International Concrete Abstracts Portal

The addition of supplementary cementitious materials (SCMs) to low-carbon concrete mixtures has been investigated in recent years as part of the sustainability of the concrete sector. Recently, most traditional SCMs, such as fly ash and blast furnace slags, have become unavailable in several developed countries, mostly due to environmental restrictions. Consequently, several new by-products from fast-growing sectors are being considered as potential replacements for traditional SCMs. However, the durability of these new by-products in low-carbon concrete has not been thoroughly explored. As a result, this paper presents the first part of a project related to an extensive experimental characterization, in which low-carbon concrete with high compactness, paste optimization, and partial cement replacement by the addition of waste by-products from the agricultural, metallurgical, paper, and glass industries is studied. Alternative SCMs including rice husk ash, biomass fly ash, rock wool residues, or waste foundry sand are incorporated into corresponding mortar matrices and the results concerning the mechanical properties (flexural and compressive strength) and durability (capillary water absorption, surface electrical resistivity, and carbonation resistance) are presented and analyzed. The outcomes indicate that it is possible to reduce the Portland cement content without compromising the mechanical and durability properties of the concrete.

The significant amount of waste generated in the processing of ornamental stones is a major problem related to civil construction. In this way, numerous international organizations and countries have performed studies on waste recycling in order to reduce its negative effects. Besides, the use of supplementary cementitious materials (SCMs) in cementitious formulations has also gained prominence in several studies aimed at improving these materials in terms of performance, sustainability, and cost. Therefore, this study examined the fresh and carbonation analysis of self-compacting concrete (SCC) made with marble and granite waste as part of ternary cement mixtures. To achieve this objective, an experimental program was developed with four mixtures of SCC. Slump flow test, T500 test, V-funnel test, L-box test, and density were conducted on the fresh concrete. The carbonation properties of the hardened concrete were also determined. The incorporation of marble and granite waste in the mixtures had no influence on the density of the self-compacting concrete and also contributed to the stabilization of the fresh-state properties. It can be inferred from the carbonate analysis that the utilization of marble and granite waste acted as fillers, contributing to the dysconnectivity of the concrete pores and improving the interaction between the concrete constituents. Thus, the results indicated that the use of marble and granite waste in the composition of ternary cement mixtures provides alternative sustainability although it is necessary to pay attention to the amount of cement replacement to avoid a reduction in resistance to carbonation.

Maintaining workability can be a challenge when the total cement content of a concrete mixture is minimized in order to lower the carbon footprint. This is especially the case in everyday concrete where Portland cement content is mostly optimized for a targeted strength. Unlike high-performance or self-consolidating concretes (SCC) which commonly have high cement or cementitious materials contents, a minimum paste volume is generally required in normal strength concrete (NSC) mixtures to ensure adequate workability for the application and to be acceptable in the field. In this study, a new generation of rheology-modifying water-reducing admixture that improves concrete rheology is used to further reduce cement content and provide favorable workability for concrete applications. Comparisons to reference concrete are presented for their fresh and hardened properties, including plastic viscosity, dynamic yield stress, finishability, pumpability, and targeted strength. By combining concrete technology and this new rheology modifying water-reducing admixture, an economical, workable low-carbon concrete can be achieved.

Achieving low carbon emissions in the concrete industry necessitates a multifaceted approach, which includes maximizing the efficacy of supplementary cementitious materials (SCMs). In this respect, this paper investigates fly ash-concrete made of fly ash from distinct burning technology, benefited by different pieces of equipment. Several aspects of fly ash-concrete performance were assessed, including hydration, mechanical properties, and eco-efficiency. The results showed that the burning technology plays an important role in fly ash reactivity. Although both approaches to mechanically activating fly ashes provide interesting results, there is an intriguing difference in the performance of the fly ash concrete. Furthermore, the lifecycle analysis underscores the potential for considerable reduction in global warming potential through the incorporation of fly ash in concrete, making it a promising avenue for reducing the industry's environmental footprint. These findings offer valuable insights for optimizing fly ash utilization and advancing the sustainability of the concrete sector.

The current mantra for our industry is “low carbon concrete,” but the question is – what do you actually mean by that? What is the benchmark you are using to say what is ‘low’– and how does that actually compare with what is being produced today? We’ve been making low-carbon concretes for decades – what we haven’t been doing is counting that carbon. Looking back at some history and at some recent projects, we can see that Low Carbon Concrete is certainly not rocket science and does in fact give us the durability and performance that we need for sustainability. The other side of the coin that we must be very wary of, in light of failures from the past, is that we produce concrete that is fit for purpose – making something that is ultra-green in the lab, but ultimately unusable in the real world serves no purpose and may even endanger lives. This paper shows a very small snapshot of the millions of cubic meters of binary, ternary, and quaternary cementitious blend concretes that have been used over the last 50 years, concentrating on more current examples showing that low carbon concrete is nothing new – it is already in major use.