Alkali-Activated Cements and Concretes

Chemical Research and Climate Change as Drivers in the Commercial Adoption of Alkali Activated Materials

“…2, with only a single published study of carbonation in fly ash geopolymers [12] and one on carbonation in slag-metakaolin blends [8]. Carbonation in alkali-activated slag systems has been claimed not to be significantly problematic based on samples synthesized in Eastern Europe in the 1970s and analyzed after more than 20 years of service [17,61,72], but it is not clear how these results will transfer to more geopolymer-like systems. Criado et al [12] observed the formation of sodium bicarbonate in their low-calcium fly ash geopolymer samples, indicating a different mechanism of carbonation via the alkali-rich pore solutions of AAMs compared to the C-S-H decalcification process observed in carbonation of Portland cement materials.…”

“…Based on these observations he developed binders called ''soilcement,'' combining aluminosilicate waste such as various types of slags with alkaline industrial waste solutions to form a cement-alternative binder. From the 1960s onwards, the Glukhovsky Institute in Kiev, Ukraine has been involved in the construction of apartment buildings, railway sleepers, road sections, pipes, drainage and irrigation channels, flooring for dairy farms, pre-cast slabs and blocks, using alkali activated blast furnace slag [57,61]. Subsequent studies of sections taken from these original structures have shown that these materials have high durability and compact microstructure [72].…”

“…In AAM chemistry, glassy aluminosilicate phases containing some calcium in materials such as fly ash, slag, calcined clay or volcanic ash react with individual alkalis or a combination of reagents which may include sodium or potassium silicate, sodium or potassium hydroxide, sodium or potassium carbonate, and sodium aluminate, to form zeolite-like phases that vary in their degree of crystallinity. AAM concrete has been shown to be quite resistant to attack by acids and by fire, and does not produce the high reaction heat associated with OPC concrete, which reduces cost when placed in large volumes such as in large foundations or a dam wall [61]. It will be shown below that AAM has in fact had a track record of successful application, but unfortunately this fact has not been recognized by the cement and concrete industry.…”

“…• Alkali activated material is the broadest classification, encompassing essentially any binder system derived by the reaction of an alkaline salt (solid or dissolved) with a solid silicate powder [10,61]. This solid can be a calcium silicate as in alkali-activation of more conventional clinkers, or a more aluminosilicate-rich precursor such as a metallurgical slag, natural pozzolan, fly ash or bottom ash.…”

Ceramic membrane synthesis based on alkali activated blast furnace slag for separation of water from ethanol

“…According to literature, porosity of alkali activated materials decreases by increasing alkalinity of the activator solution [33,34]. This porosity reduction reduces permeation flux through the membrane support.…”