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Pozzolana

 
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adutt
Progressive Member
Progressive Member


Joined: 26 Jan 2003
Posts: 43

PostPosted: Tue Oct 19, 2004 6:43 am    Post subject: Pozzolana Reply with quote

Dear Daljeet,

The  information given below about Pozzolana
cement maybe useful to you .The advantages of Pozzolana given below have
been collected from Literatures published by Cement Manufacturers . You
have rightly pointed out the  Cement Manufacturer's  claim that
Pozzolana have advantage over OPC. I think they are probably right on
the low heat of hydration property of Pozzolana cement . Some reputed
contractors involved in the  construction of water retaining structures
prefer the use of Pozzolana cement,since early shrinkage cracks due to
high heat of hydration is detremental for water retaining structures.



"A pozzolana is essentially a siliceous material, which, while in itself
possessing no cementitious properties, will in finely divided from and
in the presence of water, react with calcium hydroxide at ordinary
temperatures and form compounds having cementitious properties

Pozzolanas used in the manufacture of Portland Pozzolana Cement (PPC)
may be natural materials, such as shales, tuffs, volcanic ashes,
pumicites and diatomaceous earth. Materials processed by calcination of
soil, or fly ash, etc., are also used in the manufacture of pozzolana
cement.

Portland pozzolana cement is produced either by grinding together
portland cement clinker, pozzolana and gypsum, or by uniformly and
intimately blending portland cement and fine Pozzolana

Portland-Pozzolana cements have several advantages over Ordinary
Portland Cement, the most important being:

Concrete workability: The use of Portland pozzolana cement improves
considerably the workability of concrete.

Water permeability of concrete: Concrete permeability is greatly reduced
due to the lower porosity of the concrete.

Heat of hydration: The heat of hydration is generally reduced by 10-15%
which makes the use of Pozzolanic cements ideal when casting massive
concrete structures or concrete casting during the hot summer months.

Sulphate resistance: Experience in other countries showed that concrete
sulphate resistance is definitely increased when pozzolanic cements are
used.

Mechanical strengths: Portland - Pozzolana cements exhibit higher
long-term compressive strengths than Ordinary Portland Cement. "



With Regards



Amit Dutt

Structural Engineer

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p_kadam
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Joined: 26 Jan 2003
Posts: 165

PostPosted: Tue Oct 19, 2004 8:04 am    Post subject: Pozzolana Reply with quote

Dear friends,

Fresh feedback from sites is necessary as earlier such feedbacks in SEFI forum were not so encouraging from point of view of much delayed strength gain,erratic variations in strength.When pozzolans are used abroad regularly w/o problems,what ails here?

regards,

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