Limestone
Limestone is a sedimentary rock which is often composed of the skeletal fragments of marine
organisms such as coral,
foraminifera and molluscs. Its major materials are the minerals calcite and aragonite, which are
different crystal forms
of calcium carbonate (CaCO3).
About 10% of sedimentary rocks are limestones. The solubility of limestone in water and weak acid
solutions leads to
karst landscapes, in which water erodes the limestone over thousands to millions of years. Most cave
systems are through
limestone bedrock.
Limestone has numerous uses: as a building material, an essential component of concrete (Portland
cement), as aggregate
for the base of roads, as white pigment or filler in products such as toothpaste or paints, as a
chemical feedstock for
the production of lime, as a soil conditioner, or as a popular decorative addition to rock gardens.
To make Portland Cement—the most common type of Cement —powdered Limestone is heated in a rotary
kiln. As a source of
calcium, it joins with powdered clay to produce a product called clinker, which is then ground with
a source of sulfate,
like gypsum. It is mixed with water, sand and crushed rock to create concrete.
Gypsum
Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula
CaSO4•2H2O.[3] It is
widely mined and is used as a fertilizer, and as the main constituent in many forms of plaster,
blackboard chalk and
wallboard.
A massive fine-grained white or lightly tinted variety of gypsum, called alabaster, has been used
for sculpture by many
cultures including Ancient Egypt, Mesopotamia, Ancient Rome, the Byzantine Empire and the Nottingham
alabasters of
Medieval England. Mohs scale of mineral hardness, based on scratch hardness comparison, defines
hardness value 2 as
gypsum. It forms as an evaporite mineral and as a hydration product of anhydrite.
Gypsum plays a very important role in controlling the rate of hardening of the cement. During the
cement manufacturing
process , upon the cooling of clinker, a small amount of gypsum is introduced during the final
grinding process. Gypsum
is added to control the “setting of cement”.
Clinker
Clinker consists of various calcium silicates including alite and belite. Tricalcium aluminate and
calcium
aluminoferrite are other common components. These components are often generated in situ by heating
various clays and
limestone.[1]
Portland cement clinker is made by heating a homogeneous mixture of raw materials in a rotary kiln
at high temperature .
The products of the chemical reaction aggregate together at their sintering temperature, about 1,450
°C (2,640 °F).
Aluminium oxide and iron oxide are present only as a flux to reduce the sintering temperature and
contribute little to
the cement strength. For special cements, such as low heat (LH) and sulfate resistant (SR) types, it
is necessary to
limit the amount of tricalcium aluminate formed.
The major raw material for the clinker-making is usually limestone mixed with a second material
containing clay as
source of alumino-silicate. Normally, an impure limestone which contains clay or silicon dioxide
(SiO2) is used.
The calcium carbonate (CaCO3) content of these limestones can be as low as 80%. Second raw materials
(materials in the
rawmix other than limestone) depend on the purity of the limestone. Some of the second raw materials
used are: clay,
shale, sand, iron ore, bauxite, fly ash and slag. The clinker surface and its reactions in different
electrolytic
solutions are investigated by scanning electron microscope and atomic force microscopy.
Portland cement clinker is ground to a fine powder and used as the binder in many cement products. A
little gypsum is
sometimes added. It may also be combined with other active ingredients or chemical admixtures to
produce other types of
cement including: ground granulated blast furnace slag cement.
Cement
A cement is a binder, a substance used for construction that sets, hardens, and adheres to other
materials to bind them
together. Cement is seldom used on its own, but rather to bind sand and gravel (aggregate) together.
Cement mixed with
fine aggregate produces mortar for masonry, or with sand and gravel, produces concrete. Cement is the
most widely used
material in existence and is only behind water as the planet's most-consumed resource.
Cements used in construction are usually inorganic, often lime or calcium silicate based, and can be
characterized as
either hydraulic or non-hydraulic, depending on the ability of the cement to set in the presence of
water (see hydraulic
and non-hydraulic lime plaster).
Non-hydraulic cement does not set in wet conditions or under water. Rather, it sets as it dries and
reacts with carbon
dioxide in the air. It is resistant to attack by chemicals after setting.
Hydraulic cements (e.g., Portland cement) set and become adhesive due to a chemical reaction between
the dry ingredients
and water. The chemical reaction results in mineral hydrates that are not very water-soluble and so
are quite durable in
water and safe from chemical attack.
This allows setting in wet conditions or under water and further protects the hardened material from
chemical attack.
The chemical process for hydraulic cement found by ancient Romans used volcanic ash (pozzolana) with
added lime (calcium
oxide).
Portland cement is by far the most common type of cement in general use around the world. This cement
is made by heating
limestone (calcium carbonate) with other materials (such as clay) to 1450 °C in a kiln, in a process
known as
calcination that liberates a molecule of carbon dioxide from the calcium carbonate to form calcium
oxide, or
quicklime—which then chemically combines with the other materials in the mix to form calcium silicates
and other
cementitious compounds. The resulting hard substance, called 'clinker', is then ground with a small
amount of gypsum
into a powder to make ordinary Portland cement, the most commonly used type of cement (often referred
to as OPC).
Portland cement is a basic ingredient of concrete, mortar, and most non-specialty grout. The most
common use for
Portland cement is to make concrete. Concrete is a composite material made of aggregate (gravel and
sand), cement, and
water. As a construction material, concrete can be cast in almost any shape, and once it hardens, can
be a structural
(load bearing) element. Portland cement may be grey or white.
Bitumen
Bitumenis the heaviest material obtained from the fractional distillation process of crude
oil. It is
Black in colour
and possesses water proofing &adhesive properties. This material is further treated and blended to
make different grades
of paving grade bitumen. i.e. Bitumen 80/100 (VG-10) , Bitumen 60/70 (VG-30) and
Bitumen 30/40 (VG-40)
and meets IS
73-2006 specification.
Our Strengths in Bitumen:
Drummed : Drummed Bitumen stocked in UAE and supplied to various destinations. The main grades
are:
Bitumen 80/100
(VG-10), Bitumen 60/70 (VG-30) and Bitumen 30/40 (VG-40) the grade Bitumen 30/40 is exclusively
produced only on special
requirements. Its major application is in the airport runway constructions. Star Bulk also provides
various types of
Bitumen:
• Penetration Bitumen ( 100/120)
• Blown Bitumen (R90/15)
• Blown Bitumen (R85/25)
• Cutback Bitumen (MC-250)
• Penetration Bitumen (40/50)
Quality Control:
A Rigorous Quality Control Mechanism whereby Bitumen is tested by SGS/Geo chem and
Cotecna as per
international standard requirements, and Test reports provided to the customers.
Marketing: A Nationwide network of marketing offices and supply locations thus ensuring
efficient
distribution of the
product at locations closer to the customer. Bitumen is supplied in Bulk and Packed forms.
• BULK BITUMEN
• PACKED BITUMEN : Bitumen is packed is NEW Steel Drums ( 180 KG as well as 150 KG
Drums),
Jumbo Bags,
Flexi Bags,
Palletized.
Altnerative of Bulk Bitumen is Bitumen in Jumbo bags. Kindly click the link here for checking on Jumbo
Bags.
