The Results Of Air Permeability, Total Water Absorption, And Mortars

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Fig. 6 shows the results of air permeability, total water absorption, and voids. R mortars had lower permeability than the mortars with WTS. Air permeability of R was 1.13 x 10-13 m², a value 5 times higher than L60. The air permeability increased with increasing WTS content. The water absorption values ranged from 10.6% to 13.7%, and the voids from 9.6% to 12%. The results show that WTS replacement increased the porosity and permeability of geopolymer mortars. The geopolymer binders with WTS and the additional RHA became the mortars more consistent and difficult to mix and mold, and the entrapped air remained in the mortars.
Fig. 7 shows the capillary water absorption. The higher the WTS content in the mixture, the lower the capillary water
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The average penetrations measured in the specimens were: 78.0 mm (R), 58.5 mm (L15), 50.3 mm (L30), and 34.0 mm (L60).
The results show that R mortars had more capillary suction than mortars with WTS. According to Pavía and Treacy (2006), smaller the dimensions and more connected the pores, more evident are the capillary effects. The results of capillary tests show that the pores in R mortars had smaller dimension than WTS mortars and then the water suction was higher. The large pores in mortars with WTS difficult the capillary effect (Liu et al., 2011) and contributed to decrease the mechanical properties (Rovnaník, 2010).
Fig. 8 shows the R and L60 SEM images. Fig. 8a shows a dense matrix with some small pores distributed on material. Fig. 8b shows L60 matrix with higher porosity with larger voids when compared to R. These observations are in accordance with water absorption, voids and capillary water absorption results, which showed that the binder with WTS increased the porosity and decrease the capillary suction of the mortars (caused by the larger pores in sample). Both images revealed homogenous materials, indicating efficient mixing. Fig. 8c and Fig. 8d indicate a good bonding interface
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Conclusions

This study reports the partial replacement of MK by non-calcined WTS in the production of geopolymer with sodium silicate from RHA. The results showed that the properties of geopolymers binders are highly dependent on the WTS content in the mixture.
The binder with WTS increased the setting times, kinetics of temperature test showed low rates of geopolymerization reactions.
The workability and the mechanical properties of the geopolymer mortars decreased as the WTS content in the binder increased. The compressive strengths in all curing ages were higher than the minimum required for several types of building components. All of the mortars increased the mechanical properties with time, indicative of continuous reactions. The mortars with geopolymer binders with WTS showed larger voids and lower capillary suction when compared to reference mortars.
The findings of this experimental work show that it is technically feasible to make geopolymer with partial replacement of MK by WTS. RHA can be added to supply SiO2 to keep the molar ratios constant. It is possible to have good environmental benefits and to make an eco-friendly material using WTS and a sodium silicate solution from RHA.

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