Sewage sludge ash: A comparative evaluation with fly ash for potential use as lime-pozzolan binders

Abstract

The disposal of sewage sludge ash (SSA) has become an environmental issue due to the limited available landfilling space. This study aims at applying the finely-ground sewage sludge ash (FSSA) with quicklime and hydrated lime respectively to develop a new type of lime-pozzolan system and study the effects of different types of lime on the mechanical properties of the systems. A traditional pozzolanic material (i.e. coal fly ash (FA)) was also used to compare with the FSSA. Multiple techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA) were used to assess the hydration kinetics and microscopic characteristics of the lime-pozzolan systems. The results showed that the quicklime system exhibited lower strength than the hydrated lime system, which was due to its lower reaction degree with the FSSA and the higher porosity caused by the expansion during the vigorous hydration reaction of quicklime. Compared to FA, the FSSA attained higher strength for the whole curing period (up to 90 d) in the lime system due to the highly porous nature of FSSA leading to a lower effective water to binder ratio. However, in the hydrated lime system, due to the higher overall pozzolanic activity of FA, its long-term strength values gradually improved. Besides, calcium phosphate hydrate crystals were detected by XRD in the FSSA; while some clinotobermorite was found in the FA both from XRD and SEM, which might govern the strength gain in the lime-FA system. Overall, the application of FSSA as a pozzolan in the lime-pozzolan system could be a promising option to both relieve the waste disposal pressure and provide a potential sustainable construction material.

Highly Effective Adsorption Process of Ni(II) Ions with the Use of Sewage Sludge Fly Ash Generated by Circulating Fluidized Bed Combustion (CFBC) Technology

“…However, X-ray diffraction analysis should reveal the same crystalline phases of the substances. Similar results of XRD analysis have been found in the literature [ 30 , 31 , 32 ].…”

Mechanical Properties and Microstructure of Low Carbon Binders Manufactured from Calcined Canal Sediments and Ground Granulated Blast Furnace Slag (GGBS)

“…It can be observed that the CSS15% mortar generated 23.21 J/g of heat at around 15 h, and the CSS20% mortar generated 18.64 J/g of heat at around16 h, while the CS and CSS10% mortars generated 12.25 J/g and 12.51 J/g of heat at around 18 h, respectively. It should also be noted that the sharpness of the thermal peak can be attributed to the high stiffness of calcined sediment and slag [59]. The highest cumulative heat of hydration is obtained for the CS and CSS10% mortars with 329.45 J/g of heat and 306.66 J/g of heat, while 274.60 J/g of heat is reported for reference mortar (C).…”

“…The second peak of portlandite (for Ca(OH) 2 ) around 480 • C for the control paste (C) is much stronger than in the other mixture pastes (pastes made with slag and calcined sediment), indicating a larger quantity of Ca(OH) 2 compared to the other mixtures pastes. The presence of portlandite in hydrated mixtures can play a major role in pouzzolanic reaction [59,60]. Finally, the decarbonation is observed with a small peak for the different pastes above 900 • C. The cement paste (C) has a much weaker decarbonation peak compared to the other mixtures due to the lower content of calcite CaCO 3 .…”

Optimization of an Eco-Friendly Hydraulic Road Binders Comprising Clayey Dam Sediments and Ground Granulated Blast-Furnace Slag

“…The consumption of portlandite in blended cement by supplementary materials is a good indication of the pozzolanic potential of the used materials [39]. Several previous studies have reported similar behaviors [39,47,48]. 16 and 17 show the Inner C-S-H, which is a thin light grey (uniform) layer that surrounds the unreacted cement grains.…”