Hydration and Microstructure of Steel Slag as Cementitious Material and Fine Aggregate in Mortar

Abstract

Due to the low hydration activity and poor volume stability, extensive steel slag utilization is restricted. In this paper, the hydration process and microstructure of alkali-activated materials with steel slag as a cementitious material and fine aggregate were studied. The phase composition and micro-morphology of hydration products were measured using XRD, NMR and SEM. The response relationship between microstructure and mechanical properties during hydration was revealed. The results show that the main hydration products of the alkali-activated steel slag powder-granulated blast furnace slag powder cementitious system are Ca(OH)2 and calcium aluminosilicate hydrate (C-A-S-H) gel. With the progress of hydration, the amount of calcium silicate hydrate (C-S-H) gel and the average molecular chain length increase, Al[4]/Si decreases, while C/S increases first and then decreases, and the structure of cement paste becomes much more compact. The interface between steel slag sand and cement paste is denser than that of river sand, since the hydration occurs on the surface of steel slag sand, which leads to the formation of C-A-S-H gel and Ca(OH)2. As a result, the compressive strength of concrete prepared by steel slag sand is higher than that of river sand with the same mix proportion.

A Review of the Influence of Steel Furnace Slag Type on the Properties of Cementitious Composites

“…High pH solutions will accelerate the hydration of SFS [39], so instead of using it as an SCM in portland cement composites, SFS has also been considered for alkali-activated binders. Favorable performance has been reported for alkali-activated binders using LMF slags [40][41][42][43], EAF slags [43], BOF slags [44], and stainless steel slags [45][46][47][48]. BOF and LMF slags have also been suggested as activators for GGBFS pastes [49,50].…”

Effect of acid‐activation on CaO existential state and reactive properties of hot‐splashed steel slag in cement‐based materials

“…It can be seen from Figure 6 that the autoclave expansion rates of test specimens of the three groups increase gradually with the increase in their SSP content. When the SSP content was lower than 20%, the autoclave expansion rates of three groups were low and the soundness was perfect 32 . When the SSP content increased to 30%, the autoclave expansion rates of groups A and B were 0.568 and 0.501, respectively.…”

“…When the SSP content was lower than 20%, the autoclave expansion rates of three groups were low and the soundness was perfect. 32 When the SSP content increased to 30%, the autoclave expansion rates of groups A and B were 0.568 and 0.501, respectively. Although the specimens had not broken, the autoclave expansion rates had exceeded the standard (the autoclave expansion rate ≤0.5%).…”

“…Recently, thermal activation has also been extensively explored. At thermal activation, such as steam and autoclaved treatment, the hydration rate of SS can be accelerated, while the pore structure of concrete will be loose and porous, 32 which brings negative impacts to the durability of concrete.…”

Effects of aircraft operating fluids and environmental thermal fatigue on fly ash and steel slag based cementitious composites

“…Steel slag (SS) aggregates which are chemically similar to cement, can help prevent uneven expansion in cement-based materials, consequently improving its residual performance when exposed to higher temperatures 18 . Also, these fine aggregates were previously found to form a very strong bond with the surrounding matrix because of the partial hydration reaction on the surface of the SS particles 19 , 20 . Therefore, a reduction in the ingress of deleterious fluids can be expected.…”