Durability of concrete with calcined clays

The project is aimed at making the use of calcined clay as a supplementary cementing material (scm) in concrete more widespread. This is in the context of a potential shortage of existing scms, which makes the research of alternative materials a priority, knowing the use of scms reduces ghg emissons

Concrete is one of the most widely used construction materials around the world and the demand is expected to keep increasing in the next decades, notably in developing countries. Unfortunately, cement production is known to be one of the major sources of greenhouse gases. Thus, one of the main challenges of sustainable development consists in reducing the GHG production while increasing the concrete production. One of the most efficient ways to achieve this is to replace a part of the cement content in concrete with materials known as supplementary cementing materials (SCMs). These materials may be essentially inert and act as fillers or react with cement hydration by-products to form hydrated phases (silicates). The most widely used SCMs are fly ashes, silica fume and ground granulated blastfurnace slag, that all consist in recycled industrial waste materials. Therefore, since they are not primarily manufactured to be used in concrete, currently used SCMs are subject to supply shortage. This is especially true in the future, since the production of fly ash is directly linked to the exploitation of coal-fired thermal power plants, a type of energy production that is set to decline, due to its impact on environment and air-pollution. Natural SCMs are also known and used in concrete, but rather marginally. One variety of natural SCMs are clay-based materials that, after being processed, develop amorphous siliceous compounds that react with cement by-products through what is referred to as a pozzolanic reaction. One of the most common clay-based materials is kaolin, an argillaceous rock primarily made of kaolinite, an hydrated aluminium silicate of chemical composition Al2Si2O5(OH)4. Kaolin is widely available as deposits are present and are, or can be, mined on all five continents. Kaolinite, like clay-based minerals, naturally occurs as a layered material with alternate sheets of silica and alumina. Ground kaolinite particles have a plated or lamellar shape. High-temperature heating of ground kaolinite in a rotary kiln modifies its composition and properties by the elimination of water, hydroxyl groups (dehydroxilation) and a recombination of mineral phases, resulting in an increase in the amorphous siliceous (reactive) particles content. One of the phases obtained is the metakaolin (Al2Si2O7). which is known to exhibit pozzolanic properties and can be used as a SCM in concrete production. However, the use of metakaolin in concrete remains marginal, compared to fly ashes, silica fume and ground granulated blastfurnace slag. The quantity of available information about the use of calcined clay in concrete is relatively limited. Furthermore, the natural provenance of raw materials implies some variability in the composition. These factors may explain in a large part the fact calcined clays (CCs) are not more widely used as SCMs in concrete. The project is aimed at correcting this situation and make the use of CCs as partial cement replacement a more common and accepted practice. This would have numerous benefits, both from an economical and environmental standpoint, notably: - Decrease in the cement demand and consequent reduction in GHGs emission; - Increase in concrete durability and service life of concrete structures; - Local resources exploitation, not only in Canada and in Europe, but throughout the world, more specifically in developing countries, where the concrete demand is expected to increase; - Reduction in the raw materials transportation operations;
Project ID: 
11 753
Start date: 
Project Duration: 
Project costs: 
400 000.00€
Technological Area: 
Building materials
Market Area: 

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