Mechanical and durability assessment of sustainable paving blocks incorporating micro-sized rice husk ash and seawater

Eco-friendly paving blocks can reduce Portland composite cement consumption and freshwater demand while utilizing agricultural residues. This study investigated paving blocks incorporating micro-sized rice husk ash (mRHA) as partial cement replacement and seawater as a mixing and/or curing medium. Mixtures containing 0%, 10%, 20%, and 30% mRHA, with selected ground RHA comparisons, were evaluated based on compressive strength, water absorption, ultrasonic pulse velocity, abrasion resistance, acid resistance, embodied CO2 emissions, and production cost. The 10% mRHA mixtures exhibited the most balanced performance under zero-slump production conditions. At 28 d, mRA-ST achieved 14.30 MPa compressive strength and 8.84% water absorption, meeting SNI Grade C requirements for pedestrian applications. At 56 d, strengths reached 19.14–19.44 MPa for mRHA mixtures. The seawater-mixed 10% mRHA mixture reduced estimated CO2 emissions and production cost, indicating potential for sustainable pedestrian paving applications.ABBREVIATIONS: AWL, Abrasion Weight Loss; BFS, Blast Furnace Slag; BLA, Bamboo Leaf Ash; CCA, Corn Cob Ash; CH, Calcium Hydroxide; C-S-H, Calcium Silicate Hydrate; CS, Crushed Stone; FA, Fly Ash; FM, Fineness Modulus; gRHA, Ground Rice Husk Ash; ITZ, Interfacial Transition Zone; LOI, Loss on Ignition; NPOFA, Nano Palm Oil Fuel Ash; mRHA, micro–sized Rice Husk Ash; OPC, Ordinary Portland Cement; PCC, Portland Composite Cement; POFA, Palm Oil Fuel Ash; RHA, Rice Husk Ash; RH, Rice Husk; RRHA, Raw Rice Husk Ash; RS, River Sand; SCMs, Supplementary Cementitious Materials; SEM, Scanning Electron Microscopy; SF, Silica Fume; SNI, Standar Nasional Indonesia; SSD, Saturated Surface Dry; SWSSC, Seawater Sea–Sand Concrete; UPV, Ultrasonic Pulse Velocity; UPOFA, Ultrafine Palm Oil Fuel Ash; WA, Water Absorption