Table 5.

Summary of representative studies on alkali-activated VA-based mortars.

Binder	Types of Activators/ Alkaline Solution		Aggregates (A)	Curing Conditions	Compressive Strength	Ref.
VA 1	NH 2, NS 3, Ms 4	S/B 5	A/B 6
Volcanic Tuff < 45 µm, specific gravity = 2.38	NH (10, 12, 14, 16 M)	0.35 0.45	River aggregates (0–2, 2–4 and 4–8 mm), A/B = 2	Curing in covered molds at 90, 120, 150 °C for 72 h, then samples were kept in laboratory conditions until the test day.	25.83 MPa at 90 days	Kantarci et al. [55]
	NS (Ms = 0.6, 0.7, 0.8, 0.9, 1.0) + NH (10 M)			Curing in covered molds at 90, 105, 120 °C for 72 h then samples were kept in laboratory conditions until the test day.	37.09 MPa at 90 days
VA < 200 µm, specific gravity = 2.62	NS + NH (12 M) Mass ratio of NS/NH = 2.4	0.45	Sand (specific gravity 2.55) A/B = 2	Room temperature (27 ± 3 °C) for 7-days 80 °C for 24 h The specimens after casting were demolded and keep at ambient temp until test performed.	37.9 MPa at 90 days	Djobo et al. [22]
VA, specific gravity = 2.29 SSA 7 = 6088 cm2/g	NH (2.5, 5, 7.5, 10, 12.5 M)	0.50, 0.54, 0.58	Fine aggregate (specific gravity = 2.76) A/B = 2.0	Pre-curing: 60 °C for 3 h in an oven before demolding Then oven at 80 °C (exposed, sealed and moist cured; 1, 3 and 7 days)	31.8 MPa at 7 days (exposed)	Ghafoori et al. [46]
					26.6 MPa at 7 days (wet)
					37.7 MPa at 7 days (sealed)
VA < 440 µm	NH Na2O/SiO2 * (0.15–0.30)	0.21	Sand (density 2.56 g/cm3) (40% by wt.)	Dry curing in the open air at 90 °C for 5 days	30 MPa at 28 days for a sample with Na2O/SiO2 molar ratio of 0.30	Lemougna et al. [36]

¹ Volcanic ash; ² NaOH; ³ Na₂SiO₃; ⁴ Modulus of silica; ⁵ Solution-to-binder ratios; ⁶ Aggregate-to-binder ratios; ⁷ Specific surface area. * Composition of the samples with five Na₂O/SiO₂ molar ratios synthetized from VA into a solution of NH in distilled water.