Portland Composite Cement (PCC)

Introducing Crown Portland Composite Cement

Crown Portland composite cement is CEM-II/A-M is a cement consisting of Fly ash (PFA), slag and limestone designated by the specification of BDS EN 197-1: 2003; CEM -II/A-M (V-S-L), 42.5 N. PCC is the most suitable cement for construction in Bangladesh. CEM – II /A-M contains 80-94% Clinker, which is substantially higher than CEM – II/B-M containing 65 – 79% Clinker that will give us extra advantage in strength development and increase concrete performance.

Both slag & fly ash (PFA) are used in PCC. Percentage of SiO2 in PFA is higher than slag which is advantageous to gain more longterm strength and ensure durable concrete. The hydration process of normal cement produce CHS (durable binder) & Ca(OH)2 (non-durable binder).

The hydration process of normal cement produces calcium silicate Hydrate CHS (durable binder) & calcium Hydroxide Ca(OH)2 (non-durable binder).Calcium Hydroxide, ca(OH)2 does not contribute to gain strength. It is the weak part of reaction which is not suitable for concrete. Since PFA contains higher portion of reactive silica and slag contains alumina, it helps to convert ca(OH)2 into C-S-H to gain further strength.

Crown PCC gives you

Durability/Earthquake Resistance:
Crown PCC will give you strong & durable concrete as compared to other cements in the markets. As this cement contains fewer amounts of alkali, magnesia & free lime, it gives long term strength & durable concrete.

Higher long term strength:
Ordinary Cement usually gains strength for 90 days, whereas Crown PCC cement continues to gain strength much longer time / period due to its pozzolanic reaction. Its steady strength gaining feature gives it extra advantage for durable concrete.

Improved workability:
Concrete mix with crown PCC generally requires less water usually between 5 & 10 % by comparison with OPC mix. This gives higher strength. PFA & Slag particles work like a ball bearing around coarse cement particles. This increases the workability & eases placing of the concrete. PFA & Slag act like a plasticizer.

Minimize Bleeding:
Concrete made of crown PCC is cohesive & has a reducing bleeding capacity.
Lower Heat of Hydration:
PCC is made to have low heat of hydration. This results in lower shrinkage & easier curing.

High Chemical Resistance
Concrete mixes with PCC produce lower permeable dense concrete, which does not allow to penetrate water or air inside finish concrete. As a result reinforcement in concrete can stay long & stundy longer. This also supplemented with resistance to sulphate and chloride attacks.

Construction Advantage:
Concrete mix with Crown PCC generally requires less water. PFA particles work like ball bearing around coarse cement particles. As a result it is very easy to work with concrete mixes & mortar to have dense concrete & wonderful finishing in plaster. Concrete made with this cement has more impermeability & effective resistance to deterioration.

Suitable for construction works in Bangladesh:
The use of ordinary cement in concrete allows air, water and other pollutants to enter inside and corrodes reinforcements & deteriorates concrete which is not visible from outside. Crown PCC is an ideal cement whose PFA particles make dense & impermeable concrete. Consequently, air and water don’t enter into concrete keeping the reinforcements inside intact. Besides, crown PCC will give your constructions safe protection from pollution caused by humidity & flood water.

Consistency in quality:
We make all efforts in maintaining continuous high level of quality. We ensure the best raw materials sourcing from the best sources & maintain strict vigilance in every step of the cement production process. After production we test the cement every hour at our state-of-the-art laboratory to ensure the consistency in product quality.

Advantages of PCC in Concrete:

  • Improved pump ability
  • Compactability
  • Improved fresh concrete properties
  • Lower heat of hydration
  • Higher long term strength
  • Low permeability, dense structure
  • Optimum early strength
  • Low effective alkali content
  • High chemical resistance (Sea water, chloride diffusion, sulphate attack)

Technical Specification:

CEM-II/A-M , 42.5 N

Clinker 80-94 %
Fly Ash, Slag, Limestone 6-20 %
Gypsum 0-5 %

Benefits of Crown PCC:

  • Reduces heat of hydration, which protect cracks
  • Gains long-term strength in concrete
  • Increases workability
  • Suitable for constructions of dwellings or residential buildings or retaining concrete, canals, channels, & edging productions, in plastering, & mortar applications
  • Also suitable for ready-mixed concrete where high compressive strength is not required

Physical Properties:

Crown Cement is tested for fineness by Blaine’s air permeability method. The specific surface of cement is 350 – 450 m2/kg.
Crown Cement is tested for soundness by the Le-Chatelier method and autoclave test. The unareated cement shall have an expansion of less than 2.00 mm (Le-Chatelier method) & 0.08%
(Autoclave Method) respectively.

Setting Time:
The setting time of cement is tested by Vicat apparatus method.
Initial setting time is not less than 45 minutes.
Final setting time is not more than 420 minutes.

Compressive Strength
The compressive strength of Crown Cement is tested in compression machine.
In 2 days it is ≥ 10 MPa
In 28 days it is 42.5 – 62.5 MPa

Chemical Properties:
Insoluable residue (by mass) 5.0% max
Total Chloride Content 0.10% max
Alkali as Na2O 0.60% max