Effect of sewage sludge ash on mechanical and microstructural properties of geopolymers based on metakaolin

Abstract

This paper explored reported the effect of sewage sludge ash (SSA) on the mechanical and microstructural properties of geopolymers based on metakaolin (MK) involving two different SiO2/Na2O molar ratios (0.8 and 1.6), two temperature curing conditions (25°C and 65°C) and various ages of curing (1, 3, 7, 14, 28, 90 or 180 days). The geopolymers tests were characterized performed using different techniques: as X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and compressive strength of mortars. Tests were performed for both high (65°C) and room (25°C) temperature curing conditions lasting for 1, 3, 7, 14, 28, 90 or 180 days. The geopolymeric samples were activated using sodium hydroxide and sodium silicate solutions using two different SiO2/Na2O molar ratios (0.8 and 1.6). The compressive strength tests showed that the replacement of MK by SSA in 10 wt.% when cured at 25 °C with the highest SiO2/Na2O molar ratio reaches similar compressive strengths after 14 days of curing compared to the samples with only MK, which reached a maximum compressive strength of 50.8 MPa at 180 days. The FTIR analyses carried out in the geopolymer pastes with SSA (10 wt.% of SSA and 90 wt.% of MK) showed a formation of N-A-S-H gels in the samples cured at 25 °C. The microstructural studies by XRD, TGA and SEM pointed out the formation of a crystalline phase as Na P-type zeolite in MK/SSA based-geopolymer pastes cured at 65 °C, which explained the loss of compressive strength of the samples cured at high temperature. However, the SSA retarded the crystallization process in the MK basedgeopolymer.

Photocatalytic Degradation of Methylene Blue from Aqueous Medium onto Perlite-Based Geopolymer

“…is micrograph revealed the formation of aluminosilicate gel in the perlite structure. is change in the perlite morphology indicates the dissolution of the precursor particles by alkali solution and the formation of aluminosilicate gel in the structure of the raw material [24].…”

Evaluation of the long-term compressive strength development of the sewage sludge ash/metakaolin-based geopolymer

“…The waterglass/ binder mass ratio was set at 0.78 for all the mortars assessed in Step 1. A previous study (31), which evaluated the influence of the SiO 2 /Na 2 O molar ratio for the mortars containing 8 mol.kg -1 of NaOH, established that a SiO 2 /Na 2 O ratio of 1.6 offered the best compressive strength results.…”

“…The nomenclature for the mortars from Step 2 was simplified to MKx, considering that all of them present the same values of NaOH concentration and ε according to the given results from Step 1. In both Steps 1 and 2, all the geopolymeric mortars were prepared by maintaining the water/binder and sand/binder mass ratios at 0.6 and 2.5, respectively (31). Precursors (MK and SSA) were homogeneously mixed before adding the activating solution, which was cooled to room temperature (25°C).…”

“…Geopolymer systems seem to be another sustainable alternative for the immobilization of SSA. However, such an SSA application has not yet been properly explored, being found a few studies focused on this field (29)(30)(31).…”

Study on Solidification of Chromium-Containing Sludge With Alkali Slag Combined With Attapulgite

“…Geopolymer is an innovative alkali-activated gelling material, which is an inorganic polymer with excellent properties produced by clay and aluminosilicate at normal temperature (Lee &Lee 2015, Xia et al 2019). Compared with traditional cement, geopolymer has better mechanical properties and corrosion resistance (Istuque et al 2019). And through the mechanical properties and leaching level, the solidi cation e ciency can be analyzed intuitively (Zhang et al 2016).…”