Flexural stiffness and structural behavior of alkali-activated metakaolin faced with cement-based beams

In this work, the authors intend to experimentally analyze the viability of using geopolymers, in particular, by means of alkali-activated metakaolin as a binder in the construction of beams. For this, an experimental procedure will be used, where 15 reinforced beams will be tested. Of these, 10 are built using two geopolymers whose binders are made up of two different metakaolins (white metakaolin supplied by MetaMax and brick-colored metakaolin supplied by Argeco) and the remaining 5 beams will be built with Ordinary Portland Cement mortar. The beams (b = 100 mm x h = 150 mm x L = 1500 mm) were built in groups of 3, with identical reinforcement (reinforcement ratios of 0.38%, 0.57%, 0.75%, 1.01% and 1.34%). They have the particularity of having dimensions smaller than the ones in the practice of Civil Engineering. The beams were tested under 4-point load scheme until failure were carried out. This scheme allowed the evaluation of the necessary parameters to proceed with the evaluation of the structural behavior of the beams, namely in terms of the elastic phase, the development of cracking and plastification, including ultimate strength, ductility and beam failure. It can be concluded that beams constructed with metakaolin offer a viable alternative to cement beams, exhibiting comparable structural behavior and often displaying equivalent or higher strength values. For instance, in relation to yielding loads, white metakaolin beams exhibit an average reduction of approximately 10%, while brick-colored metakaolin beams show similar values (with a non-significant reduction of 1.5%). Notably, metakaolin beams demonstrate distinctive behavior compared to cement beams concerning cracking loads, showcasing an average reduction of approximately 45%. In terms of elastic flexibility under bending, metakaolin beams also exhibit discernible differences in comparison to cement beams. The average deflection at the yield point is 30% higher for white metakaolin beams and 13% higher for brick-colored metakaolin beams. •Metakaolin alkali-activated material for construction of beams.•Experimental analysis of behavior of beams under bending.•Elastic phase behavior; Cracking development phase; Plasticization phase.•Cracking load; Yielding load; Ultimate load; Failure.•Confrontation with OPC beams; Comparing loads, displacements and stiffness.