it should be dry/wet.
• Make sure that it has passed the sieve size test and
is correctly graded.
• Different applications require different standards of aggregates; be wary of that.