The addition of a small portion of granite polishing waste in the design mix results in:

Detailed Explanation: Granite Polishing Waste Improves Packing Density

Why D (Improved packing density) is correct: Granite polishing waste (GPW) is an ultra-fine residue generated during the polishing of granite surfaces. Its particle size is very small — finer than cement — allowing it to fill the interstitial voids between sand particles that would otherwise remain empty or be filled by excess paste. This void-filling action improves the packing density of the mix.

Effects of Granite Polishing Waste on Concrete

Effect	Mechanism	Result
Improved packing density	Ultra-fine GPW particles fill voids between sand grains	Denser matrix; less void space
Reduced void ratio	Less empty space in the aggregated skeleton	Lower porosity; better impermeability
Reduced porosity	Tighter particle packing reduces capillary channels	Lower permeability; better durability
Reduced sand consumption	GPW partially replaces natural sand	Environmental benefit; waste utilisation
Improved mortar performance	Better particle gradation fills size gaps	Stronger interface bond; lower paste demand

Why the Other Options Are Wrong

Option	Why Incorrect
A. Lighter concrete	Granite is a dense rock (≈2700 kg/m³); GPW increases density, not lightens it
B. Higher void ratio	GPW fills voids; void ratio decreases, not increases
C. Decreased strength	Better packing density → less void space → higher strength or at worst maintained strength
D. Improved packing density	Correct: GPW fills inter-particle voids; better gradation; denser concrete

• Granite polishing waste as sand replacement → improved packing density.
• Also reduces void ratio, reduces porosity, and improves mortar workability as a filler.
• Industrial waste utilisation (GPW, fly ash, GGBS, silica fume) improves both concrete properties and sustainability.