The environmental credentials of hydraulic lime-pozzolan concretes

Abstract

This research considers the compressive strength, embodied CO 2, embodied energy and binder intensity of hydraulic lime-pozzolan concretes, in comparison with those of Portland-cement based concretes of equivalent 28-day compressive strength. Production of a lime-pozzolan concrete with a 28-day cube strength of approximately 50 MPa and an elastic modulus of 20GPa has demonstrated the feasibility of producing modern, structural grade hydraulic lime-pozzolan concretes. Furthermore, construction and testing of two reinforced lime-pozzolan concrete beams has demonstrated the possibility of producing structural elements with a finished appearance and flexural behaviour similar to Portland cement concrete. This paper reflects on the value of this new material's technological progress in the context of the industry wide search for low carbon cements. Results of the research reported in this paper demonstrate that the use of aluminosilicate byproducts, specifically ground granulated blastfurnace slag and silica fume, in combination with naturally hydraulic lime can realise savings in environmental impact; but that the savings are both future-orientated and highly dependent on the boundaries of the analysis. When considering only the secondary impacts of ground granulated blastfurnace slag and silica fume production, a ternary combination was observed to result in a lime-pozzolan concrete with a 28-day cube strength of 33MPa and an embodied-CO 2 of 95 kgCO 2 /m 3 , 64% lower than a CEMI, and 41% lower than a CEMIII/A concrete of equivalent strength. Both mass and economic allocation procedures were, however, shown to have a very detrimental effect on the environmental credentials of silica fume and thus also on hydraulic lime-concretes containing this pozzolanic addition. It is recognised that technical performance alone cannot be used to assess or compare the merits of any new material. This paper focus on the production, environmental impact and long-term availability of individual constituents of this novel binder, with a view to addressing important questions about the viability and desirability of reproducing this novel cementitious system in a commercial setting. Such information is acknowledged to be critical in the dialogue about the potential adoption and development of this emerging binder technology.

The development of a low carbon binder produced from the ternary blending of cement, ground granulated blast furnace slag and high calcium fly ash: An experimental and statistical approach

“…GGBS is one viable alternative SCM in the production of binary and ternary blended cements, and useful in different applications such as concrete production, soil stabilization and road construction [16][17][18]. GGBS, is a by-product of the iron industry and is extracted from blast furnaces [19]. Due to the chemical and physical properties of GGBS, it has many advantages relative to OPC, such as improved workability, enhanced durability and increased compressive strength [1,[20][21][22].…”

Evaluation of pozzolime mixtures as a sustainable binder to replace portland cement in structural concrete

“…Pozzolana-Lime cements are one of a number of 'second generation' low-carbon cements being developed to meet the demand for concrete in construction [1].…”

The effects of silica fume and hydrated lime on the strength development and durability characteristics of concrete under hot water curing condition

“…With the extensive use of Portland cement, it is inevitable that such idea of sustainable concrete can be accomplished. However, if the cement manufacturing is tend to shift with the mixture of 'second generation' or 'low carbon' binders [7], the idea of achieving sustainable concrete may emerge to existence.…”

“…[8][9][10][11]. Hydraulic lime, being one of the oldest binders contributes substantial history in construction practices and manufacturing [7]. Furthermore, SCMs broadly pozzolans, have also been considered as a viable approach to be used as an alternative binder [7].…”

“…Hydraulic lime, being one of the oldest binders contributes substantial history in construction practices and manufacturing [7]. Furthermore, SCMs broadly pozzolans, have also been considered as a viable approach to be used as an alternative binder [7]. Pozzolans normally results in poor performance and low strength development at early stages due to absence of adequate quantities of Ca(OH)2 [12].…”