Browsing by Author "Fanijo, Ebenezer O."

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    Alkali-silica reaction (ASR) in concrete structures: Mechanisms, effects and evaluation test methods adopted in the United States
    Fanijo, Ebenezer O.; Kolawole, John Temitope; Almakrab, Abdullah (2021-12)
    Alkali-silica reaction (ASR) and its associated deformation are major durability problems in concrete structures and was reported as far back as the 1940s by Stanton (2008) [1]. This deleterious reaction causes excessive expansion and cracks that can lead to severe degradation of the concrete structures. Despite the age-long discovery and numerous ASR studies, understanding the ASR mechanism remains challenging due to complex processes and reactions. This paper presents a review of ASR in concrete structures and details the factors associated with ASR, the reaction mechanism and chemistry, and its adverse effect on concrete structures. The alkalis in the pore solution, the reactive amorphous silica present in aggregates, and the presence of moisture (with other external climatic inputs) are the key factors responsible for ASR. The study also provides a critical assessment of the various test methods for ASR evaluation in the United States. A case study correlating the results (from the literature) of three prominent test methods was also carried out. From this review, the new miniature concrete prism test (MCPT) method was concluded to be rapid, reliable, and capable of determining the influence of aggregate reactivity, alkali availability, and exposure conditions as compared to other methods.
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    A Review of the Influence of Steel Furnace Slag Type on the Properties of Cementitious Composites
    Brand, Alexander S.; Fanijo, Ebenezer O. (MDPI, 2020-11-19)
    The type of steel furnace slag (SFS), including electric arc furnace (EAF) slag, basic oxygen furnace (BOF) slag, ladle metallurgy furnace (LMF) slag, and argon oxygen decarburization (AOD) slag, can significantly affect the composite properties when used as an aggregate or as a supplementary cementitious material in bound applications, such as concretes, mortars, alkali-activated materials, and stabilized soils. This review seeks to collate the findings from the literature to express the variability in material properties and to attempt to explain the source(s) of the variability. It was found that SFS composition and properties can be highly variable, including different compositions on the exterior and interior of a given SFS particle, which can affect bonding conditions and be one source of variability on composite properties. A suite of tests is proposed to better assess a given SFS stock for potential use in bound applications; at a minimum, the SFS should be evaluated for free CaO content, expansion potential, mineralogical composition, cementitious composite mechanical properties, and chemical composition with secondary tests, including cementitious composite durability properties, microstructural characterization, and free MgO content.
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    Stabilization of a Clayey Soil with Ladle Metallurgy Furnace Slag Fines
    Brand, Alexander S.; Singhvi, Punit; Fanijo, Ebenezer O.; Tutumluer, Erol (MDPI, 2020-09-24)
    The research study described in this paper investigated the potential to use steel furnace slag (SFS) as a stabilizing additive for clayey soils. Even though SFS has limited applications in civil engineering infrastructure due to the formation of deleterious expansion in the presence of water, the free CaO and free MgO contents allow for the SFS to be a potentially suitable candidate for clayey soil stabilization and improvement. In this investigation, a kaolinite clay was stabilized with 10% and 15% ladle metallurgy furnace (LMF) slag fines by weight. This experimental study also included testing of the SFS mixtures with the activator calcium chloride (CaCl2), which was hypothesized to accelerate the hydration of the dicalcium silicate phase in the SFS, but the results show that the addition of CaCl2 was not found to be effective. Relative to the unmodified clay, the unconfined compressive strength increased by 67% and 91% when 10% and 15% LMF slag were utilized, respectively. Likewise, the dynamic modulus increased by 212% and 221% by adding 10% and 15% LMF slag, respectively. Specifically, the LMF slag fines are posited to primarily contribute to a mechanical rather than chemical stabilization mechanism. Overall, these findings suggest the effective utilization of SFS as a soil stabilization admixture to overcome problems associated with dispersive soils, but further research is required.