LIGHT WEIGHT CEMENT AND AGGREGATE 

A pozzolan is a “siliceous or siliceous and aluminous material, which in itself possesses little or no cementitious valve but will, in finely divided form and in the presence of moisture, chemically react
with calcium hydroxide at ordinary temperatures to form compounds possessing cementitious properties” (ASTM)

Cement consists of three types of materials; (1) limestone (CaCO₃), (2) aluminum silicate
(clay or shale), and (3) inert materials such as sand and gravel. The limestone and clay are fired together in   a rotary kiln. The limestone decomposes to lime (CaO) which reacts with the clay or
shale to form “clinker”. Clinker consists of tricalcium silicate, dicalcium silicate, tricalcium
aluminate, and tetra calcium aluminate ferrite. The clinker is finely ground generally in a ball mill
to make “cement”.

In “Portland-pozzolan” cement 15 to 40% of the cement can be replaced by zeolite which is a pozzolan.

Bear River Zeolite Plant, Preston, Idaho July 2006
Preparations are being made for a new grinding facility for pozzolan for
concrete industry. (August 2006 estimate)
 

• INCREASED COMPRESSIVE STRENGTH due to the porous crystalline structure and high
  surface area of the zeolite, the hydrated phases of lime pozzolan are enhanced and this
  increases the compressive strength.

• DECREASES ALKALI-SILICA EXPANSION. BRZ allows the use of clinkers with more than
  0.60% Na₂O. (Limit of ASTM description).

• HELPS RESIST UNDERWATER CORROSION

• POWER SAVINGS The production of 1 kg of clinker requires 900 Kcal of energy. Ten tons of
  BRZ™ used as pozzolan saves about 1 ton of fuel.

• IMPROVED CHEMICAL RESISTANCE especially in salt water applications

• DECREASE INSTABILITY CAUSED BY EXCESS LIME IN THE SET CEMENT
   

BRZ™ can be heat treated to form lightweight cement. When heated it loses water. When mixed
into a cement mixture it rehydrates and releases air. The “foam” or “air entrainment” increases
strength and decreases weight. BRZ can be used to replace fused silica in light weight cement.

BRZ™ expands into a lightweight aggregate at temperatures between 1200^o and 1400^o C.

Its density is about 0.8 gcc and it has a porosity of up to 65%. Light aggregate is commonly used
in Japan.

•  
  Mineral:         Primarily clinoptilolite (see spec sheet)

• Sodium:        Low sodium content, less than 0.5%

• Surface Area:          High surface area, 24.9 square meters/gram

• Weight:         Bulk density, 55 pounds per cubic foot

• Moisture:      Holds up to 55% of its weight in water