Sustainable cementitious materials: exploring alkali-activated binders with natural pozzolan

The present paper describes the potential use of NP from Algeria for the production of a new AAB. CEMII 42.5 cement is added to the NP as calcium resource. The mixtures are then activated by NaOH, Na2SO4 and Na2SiO3 at concentrations of 3, 7 and 11%. The chemical activators are both added in liquid and/or solid form to develop a one-part alkali-activated material. XRD, ATG/ATD and SEM/EDS are used to assess microstructure and elemental composition of the hydration products. Fresh properties, such as, consistency and setting time of various mixtures and compressive strengths of AABs specimens cured for 7, 28, 90 and 420 days are determined. The cement carbon footprint vs strength ratio (kg·CO2·eq/MPa) is suggested as an indicator to highlight the environmental contribution of the AABs. The results indicate that AABs show different strength levels depending on the activator type and its concentration. Maximum 28-day compressive strength of 25.2 MPa is achieved with 7 % Na2SiO3. A high early strength development is also noted since more than 50% of the strength could be achieved within 7 days. Finally, the environmental advantage is demonstrated as the global warning of the AABs can be 70% lower than that of OPC.