Typically, concrete designers use fly ash a partial replacement for portland cement at values up to 30 percent of the total cementitious composition. The use of high percentages (high volumes) of fly ash in concrete have been studied extensively over the last 15 years and the benefits have been well documented.

By reacting with free lime to form additional binder material, the permeability of concrete made with fly ash is lower than that made without it. Since virtually all durability aspects of concrete are improved with a reduction in permeability, the use of fly ash improves concrete durability. In addition, concrete water demand is typically reduced when using fly ash, leading to a lower water/cementitious ratio thus increasing strength. See similar questions...

For mix design purposes, fly ash itself should be considered like portland cement, except that the specific gravity for fly ash is different. The specific gravity of portland cement is typically 3.15, while the specific gravity of fly ash may range from 2.2 to 2.8, depending on fly ash composition. Therefore, if a certain percentage of cement is replaced with fly ash on a mass basis, simply multiply the initial portland cement quantity by the percent replacement. See similar questions...

Answer: This is not true. In-fact the advantages of addition of fly ash are many, a few of which are listed below: See similar questions...

Although the terms cement and concrete often are used interchangeably, cement is actually an ingredient of concrete. Concrete is basically a mixture of aggregates and paste. The aggregates are sand and gravel or crushed stone; the paste is water and portland cement. Concrete gets stronger as it gets older. Portland cement is not a brand name, but the generic term for the type of cement used in virtually all concrete, just as stainless is a type of steel and sterling a type of silver. See similar questions...

Since the water/cement ratio controls the strength of the concrete, water cannot be added above the maximum established water/cement ratio for that particular concrete mixture. If more water is needed, then a proportional amout of cement MUST be added to maintain the water/cement ratio. Every gallon of water added to a cubic yard of concrete, above the design water/cement ratio, will decrease the compressive strength of that concrete by approximately 200 psi. See similar questions...

Answer: The water cement ratio is very important with regards to the strength of concrete. The strength of concrete is inversely proportional to the water cement ratio i.e. with teh increase in water content the compressive strength of concrete decreases and vice versa. See similar questions...

For a passenger vehicle driveway and footpath a Grade 20 (20 MPa) concrete is usually used. For a more heavy duty application eg truck driveway a Grade 25 (25 MPa) concrete should be used. The following indicates the quantity required of each material to make up to one cubic metre of Grade 20 or Grade 25 concrete. This is a guide only. Less water may be required due to inherent dampness of materials particularly sand. See similar questions...

Fly Ash is a pozzolan. A pozzolan is a siliceous and/ or siliceous and aluminous material which in itself is not cementitious but will, in the presence of moisture and temperature > 40°F (> 5C), combine with calcium hydroxide to form cementitious compounds. The major use of fly ash is as a partial replacement for cement in concrete. The amount of cement replaced depends on the fly ash type, the fly ash quality, the application and the atmospheric conditions. See similar questions...

Answer: Cement (sometime referred to as Portland Cement or hydraulic cement) is one component of concrete. Cement is to concrete what flour is to a loaf of bread. Concrete is basically a mixture of 2 components: aggregates and paste. The paste, comprised of cement and water, binds the aggregates (sand and stone or grael) into a rocklike mass as the paste hardens because of the chemical reaction of the cement and water. This reaction is called hydration. See similar questions...

Cement (sometime referred to as Portland cement or hydraulic cement) is one component of concrete. Cement is to concrete what flour is to a loaf of bread. Concrete is basically a mixture of 2 components: aggregates and paste. The paste, comprised of cement and water, binds the aggregates (sand and stone or gravel) into a rocklike mass as the paste hardens because of the chemical reaction of the cement and water. This reaction is called hydration. See similar questions...

The invention of portland cement is credited to an English stone mason named Joseph Aspdin. He obtained a patent for portland cement 1824. He called his new product Portland Cement because when hardened, it resembled the color of natural stone quarried on the Isle of Portland in the English Channel. Concrete was used on a very limited basis from its inception through the late 1800's. See similar questions...

Fly ash is produced through the combustion of coal used to generate electricity. After coal is pulverized, it enters a boiler where flame temperatures reach up to 1500 degrees Celsius. Upon cooling, the inorganic matter transforms from a vapor state to a liquid and solid state. During this process individual, spherical particles are formed. This is fly ash. It is then collected by either using electrostatic precipitators, baghouses or a combination of both. See similar questions...

Fly ash is classified by the EPA as a non-hazardous product. As indicated by the MSDS, it is a relatively inert material. Fly ash is a product of coal combustion thus possesses no significant risk of fire or explosion. Fly ash is similar to sand in composition and consistency. When transporting and handling fly ash, the recommended precautions for safe handling as outlined on the product MSDS should be followed. See similar questions...