Fluidized Bed Coal-Bark Fly Ash Geopolymer With Additives Cured at Ambient Temperature

Abstract

In this research, the properties of fluidized bed coal-bark fly ash geopolymer mortar containing additives viz., ordinary Portland Cement (OPC) and micro silica (MS) were studied. The fluidized bed coalbark fly ash was a waste from a power plant boiler in Khon Kaen, Thailand. The geopolymer mortar was made from fluidized bed coal-bark fly ash, sand, sodium silicate solution, NaOH solution, and additives. The additives were used to replace the fluidized bed coal-bark fly ash at the level of 0 -15 % by weight. The mortars with liquid alkaline/ash ratios of 0.9-1.4, sodium silicate/NaOH ratios of 0.33-3.00, NaOH concentrations of 5-15 molars, OPC and micro silica contents of 0 -15 % by weight of fly ash, and curing at ambient temperature were tested. The geopolymer mortars with 28-day compressive strengths between 5.5 and 27.0 MPa and densities between 1970 and 2175 kg/m 3 were obtained. The addition of OPC and micro silica enhanced the strength development of geopolymer mortar with the optimum OPC content of 10 % and micro silica content of 15 %. It is shown here that the fluidized bed coal-bark fly ash geopolymer mortar containing OPC and micro silica as additives with ambient temperature curing possesses sufficient strength. The use of this product can reduce the energy consumption in cement production and increases the sustainability of construction industry.

Utilization of Fly Ashes from Fluidized Bed Combustion: A Review

“…It can be stated that FBCFA could be suitable for an alkali-activated material precursor, but often co-binders or pre-treatment of fly ash is needed. The studies acknowledged the low reactivity of FBCFAs in alkali-activation due to their crystalline nature, but compressive strengths of 10-30 MPa were often achieved [130][131][132][133][134][135][136][137][138][139], which is enough for most mortar-and paste-type applications. Even up to 50 MPa was reached [140] when most of the binder was slag-based and fly ash amount was 10-20 wt %.…”

Influence of the Composition and Curing Time on Mechanical Properties of Fluidized Bed Combustion Fly Ash-Based Geopolymer

“…FBC ash-based geopolymers are able to achieve high values of basic mechanical properties such as compressive strength, gaining from 40 up to over 70 MPa [ 38 , 39 , 40 , 41 ]. However, many studies report smaller values of compressive strengths, especially when FBC ash is the only raw material [ 42 , 43 , 44 , 45 , 46 ]. Some studies describe the possibilities of enhancement of the reactivity of FBC ash leading to a higher strength, for instance by an alkali fusion pretreatment [ 45 , 47 ] or high-shear granulation [ 48 ] of raw material.…”

“…Some studies report preparation of geopolymers using FBC ash as the only raw material [ 38 , 39 , 42 , 43 , 44 , 45 , 46 , 49 ]. However, it is also popular to blend FBC ash with a variety of additional materials such as kaolinitic clay, pulverized coal combustion fly ash, metakaolin, cement, or blast furnace slag [ 39 , 40 , 41 , 43 , 46 , 47 , 48 , 50 , 51 ].…”

“…In addition, most of the studies to date describe a material cured at elevated temperatures [ 42 , 43 , 44 , 45 , 49 , 50 , 53 , 54 ], while the current work presents the FBC fly ash geopolymer produced at ambient temperature, which is better for both ecological and economic reasons. The previous investigations were frequently based on geopolymers activated with a high NaOH concentration (10–15 mol/L) [ 40 , 41 , 42 , 43 , 44 , 46 ] while the following paper presents a good mechanical performance of a geopolymer activated with NaOH of a lower concertation (6 mol/L). Low concentration of an activator is another factor decreasing production costs and negative environmental impact.…”

Curing Time and Temperature Effect on the Resistance to Wet-Dry Cycles of Fly Ash Added Pumice Based Geopolymer

“…Fly ash and pulverized pumice are two materials that fulfill these conditions sufficiently. Fly ash which is a kind of industrial waste material captured in the chimney filters of coal-fired power plants is widely investigated for usage in geopolymer production and conventional concretes [14][15][16]. Pumice is an aluminosilicate type natural lightweight volcano rock which is similar molecular structure as fly ash.…”