Louisiana’s Sugarcane Bagasse Ash Utilization for Partial Cement Replacement in Concrete for Transportation Infrastructure Applications

This study evaluated the properties of sugarcane bagasse ash (SCBA) obtained from different production processes for use as partial replacement of cement: (1) minimally post-processed (MP) SCBA, obtained by sieving and grinding SCBA from Louisiana’s sugarcane field production; (2) fully post-processed (FP) SCBA, obtained by sieving, further burning under controlled conditions at temperature T, and grinding field-produced SCBA, denoted as FP-T; and (3) laboratory-produced (LP) SCBA, obtained by controlled burning at temperature T of bagasse fibers and grinding of the obtained ashes, denoted as LP-T. The temperatures of burning, T, for FP-T and LP-T SCBA were varied between 450 and 650 °C at 50 °C intervals. The significance of this study is the valorization of agricultural waste for the production of low-carbon concrete for transportation applications in Louisiana, and other locations where SCBA are produced from a low-efficiency boiler in a sugar mill. A comprehensive characterization of the different SCBA materials was conducted, including scanning electron microscopy (SEM)-energy dispersive X-ray spectroscopy (EDS), X-ray powder diffraction (XRD), laser diffraction particle size analysis, Chapelle’s test, strength activity index (SAI), loss on ignition (LOI), and moisture content. Experimental results showed that all LP-T and FP-T SCBAs met ASTM C618 chemical requirements and SAI requirements for Class N pozzolans. By contrast, MP SCBA did not meet these requirements, thus resulting in unsuitable SCM application. LP calcinated at 650 °C and FP calcinated at 450 °C exhibited the greatest SAI and SiO 2 + Al 2 O 3 + Fe 2 O 3 among LP-T and FP-T SCBAs, respectively. Based on a combination of properties and production practicality considerations, FP calcinated at 450 °C was identified as the most promising SCM-grade SCBA for large-scale production in Louisiana, and was used to further evaluate the fresh and hardened properties of concrete incorporating SCBA at 10%, 20%, 30%, and 40% cement replacement by mass. A decrease in workability as well as 28- and 90-day compressive strength with the increase in SCBA content was observed. However, the relative strength gain from 28 to 90 days and the 90-day surface resistivity increased with increments in SCBA dosage. Characterization of cement-SCBA paste through XRD and SEM revealed portlandite consumption and densification of the cementitious matrix from 28 to 90 days, thus suggesting the pozzolanic activity of SCBA.