Abstract
To clarify the role of steel slag powder in blended cement, steel slag powders with different amounts and particle sizes were mixed into blended cement and the inert quartz powder was selected as the reference. The influences of steel slag powder with different amounts and particle sizes on the hydration and hardening properties of blended cement were studied from hydration heat, nonevaporable water content, porosity, hydration products, and strength. The results show that the influence coefficient of nonevaporable water content (ՓWn) of blended cement paste is in an exponential relationship with the amount of steel slag powder. Moreover, at a dosage of 30%, ՓWn of blended cement gradually decreases with the increase of steel slag particle size. Both the early and late compressive strengths of blended cement are in a binomial relationship with the amount of steel slag powder. The influence coefficient of steel slag powder on the compressive strength of blended cement is negative at the age of 3 days, whereas it is positive at the age of 28 days. The chemical filling effect of 30% steel slag powder with different particle sizes in the blended cement paste is very small, only 1.13%–5.06%. The hydration products of blended cement containing steel slag are mainly amorphous C-S-H gels and platy Ca(OH)2, and their density are consistent with the law of their porosity.
Highlights
It is well known that cement-based material is a nonhomogeneous and multiphase porous material [1,2,3]. e pore structure and hydration reaction characteristics are two key factors that affect the overall performance of cement-based materials [4,5,6,7]
According to a lot of scholars’ research, the influences of supplementary cementitious materials components on the properties of cement-based composites include two aspects: chemical action and the physical action [11,12,13]. e chemical action is not related to only the intrinsic activity of the supplementary cementitious component itself and its interaction with cement clinker, while the physical action is mainly related to the filling role of the supplementary cementitious component on the system and effect on the pore structure [14,15,16,17,18]
The cement clinker firstly starts hydration and hardening reaction, resulting in the formation of the system framework by the hydration products [25, 29, 30]. e effect of steel slag as a supplementary cementitious component on the hydration and hardening of blended cement includes two aspects, i.e., the filling role and the hydration effect. e former leads to the change of pore structure, whereas the latter is reflected in the change of hydration degree of composite cementitious materials
Summary
It is well known that cement-based material is a nonhomogeneous and multiphase porous material [1,2,3]. e pore structure (including porosity and pore size distribution) and hydration reaction characteristics (including hydration degree, hydration product type, and quantity) are two key factors that affect the overall performance of cement-based materials [4,5,6,7]. E effect of steel slag as a supplementary cementitious component on the hydration and hardening of blended cement includes two aspects, i.e., the filling role and the hydration effect. Most of the current studies in literature focus on the mechanical properties and application effects of steel slag powder in cement and concrete, less paying attention to directly reveal the physical effect (namely, filling role) and chemical effect (namely, hydration role) of steel slag powder with different particle sizes or additional amounts in blend cement. E influences of steel slag powder with different amounts or particle sizes on the hydration and hardening properties of blended cement were studied from hydration heat, nonevaporable water content, porosity, hydration products, and strength. The inert quartz powder, whose particle size distribution is similar to that of the steel slag powder, was selected as the reference so as to initially reveal the role or contribution of steel slag powder in the hydration and hardening of blended cement. e results of this study guide how to select or determine the best particle size or addition amounts of steel slag powder in blended cement, which is meaningful or valuable for the efficient application of steel slag powder building materials
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