Alkali activation of Sirjan pozzolan

The use of alkali-activated cementitious materials especially over the past decades has significantly been increased not only due to their potential in reducing CO2 emission from manufacture of Portland cements, but also due to their superior long-term engineering properties. Alkali-activation process, which was originally limited to slag cements, recently has been extended for several industrial mineral by-products and waste materials. Alkali-activated materials can be simply formed by mixing some alkali-activator with a wide variety of glassy silica and alumina rich minerals such as: clay, ground rock, ash, and slag. These materials that are inorganic or mineral polymers based on alumina and silica can be regarded as amorphous analogues of natural zeolites resulting from geosynthesis. Geopolymer cements are a group of alkali-activated material exhibiting superior engineering properties compared to Portland cement. They exhibit a number of good engineering properties including relatively high compressive strength, short to long setting times, and relatively low pore volume. This work investigates the possibility of utilizing natural pozzolan as a raw material in the production of geopolymer cements. Using Sirjan natural pozzolan and different alkali-activators based on combinations of Na2SiO3 and NaOH, a number of natural-pozzolan-based geopolymer cements were designed and prepared. Setting time, workability, and 28-day compressive strength of the systems were studied. The results obtained reveal that Sirjan pozzolan can be activated using a proportioned mixture of Na2SiO3 and NaOH resulting in the formation of a geopolymer cement system exhibiting suitable workability and relatively high 28-day compressive strength up to 56 MPa. The setting times of all the systems however are very long. Such long setting times could strongly restricts the application of the material, because before any actual setting due to geopolymerization reactions the material will lose water and dry unless being kept in an atmosphere of 100% relative humidity.

Alkali activation of Sirjan pozzolan Keywords:

Geopolymer Cement , Natural pozzolan , Alkali - activator , Workability , Compressive Strength , Setting time