Chapter 7 - CO2 Reduction Assessment of Alkali-Activated Concrete Based on Korean Life-Cycle Inventory Database

Abstract

Although the alkali-activated (AA) concrete is generally regarded as one of the most effective technologies in the concrete industries to reduce CO2 emissions, very few investigations on the assessment of CO2 reduction of such concrete have been published. The present study reports an evaluation procedure of CO2 reduction of AA concrete, based on the Korean Life-Cycle Inventory database and extensive test data mostly compiled from Korean journals. The studied system is from cradle to preconstruction. CO2 reduction for secondary precast concrete products is also evaluated with reference to practical examples when ground granulated blast furnace slag (GGBFS) cement is replaced with AA GGBFS binder. The comparisons of the performance efficiency indicators, binder, and CO2 intensities reveal that the contribution of binder to total CO2 emission is more significant in ordinary Portland cement (OPC)-based concrete than in AA concrete, while the contribution of aggregate transportation becomes more critical in AA concrete than in OPC-based concrete. The reduction rate of CO2 emission of AA concrete relative to OPC concrete commonly ranges between 55% and 75%. In addition, the CO2 reduction rate in secondary precast concrete products using AA GGBFS binder instead of GGBFS cement can be evaluated to be approximately 20% when total aggregate-to-binder ratio ranges between 3.0 and 4.0. On the other hand, Ca(OH)2-based AA GGBFS concrete shows approximately 2.4 times lower CO2 intensity than OPC concrete. Overall, the slope of the increasing rate of CO2 intensity against binder intensity is lower in Ca(OH)2-based AA GGBFS concrete than in OPC-based concrete.