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Our company The Grant Group is pioneer in the supply of Portland cement in bags and in bulk. We provide a complete solution and are fully capable to meet all the future demands of Portland cement.
We pride ourselves in the constant quality of our Portland cement and in the numerous projects that our Portland cement is used in. Our quality management system exists to demonstrate our genuine commitment to those we serve our products and assures all standards, both local and international.
Our goal is to develop customers that are not just satisfied; in our 36 years of service we want our customers to be delighted with our products and services. We are committed to being responsible to the needs of our customers.
PORTLAND CEMENTS:
PORTLAND COMPOSITE CEMENTS:
HIGH PERFORMANCE CEMENTS :
SPECIAL CEMENTS:
Global demand for cement will grow 4.8 percent annually to 2008. Developing parts of Asia as well as Eastern Europe and Latin America will have strong demand for cement and indicate the robust growth momentum. The performance of the cement industry was equally impressive. Cement consumption touching an unprecedented level of 93% and the waning difference between demand and supply and its likely to continue its impressive performance.
Although cement consumption is closely tied to overall construction industry performance, cement is somewhat protected from extreme cycles because cement is used in nearly every type of construction. While individual construction markets have their own distinct business cycles, at any given time cement is usually needed by at least one segment of the construction industry.
The cement business, however, is fairly seasonal. Nearly two-thirds of cement consumption occurs in the six months between May and October. The seasonal nature of the industry can result in large swings in cement and clinker (unfinished raw material) inventories at cement plants over the course of a year. Cement producers will typically build up inventories during the winter and ship them during the summer. The cement industry is also regional in nature. Because the cost of shipping cement quickly overtakes its value, customers traditionally purchase cement from local sources. Nearly 96% cement is shipped to consumers by truck. Barge and rail modes account for the remaining distribution modes.
Concrete Basics (How concrete is made)
Concrete provides a seamless solid approach, which is extremely durable and hardwearing.
In its simplest form, concrete is a mixture of paste and aggregates. The paste, composed of Portland cement and water, coats the surface of the fine and coarse aggregates. Through a chemical reaction called hydration, the paste hardens and gains strength to form the rock-like mass known as concrete.
Within this process lies the key to a remarkable trait of concrete: it's plastic and malleable when newly mixed, strong and durable when hardened. These qualities explain why one material, concrete, can build skyscrapers, bridges, sidewalks and superhighways, houses and dams.
Proportioning
The key to achieving a strong, durable concrete rests in the careful proportioning and mixing of the ingredients. A concrete mixture that does not have enough paste to fill all the voids between the aggregates will be difficult to place and will produce rough, honeycombed surfaces and porous concrete. A mixture with an excess of cement paste will be easy to place and will produce a smooth surface; however, the resulting concrete is likely to shrink more and be uneconomical.
A properly designed concrete mixture will possess the desired workability for the fresh concrete and the required durability and strength for the hardened concrete. Typically, a mix is about 10 to 15 percent cement, 60 to 75 percent aggregate and 15 to 20 percent water. Entrained air in many concrete mixes may also take up another 5 to 8 percent.
Portland cement's chemistry comes to life in the presence of water. Cement and water form a paste that coats each particle of stone and sand. Through a chemical reaction called hydration, the cement paste hardens and gains strength. The character of the concrete is determined by quality of the paste. The strength of the paste, in turn, depends on the ratio of water to cement. The water-cement ratio is the weight of the mixing water divided by the weight of the cement. High-quality concrete is produced by lowering the water-cement ratio as much as possible without sacrificing the workability of fresh concrete. Generally, using less water produces a higher quality concrete provided the concrete is properly placed, consolidated, and cured.
Other Ingredients
Although most drinking water is suitable for use in concrete, aggregates are chosen carefully. Aggregates comprise 60 to 75 percent of the total volume of concrete. The type and size of the aggregate mixture depends on the thickness and purpose of the final concrete product. Almost any natural water that is drinkable and has no pronounced taste or odor maybe used as mixing water for concrete. However, some waters that are not fit for drinking maybe suitable for concrete.
Excessive impurities in mixing water not only may affect setting time and concrete strength, but also may cause efflorescence, staining, and corrosion of reinforcement, volume instability, and reduced durability. Specifications usually set limits on chlorides, sulfates, alkalis, and solids in mixing water unless tests can be performed to determine the effect the impurity has on various properties. Relatively thin building sections call for small coarse aggregate, though aggregates up to six inches (150 mm) in diameter have been used in large dams. A continuous gradation of particle sizes is desirable for efficient use of the paste. In addition, aggregates should be clean and free from any matter that might affect the quality of the concrete.
Hydration Begins
Soon after the aggregates, water, and the cement are combined, the mixture starts to harden. All Portland cements are hydraulic cements that set and harden through a chemical reaction with water. During this reaction, called hydration, a node forms on the surface of each cement particle. The node grows and expands until it links up with nodes from other cement particles or adheres to adjacent aggregates.
During placement, the concrete is consolidated to compact it within the forms and to eliminate potential flaws, such as honeycombs and air pockets. For slabs, concrete is left to stand until the surface moisture film disappears. After the film disappears from the surface, a wood or metal hand float is used to smooth off the concrete. Floating produces a relatively even, but slightly rough, texture that has good slip resistance and is frequently used as a final finish for exterior slabs. If a smooth, hard, dense surface is required, steel troweling follows floating.
Special techniques are used for curing concrete during extremely cold or hot weather to protect the concrete. The longer the concrete is kept moist, the stronger and more durable it will become. The rate of hardening depends upon the composition and fineness of the cement, the mix proportions, and the moisture and temperature conditions. Most of the hydration and strength gain take place within the first month of concrete's life cycle, but hydration continues at a slower rate for many years. Concrete continues to get stronger as it gets older.
Concrete is produced in four basic forms, each with unique applications and properties. Ready mixed concrete, by far the most common form, accounts for nearly three-fourths of all concrete. It's batched at local plants for delivery in the familiar trucks with revolving drums. Precast concrete products are cast in a factory setting. These products benefit from tight quality control achievable at a production plant. Precast products range from concrete bricks and paving stones to bridge girders, structural components, and panels for cladding.
Concrete masonry, another type of manufactured concrete, may be best known for its conventional 8 x 8 x 16-inch block. Today's masonry units can be molded into a wealth of shapes, configurations, colors, and textures to serve an infinite spectrum of building applications and architectural needs. Cement-based materials represent products that defy the label of "concrete," yet share many of its qualities. Conventional materials in this category include mortar, grout, and terrazzo. Soil-cement and roller-compacted concrete-"cousins" of concrete-are used for pavements and dams. Other products in this category include flowable fill and cement-treated bases. A new generation of advanced products incorporates fibers and special aggregate to create roofing tiles, shake shingles, lap siding, and countertops. And an emerging market is the use of cement to treat and stabilize waste.
Cement manufacturing is the basic processing of selected and prepared mineral raw materials to produce the synthetic mineral mixture (clinker) that can be ground to a powder having the specific chemical composition and physical properties of cement." Cement manufacture, like many other manufacturing processes, begins at the mine, where the raw materials like limestone, silica, aluminates, feric minerals and others are obtained. Some typical materials used for calcium carbonate in cement manufacturing are limestone, chalks, marbles, marls, and oyster shell. Some typical materials used for alumina in the cement manufacturing are shale, clay, slags, fly ash, bauxite, alumina process waste, and granite. Some typical materials used for silica in cement manufacturing are sand, clay, claystone, shale, slag, and fly ash. Some typical materials used for iron in cement manufacturing are iron ores, blast furnace flue dusts, pyrite clinker, mill scale, and fly ash.
Concrete is easy to work with, versatile, durable, and economical. By observing a few basic precautions, it is also safe-one of the safest building materials known. Over the years, relatively few people involved in mixing, handling, and finishing concrete have experienced injury. Outlined below are some simple suggestions-protection, prevention, common sense precautions-useful to anyone working with Portland cement and concrete.
The jobsite should be adequately marked to warn the public of construction activities. Fences, barricades, and warning signs can be used to restrict public access. And the work area should be kept clean and uncluttered to minimize hazards to workers. Remember: safety is the job of everyone onsite.
The A-B-Cs of fresh concrete's effect on skin are:
Warning
Contact with wet (unhardened) concrete, mortar, cement, or cement mixtures can cause SKIN IRRITATION, SEVERE CHEMICAL BURNS (THIRD-DEGREE), or SERIOUS EYE DAMAGE. Frequent exposure may be associated with irritant and/or allergic contact dermatitis. Wear waterproof gloves, a long-sleeved shirt, full-length trousers, and proper eye protection when working with these materials. If you have to stand in wet concrete, use waterproof boots that are high enough to keep concrete from flowing into them. Wash wet concrete, mortar, cement, or cement mixtures from your skin immediately. Flush eyes with clean water immediately after contact. Indirect contact through clothing can be as serious as direct contact, so promptly rinse out wet concrete, mortar, cement, or cement mixtures from clothing. Seek immediate medical attention if you have persistent or severe discomfort.
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