Optimization of eco-friendly materials by alkali activation of the sewage sludge ash (SSA) to reduce carbon footprint

Figures & data

Table 1. Chemical oxide composition for SSA and GGBS.

Item	GGBS	SSA
SiO2	33.08	34.02
Al2O3	9.96	8.78
Fe2O3	0.954	11.8
CaO	40.1	20.3
MgO	4.18	2.53
K2O	0.722	1.18
Na2O	0.58	0.808
P2O5	0.0498	6.02
TiO2	0.685	1.86
SO3	2.13	11
MnO	4.11	0
LOI	0.1	0.57
Total	99.94	99.975

Table 2. The studied mixes composition containing GGBS and SSA materials.

Mix	GGBS %	SSA %	SH: SS %	Calcium Hydroxide %	Water (By mass)
A1	70	20	10:10	10	0.24
A2	70	20	5:10	10	0.24
A3	70	20	10:05	10	0.24
A4	70	20	5:05	10	0.24

Figure 1. The X-ray diffraction patterns of slag and SSA materials and geopolymer specimens. (Q: Quartz, C–S–H: CaH₂O₄Si, N: Anhydrite, AK: Akermanite, A: Albite, H: Hematite and Z: Zeolite)

Figure 2. FTIR spectra of GGBS and SSA raw materials and geopolymer specimens (cured at 90 days) with different percentages of alkaline activator [1: Stretching vibration of O–H bond, 2: Bending vibration of H–O–H, 3: Stretching vibration of CO₂, 4: Asymmetric stretching vibration of (T–O–Si), 5: Symmetric stretching vibration of (Si–O–Si), 6: Stretching vibration of Carbonate 7: stretching vibration of (Si–O), 8: stretching vibration of (Fe–O), 9: stretching vibration of [(N, C)–A–S–H], 10: stretching vibration of (C–S–H) and 11: Zeolite formation].

Figure 3. SEM micrographs of A1, A2, A3 and A4 geopolymer pastes at 90 days.

Figure 4. Compressive strength for hardened geopolymer specimens.