What pozzolana means?
: finely divided siliceous or siliceous and aluminous material that reacts chemically with slaked lime at ordinary temperature and in the presence of moisture to form a strong slow-hardening cement.
What is meant by 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.
What makes a material pozzolanic?
Pozzolanic material should consist of siliceous or a combination of siliceous and aluminous material in a finely divided form that in the presence of moisture will react with calcium hydroxide, at ordinary temperatures, to form compounds possessing cement properties.
What are the examples of pozzolans?
Natural pozzolana (pozzolanic ash), silica fume (from silicon smelting), fly ash, and rice husk ash are examples of pozzolans. Silica fume (microsilica) is an amorphous form of silicon dioxide (silica). It is in the form of spherical particles with an average particle diameter of 150 nm.
What is pozzolana used for?
Uses of Portland Pozzolana Cement Used in hydraulic structures, marine structures, construction near the sea shore, dam construction etc. Used in pre-stressed and post-tensioned concrete members. Used in masonry mortars and plastering. As it gives better surface finish, it is used in decorative and art structures.
Why pozzolana is used in cement?
What does a pozzolan do in the concrete? A. 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.
Why do we use Pozzolans in concrete?
What is the action of retarder?
Retarders for concrete are used to delay the initial setting time of the concrete upto an hour. They are generally used in the hot weather condition to counter the rapid hardening due to high temperature, thus allowing the time for mixing, transporting and placing. Retarders also acts as water reducers.
What are pozzolanic materials and how they are derived?
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.
What made pozzolana so special?
Roman engineers used two parts by weight of pozzolan mixed with one part of lime to give strength to mortar and concrete in bridges and other masonry and brickwork. During the 3rd century bce the Romans used pozzolana instead of sand in concrete and mortared rubblework, giving extraordinary strength.
Is cement a pozzolan?
properties. 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.
Which of the three following are a type of pozzolan?
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.
Which is the best definition of the word pozzolanic?
Define pozzolanic. pozzolanic synonyms, pozzolanic pronunciation, pozzolanic translation, English dictionary definition of pozzolanic. also poz·zo·la·na or poz·zuo·la·na n. 1. A siliceous volcanic ash used to produce hydraulic cement. 2. Any of various powdered substances that react with…
What makes a pozzolan a cementitious compound?
Pozzolans are a broad class of siliceous or siliceous and aluminous materials which, in themselves, possess little or no cementitious value but which will, in finely divided form and in the presence of water, react chemically with calcium hydroxide (CaOH 2) at ordinary temperature to form compounds possessing cementitious properties.
When to use pozzolanic or mineral admixtures?
The pozzolanic or mineral admixtures are generally added as partial replacement of the portland cement according to weight of cement. 01. Fly Ash Fly ash is also known as a pulverized-fuel ash.
When did the use of pozzolans become common?
Over the course of the 20th century the use of pozzolans as additions (the technical term is “supplementary cementitious material”, usually abbreviated “SCM”) to Portland cement concrete mixtures has become common practice.