Enhancing concrete sustainability with spent diatomaceous earth from the wine industry: Long-term experimental and statistical analysis

Abstract

[EN] Spent diatomaceous earth, a by-product of wine filtration, holds significant prom-ise for use in concrete mixtures due to its pozzolanic properties, which enhanceconcrete performance. This research explores the application of spent calcineddiatomaceous earth (SCDE), heat-treated at 700 C to remove organic content, as apartial substitute for cement or sand in concrete. The high silica content of SCDEcontributes to the formation of additional calcium silicate hydrates during thehydration process, leading to improvements in mechanical strength over time.The study includes a preliminary analysis of cement replacements ranging from5% to 10% and sand replacements from 2.5% to 15%, assessing their effects onworkability, density, water absorption, and compressive strength at 7 and 28 days.The testing program focuses on three key compositions: the reference concreteand optimal mixtures with 10% cement and 5% sand replacements. Compressivestrength tests are conducted at 7, 28, 90, 180, and 360 days. The results, validatedthrough ANOVA, demonstrate the influence of SCDE on concrete strength overtime, with distinctive behavior patterns identified for different mixtures. Thestrength of concrete with replacements correlates with the reference strength,with a multiplicative factor that varies from 7 to 90 days and then. When SCDEreplaces cement, the factor is less than one before 28 days due to the slow pozzola-nic reaction, whereas for sand replacement, it always exceeds one because of theinitial filler effect. After 90 days, the strength multiplicative factors are 1.13 forcement replacement and 1.30 for sand replacement, demonstrating the potentialof SCDE for sustainable concrete manufacturing and its positive long-term impacton mechanical performance.