Lightweight Aggregate Concrete: Types, Properties And Factors Affecting Mix Design

LWAC is the popular type of light weight concrete, in which lightweight aggregates are used. The lightweight aggregates are relatively new materials. These have a unit weight up to 12kN/m3. The LWA can be either natural or artificial or manufactured. The natural aggregates include volcanic cinder, dolomite or pumice. The artificial aggregates can be blast furnace slag, sintered fly ash or bloated clay.



Classification of  Lightweight Aggregates

As per BIS, the LWA can have the following classification. 

    • Naturally Occurring LWA
    • Industrial by-product LWA
    • Artificial or Manufactured LWA

Naturally Occurred LWA

The natural aggregates are available naturally. These aggregates are chemically inert and usually has a relatively high amount of silica about 75%. The common examples of this type are:
  • Pumice
  • Silica Sand
  • Volcanic Tuffs
  • Gravel and Crushed Stone
  • Volcanic Slag

Industrial by-product LWA

These are basically categorized under artificial aggregates. But due to their availability, they are considered as industrial aggregates. Some of them are:


  • Foamed Blast Furnace Slag
  • Sintered -Pulverised Fuel Ash

Artificial or Manufactured LWA

These are mostly produced in the rotary kiln. The raw materials are clay, shale, slate or pulverized fuel ash. These are subjected to either expansion or agglomeration. The common examples are:
  • Expanded Shale
  • Expanded Clay
  • Brick Rubber
  • Pelletized material
  • Vermiculate

Properties of Lightweight Aggregate Concrete



Commonly the LWA have a lower density, highly durable, low shrinkage and low thermal conductivity. The strength of the LWA particles decreases with decreasing density.
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