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 cement (PC), based on stoichiometric calculations. Then, the SF content for maximum packing density was obtained using analytical particle packing models and experimental tests. The compressive strength of the pastes was also measured. The results showed that the theoretical SF content for consuming CH is 15.6%, replacing PC. According to the packing density analytical models, the ideal SF content is 15% of the total fine materials. However, the experimental results indicated the use of a smaller SF content (10%). This difference between theoretical and experimental results is probably due to the high specific surface of the SF, which results in important surface forces between the grains, particle agglomeration and difficulty in SF densification with water.

Mix design of eco-efficient high-strength mortars optimized by the compressible packing model

“…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%).…”

Measuring packing density and water demand of Portland cement and SCMs by the mixing energy method

“…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.…”

Review of the Effects of Supplementary Cementitious Materials and Chemical Additives on the Physical, Mechanical and Durability Properties of Hydraulic Concrete

“…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.…”

“…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 ].…”