Page 48 - CAPE Green Engineering Syllabus 2016.docx_Neat

5.0 The composition and the Hydration process of OPC

5.1 The composition of the Portland cement

Four main compounds of Ordinary Portland cement.

1. Tricalcium silicate C3S

2. Dicalcium silicate C2S

3. Tricalcium aluminate C3A

4. Tricalcium aluminoferrite C4AF

5.2 The hydration process of the Portland cement

On mixing these compounds with water (H2O) the following reaction known as “HYDRATION” takes
place.

C2S = CSH + Ca(OH)2
C3S + H2O
C3A
C4AF

The result of hydration is a glue like substance known as Calcium Silicate Hydrate (CSH) and relatively
weak bonding materials known as calcium hydroxide (Ca(OH)2) are produced.

5.1 The effect of Pozzolanic material on OPC

Ca(OH)2 +(SiO2)/(Al2O3)+ H2O == CSH

CSH Calcium Silicate Hydrate

*The reaction can be more complicated and balanced as shown below.

Pozzolanic reaction is acid-base reaction between calcium hydroxide (Portlandite), or (Ca(OH)2), and
silicic acid (H4SiO4)
Ca(OH)2 + H4SiO4 —> Ca2+ + H2SiO42- + 2 H2O —> CaH2SiO4 · 2 H2O

Please NOTE: *The students are not required to memorise these equations.

6.0 Quality management and health and safety on using Portland cement

TCL states that quality is at the forefront of their business. Having been in the business of building a
region for close to 60 years, they have learnt a thing or two about consistently manufacturing quality
products. Their products have been used successfully in the building of; homes, schools, hospitals and
bridges throughout Trinidad and Tobago and the Caribbean region for decades. TCL continues to be
the brand of choice for users when it comes to making decisions on sheltering their families and loved
ones. TCL’s products have stood the test of time, not by chance, but simply because of the due

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