Building and construction materials

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Building stone

Cut and dressed into blocks and used for buildings, kerb stones, floors and kitchen surfaces.

Common building stones: Limestone, sandstone, granite and marble, Slate is used for roofing as its cleavage allows it to split into thin sheets

Its must be:

- Competent with high load-bearing strength

- Well jointed so blocks can be easily extracted or soft enough to be sawn into blocks

- Attractive visually

- Occur in thick, uniform units with few weaknesses or structures

- Impermeable and resistant to mechanical + chemical weathering

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Aggregate

Natural aggregate:

- Sand and gravel (clean with no impurities like clay), mainly extracted from recent Quaternary river, glacio-fluvial and shallow marine deposits

- Beds should be thick without lateral/vertical variation

Sand = used for mortar, concrete, ballast and as an abrasive  Pure quartz sand = Glass-making

Gravel = used to make concrete, must contain rounded pebbles so they can slide over eachother when poured

Crushed rock aggregate:

- Mainly for roadstone

- Hard rocks crushed can be igneous. gneiss, limestone and greywacke along with industrial waste

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Roadstone

Crushed aggregate mixed with bitumen (semi-solid hydrocarbon fraction of crude oil)

- Used to surface roads, roads are constructed in layers with a base-course overlain by a top wearing-course.

Must be:

- Strong, high impact and crushing strength, withstand traffic weight

- Resistant to abrasion and mechanical weathering (freeze-thaw)

- Impermeable and resistant to chemical corrosion (gritting and chemical spills)

- Skid resistant, every chipping must be made of more than one mineral with different hardness so they wear down at different rates and do not polish

- Bond well with bitumen

Basalt and dolerite are best, Granite is bad as it polishes, local sources used mean variety

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Brick clay

Made from clay, mudstone or shale

- Different composition = Different colours and types

- Clay moulded into the required shape and fired at high temperatures in a kiln

- Thick beds with constant composition required

- 40% of British Bricks made from Jurassic Oxford Clay which has a high carbon content which acts as an internal fuel. (Less energy needed, reduces costs)

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Manufacture of cement and concrete

Cement made from a mix of crushed limestone or chalk mixed with some clay/shale.

- Limestone gives calcium carbonate and clay provides silica and alumina

- Roasted in a rotary kiln at around 1500°C and 5% gypsum added to prevent quick setting

- Concrete is made by mixing cement with sand and gravel/crushed rock

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