Frequently Asked Questions

R & D

 

FAQ on Cement

1. What are the different grades of Ordinary Portland Cement (OPC) ?

The Sri Lanka Standard Institute (SLSI) has classified OPC in two different grades namely 32.5 N and 42.5 N.  The classification is mainly based on minimum compressive strength requirement of cement – sand – water in N/mm2 at 28 days.  Only OPC of strength class 42.5 N is recommended for high strength concrete.


2. Is there any shelf life of cement ?

Cement is a hygroscopic material,  meaning that it absorb moisture,  when cement absorb moisture it undergoes hydration resulting formation of lumps.  Cement will remain in good condition as long as it does not come in contact with moisture.  Normally shelf life of cement is three (3) months.


3. How fineness of cement affect strength gain ?

Fineness differs as the surface area of cement particle present in per unit weight, which implies that more fineness means more particle in unit weight.  This enhances the reaction rate which in turn will result in faster gain of  strength at early stages.


4. What is Blended Cement ?

Blended Cement are the cement obtained by intergrinding or blending of Supplementary Cementitious Materials such as fly ash, slag, silica fume, rice hull ash or Meta kaolin with Portland cement clinker.
 


5. How does Blended Cement affect durability ?

Supplementary Cementitious Material in blended cement react with hydrated lime formed by hydration of Portland cement and forms a strength contributing chemical phase resulting a impermeable layer to sulphate and chloride ions.
 


FAQ on Dry Mortar Products

1.What is dry mortar ?

Dry mortar is made out of mixing cement with filler such as sand and chemicals to result a product with enhanced workability and strength.  This is a replacement for job site mix mortar.
 


2. Why cement cannot be used for fixing porcelain tiles ?

Porcelain tiles are high strength and high dense tiles with negligible water absorption.  Water retention of cement paste is very poor and leads to a weak bonding with porcelain tiles.
 


3.Should I use tile adhesive on the wall ?

Yes.  These tile adhesives are highly recommended for tiling on a wall and can be continued without a support and can fix tile from top to bottom.
 


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