Influence of Electrostatic Precipitator Ash “Zolest-Bet” and Silica Fume on Sulfate Resistance of Portland Cement

• Main Authors: Yury Barabanshchikov, Kseniia Usanova, Stanislav Akimov, Aleksandr Uhanov, Andrej Kalachev
• Format: Article
• Language: English
• Published: MDPI AG 2020-11-01
• Series: Materials
• Subjects: concrete; cement; fly ash; strength; thermal expansion; shrinkage
• Online Access: https://www.mdpi.com/1996-1944/13/21/4917

The influence of the electrostatic precipitator ash “Zolest-bet” and silica fume on the sulfate resistance of Portland cement was studied. The evaluation criteria were the expansion, strength, density, and appearance of the samples, hardened in a 5% Na₂SO₄ solution starting from 3 days of age for 192 days at a temperature of 20 °C and 148 days at 40 °C. The mixture with the silica fume additive had the minimum expansion under the Na₂SO₄ action, and the mixture with the fly ash “Zolest-bet” additive had the greatest expansion. Zolest-bet ash in pure water shrank the mixture by 0.19 mm/m by the end of the hardening period, and it gave a linear expansion of 0.23 mm/m in a Na₂SO₄ solution after hardening. The mixture can be considered sulfate resistant at a given value of linear expansion. Despite the greatest expansion, the compressive strength of the samples with the Zolest-bet additive was found to be the highest at hardening in both environments. The flexural strength was found to be the highest after being in Na₂SO₄ solution. The sulfate resistance of the mixture with silica fume was higher than that of the mixture based on sulfate-resistant cement. This mixture did not have expansion in comparison with the initial length, instead it shrank, while the expansion of sulfate-resistant cement was 0.006% over the control period. The compressive strength of the mixture with the silica fume additive was slightly inferior to the strength of the mixture with Zolest-bet ash.