Portland Versus Alkaline Cement: Continuity or Clean Break: “A Key Decision for Global Sustainability”

Abstract

This review undertakes rigorous analysis of much of the copious literature available to the scientific community on the use of alkali-activated binders (AABs) in construction. The authors’ main intention is to categorically refute arguments of that part of the scientific community underestimating or even dismissing the actual potential of AABs as alternatives to Portland cement (PC). The main premise invoked in support of those arguments is a presumed lack of material resources for precursors that would make AAB industrial-scale production unfeasible anywhere on the planet (a substantial number of scientific papers show that the raw materials required for AAB manufacture are in abundance worldwide). The review also analyses the role of alkaline activators in the chemistry of AABs; it is important to clarify and highlight that alkaline activators are not, by any means, confined to the two synthetic products (caustic soda and waterglass) mostly employed by researchers; other sustainable and efficient products are widely available. Finally, the review deals with the versatility of AAB production processes. The technologies required for the large scale manufacturing of AABs are mostly already in place in PC factories; actually no huge investment is required to transform a PC plant in a AAB factory; and quality and compositional uniformity of Alkaline Cements (binders produced through an industrial process) would be guaranteed. The last conclusions extracted from this review-paper are related with: i) the low carbon footprint of one-part AABs and ii) the urgent need of exploring standardization formulas allowing the commercial development of (sustainable) binders different from PC.

Evaluation of the Effect of Granite Waste Powder by Varying the Molarity of Activator on the Mechanical Properties of Ground Granulated Blast-Furnace Slag-Based Geopolymer Concrete

“…Of that consumption, 67,000 million tons are transformed into atmospheric pollution, such as carbon dioxide, or become solid waste, such as the plastics that enter the oceans each year. Of the remaining 35,000 million tons, only 8400 million tons are reused [1,2]. The construction materials manufacturing industry, notably the concrete sector, is having difficulty meeting market demand due to the scarcity of limestone of higher quality [3].…”

“…Geopolymer binder is recognized as a viable alternative to cementitious material because of its inherent merits of low embodied energy and lower carbon emission into the environment [6]. Geopolymer concrete (GPC) is formulated by the activation of industrial by-products containing supplementary cementitious materials with alkaline activators [2,7]. GPC applicability is mainly confined to off-site precast and modular construction because of its curing needs and safety concerns over exposure of untrained employees to alkaline activators [8,9].…”

Impact of Na/Al Ratio on the Extent of Alkali-Activation Reaction: Non-linearity and Diminishing Returns

“…One of the most promising alternatives is alkali-activated materials (AAM) ( Rivera et al, 2021 ; van Deventer et al, 2021 ), also referred to as geopolymers. The terms geopolymers ( Davidovits, 1989 ), inorganic polymers ( Van Wazer, 1970 ), alkali-activated cement ( Palomo and López de la Fuente, 2003 ), and geocement ( Krivenko, 1994 ) are all used to describe these binding materials, which can provide comparable, or higher performance than the traditional cementitious binders ( Wang et al, 2019 ; Alzeer et al, 2021 ) with significantly lower greenhouse emissions ( Gartner, 2004 ; Palomo et al, 2021 ).…”

Flexural Performance and Microstructural Studies of Trough-Shaped Geopolymer Ferrocement Panels

“…To transform the portland cement manufacturing industry into an AAB factory did not require a huge investment for the large scale production of AABs. Therefore, in the current circumstances it is required to explore the standardization formulas for the commercial development of AABs in the construction sector [ 24 ]. It has been observed from the Feret equation that a significant amount of cement is needed to achieve the same compressive strength as that of the alkali-activated concrete.…”