This report presents a meticulous synthesis of collaborative interlaboratory research conducted within the purview of the RILEM Technical Committee 294-MPA, with two expert groups named RRT1 and RRT2, and encompassing ten participants from Belgium, China, Finland, India, Italy, Japan, the Netherlands, and the United Kingdom. The RRT1 expert group mainly focused on the ground granulated blast furnace slag-based alkali-activated concrete (GGBFS-based AAC) mix design and mechanical properties. In turn, the RRT2 expert group focused on the fresh properties of GGBFS-based AAC. The investigation, conducted between 2020 and 2024, aimed to establish globally reproducible mix design and mixing protocols for GGBFS-based AAC. Developed by the RRT1 and RRT2 expert groups, these protocols have emerged through iterative experiments followed by a comprehensive interlaboratory study. The outcomes highlight the reliable production of GGBFS-based AAC across participants, with minor deviations in fresh and mechanical properties that are largely consistent with those observed in Portland cement concrete (PCC). The primary objective of the developed GGBFS-based AAC mix design was to achieve a defined consistence class S4, while targeting a compressive strength threshold of approximately 50 MPa at 28 days. This objective was effectively realized, with the average compressive strength values reaching 56 MPa at 28 days and 64 MPa at 720 days. While the average splitting tensile strength stabilized at 3.2 MPa over the 720 day period. These findings underscore the growing importance of AAC within the construction sector, particularly due to its reproducible and reliable experimental results, as the industry increasingly shifts toward more sustainable alternatives to traditional cement-based materials.

Under the directives of the RILEM Technical Committee 294-MPA, this publication reports on the findings of an interlaboratory study that tested fiber-reinforced GGBFS-based alkali-activated concrete (FRAAC), with participants from Belgium, India and Slovenia. The research also elaborates prediction models for the tensile splitting strength of GGBFS-based FRAAC. This research endeavoured between 2020 and 2024 to find a globally reproducible FRAAC mix that could attain the required mechanical strength and workability criteria. The primary goal of the interlaboratory study was to generate FRAAC without the use of superplasticizers in order to maintain an S4 class consistency slump and achieve the desired 28-days cube compressive strength of 40 MPa. Steel and PVA fibers were determined to be incorporated to the GGBFS-based AAC mix at 0.3 and 0.1% volume fractions, respectively, through iterative interlaboratory investigations. Experimental program was conducted to examine the compressive and tensile splitting strength of these FRAAC combinations at different curing ages, ranging from 1 to 720 days. The findings indicate that while there were a few interlaboratory variations in the mechanical properties, the FRAAC produced was uniform across all participants. The desired compressive strength of 40 MPa was attained by GGBFS-based FRAAC with both steel and PVA fibers at 28 days. Although FRAAC containing steel fibers exhibited the higher early compressive strength, FRAAC prepared with steel and FRAAC prepared with PVA both demonstrated a 720-days compressive strength of about 61 MPa. The FRAAC mixes with steel fiber additions exhibited a tensile splitting strength that was approximately 30% higher than the mix with PVA fibers. Nonetheless, at all ages, the tensile splitting strength of both FRAAC mixes was clearly higher than 2 MPa. These results support reliable and consistent experimental findings, which allude towards FRAAC as a sustainable substitute for conventional Portland cement concrete.