Algeria Concrete, Algeria Concrete knowledge

Concrete As a Carbon Sink

The topic of global climate change is frequently in the news. The International Panel on Climate Change (IPCC) reports that the increase in the concentration of many compounds in the atmosphere will impact global climate. The most notable of the long-lived greenhouse gases are carbon dioxide and methane. Using concrete for building structures and infrastructure can contribute to the emission of carbon dioxide. Almost all construction processes from manufacturing, through transportation of materials and installation use energy, and much of this energy may come from the burning of fossil fuels.

What most people do not realize is that the release of CO2 from calcination in the manufacture of portland cement may be part of a cyclic process and is partially carbon neutral in smaller timeframes such as decades. It may be fully carbon neutral in longer timeframes. Concrete can absorb carbon dioxide and store it in a process commonly referred to as carbonation. This may be viewed simply as an additional, alternative loop of the complex carbon cycle. Carbon dioxide may be absorbed by concrete in its many forms such as buildings, bridges and pavements. Concrete does not even necessarily have to be directly exposed to the atmosphere for this process to occur. Underground concrete piping and foundations can absorb CO2 from air in the soil, and underground and underwater applications might absorb dissolved carbon dioxide (carbonates) present in groundwater, freshwaters and saltwaters.

Self-Cleaning Concrete

Self-cleaning buildings and pollution-reducing roadways: These may sound like futuristic ideas, but they are realities of some of today’s concrete. Recently introduced formulations of cement are able to neutralize pollution. Harmful smog can be turned into harmless compounds and washed away. Anything made out of concrete is a potential application, because these cements are used in the same manner as regular portland cements. These products provide value through unique architectural and environmental performance capabilities.

Proprietary technology (based on particles of titanium dioxide) is what makes this cement special—capable of breaking down smog or other pollution that has attached itself to the concrete substrate, in a process known as photocatalysis.

Supplementary cementitious materials are used in addition to or as partial replacement of portland or blended cement in concrete. Chemical composition, specification, and different classes of fly ash, ground granulated blast-furnace slag, silica fume and natural pozzolans are described. Covers effects on freshly mixed concrete like water requirements, bleeding, air content, heat of hydration and setting time. Properties of hardened concrete discussed include strength, abrasion, freeze-thaw, deicer-scaling resistance, sulfate resistance, alkali-silica-reactivity, drying shrinkage, permeability, and carbonation. By S.H. Kosmatka, B. Kerkhoff, and W.C. Panarese

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