Agricultural wastes with a high silica content, such as sugarcane bagasse ash (SCBA), are abundant and can be used as a supplementary cementitious material (SCM). Prior to burning the waste, previous studies have used acid treatments to remove metal impurities as well as increase the amount of silica that can be extracted. However, the chemical dangers associated with the use of acids at high concentrations are a deterrent to treatment as part of an eco-friendly process of adopting agricultural wastes as SCMs. In view of the chemical risks, the current study investigates the effect of performing treatments on sugarcane bagasse with a low concentration acid of 0.1 M on the early compressive strength of cement mortar. Mix proportions are prepared for all sample types, which are control samples with no SCM and samples with 5, 7.5, and 10 silica from untreated and treated SCBA as the SCM. After seven days of curing, the compressive strength of the samples was evaluated, and selected samples were scanned using a field emission scanning electron microscope (FESEM) to analyze their morphology. Cement replacement with 7.5 silica extracted from treated SCBA resulted in the highest compressive strength of 6.25 MPa, which is an increase of 46.72 from that of the control sample mix. Observation of FESEM micrographs revealed that high silica content resulted in compressive strength reduction owing to its disruption on the binding material microstructure. © 2023, The Author(s), under exclusive licence to Shiraz University.