Capability of R3 test to evaluate pozzolanicity of ground raw and calcined sugarcane bagasse ashes

Sugarcane bagasse ash (SCBA) is a by-product of sugar and ethanol production and is largely disposed in landfills. Although the SCBA feasibility as pozzolanic material has been widely explored, traditional screening reactivity tests have shown inappropriate to evaluate alternative supplementary cementitious materials (SCM). The R3 test is a novel method to assess the reactivity of SCMs in a simplified system without Portland cement. This work aims to investigate the capability of the R3 test methods to measure the reactivity of ground raw (SCBA) and calcined (SCBA600) sugarcane bagasse ashes benchmarked against 2,7, 28, and 90-days compressive strength of mortars using SCM as cement replacement. Besides SCBA specimens, two traditional SCMs, silica fume (SF) and metakaolin (MK), were also evaluated. As expected, the R3 test obtained the same order regarding the reactivity of the studied SCMs for the three methods, from the highest to the lowest MK > SF > SCBA600 > SCBA. Regarding the R3 heat release evolution, raw and calcined sugarcane bagasse ashes had a very analogous trend and slow reaction of hydration. In R3 bound water results, a more prominent distinction was verified between SCBA and SCBA600. Moderate to poor correlations are observed between the R3 CH consumption and the portlandite content of cementitious pastes. The benchmark test confirmed the slow reaction of the studied ashes, presenting a significant increase in compressive strength only after 28 days. R3 test results correlate well (R2 ≥ 0.85) with the relative compressive strength of mortars at 7 days. Only a moderate relationship exists between the R3 tests and the relative strength at 28 days, decreasing at 90 days. This contribution indicates that the R3 test methods are sensible to evaluate the early age pozzolanic reactivity of SCBA and SCBA600.