Monday, September 21, 2009

Concrete Materials

A:  Concrete Materials


   I.  Traditional Concrete

       










Traditional Concrete Samples
Image source by www.wfdecor.com






 


                      

How is it made?

Concrete requires the right temperature and the basic three components; Portland cement, water, and aggregate (rock and sand). When mixed together appropriately, additional additives made me include such as:



Accelerating admixture
   Calcium, reduced seeting time and accelerates strength.

Retarding admixture
   Retarder is set in hot weather condition to delay setting time.

Fly Ash
   A by-product of coal burning plants. Fly ash can replace up to 15-30% of cement mix. It helps improve workability, increses air entrainment by durability, and provides a mroe workable mixture.

Molecular structure of concrete 


 








Molecular structure of concrete
Image source by www.elkem.no








   II.  Shotcrete







Shotcrete concrete being sprayed
Image source by www0.planete-tp.equipement.gouv.fr

   



How is it made?

A form of concrete that uses the basic applied properties of traditional concrete except it's final process is different. Shotcrete is concrete, funneled through a tube to pour onto a slab or wall on site into a formwork or frame. The are two primary methods of applying shotcrete; dry-mix and wet-mix.



Dry-mix
This occurs when the aggregates and cement are mixed together. the materials is sent through the tube system to be compressed by air and meeting water at the nozzle to mix it.


Wet-mix
The elements of concrete are pre-mix and the material is sent through a tube system. The concrete is funneled through the tube until it meets the compressed air, used for spray


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