Drying shrinkage and strength of GGBS and sawdust incorporated OPC mortar

Sawdust is an excellent bio based waste material that can be effectively used in replacing fine aggregate in concrete or mortar. The available research output related to sawdust incorporated concrete is limited; however, valuable information on strength of sawdust concrete can be found. This study aimed to obtain compressive strength, flexural strength and drying shrinkage of GGBS and sawdust incorporated mortar. The maximum size of fine aggregate and sawdust is of 2.36 mm and 1.18 mm, respectively. Mortar specimens were prepared by changing the amount of GGBS as 0%, 50% and 70%. The amount of sawdust was kept constant. The measured density of sawdust mortar shows a significant difference with initial assumed density which questions the accuracy of the initial mix design of sawdust mortar. Water absorption in sawdust mortar at 7 days is approximately 14% with a slight decrease at 28 days. The highest compressive strength is achieved when the amount of GGBS replacement is 50%. The addition of extra alkali has not shown additional strength development or visible chemical reaction with sawdust. Drying shrinkage at 28 days in all specimens is in the range of 200-400 microns; however, it is increasing up to 1000 microns at 90 days. The results show that the sawdust replacement in mortar could still maintain some structural properties; however, the effect on durability properties should be investigated further.