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Constr. Mater., Volume 3, Issue 3 (September 2023) – 4 articles

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17 pages, 6944 KiB  
Article
Effect of Process Parameters on the Physical and Mechanical Properties of Cornstarch-Based Construction Materials
Constr. Mater. 2023, 3(3), 320-336; https://doi.org/10.3390/constrmater3030021 - 01 Sep 2023
Viewed by 1067
Abstract
Concrete is used globally due to its useful mechanical and durability properties. However, concrete requires a massive amount of cement, which is the second-largest source of carbon emission (5–7% of global CO2 emissions) due to its high energy consumption. The gelatinization effect [...] Read more.
Concrete is used globally due to its useful mechanical and durability properties. However, concrete requires a massive amount of cement, which is the second-largest source of carbon emission (5–7% of global CO2 emissions) due to its high energy consumption. The gelatinization effect of corn starch as a binder has been explored in the place of cement in concrete. However, there is a need to optimize the various processing conditions to enhance the material strength of the corn starch-based material known as CoRncrete. Two experiments were conducted to optimize the ratio of sand, starch, water, curing temperatures, and time. The compressive and tensile strength of the CoRncrete samples were analyzed. The results showed that the optimum processing conditions having a sand grain size of 0.250–0.425 mm, a mixture ratio of starch, water, and sand 1:1:5, and curing temperature and time of 110 °C and 24 h can yield a maximum compressive strength up to 18.9 MPa. Statistical analysis revealed that the size of sand grains and curing temperatures had the most significant impact on the material’s strength. Microstructural analysis, employing scanning electron microscopy (SEM) and micro-computed tomography (microCT), unveiled numerous internal pores and cracks within the hardened cubic blocks, which significantly decreased the strength. Consequently, future investigations should concentrate on reducing internal pore spaces and cracks to enhance the durability of CoRncrete. Full article
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15 pages, 17678 KiB  
Article
Strength and Resistance to Sulfates, Carbonation and Chlorides Ingress by Substitution of Binder by Hydrotalcite in Several Cement Types
Constr. Mater. 2023, 3(3), 305-319; https://doi.org/10.3390/constrmater3030020 - 30 Aug 2023
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Abstract
Currently, the cement sector has become aware of the economic and environmental advantages of replacing clinker with other supplementary cementitious materials that have a lower carbon footprint in the design of eco-cements. In this study, hydrotalcite, a natural as well as synthetic clay, [...] Read more.
Currently, the cement sector has become aware of the economic and environmental advantages of replacing clinker with other supplementary cementitious materials that have a lower carbon footprint in the design of eco-cements. In this study, hydrotalcite, a natural as well as synthetic clay, which can be fabricated at the cement plant site, was used as such an addition. The objective of this work was to evaluate the behavior of its physical–mechanical properties and durability in pastes and mortars, using a magnesium-type commercial hydrotalcite, Mg6Al2(OH)16CO3·4H2O, as a substitute material for 10, 20 and 30% by weight of ordinary Portland cement (OPC). The mechanical strength was not affected by the substitution, the resistance to chlorides increased, as the hydrotalcite (HT) was able to bind chlorides, and the resistance to carbonation increased at 3 months but was almost the same as the reference specimen at 6 months, which indicates the need to have longer test durations. Full article
(This article belongs to the Special Issue Modelling and Analysis of Concrete Degradation)
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18 pages, 17124 KiB  
Article
Application of Bilinear Softening Laws and Fracture Toughness of Foamed Concrete
Constr. Mater. 2023, 3(3), 287-304; https://doi.org/10.3390/constrmater3030019 - 03 Aug 2023
Viewed by 820
Abstract
This study examined the fracture and failed performance of foamed concrete materials by testing normalized notched beams under three-point bending via three methods: inverse analysis, digital image correlation (DIC), and finite element modeling (FEM). It also discussed both experimental and FEM characteristics. However, [...] Read more.
This study examined the fracture and failed performance of foamed concrete materials by testing normalized notched beams under three-point bending via three methods: inverse analysis, digital image correlation (DIC), and finite element modeling (FEM). It also discussed both experimental and FEM characteristics. However, inverse analysis is only applicable for specimens with a notch height of 30 mm. Bilinear softening of the tested beams was estimated to identify the fracture energy (GF), critical crack length (ac), and elastic modulus (E). Additionally, the fracture toughness was calculated by adopting the double-K method (initiation fracture, unstable fracture, and cohesive fracture). Two-dimensional FEA modeling of the fracture was conducted using the traction-separation law (TSL), incorporating the extended finite element method (XFEM) and cohesive zone (CZM) techniques. A finite element sensitivity for the XFEM and CZM was performed, with the global mesh size of 2 and the damage stabilization cohesion of 1 × 10−5 showed good convergence and were used in other models. Further comparison of the DIC experiment findings with those from the FEM demonstrated good agreement in terms of crack propagation simulation. Full article
(This article belongs to the Special Issue Modelling and Analysis of Concrete Degradation)
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11 pages, 2475 KiB  
Article
Sustainable Alternatives to Cement: Synthesizing Metakaolin-Based Geopolymer Concrete Using Nano-Silica
Constr. Mater. 2023, 3(3), 276-286; https://doi.org/10.3390/constrmater3030018 - 10 Jul 2023
Cited by 4 | Viewed by 1196
Abstract
The emission of carbon dioxide gas from the cement manufacturing industry has raised concerns about global warming. Geopolymer concrete (GC) is gaining attention as a sustainable and environmentally friendly alternative to traditional cement concrete. The current study focused on using local clay to [...] Read more.
The emission of carbon dioxide gas from the cement manufacturing industry has raised concerns about global warming. Geopolymer concrete (GC) is gaining attention as a sustainable and environmentally friendly alternative to traditional cement concrete. The current study focused on using local clay to synthesize and characterize metakaolin-based GC with varying percentages of nanosilica (NS) (1.5%, 3.0%, 4.5%, 6.0%, and 7.5% by weight of MK content) using NaOH/sodium silicate. The geopolymer specimens were cured at room temperature for 28 days, and their workability, compressive, tensile, and flexural strengths were measured to evaluate the influence of NS on the concrete’s mechanical properties. The study found that the compressive, tensile, and flexural strengths of the GC increased gradually up to 6.0% NS, but any further increase in its ratio resulted in a reduction in mechanical characteristics. The study concludes that the addition of 6.0% NS in metakaolin (MK)-based GC produces the highest mechanical properties, improving the compressive strength of the GC mix by 34.3% compared to the control GC mix and improving the flexural and split tensile strengths by 39% and 37%, respectively, compared to control GC strengths. Furthermore, the statistical analysis confirms nano-silica’s significant impact on geopolymer concrete’s mechanical properties, emphasizing its role in improving performance and sustainability as an alternative to cement-based materials. Full article
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