ALTERNATIVE BINDER SYSTEM

ALTERNATIVE BINDER SYSTEM

1. Alkali Activated Binder

   • Characteristics
     • - Use GGBS as precursor
       • Latent hydraulic material
         • Slow reaction with water
           • Similar with OPC
         • Rapid at beginning
     • Basic Precursor material
     • Form calcium hydrates
       • Interconnected network
         • hold aggregates
         • similar with cement pate
   • Classification
     • Alkali hydroxide activated
       • Use alkali metal hydroxide
     • Alkali Silicate activated
       • Use alkali metal silicate
     • Alkali carbonated activated
       • Use sodium carbonate, less corrosive
       • Potassium carbonate is the most effective activator
       • Followed by potassium carbonate + sodium carbonate
       • Characeteristics
         • Give higher strength and good durability at later age
         • Low early strength & long setting time
     • Alkali sulfate activated
       • Supersulfated cement
       • Composition
         • 80-85% GGBS
         • 10-15% anhydrite form of calcium sulfate & alkali activators (eg: cement or clinker)
         • Sulphate source - gypsum in anhydrite form or dihydrate form
           • Flue gas de-su;pharization gypsum
             • Use limestone to remove sulphur diocide from flue gas
           • Phosphogypsum
             • by-product of manufacturing phosphorus fertilizer
             • consist of safety level of radioactive component
           • Fluoro-gypsum
           • sodium sulfate
           • red gypsum
             • by-product of manufacturing titanium oxide
             • have radioactive content, produced from Natural Occuring Radioactive Materials
       • Unburned cementitious materials
         • Chemical resistance
         • low heat generation
         • long setting time
           • caused by low pH value of gypsum
             • not enough to activate GGBS
       • Final product = C-S-H & ettringite
         • strength developement
         • Pore refinements

2. Geopolymer Binder System

   • alternative cementitious materials
   • combine material rich in silica & alumina
     • dissolved alumina & silica undergoes geopolymerization to form 3D amorphous aluminosilicate network
   • synthesized by activating fly ash / metakaolin with strong alkali solutions
     • KOH
     • NaOH
     • Soluble silicate, sodium silicate
   • increaee in concentration of sodium silicate
     • slow down the crystallization of zeolites
       • reductionn or absence or systalline product
         • higher compressive strength of geopolymers
     • alkali activation process is accelerated