Construction Materials: Stone Properties, Cement Standards, and Concrete Testing

Posted on Nov 21, 2025 in Geology

Properties of Natural Stones

Granite: Primitive Plutonic Rock

  • Origin: Primitive rock, plutonic origin.
  • Composition: Quartz (30–35%), Feldspar (50%), and Mica (15–20%).
  • Structure: Multi-phase, polycrystalline structure; homogeneous, small grains.
  • Mechanical Properties: High mechanical compressive strength, high density, high degree of compactness.
  • Behavior: Almost isotropic behavior; hard to sculpt, easy to polish.
  • Vulnerabilities: Problems due to freeze-thaw cycles and changes in the feldspars.

Sandstone: Mechanical Sedimentary Stone

  • Origin: Sedimentary stone (mechanical).
  • Composition: Mainly made up of silica (SiO₂).
  • Structure: Homogeneous, highly porous.
  • Mechanical Properties: Low mechanical strength, low density, low degree of compactness.
  • Resistance: Low impact resistance and abrasion resistance.
  • Workability: Hard to polish, easy to sculpt.
  • Uses: Used as tiles and slabs (poor paving material).
  • Vulnerabilities: Problems caused by freeze-thaw cycles and increasing permeability over time.

Limestone: CaCO₃ Sedimentary Stone

  • Origin: Sedimentary stone obtained by precipitation of CaCO₃.
  • Uses: Raw material for lime and cement production.
  • Structure: Small and homogeneous grains; low porosity; usually has voids.
  • Mechanical Properties: Medium mechanical strength; medium/high density.
  • Resistance: Medium resistance to impact and abrasion.
  • Workability: Good workability (some can be polished).
  • Vulnerabilities: Attacked by acids; problems due to acid attack in urban environments.

Marble: Metamorphic Stone (from Limestone)

  • Origin: Metamorphic stone (formed from limestone).
  • Composition: Composed of calcium carbonate (CaCO₃).
  • Vulnerabilities: Attackable by acids (less so than limestone).
  • Mechanical Properties: High mechanical strength, high density, high degree of compactness.
  • Resistance: High abrasion and impact resistance.
  • Workability: Good workability (can be polished).
  • Aesthetics: Richest in color and veins.

Slate: Metamorphic Stone

  • Origin: Metamorphic stone.
  • Composition: Composed mainly of quartz and feldspars.
  • Structure: Laminar structure (cleavage planes); very small grains.
  • Behavior: Anisotropic mechanical behavior; very high density; very high degree of compactness.
  • Durability: Not affected by the freeze-thaw cycle.
  • Workability: Good workability (can be polished).
  • Uses: Used in roofs, cladding, and pavement.

Basalt: Igneous Volcanic Stone

  • Origin: Igneous volcanic stone.
  • Composition: Mainly composed of feldspar.
  • Structure: Heterogeneous/vitreous structure; very fine grain.
  • Mechanical Properties: High hardness, high compression strength, high density (voids not considered).
  • Resistance: High impact and abrasion resistance.
  • Workability: Hard to cut and sculpt.
  • Uses: Used in pavements.

Alabaster: CaSO₄ Sedimentary Stone

  • Origin: Sedimentary stone made by crystallization of CaSO₄.
  • Structure: Fine grain (slightly veined, soft).
  • Mechanical Properties: Low compression strength; medium-high density; low impact and abrasion resistance.
  • Workability: Easy to cut and sculpt.
  • Aesthetics: Translucent with thickness (used as a light element).

Commercial Types of Cement

  1. Common Cements:
    • CEM I (Portland Cement)
    • CEM II (Portland Cement + Additions)
    • CEM III (Blast Furnace Cement)
    • CEM IV (Pozzolanic Cement)
    • CEM V (Composite Cement)
  2. Common Cements with Additional Characteristics:
    • Sulphate Resistant Cement (SR)
    • Marine Resistant Cement (MR)
    • Low Hydration Heat Cement (LH)
  3. Mortars Cement
  4. White Cement
  5. Cement for Special Uses
  6. Calcic-Aluminate Cement

Cement Composition and Hydraulic Binders

Cement Components

CEMENT = CLINKER + GYPSUM + ADDITIONS

  • Clinker: Artificial product with hydraulic properties; it can be white or gray.
  • Gypsum: Usually added around 3% to regulate the setting process.
  • Additions: Granulated blast furnace slag, silica fume, pozzolanic materials, siliceous fly ash, limestone (with TOC < 0.5%), burnt shale, calcareous fly ash, natural crushed pozzolana, limestone (with FOG < 0.2%).

Hydraulic Indexes and Moduli

These measures quantify a binder’s capacity to harden under water, based on its chemical composition.

  • Vicat Hydraulic Index (IH): IH = (S + A) / C
  • Loftus Hydraulic Index (IH): IH = (S + 0.2A) / C
  • Hydraulic Moduli (M): Increase of hydraulic index. M = C / (S + A + F) = 1 / IH

Note: S=Silica, A=Alumina, C=Calcium Oxide, F=Iron Oxide.

Morphology of Natural Stones

  1. Ashlar
  2. Rubble Ashlar
  3. Masonry
    • Masonry Ashlar (regular cuboid)
    • Rubble Masonry (irregular)
    • Bedded (with lime, cement, bitumen, or chalk)
    • Cyclopean (large size)
    • Faced or Textured (visual appeal)

Concrete Workability and Consistency Testing

Slump Cone Test

The Slump Cone Test is performed to check the workability of freshly made concrete and therefore the ease with which concrete flows. It can also be used as an indicator of an improperly mixed batch. The test is popular due to the simplicity of the apparatus used and the straightforward procedure.

Applicability (Based on Slump Value):

  • Precast Concrete
  • Reinforced Concrete
  • Highly Reinforced Concrete
  • Slender Elements or Pumped Concrete
  • Not Usable (Very low or very high slump)

Consistency

Consistency is defined as the ability of fresh mixed concrete to flow, representing the degree of wetness of the concrete.

Obtention and Setting of Lime

Lime Production Process

  1. Extraction of Limestone
  2. Crushing of Limestone
  3. Calcination (Heating Limestone)
  4. Cooling
  5. Inspection and Sieving
  6. Grinding and Powdering

Chemical Reactions

Quicklime Production (Calcination)

Quicklime (CaO) is obtained from limestone (CaCO₃) by heating up to 900–1000ºC:

Limestone + Heat = Quicklime + Carbon Dioxide

CaCO₃ + Q → CO₂↑ + CaO

Hydration of Quicklime (Slaking)

This process is carried out by air exposure, sprinkling/spraying, or immersion:

CaO + H₂O = Ca(OH)₂ + Q↑ (Heat released)

Setting of Hydrated Lime (Carbonation)

Ca(OH)₂ + CO₂ = CaCO₃ + H₂O↑

Lime Cycle Summary

Limestone (CaCO₃) → Heated → Quicklime (CaO) → Water Added → Slaked Lime (Ca(OH)₂)