Authors:

Anel Zhussupbekova

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About Paper:

Concrete is the most widely used construction material with cement providing its strength. However, cement production accounts for 8% of global CO2 emissions. Traditional supplementary cementitious materials (SCMs), such as fly ash or slag, reduce CO2 emissions by partially substituting cement, but their declining availability creates a supply gap that needs to be addressed. This research investigates Nontraditional Natural Pozzolans (NNPs), namely volcanic ashes and calcined clays, as viable alternatives to traditional SCMs. It seeks to determine whether NNPs can effectively replace traditional SCMs while preserving or improving mechanical and durability properties of concrete. The study examines the concrete cores from field slabs containing NNPs and explores the synergistic effect of NNPs and nano-silica admixtures through their hydration kinetics on paste samples. To evaluate mechanical properties, compressive strength tests are conducted on laboratory-prepared mortar cubes containing NNPs and nano-silica admixtures at different testing ages. Hydration kinetics are studied using differential scanning calorimetry (DSC) and isothermal calorimetry (IC) tests. Previous studies indicate that NNPs can enhance concrete's mechanical properties and durability, making them viable SCMs alternatives. However, their behavior under varying conditions - such as different temperatures, water-to-cementitious ratio, and cement chemical composition - remains uncertain. Additionally, while various admixtures, like water-reducing agents or air-entraining agents, are commonly used improve the early-age strength, the effect of nano-silica admixtures is still unknown. This study aims to provide practical data on the effect of NNPs for the concrete industry to address the supply gap and environmental concerns associated with cement production. Keywords: Concrete; CO2 Emissions; Traditional Supplementary Materials (SCMs); Nontraditional Natural Pozzolans (NNPs); Hydration Kinetics

Source:

Purdue University / 2024

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Co-authors:

Anel Zhussupbekova