Title:
Ternary and Quaternary Cements for Sustainable Development
Author(s):
Moncef Nehdi
Publication:
Concrete International
Volume:
23
Issue:
4
Appears on pages(s):
36-44
Keywords:
DOI:
Date:
4/1/2001
Abstract:
The cement and concrete industry is gradually shifting towards high performance concrete for better durability and self-compacting concrete to reduce labor and construction time; materials that often require high portland-cement contents. On the other hand, pressure from both the public and legislature for a more rational use of cement will be growing. Indeed, the world’s annual cement production is expected to reach almost 2 billion tonnes by year 2010. With portland cement as the predominant cementing material, this would translate into 2 billion tonnes of CO2 released into the atmosphere each year, exacerbating the threatening problem of global warming. To balance the requirements for higher-performance cements and sustainable development, the industry is progressively resorting to blended cements (mostly binary systems) including additions of industrial by-products, such as fly ash, slag, and silica fume. These environmentally friendly binary cements usually enhance concrete durability in hostile environments. They are often associated with shortcomings, however, such as the need to moist-cure concrete for longer time, low early-age strengths, increased demand for costly chemical admixtures, cracking tendency due to plastic shrinkage, and durability problems due to deicing salts. There is growing interest in ternary and quaternary cements that could be optimized to achieve a synergistic effect allowing component ingredients to compensate for their mutual shortcomings, thus providing advantages over binary systems. This article provides a critical overview of the principles governing the behavior of such composite cements.