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International Concrete Abstracts Portal

Showing 1-5 of 137 Abstracts search results

Document: 

SP-362_69

Date: 

June 18, 2024

Author(s):

Eliana Soldado, Hugo Costa, Ricardo do Carmo, and Eduardo Júlio

Publication:

Symposium Papers

Volume:

362

Abstract:

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.

DOI:

10.14359/51742019


Document: 

SP-362_64

Date: 

June 17, 2024

Author(s):

Ying Wang, Jesus Gonzalez, Craig W. Hargis

Publication:

Symposium Papers

Volume:

362

Abstract:

This paper discusses the results of a 5-10% vaterite replacement of SCMs in certain blended cements. In cement-fly ash blended cement, a 10% vaterite replacement of fly ash achieved a 40% higher strength at 1 day and maintained a consistently higher strength than the cement-fly ash blended cement control through 56 days. A 10% vaterite replacement of slag in a cement-slag blended cement achieved approximately 20% higher strength at 3 days. For a cement-slag-fly ash blended cement, a 10% replacement of fly ash with vaterite achieved a 30% to 50% strength increase through 7 days, and a 50 to 110-minute reduction in the initial setting. The bulk resistivity of all the blended cement was increased after including vaterite, indicating the potential for better durability. The alkali-silica reaction test resulted in low amounts of expansion confirming the vaterite-blended cements’ durability. Hydration analysis using isothermal calorimetry and thermogravimetry also showed extra early-age hydration reactions due to vaterite inclusion. Using vaterite in blended cement can help reduce the embodied carbon and enhance many of the engineering properties, such as setting time, early-age strength, and durability.

DOI:

10.14359/51742014


Document: 

SP-362_34

Date: 

June 14, 2024

Author(s):

Mara M. L. Pereira, Arthur A. Palma e Silva, and Valdirene M. S. Capuzzo

Publication:

Symposium Papers

Volume:

362

Abstract:

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.

DOI:

10.14359/51741003


Document: 

SP-362_43

Date: 

June 14, 2024

Author(s):

Lesley Ko, Jeffery Bury, Charles Nmai

Publication:

Symposium Papers

Volume:

362

Abstract:

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.

DOI:

10.14359/51741012


Document: 

SP-362_39

Date: 

June 14, 2024

Author(s):

Antonio Telesca, Milena Marroccoli, Neluta Ibris, Fulvio Canonico, Daniela Gastaldi

Publication:

Symposium Papers

Volume:

362

Abstract:

Belite cements (BCs) have been suggested as innovative environmentally-friendly materials, since they can allow a reduction of CO2 emissions up to about 30% with respect to normal portland cements (NPCs); furthermore, the manufacturing process of BC, compared to that of NPC, is characterized by reduced limestone requirement, lower synthesis temperatures and, consequently, reduced specific fuel consumption. The peculiar composition of BC can also be exploited for achieving valuable technical properties (e.g. better durability against sulfate and carbonation attacks as well as low heat of hydration). This paper examines the influence of temperature (20°C and 40°C) on the hydration behavior and the technical properties of a pilot-scale industrial BC (w/c=0.50) up to 180 days. An NPC class 52.5 R was employed as a reference term. It was found that, compared with NPC, BCs showed lower mechanical properties at early ages (2 days), while at longer curing periods, the compressive strength values were always greater at both 20°C and 40°C. However, stability tests displayed that BCs shrank less than NPC in the air, while they exhibited approximately the same expansion values when submerged in water. BC pastes showed the best hydration behavior for curing periods longer than 28 days.

DOI:

10.14359/51741008


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