Bending strength characteristics of sawdust- crete laminated composite slab

Abstract

This paper presents the bending characteristics of sawdust-crete laminated composite slab. The materials used in the laboratory experiments include: Ordinary Portland Cement, river sand, gravel, sawdust, plywood, nails, reinforcement bars, stirrups and water. Manual mixing method was adopted and all sawdust-crete ingredients were batched by weight. A total of 48 slabs of size 1200mm x 1000mm x 100mm, 1200mm x 1000mm x 125mm, 1200mm x 1000mm x 150mm and 1200mm x 100mm x 175mm were cast for flexural strength from the mix ratios 0.75:1:2:2 and 0.75:1:3:3. Out of the 48 slabs cast, 32 were produced from sawdust-crete laminated composite (with 12.5mm and 20mm as the thickness of plywood for the laminate), 8 were produced from normal concrete ingredients (coarse aggregates, fine aggregates, cement and water) with 10mm rebar and mix ratio of 0.45:1:2:4. The remaining 8 slabs were made from plain sawdust-crete with mix ratio of 0.75:1:3:3. During the experiment, the maximum deflection for the slab was observed to occur at the slab with size 1200mm x 1000mm x 100mm no matter the core content used to produce the slab while the minimum deflection occurs at the size 1200mm x 1000mm x 175mm. The deflection of slab decreases with increase in slab thickness while flexural strength increases with increase in slab thickness. The flexural strength results of slab were compared by percentage difference and the results shows that there is significant difference between the two sets of slabs. Also, by comparing the results of plain sawdust-crete slab to that of sawdust-crete laminated composite slab, the result show that laminates with plywood increases flexural strength up to 68.4%. Conclusively, laminated sawdust-crete can be used for slabs that is not carrying too much load like residential houses.