Basic oxygen furnace slag (BOFS) is a waste product generated during steel production. The utilization of BOFS in construction applications is considerably limited because of its inherent characteristics leading to volumetric expansion behavior caused by the chemical reaction between free lime (f-CaO) and water. The main objective of this paper is to investigate the material properties of normal mortar and geopolymer mixtures that contain BOFS aggregates. Three different aggregates were used to compare their performance, including siliceous river sand, fresh BOFS aggregate (within 1-month age), and stockpiled (more than 5-year age) BOFS aggregate. Test methods included a compressive strength test, accelerated mortar bar expansion test, and thermal conductivity test. Test results revealed that (1) geopolymer mixtures containing BOFS aggregate had comparable compressive strength with mortar mixture with river sand, (2) geopolymer mixtures have very low volume expansion, (3) thermal conductivity of geopolymer mixtures having both river sand and BOFS was lower than normal cement mortar mixture containing river sand. Therefore, geopolymer technology seems a key solution for converting BOFS slag into valuable construction materials. Therefore, a geopolymer mixture containing BOFS aggregate can be used as an energy-saving material.
As one of the by-products in the steel industry, granulated blast furnace slag (GBFS) is widely used as an aggregate or a pozzolanic material (a partial replacement for Portland cement) in the concrete mixture after the crushing or grinding process. However, using a basic oxygen furnace slag (BOFS) as a cementitious material is limited because of its inherent shortcomings such as low cementing property and undesirable expansion characteristics due to free lime. To overcome BOFS’s these properties, the BOFS was ground, blended with the ground granulated blast furnace slag (GGBFS), and used as a pozzolanic material in this research. A total of five mortar mixtures were developed, including ordinary Portland cement (OPC) as a control group, two binary mixtures, and two ternary blended mixtures with 50% cement replacements by GGBFS and BOFS by weight percentages. Properties of these mixtures were evaluated according to ASTM C 989 and C 311 standard specifications that include compressive strength, alkali-silica reaction (ASR), and sulfate resistance tests. Moreover, basic material characterization of GGBFS and BOFSs was investigated by X-ray diffraction (XRD), chemical composition analysis (XRF), and particle size distribution (PSD). The test result shows that the blended mixture with 15% BOFS and 35% GGBFS satisfied the strength activity index and good ASR and sulfate resistance.
. This paper evaluates the thermal performance of non-autoclaved aerated concrete (NAAC) produced with crushed waste glass bottle aggregate and glass fiber. A total of six different mixtures, including the partial substitutions of normal sand with waste glass sand (WGS) (0%, 15%, and 30%) and glass fiber (1%, 2%, and 3%), were designed. After the compressive strength and thermal conductivity (λ) of each NAAC mixture were firstly determined, the potential of NAAC to improve the thermal performance of student residential buildings was assessed. The energy-saving effect of NAAC was simulated using Autodesk Revit software tools in two different cities, Nur-Sultan in Kazakhstan and Boston in the USA. Moreover, annual heat loss was calculated. Test results present that the increase of WGS and glass fiber contents leads to increasing compressive. Interestingly, while increasing WGS content in the mixture decreases λ, increasing fiber content increases λ despite a slight variation. The lowest annual heat loss was obtained from the mixture containing 70% normal river sand, 30% WGS, and no glass fiber. 70NS-30WG-0GF. Finally, the energy performance simulation result indicates that NAAC used in a residential building leads to significant energy savings compared to normal concrete and brick structure.
Ordinary Portland cement (OPC) is one of the most widely used construction materials in civil engineering infrastructure construction but it is susceptible to sulfate attack. One of the ways to improve the sulfate resistance of an OPC mortar/concrete is to replace a certain amount of OPC with different pozzolanic materials such as ground granulated blast furnace slag (GGBFS) and metakaolin. The use of pozzolanic materials to mortar/concrete not only enhances durability but also reduces carbon dioxide (CO2) emission due to the less usage of OPC at the initial construction state. As considering these aspects, limestone calcined clay cement (LC3) has been developed in recent decades. However, the influence of LC3 on sulfate attack resistance has not been fully evaluated. Therefore, this study investigated the efficiency of LC3 mortar mixtures against sulfate attack at an early age (approximately 4.5 months) after two different curing periods, namely 1-day and 3-day curing, since the strength of the LC3 mixture is lower than OPC mixtures. To evaluate the synergistic effect of a combination of LC3 and GGBFS on the sulfate resistance, the LC3 and OPC mixtures containing 25% GGBFS were also assessed in terms of density, porosity, compressive strength, volumetric expansion, and weight changes. The experiment results show that the expansion of the LC3 mixture regardless of the addition of GGBFS and an initial curing strength made a plateau after a rapid increase up to 7 days, while the expansion of the OPC mixture kept increasing throughout the period. Furthermore, the addition of GGBFS to OPC or LC3 mixture provides the synergistic effect on reducing the expansion due to sulfate attack. Therefore, if LC3 mixture has high initial strength (min. 15 MPa) and dense microstructure to minimize the penetration of sulfate ion into the mixture, it is expected that LC3 mixture is more efficient than OPC mixture against the sulfate attack.
To decrease greenhouse gas emissions and maintain sustainable economic growth, the cement industry has developed limestone calcined clay cement (LC3). Many researchers have started to investigate the performance of LC3 as a construction material. However, the strength development of LC3 has diverging or opposite views. In this research, the strength development characteristics of ordinary Portland cement (OPC) and LC3 with different combinations of medium reactive ground granulated blast furnace slag (GGBFS) have been compared using compressive strength and ultrasonic pulse velocity, and maturity tests. The test result shows that the LC3 concrete has a similar 28-day compressive strength to OPC concrete despite developing a lower early age. Ultrasonic pulse velocity test results have matched compressive strength test results. The predicted compressive strengths using 7-day maturity data were comparable to actual strength results.
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