INFLUENCE OF HYDROXYPROPYL METHYLCELLULOSE HPMC DOSAGE ON SETTING AND STRENGTH OF CEMENT MORTAR WITH PARAFFIN-TREATED SAWDUST

Incorporating sawdust into cement mortars can reduce their environmental footprint, but it is often accompanied by lower performance and increased variability. To date, the influence of hydroxypropyl methylcellulose (HPMC) dosage in mortars containing paraffin-coated sawdust at a fixed water-to-cement ratio remains scarcely documented. The objective of this study is to isolate and quantify, at a strictly fixed water-to-cement ratio (w/c = 0.40) and 2% paraffin-treated sawdust, the effect of HPMC dosages of 0%, 1%, and 2% (by cement mass) on setting times and 28-day mechanical strengths, with result dispersion treated as an explicit indicator of reproducibility. The experimental program includes Vicat setting-time measurements, three-point bending tests for flexural strength, and 28-day compressive strength tests, complemented by one-way ANOVA and Tukey’s post hoc procedure. HPMC delays setting: the initial setting time increases from 115 min (0%) to 150 min (1%) and 145 min (2%), while the final setting time increases from 165 min (0%) to 250 min (1%) and 240 min (2%). An optimum is observed at 1% HPMC (flexural strength: 4.56 ± 0.37 MPa; compressive strength: 29.68 ± 3.27 MPa), whereas 2% reduces compressive strength (25.04 ± 5.93 MPa) and increases dispersion. These results identify a practical formulation window for producing more reliable sawdust-modified mortars and support their relevance for sustainable construction.