Physical And Mechanical Characteristics of Lightweight Concrete

The following are the properties of LWAC
  • Particle Size, Shape and Surface Texture 
  • Specific Weight, Density, and Bulk Density 
  • Water Absorption Capacity 
  • Unit Weight 
  • Compressive Strength 

Particle Size, Shape and Surface Texture

The shape of LWA is rounded, angular and irregular in shape. The shape of LWA aggregates will vary based on the manufacturing process. Surface texture may be smooth with a small number of pores or irregular with a large rock marked surface. The surface texture and the shape are very important in the mix design procedure, as they will control the degree of moisture absorption and will affect the workability of fresh concrete.
The granularity of LWA is related to the quality of the aggregate. The size will vary from 5mm to 20mm.

Specific Weight, density, and Bulk Density

Specific weight of the LWA is equivalent to the weight of the unit volume of the porous material (including the pores in particle). The density of LWA is lower than that of normal weight aggregate.

For coarse LWA density varies from 600kg/m3 to 1600kg/m3. For fine aggregates, the density will change from 1300 kg/m3 to 1850 kg/m3.
The bulk density of LWA is based on the weight of 7 to 15mm grains. The bulk density of the LWA can vary from 1/3rd to 2/3rd times that of normal weight aggregates. The order of bulk density of LWA is 700kg/m3 to 800 kg/m3.

Water Absorption Capacity

The water absorption capacity of the coarse LWA is in the range of 5% to 30% while for fine LWA it is 5% to 15%. Pumice LWA has high water absorption capacity and the maximum capacity is 50%.

Unit Weight

For Coarse LWA unit weight is 1000 kg/m3 to 1700 kg/m3 and for fine LWA it is 1300 to 1600 kg/m3. For pumice stones, the unit weight varies from 1200 to 1600 kg/m3.

Compressive Strength

The compressive strength of coarse LWA is 10 to 60MPa. For Fine LWA it is in the range of 20 to 50MPa. This is the raw material, expanded clay. For pumice based LWAC, the compressive strength varies from 5 to 15MPa.

Production of Lightweight Concrete (LWAC)

The LWAC can be manufactured by proper and efficient mixing, transporting and compacting of the binder material(cement), water, fine aggregate and the lightweight aggregates. The production or the different stages of manufacturing of LWAC is same as that of natural or the ordinary concrete.
  • Effective batching 
  • Proper mixing 
  • Correct transporting 
  • Sufficient compaction after the proper placing 
  • Efficient curing, are the important steps that will influence the maximum or the best qualities of LWAC. 

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Factors Affecting the Strength and Density of Concrete

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