A S t u d y o n t h e H y d r a t i o n C h a r a c t e r I s t I c s
645
A STUDY ON THE HYDRATION CHARACTERISTICS OF EAF
REDUCING SLAG BY THE USE OF GYPSUM
Ji-Ho Kim
1*
, Jin-Man Kim
2
, Sun-Mi Choi
3
1
Dept. of Architectural Engineering, kongju National University, Republic of Korea
2
Dept. of Architectural Engineering, kongju National University, Republic of Korea
3
Dept. of Architectural Engineering, kongju National University, Republic of Korea
Abstract
CA minerals manufactured by steel industry byproducts show very rapid hydration
characteristics when contacting with water; however, after passing a certain time, they
no longer show the hydrate characteristics. This is due to form the waterproofing CAH
gel films around the particles to block the water and not to hydrate any more. In order to
solve this problem, we tried to make continuous hydration environment on the particles
of EAF reducing slag by the mixture of gypsum.
According to the results of this experiment, when gypsum is mixed with about 30%, the
hydration heat is falling up to 60
℃
at the early age within 1hour, the hydration index to
be improved to 129%, and the change of length to be stable to low level.
Key words
: EAF reducing slag, gypsum, ettringite, rapid hydration characteristics
1. Introduction
Korea is one of the top 10 countries in the world for its greenhouse gas discharge for a
total of 620 million tons of CO
2
in 2007. In particular, the country has a high level ratio of
heavy chemical industry in steel, petro-chemical, and cement industries compared to
other advanced countries and the cement industry from the total CO
2
volume discharges
approximately 6% of total greenhouse gas. Therefore, in order to reduce the CO
2
generation volume in the cement industry, Korea has active facilitation of increasing the
mixed material for the Portland cement, expansion of mixed cement production ratio,
development research of cement alternative material, and others.
1)
In the meantime, one of the byproducts of steel industry, EAF reducing slag that contains
massive amount of f-CaO, which is known to have the hazard of expanded collapse that
causes recycling to be extremely difficult. However, as a result of advance research, the
chemical composition is similar to the regulated setting cement and f-CaO is very stable
through rapidly cooling. Also hydration activity is increased. So we confirmed the EAF
Reducing slag to be inorganic binder as cement replacement. However, in the advanced
studies, the CAH gel membrane that has high initial thermal hydration and continuous
hydration was formed to generate the problem of low long-term strength and low volume
stability.
Therefore, this study was undertaken to supplement problems in the inorganic binder of
the atomizing EAF Reducing Slag powder that was displayed in the advanced studies.
The gypsum was added to the atomizing EAF Reducing Slag powder to generate the
expandable ettringite and it was intended to build up the environment for continuous
hydration reaction for the fine powder by continuously supply the moisture into the fine
powder by destroying the CAH gel membrane.
