Building materials: Properties of Building Materials; Types of Building Materials:  Stones & Bricks

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Properties of Building Materials

Physical Properties: Identified by visual observation & Hand tools

Chemical Properties: Identified based on the effect of different chemicals

Thermal Properties: Effect of Heat

Types of Building Materials

Stone

Stone is the naturally available construction material and is obtained from a quarry, process of extracting stones by excavating, wedging, heating & blasting is called quarrying and is composed of different minerals and with different processes.

Classification of stones:

Geological Classification:
Igneous Rocks
  • Solidification of molten mass above or below the earth’s surface.
  • Crystalline glossy or fussed texture
  • Ex: – Granite, Basalt, Diorite, Trap dolerite, Syenite, Pegmatite, Gabbro etc.
Sedimentary Rocks
  • Gradually deposition of sand, clay, debris, etc. by the action of rain, wind, sun etc.
  • Stratified
  • Ex: – limestone and sandstone, conglomerate, gypsum, dolomite, magnesite, chalk, shale, kankar,Tripoli, diatomite, etc.
Metamorphic Rocks
  • Change in texture or mineral composition of rocks under heat and excessive pressure
  • Ex: – marble, Gneiss, Quartzite, Slate, Schist, etc.
Physical classification:
Stratified Rocks:
  • Distinct layers which can be separated
  • E.g.: limestone, slate, and sandstone.
Unstratified Rocks:
  • No sign of strata
  • E.g.: granite, marble, etc.
Chemical classification:
Silicious Rocks
  • Silica as the main constituents
  • E.g.: granite, quartzite, gneiss etc.
Argillaceous Rocks
  • Clay or Alumina as main constituents
  • E.g. of silicious rock: slate, laterite, kaolin, etc.
Calcareous Rocks
  • Lime or calcium
  • E.g.: limestone, marble, etc.

Important building stones:

1. Granite

  • mainly composed of quartz, felspar, mica

What is Feldspar?

“Feldspar is no other than silicate of aluminum with varying amounts of potash, soda, or lime.

  • Sp. Gravity -= 2.64
  • Compressive strength = 70 – 130 MN/m2
  • color depends on felspar – brown, grey, green, pink
  • Offer high resistance to weathering
  • Easily polished and worked
  • Used for the external facing of buildings

2. Slate

  • Argillaceous rock
  • Alumina + sand /carbonate of lime
  • Sp. Gravity = 2.8
  • Compressive strength = 60-7- MN/m2
  • Grey/dark blue color
  • Hard, tough, fine-grained
  • Used in cisterns
  • Slate as tiles, an excellent roof covering material.

3. Gneiss

  • Gneiss:
  • A silicious rock
  • Composed of quartz and felspar
  • More easily worked than granite
  • Used for street paving

4. Sandstone

  • Silicious sedimentary rock.
  • Composed of quartz, lime, and silica
  • Sp. Gravity = 2.65- 2.9
  • Compressive strength = 35 -40 MN/m2
  • White, grey, brown, pink, etc.
  • Strong and durable
  • Used for ashlar works, moldings, carvings, etc.

5. Limestone

  • Sedimentary rock of calcareous variety
  • Sp. Gravity = 2.6
  • Brown, yellow, dark grey colors
  • Used large quantities in blast furnaces
  • Used as stone masonry for walls.

6. Marble

  • Metamorphic rock of calcareous variety
  • Sp. Gravity = 2.7
  • Very hard, ornamental work, takes a fine polish
  • Carving, decoration
  • Kankar
  • Impure limestone containing 30 % alumina & silica
  • Used for foundations of buildings

7. Laterite

  • Laterite contains a high percentage of iron oxide.
  • Porous and cellular structure
  • Sp. Gravity = 2 -2.2
  • Laterite blocks are suitable for light roads, and inferior buildings.
  •  a very good road metal

8. Moorum

  • Decomposed laterite
  • Deep brown or red color
  • Used in  garden walks & paths

9. Quartzite

  • Siliceous sandstones
  • Strong, durable, used as road metal/ railway ballast

Bricks

Bricks are construction materials made by moulding the tempered clay to a suitable shape and size which is in a plastic condition, dried in sun, and burnt in a kiln or clamp.

Brick clay contains (20-30) % Alumina

                                  (50-70) % Silica

Other constituents are lime, magnesia, sodium, potassium, manganese, and Iron oxide.

Excess of Alumina,Silica & Lime

Alumina – brick crack/warp on drying

Silica – brick brittle and weak

Lime –  brick to melt and distort during burning

Alkaline salt – efflorescence

Manufacture of Bricks:

Preparation of Brick clay
  • Earth left for atmospheric action for a few weeks after digging called weathering.
  • 1.5 – 2.5 m3 of brick soil – 1000 bricks
  • Tempered in pug mills
  • Process of mixing clay, water, and other ingredients is known as Kneading.
Moulding bricks:
  • Handmade bricks superior to machine-made bricks
  • Drying of Bricks:
  • Bricks are arranged in rows on their edges on a slightly raised ground called hacks.
  • Burning of bricks:
  • Clamp burning = 60 % out-turn
  • Kiln burning = 80 – 90 % out-turn
  • Takes 24 hrs. at 1000 – 1200 0c.
  • Cool for 12 days

Classification of Bricks:

1. First Class:
  • Well burnt, smooth, even surface, rectangular, uniform reddish.
  • Water absorption (≤ 20 %) at 24 hrs.
  • Min. crushing strength = 10.5 MN/m2
2. Second Class:
  • Slightly overburnt, rough, no perfect rectangle
  • Water absorption (≤ 22 %)
3. Third Class:
  • Under burnt, soft, easily broken
  • Water absorption (≤ 25 %)
4. Jhama bricks
  • Over burnt, irregular, dark bluish color

What is the size of the Brick?

  •  Size of Brick = (19 cm * 9 cm * 4 cm)

                          Or (19 cm * 9 cm * 9 cm)

  • Sp. Gravity = 2
  • For 1 m3 of brick masonry = 550 machine-made bricks

                                                  500 handmade bricks

Special Bricks:

Squint bricks: construction of acute and obtuse squint quoins

Paving bricks: used for street pavements

Round bricks: circular pillars

Perforated & Hollow: Partitions walls

Refractory Bricks: withstanding temperature, low Coeff. of expansion & contraction.

  • Acid Bricks: (fire Bricks & silica bricks)
  • Basic Bricks: ( Dolomite bricks, Magnesite bricks and bauxite bricks)
  • Neutral Bricks: (Chrome bricks, chrome-magnesite Bricks, spinel Bricks)


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