THE USE OF ACA AS ACTIVATOR IN HYBRID CEMENTITIOUS BINDERS AND DRY MIX FORMULATIONS

Amorphous Calcium Aluminate a special cementitious admixture with a mole ratio (CaO : Al2O3) of 12:7

In contact with water hydration takes place in seconds ; up to three times more effective than regular calcium aluminates

Contrary to regular calcium aluminate where main phase formed is monocalcium aluminate (CA) , Amorphous Calcium Aluminate forms C12A7.

On hydration a chemical reaction takes place whereby alumina ions are released most quickly from the main phase 12CaO? 7Al2O3 (C12A7-mayenite) reacting instantly with available calcium and sulphate ions forming high amounts of ettringite crystals (Aft) a tri-sulpho-aluminate salt and monosulfate (Afm phase).

Test results show that the hydration process works independently of other cement-bound components and in a so-called hybrid binder system such as GGBS, Fly-Ash, Metakaolin Limestone etc. and can therefore be referred to as cement accelerator and strength improver.

Production does not require any use of fossil fuel and no or limited amounts of sulfur dioxide, nitrogen dioxide and carbon dioxide are emitted.

Part replacement / addition to cementitious (hybrid) binders accounts for ;

• accelerated set
• fast autogenous drying
• sharp increase of strength
• no loss of strength in time
• reduced pores and pore size microstructure
• binding excess water
• shrinkage compensation through expansion
• lower heat on hydration
• higher density

The high effectiveness of CALUMEX ACA types allows a significant reduction of the total binder in mortars and concrete - in winter time less or no additional energy is needed to accelerate the hydration of mortar or concrete , this and the low footprint in itself contributes to a substantial reduction in CO2 emissions.

CALTRA offers three types ;

CALUMEX SC-A for extreme fast setting - waterplug , postfix ,urgent repairs

CALUMEX HPH-10 changed chemistry delays the setting to ~10 minutes

CALUMEX XT-20 offers an open time of ~20 minutes ideal for most applications like grouts tile adhesives , SLU's , fast set repair mortars etc.

to fascilitate the use of these extreme effective accelerators we developed a dedicated organic retarder to extend the working time up to 90 minutes

DELTA 20

DRY MIX

The fast formation and high amount of fibrous ettringite crystals are proofed to be very beneficial in dry-mixes be it cementitious or gypsum based;

• fast set and high early strength
• better adhesion (even on wet substrates)
• increased pull off strength
• less pores and smaller pore size
• fast autogenous drying
• shrinkage compensation

Benefits mentioned allow formulators to formulate their products using ;

• lower binder content
• use of hybrid cements
• reduced amount of redispersible powder
• use of granulated concrete as filler