Pozzolanic cements are mixtures of portland cement and a pozzolanic material that may be either natural or artificial. The natural pozzolanas are mainly materials of volcanic origin but include some diatomaceous earths. Artificial materials include fly ash, burned clays, and shales.
What is pozzolanic explain various pozzolanic materials?
Pozzolanic materials are siliceous and aluminous materials, possessing little or no cementitious value by themselves, but in finely divided form and in the presence of moisture react chemically with calcium hydroxide liberated on hydration of cement at ordinary temperature to form compounds, possessing cementitious …
What are types of pozzolans?
The most common natural pozzolans used in concrete applications today include calcined clay, calcined shale and metakaolin. Other types of natural pozzolans that are used less in modern applications include volcanic ash, volcanic glass (pumicite and obsidian) and rice husk ash, among others.
Is pozzolana an admixture?
Pozzolanic or Mineral admixtures refer to the finely divided materials which are added to obtain specific engineering properties of cement mortar/concrete. … Popular examples of mineral admixtures are silica fume, fly ash, blast furnace slag etc.
What are the admixtures?
Admixtures are ingredients that are added to the concrete batch immediately before or during mixing. They confer certain beneficial effects to concrete, including frost resistance, sulfate resistance, controlled setting and hardening, improved workability, increased strength, etc.
What are the advantages of pozzolanic materials?
The advantages of using pozzolans in concrete include the following: (1) material cost reduction when a part of the cement is replaced by pozzolans, which are low cost (with some of them being natural or industrial by-products/wastes) and pollution free; (2) environmental cost reduction in relation to reducing the …
What is pozzolanic action?
From Wikipedia, the free encyclopedia. The pozzolanic activity is a measure for the degree of reaction over time or the reaction rate between a pozzolan and Ca2+ or calcium hydroxide (Ca(OH)2) in the presence of water.
How is pozzolana classified?
The designation pozzolana is derived from one of the primary deposits of volcanic ash used by the Romans in Italy, at Pozzuoli. The modern definition of pozzolana encompasses any volcanic material (pumice or volcanic ash), predominantly composed of fine volcanic glass, that is used as a pozzolan.
Why pozzolana is used in cement?
The benefits of pozzolan use in cement and concrete are threefold. … Pozzolans can be used to control setting, increase durability, reduce cost and reduce pollution without significantly reducing the final compressive strength or other performance characteristics.
What is Colour cement?
Coloured cements are made by grinding 5 to 10 percent of suitable pigments with white or ordinary gray portland cement. Air-entraining cements are made by the addition on grinding of a small amount, about 0.05 percent, of an organic agent that causes the entrainment of…
Which is not pozzolanic materials?
Which of the following is not a pozzolanic material? Explanation: Pozzolans are silicate based materials that form cementitious materials. Fly ash, silica fumes and slag are composed of oxide of silicon. Cinder is a coal residue.
What is cementitious material?
(materials) Any of various building materials which may be mixed with a liquid, such as water, to form a plastic paste, and to which an aggregate may be added; includes cements, limes, and mortar.
What is the difference between pozzolanic and cementitious materials?
The principal cementitious material in concrete is portland cement. … Some of these materials are called pozzolans, which by themselves do not have any cementitious properties, but when used with portland cement, react to form cementitious compounds. Other materials, such as slag, do exhibit cementitious properties.
What is concrete workability?
Workability of Concrete is a broad and subjective term describing how easily freshly mixed concrete can be mixed, placed, consolidated, and finished with minimal loss of homogeneity.
What is strength activity index?
The strength activity index is the ratio of the strength of the POFA-cement mortar to the strength of the reference (cement mortar) at each specific curing time. The rate of strength development of cement mortar relies principally on its hydration rate.
What is CSH in concrete?
Calcium-silicate hydrate (C-S-H) is the main binder in cement and concrete. It starts forming from the early stages of cement hydration and it progressively densifies as cement sets.
What is in fly ash?
Fly ash consists primarily of oxides of silicon, aluminum iron and calcium. Magnesium, potassium, sodium, titanium, and sulfur are also present to a lesser degree. When used as a mineral admixture in concrete, fly ash is classified as either Class C or Class F ash based on its chemical composition.
Why do we use pozzolans?
Pozzolans reduce bleeding because of fineness; reduce the maximum rise in temperature when used in large amounts (more than 15% by mass of cementitious material) because of the slower rate of chemical reactions; which reduce the rise in temperature.
Is lime a pozzolanic material?
The residue of fuels from lime burning, whether from coal-, coke-, or wood-fired kilns, known as lime-ash, is well known historically as a pozzolan and is still available. (8) Other vegetable ashes, such as rice husk ash, are used as pozzolans in other parts of the world. Bone ash is also known to have been used.
What is the full form of PPC cement?
Portland Pozzolana Cement (PPC) is manufactured by a combination of pozzolanic materials. Pozzolana is an artificial or natural material that has silica in it in a reactive form. Along with pozzolanic materials in specific proportions, PPC also contains OPC clinker and gypsum.
What are admixtures examples?
There are two types of admixtures, viz., chemical admixtures and mineral admixtures. Accelerators, Retarders, Water-reducing agents, Super plasticizers, Air entraining agents etc. are the commonly used chemical admixtures. Fly-ash Blast-furnace slag, Silica fume and Rice husk Ash are the examples of mineral admixtures.
What are admixtures and uses?
Admixtures are used in concrete to alter its properties in various ways. Some common uses include improving workability, increasing or decreasing cure time, and increasing concrete strength. Admixtures can also be used for aesthetic reasons, such as to change the color of the cement.
What are the admixtures used in RMC?
Concrete admixtures are of different types and they are as follows:
- Water Reducing Admixtures.
- Retarding Admixtures.
- Accelerating Admixtures.
- Air entraining concrete admixture.
- Pozzolanic Admixtures.
- Damp-proofing Admixtures.
- Gas forming Admixtures.
- Air detraining Admixtures.