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Shotcrete materials
Published in Dudley Robert (‘Rusty’) Morgan, Marc Jolin, Shotcrete, 2022
Dudley Robert (‘Rusty’) Morgan, Marc Jolin
There has been some use of Ground Granulated Blast Furnace Slag (GGBFS) in shotcrete in North America, but mainly in areas where fly ash is not readily available. It is used for much the same reasons that fly ash is used in shotcrete. In concrete, GGBFS is often used at cement replacement values of 40% to as much as 70%. Wet-mix shotcrete with such high cement replacement value is now also being used in thick structural shotcrete applications because of thermal control requirements. It is possible in such shotcrete to keep peak temperatures in structural elements 1.0 to 1.8 m thick below 60°C, which is important in mitigating differential thermal stress-induced cracking. Care is, however, required in the shotcrete mixture design to provide a mix with suitable shootability and finishability (resistance to sagging or sloughing). Incorporation of hydrophilic natural microfibres (either cellulose or hemp-based) has been found to be important in this regard. A case history example of the use of such high volume slag shotcrete mixes in heavily reinforced structural shotcrete walls in an underground station is presented in Section 10.3. Performance requirements for GGBFS can be found in ASTM C989 and CSA A3001(in CSA, 2018).
Validation and application of a multi-phase hydration model for the back-analysis of properties of jet-grouted structures
Published in Günther Meschke, René de Borst, Herbert Mang, Nenad Bićanić, Computational Modelling of Concrete Structures, 2020
In order to reduce costs in jet-grouting applications, blended cements obtained from mixing OPC with ground granulated blast-furnace slag (GGBFS) are mainly used. GGBFS is formed between 1350–1550°C in the manufacturing process of steel, when limestone reacts with material rich in Si02 (S) and Al2O3 (A) associated with the ore or present in the ash of the coke. If cooled rapidly below 800°C, which is performed by spraying droplets of the molten slag with high-pressure jets of water, a wet, sandy material is obtained which, when dried and ground, gives GGBFS, containing over 95% of glass. Similar to cementitious materials, slag glass can be considered as a system of C-A-S, see Table 3.
Pyrometallurgical Process for Recycling of Valuable Materials and Waste Management: Valorisation Applications of Blast Furnace Slags
Published in Hossain Md Anawar, Vladimir Strezov, Abhilash, Sustainable and Economic Waste Management, 2019
Sara Yasipourtehrani, Vladimir Strezov, Tim Evans, Hossain Md Anawar
GGBFS has appropriate shape and micro-aggregate effect that recovers the chemical stability and strength of concrete and diminishes the heat of hydration. Also, the grinding methodology will affect the properties of GGBFS. Fine grinding enhances the surface area and this will improve the mechanical activation (Kumar et al., 2008). When the mechanical reactivity is increased, the strength of concrete and cement are improved. When GGBFS, which has high amount of SiO2, is used instead of Portland cement in the process of concrete manufacturing, the strength and water permeability of concrete will increase (Nazari and Riahi, 2011). Using GGBFS to about 45wt% is beneficial for increasing the tensile strength of concrete (Nazari and Riahi, 2011), while more than this amount is not appropriate since the amount of CaO is reduced, but is required in the concrete structure (Nazari and Riahi, 2011). GGBFS can be additionally crushed and used as road construction base material (Barati et al., 2011). BFS could be also utilised in the glass and ceramic production (Francis, 2005). The chemical and mechanical properties of glass-ceramic produced from slag, affect the mechanical quality of product and make the use of it possible in application such as concrete and cementitious material (Wang et al., 2010).
Investigation on rapid solidification of waste dredged sludge with magnesium phosphate cement modified by GGBFS
Published in European Journal of Environmental and Civil Engineering, 2022
Ground granulated blast furnace slag (GGBFS) is a glassy substance formed mostly by GGBFS melted by blast furnace iron making and quenched. The main components are CaO and Al2O3, accounting for 95% of the total, with high potential activity. Generally, GGBFS is used as an active mineral admixture and activated by alkali. Ca(OH)2 react with the activated SiO2 and Al2O3 in the GGBFS to produce gelling substances hydrated calcium silicate (CSH) and hydrated calcium aluminate (CAH). The Al2O3 in the GGBFS is an amphoteric oxide. Theoretically, it react with NH4H2PO4 to form insoluble precipitates. To reduce curing costs, it is necessary to use industrial by-product instead of MgO to solidify sludge. However, detailed literature about the addition of GGBFS to MPC to solidify dredged sludge with high water content has not yet been seen.
Towards Understanding the Rheological Properties of Slag-Cemented Paste Backfill
Published in International Journal of Mining, Reclamation and Environment, 2021
Bolin Xiao, Mamadou Fall, Anis Roshani
During the last decades, many properties of cementitious materials (e.g., mortar, concrete) in the presence of GGBFS have been studied, such as strength and rheology [38–43], permeability [44–48], creep and shrinkage [49–51], resistance to freeze-thaw [52–57], sulphate resistance [58–60], alkali-silica reactivity [61–66], resistance to chloride penetration, and chloride-binding capacity [65,67–69]. In most cases, the use of GGBFS in these cementitious materials has brought many advantages. Based on the aforementioned researches, partial replacement of cement with GGBFS improves its workability, decreases the heat generated by hydration, increases resistance to sulphate attack, and reduces permeability and chloride ion diffusion into concrete. However, it should be underlined that, since concrete is different from CPB, the aforementioned information or knowledge about the effects of GGBFS on the properties of concrete, may not be suitable or transferable to CPB.
Effects of elevated temperatures on the properties of ground granulated blast furnace slag (GGBFS) based geopolymer concretes containing recycled concrete aggregate
Published in European Journal of Environmental and Civil Engineering, 2022
Özge Topal, Mehmet Burhan Karakoç, Ahmet Özcan
GGBFS with specific surface area of 3396 cm2/g was used as raw material in the production of geopolymer concrete. The chemical composition of the GGBFS was: 32.47% SiO2, 9.94% Al2O3, 1.25% Fe2O3, 32.45% CaO, 9.31% MgO, 0.82% SO3, 0.33% S−2, 0.31% Na2O, 0.85% K2O, 1.16% TiO2, 3.51% Mn2O3, 3.6% LOI. Mixture of Na2SiO3 and 10 M NaOH solution was used as the alkali activator. In the mixtures, 5 groups of geopolymer concrete were produced by using 0, 25, 50, 75 and 100% RCA instead of river aggregate. Preparation, curing and exposure to elevated temperatures of gepolymer concrete mixtures are given in Figure 1.