Why SRMs Are Added In Concrete

SRMs (Secondary Raw Materials) or SCMs (Secondary Cementitous materials) are added to concrete systems mostly in replacement mode ( They replace a part of cement ).

If this trend continues than we would need less cement production and hence lesser consumption of energy. These cement replacing SRMs also improve the fresh and hardened properties of concrete.

Different SRMs behave differently and can have following effects in concrete.

Dilution Effect

Although the cement quantity has been diluted, yet some efficient SRMs are added which improve the properties of cementitious systems.

Physical Packing Effect

Using smaller sized SRMs in binder phase or in small sizes of sand between the range of (0.063-0.15mm) will reduce the inherit porosity and for a given mixing water content, more water will be accommodated thus reducing the effective water cement ratio in the mix. This would enhance strength.

Chemical Or Pozzolanic Effect

If the SRMs added in cement replacement has sufficient amorphous SiO₂. The pozzolanic reaction would start however if the added material is inert like limestone powder, pozzolanic reaction should not be excepted.

As a result of pozzolanic reaction, another kind of hydration products would be produced after precipitation resulting in internal micro structure would become more dense and hence will impart more strength.

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