African Design Magazine ADM #40 May 2018 | Page 50
TECHNOLOGY
THE INFLUENCE OF GROUND FLY ASH
ON CEMENT HYDRATION AND
MECHANICAL PROPERTY OF MORTAR
In this study, the ground fly ash is made of ordinary grade I fly ash by grinding.
Compared with grade I fly ash, the influence of ground fly ash on cement
hydration and mechanical property of mortar was investigated. The results
show that ground fly ash can improve the hydration of cement at all the ages
compared with grade I fly ash, and not only does its pozzolanic reaction start
earlier, but the reaction degree is higher and the speed is quicker.
Jingjing Feng, 1 Jianwei Sun, 2,3 and Peiyu Yan 3
1
College of Hydraulic and Civil Engineering, Shandong Agricultural University, Tai’an, Shandong 271018, China
2
School of Mechanics and Civil Engineering, China University of Mining and Technology, Beijing 100083, China
3
Department of Civil Engineering, Tsinghua University, Beijing 100084, China
Correspondence should be addressed to Jingjing Feng; [email protected]
Academic Editor: Evangelos J. Sapountzakis
Source: Advances in Civil Engineering, vol. 2018, Article ID 4023178, 7 pages, 2018.https://doi.org/10.1155/2018/4023178.
B
efore three days, the contribution
of ground fly ash to the strength
is mainly due to physical filling
and microaggregate effect. After that,
the contribution of pozzolanic effect to
the strength becomes obvious and can
significantly increase the compressive
strength after 60 days and the flexural
strength after 28 days. The ground fly ash
is better than grade I fly ash to optimise
the pore structure of hardened pastes.
It can significantly reduce the number
of harmful pores (>20 nm) and increase
the number of harmless pores (<20 nm),
which refines the pore structure and
makes the structure denser.
1. Introduction
Fly ash is a by-product from the residue
of coal combustion, and it is a kind of
pozzolana. Fly ash tends to be spherical
with micrometres to millimetres particles
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AFRICAN DESIGN MAGAZINE © | MAY 2018
and has a relatively high reactivity
depending on the chemical formation
of its individual particle [1]. These made
the demand of fly ash grow steadily
over the past 30 years [2, 3], especially
in concrete and construction industries
[3, 4]. Therefore, fly ash has become the
most widely used mineral admixture
in all kinds of concrete [5, 6]. The main
chemical components of fly ash are
Al2O3, SiO2, and Fe2O3 [7] and fly ash
consists of a major amorphous phase
and a small amount of crystalline phases
[8, 9]. At early stages of hydration, fly ash
particles often act as microaggregates
to fill the pores of binders and nuclei
for the hydration products [10], while at
later stages, the chemical effect of fly ash
works. Fly ash can react with Ca(OH)2,
which is a product of cement hydration,
to form C–S–H gel [11, 12]. This is the
so-called pozzolanic reaction. The