237 / 2022-06-15 09:00:56

Effect of Using Biomass Wood Ash in a Geopolymer Mortar System as a Partial Substitute for Fly Ash on Engineering Properties

Biomass Wood Ash; Hybrid industrial by-products; Geopolymer Mortar; Mechanical properties

Research on biomass energy has become very popular due to its attractive properties such as being renewable and reliable. However, solid waste products coming from biomass energy facilities are still a significant issue to deal with. Therefore, one of these solid waste products Wood Ash (WA) which is an inorganic and organic residue that remains from burning the forestry products, has been started to use in concrete production studies. In this paper, a geopolymer mortar mix design was prepared to evaluate the suitability of the inclusion of WA as a partial replacement material for Fly Ash (FA) in the blended geopolymer mortars. Specimens were named in Table 1 as W0, W10, W30, and W50 according to the four different binder replacement percentages of 0%, 10%, 30%, and 50% respectively. (Table 1.) To observe the effect of wood ash replacement on the engineering properties, compressive strength test, flexural strength test, XRD analysis, and TGA analysis of geopolymer mortar specimens with blended FA and WA at 1-3-7 days of curing age were evaluated and studied.



Compressive strength and flexural strength results showed that the strength properties of all blended geopolymer mortar specimens were higher compared to the control specimen (W0). W0 specimens showed increasing values from 1 day to 7 days of curing age. However, W10 and W50 specimens demonstrated similar strength values at all curing ages, only W30 specimens showed a higher compressive strength value on 7 days of curing age than 3 days of curing age. (Fig 1.) On the other hand, even though W10, W30, and W50 specimens demonstrated similar flexural strength values until 3 days of curing, both W30 and W50 specimens showed decreasing flexural strength values from 3 days of curing age to 7 days. As a result, only W10 specimens reached to highest at 7 days of curing with an increasing trend. (Fig 2.)



The intensity of the main quartz peak at 26.57 2θ increased with the 10% WA replacement however higher than 10% WA replacement made the main quartz peak decrease.  At 7 days of curing age, XRD results confirmed the formation of mullite, C–S–H (II) gel, and Al-tobermorite phases for mortar specimens containing 30% and 50% of WA while C–S–H (II) gel was not observed for W0 and W10. (Fig 3.)



According to the thermogravimetric analysis (TGA) graph of geopolymer mortar specimens at 7 days, W10 specimens observed the least weight loss whereas the highest mass loss was observed in W50 samples until 1000°C.