concrete - Chemical Properties and Physical Properties

Posted by Mr.Building Material , Labels: , Saturday, 17 March 2012 06:52

CHEMICAL PROPERTIES 
The chemical properties of aggregates have to do with the molecular structure of the minerals in the aggregate particles.

  • Stripping (HMA)
Although the displacement of asphalt on the aggregate particle surface by water (stripping) is a complex phenomena and is not yet fully understood, mineralogy and chemical composition of the aggregate have been established as important contributing factors (Roberts et al., 1996).  In general, some aggregates have an affinity for water over asphalt (hydrophilic).  These aggregates tend to be acidic and suffer from stripping after exposure to water.  On the other hand, some aggregates have an affinity for asphalt over water (hydrophobic).  These aggregates tend to be basic and do not suffer from stripping problems.  Additionally, an aggregate’s surface charge when in contact with water will affect its adhesion to asphalt cement and its susceptibility to moisture damage.  In sum, aggregate surface chemistry seems to be an important factor in stripping.



  • Alkali-Aggregate Reaction (PCC)

Alkali-aggregate reaction is the expansive reaction that takes place in PCC between alkali (contained in the cement paste) and elements within an aggregate.  The most common is an alkali-silica reaction.  This reaction, which occurs to some extent in most PCC, can result in map or pattern cracking, surface popouts and spalling if it is severe enough.






Physical Properties


The physical properties of aggregates  are those that refer to the physical structure of the particles that make up the aggregate. 
Commonly measured physical aggregate properties are :
  • Gradation and size
  • Toughness and abrasion resistanc
  • eDurability and soundness
  • Particle shape and surface texture
  • Specific gravity
  • Cleanliness and deleterious materials.




















 Aggregates Before a Soundness Test








                                                                                                  
 Aggregates After a Soundness Test

1 Response to "concrete - Chemical Properties and Physical Properties"

  1. Farah Says:
    20 March 2012 at 07:00

    so amazing about the soundness test..POWERFUL to make the aggregate crack..

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