1. New concrete with a low environmental load through the use of geopolymer method

  • Proposal of a technique to manufacture geopolymer concrete with a low environmental load using coal ash
  • Can presumably reduce CO2 emissions by about 90% compared to normal cement

The volume of CO2 emissions in the production of normal cement used for concrete accounts for about 7% of the total emitted into the atmosphere by industries worldwide. Against this background, the RTRI proposed a method to manufacture concrete with a low environmental load using a geopolymer method that involves mixing and solidifying coal ash and an alkaline silicate solution. The technique also solves the environment-related issues including the problem of coal ash disposal in question. An acid proof test on the cement and geopolymer indicated that no change occurs in the geopolymerfs appearance (Fig. 1). In addition, no deterioration products were generated in an area where a small volume of sulfur component penetrated from the surface. These results indicate that the geopolymer offers high resistance against acid deterioration, freezing/thawing and alkali aggregate reaction. This makes it suitable for application even to lightweight concrete using artificial lightweight aggregate, which tends to deteriorate due to frost damage and alkali aggregate reaction. Through basic testing, the RTRI found that the compressive strength of the geopolymer concrete bears a correlation to the mole ratio of alkali to water in the alkali solution (Fig. 3). By selecting a mole ratio that gives the necessary compressive strength, therefore, it is possible to freely produce concrete with the desired target strength.

With the aim of putting geopolymer concrete to practical use, the RTRI plans to discuss its application to factory-made concrete products including lightweight concrete sleepers.

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