Comparison of the Silica Fume Content for High-Strength Concrete Production: Chemical Analysis of the Pozzolanic Reaction and Physical Behavior by Particle Packing
Abstract:Silica fume (SF) is the most commonly mineral admixture used for the production of high-strength concrete (HSC) due to its chemical characteristics of pozzolanic reactivity and physical filling effect. The objective of the present work is to compare the SF content by the chemical analysis of the pozzolanic reaction and the physical behavior by particle packing techniques. The first step of the study was to analyze the SF content to consume the calcium hydroxide (CH) produced during the hydration of Portland ce… Show more
“…Finally, fixing the Portland cement replacement ratio allows the optimization of limestone filler and sand for the packing density that helps decrease the CO 2 emission of the mortars. Equation 7calculates the maximum replacement level of cement by SCM (% 𝑆𝑆𝐶𝐶𝑆𝑆), where % 𝐶𝐶𝑎𝑎(𝑂𝑂𝑂𝑂) 2 is the available Portlandite content at 91 days and 𝐶𝐶ℎ𝑎𝑎𝑝𝑝𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎 is the modified Chapelle test result (expressed as g𝐶𝐶𝑎𝑎(𝑂𝑂𝑂𝑂) 2 /gSCM) [60], [61]. Therefore, considering the 19.16% of portlandite content in cement and the modified Chapelle test results, the maximum substitution rate (% 𝑆𝑆𝐶𝐶𝑆𝑆) was calculated for the fly ash (22.47%), metakaolin (13.14%) and silica fume (13.05%).…”
The production of eco-efficient cement-based materials is essential to reduce CO2 emissions from the construction industry. A substantial reduction in global CO2 emissions can be achieved by using clinker in mortar and concrete more efficiently and using low-CO2 minerals as partial replacements for Portland cement. However, the proportioning of eco-efficient composites is complex and the reduction in clinker content may affect its properties. This paper aims to optimize the mix design of high-strength mortars containing supplementary cementitious materials (limestone filler, fly ash, metakaolin, silica fume). The compressible packing model associated with a simplex mixture design were used together with chemical parameters, to limit the amount of active SCMs for the model iterations. The results show a significant decrease in the environmental impact of the mortars, which presented compressive strengths between 76 and 118 MPa at 91 days and binder indexes between 10 and 15 kg/m3/MPa. The reactivity of the SCMs (based on the modified Chapelle test) were successfully used to establish the Portland cement substitution (up to 13%), preventing the presence of unreacted SCMs and optimizing the use of limestone filler and sand, which have a lower environmental impact. The high-performance blends reached 8.73 kg CO2e/MPa, up to a 30% reduction in CO2e emissions compared to the mortar with only Portland cement.
“…Finally, fixing the Portland cement replacement ratio allows the optimization of limestone filler and sand for the packing density that helps decrease the CO 2 emission of the mortars. Equation 7calculates the maximum replacement level of cement by SCM (% 𝑆𝑆𝐶𝐶𝑆𝑆), where % 𝐶𝐶𝑎𝑎(𝑂𝑂𝑂𝑂) 2 is the available Portlandite content at 91 days and 𝐶𝐶ℎ𝑎𝑎𝑝𝑝𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎 is the modified Chapelle test result (expressed as g𝐶𝐶𝑎𝑎(𝑂𝑂𝑂𝑂) 2 /gSCM) [60], [61]. Therefore, considering the 19.16% of portlandite content in cement and the modified Chapelle test results, the maximum substitution rate (% 𝑆𝑆𝐶𝐶𝑆𝑆) was calculated for the fly ash (22.47%), metakaolin (13.14%) and silica fume (13.05%).…”
The production of eco-efficient cement-based materials is essential to reduce CO2 emissions from the construction industry. A substantial reduction in global CO2 emissions can be achieved by using clinker in mortar and concrete more efficiently and using low-CO2 minerals as partial replacements for Portland cement. However, the proportioning of eco-efficient composites is complex and the reduction in clinker content may affect its properties. This paper aims to optimize the mix design of high-strength mortars containing supplementary cementitious materials (limestone filler, fly ash, metakaolin, silica fume). The compressible packing model associated with a simplex mixture design were used together with chemical parameters, to limit the amount of active SCMs for the model iterations. The results show a significant decrease in the environmental impact of the mortars, which presented compressive strengths between 76 and 118 MPa at 91 days and binder indexes between 10 and 15 kg/m3/MPa. The reactivity of the SCMs (based on the modified Chapelle test) were successfully used to establish the Portland cement substitution (up to 13%), preventing the presence of unreacted SCMs and optimizing the use of limestone filler and sand, which have a lower environmental impact. The high-performance blends reached 8.73 kg CO2e/MPa, up to a 30% reduction in CO2e emissions compared to the mortar with only Portland cement.
“…Furthermore, the compaction energy is limited to the centrifugal energy used. The wet packing method [11] has been successfully used for measuring the packing density of cement pastes with a wide range of w/s ratios [29], [30] and it has also been successfully applied to the design of ecofriendly concretes [31]- [33] using particle packing theories, resulting in mixtures with low cement consumption.…”
Wet packing methods evaluate the packing density of fine materials through the determination of the apparent density and voids content of pastes with different water to solids (w/s) ratios. Its goal is to estimate the minimum water demand to achieve the maximum solids concentration in the mixture, a parameter applied to the mix design of cementitious composites based on particle packing theories. Since most methods based on apparent density are time-consuming and require a high volume of materials, this paper aims to evaluate the mixing energy method as an alternative for the wet packing method and to adapt it to be used for SCMs (supplementary cementitious materials). With a reduced time and material to perform the test, results demonstrate a better precision of the mixing energy due to its discrete measurement. The ideal water flow and initial volume of materials to perform the test on cement and SCMs are discussed.
“…Dry silica is stored in silos and hoppers, while wet products are stored in tanks. The chemical composition of silica fume is given in Table 3 [65][66][67][68][69][70]. Silica fume consists of very fine vitreous particles with a surface area on the order of 20,000 m 2 /kg, which is approximately 100 times smaller than the average cement particle.…”
Section: Silica Fume (Sf)mentioning
confidence: 99%
“…Dry silica is stored in silos and hoppers, while wet products are stored in tanks. The chemical composition of silica fume is given in Table 3 [ 65 , 66 , 67 , 68 , 69 , 70 ].…”
Supplementary cementitious materials (SCMs) and chemical additives (CA) are incorporated to modify the properties of concrete. In this paper, SCMs such as fly ash (FA), ground granulated blast furnace slag (GGBS), silica fume (SF), rice husk ash (RHA), sugarcane bagasse ash (SBA), and tire-derived fuel ash (TDFA) admixed concretes are reviewed. FA (25–30%), GGBS (50–55%), RHA (15–20%), and SBA (15%) are safely used to replace Portland cement. FA requires activation, while GGBS has undergone in situ activation, with other alkalis present in it. The reactive silica in RHA and SBA readily reacts with free Ca(OH)2 in cement matrix, which produces the secondary C-S-H gel and gives strength to the concrete. SF addition involves both physical contribution and chemical action in concrete. TDFA contains 25–30% SiO2 and 30–35% CaO, and is considered a suitable secondary pozzolanic material. In this review, special emphasis is given to the various chemical additives and their role in protecting rebar from corrosion. Specialized concrete for novel applications, namely self-curing, self-healing, superhydrophobic, electromagnetic (EM) wave shielding and self-temperature adjusting concretes, are also discussed.
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