Engineered Concrete through Tailored Cementitious Materials by Tribochemistry, Surface Treatment and Activation

点击翻译按钮获取中文摘要

The production of cement—the world’s most widely used construction material—causes about 5% of the total CO2 caused by human activity. The cement/concrete industries have committed to reduce their greenhouse emissions by reducing the amount of cement clinker in concrete. One such means is using supplementary cementitious materials (SCMs) from industrial by-products (silica fume, slag, fly ash) and alternative SCMs (ASCMs: glass powder, metakaolin, calcined clays) that can partially or totally replace cement in concrete. Although concretes with SCMs can yield equivalent or higher properties than plain concrete, their potential has yet to be fully be exploited. In any cases, low early strength, long setting time, poor dispersion, slow reactivity, chemical shrinkage, and concrete cracking are reported. This research program focuses on optimizing SCM properties with tribochemistry, surface chemical activation, dispersion, and packing-density tools to design durable, sustainable concrete structures. The grinding of solid-like cement and SCMs generates complex transformations. The mechanical energy disrupts the materials’ atomic and molecular structures, producing cracks, micro-defects and new surfaces. The energy in the micro-defects of the crystalline structure can modify and complexify solid-particle reactivity and rheology. This effect is more complex when different materials (clinker, SCMs, ASCMs) are interground. Chemical activation can also be used to increase SCM and ASCM hydration. In this program, SCMs will be tailored through grinding and surface treatment to engineer concretes with high particle-packing densities. The milled surface-treated mixtures will be analyzed with microscopic and spectroscopic techniques. Tribochemical effects of SCMs will be investigated on binder hydration and activation of portland cement-free binders through calorimetry, nano-indentation, and electron-microscopic measurements. Understanding the effect of material grinding on particle surfaces (tribochemistry) and surface treatment coupled with an optimized packing density of the binder will provide better mastery over the hydration process. These synergetic effects will be modulated to tailor a concrete with optimized rheology, mechanical performances, and durability. Results obtained from this modeling will be validated on pilot-scale and in situ experimental concretes. In addition to train HQP readily available for the Canadian construction industry, the outcome will be a major database and model accessible to the concrete industry for building durable and sustainable infrastructures in Canada.