Setting time and microstructure of Portland cement-bottom ash–sugarcane bagasse ash pastes
Monatsh Chem
Setting time and microstructure of Portland cement-bottom ash-sugarcane bagasse ash pastes
Aniruj Akkarapongtrakul 0 1 2 3
Phongthorn Julphunthong 0 1 2 3
Thanongsak Nochaiya 0 1 2 3
0 Department of Civil Engineering, Faculty of Engineering, Naresuan University , Phitsanulok 65000 , Thailand
1 Department of Physics, Faculty of Science, Naresuan University , Phitsanulok 65000 , Thailand
2 & Thanongsak Nochaiya
3 Research Center for Academic Excellence in Applied Physics, Naresuan University , Phitsanulok 65000 , Thailand
Bottom ash (BA) and sugarcane bagasse ash (SCBA) are by-products from power plants and the sugar industry and they have a great potential to be used in greenconcrete structure applications. This study reports the effects of BA and SCBA on the properties of Portland cement (PC) pastes and mortars as cement replacement, by up to 20 percent by weight. All mortars had a water to binder ratio (w/PC ? BA, w/PC ? SCBA, and w/PC ? BA ? SCBA) of 0.5. Normal consistency, setting time, compressive strength, and microstructure (using scanning electron microscope, SEM) were systematically investigated. The results showed that the water requirement for a normal consistency was decreased with increasing BA content. The addition of SCBA, on the other hand, caused the water requirement to increase. The initial and final setting times of all pozzolan mixes were longer when compared to that of PC mix. The compressive strengths of all mixtures with BA were similar to that of the PC mix at 90 days. In addition, the SEM micrograph of pastes confirmed a good pozzolanic reaction between ash particles and Portland cement, resulting in an increase in the compressive strength of the mortars, especially after a period of time (more than 28 days).
Graphical abstract; Bottom ash; Sugarcane bagasse ash; Pozzolanic reaction; Hydration reaction
Introduction
Cement is the principal material used in the production of
concrete, which is the most important material in the world.
Concrete forms the basis of the construction industry today,
but it emits CO2 at a rate of 0.7–1.1 tons for every ton of
cement produced [
1
]. To reduce the amount of CO2
emissions from the cement industry, the manufacturing
process has to be improved to reduce its emissions of air
pollution [
2
]. Methods of reducing air pollution include
utilizating supplementary cementitious materials such as
natural pozzolans material [
3–5
].
Bottom ash (BA) is a by-product of the combustion of
coal in power plants and is formed when ashes at the
bottom of the furnace are consolidated. Bottom ash
particles are physically coarse, porous, granular, and graying
color. The world production of coal ash was approximately
459 million tons in 1992 [
1
] while the output of lignite BA
at Mae Moh power plant in the north of Thailand is about
0.8 million tons per year [
6
]. Many researchers have
reported that BA contains a high silica and alumina
contents similar to fly ash. Furthermore, it has been reported
that the pozzolanic reactivity BA may improve the
compressive strength of concrete [
7–9
]. Several researchers
[
10, 11
] found that grinding BA can increase its pozzolanic
activity in the concrete and make it suitable for use as a
partial replacement in Portland cement.
Sugarcane bagasse ash (SCBA), which is a by-product
of the burning of sugarcane bagasse from the sugar
industry, has recently been accepted as a pozzolanic
material and can be used as a supplementary material in
cement-based materials [
12–16
]. However, the SCBA is a
pozzolanic material with high silica content, which could
also be used as a pozzolan [
15
]. This ash is generally
disposed in landfills every day, leading to environmental
problems in the region. Since the SCBA received from the
sugar industry has a large particle size and high porosity,
Fig. 1 Normal consistency of
PC containing BA and SCBA
paste
the concrete made with it needs higher water content that
gives the concrete lower mechanical properties. However,
when SCBA is ground into small particles, the properties of
the cement-based materials containing ground SCBA
improves significantly [
17
]. Ganesan et al. [
15
] reported
that the SCBA was an effective mineral admixture, with
20% by weight of the binder as optimal replacement ratio
of cement. The 28- and 90-day compressive strengths have
been higher than that of the mix without SCBA.
The relationship between the microstructure and
compressive strength of BA and SCBA blended cement is not
well reported. Consequently, this research investigated the
effect of ground BA and SCBA on the microstructure,
setting time and compressive strength of pastes and mortars
and compared them to the PC control mix. This knowledge
could be beneficial and used commercial to incorporate
these wastes products into concrete, leading to a reduction
in the amount of cement used and environmental problems
associated with cement production.
Results and discussion
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