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International Concrete Abstracts Portal

Showing 1-5 of 744 Abstracts search results

Document: 

SP361

Date: 

March 1, 2024

Author(s):

ACI Committees ACI Committees 130 and E702

Publication:

Symposium Papers

Volume:

361

Abstract:

Concrete has played a pivotal role in shaping the modern world’s infrastructure and the built environment. Its unparalleled versatility, durability, and structural integrity have made it indispensable in the construction industry. From skyscrapers to long-span bridges, water reservoirs, dams, and highways, the ubiquitous presence of concrete in modern society underscores its significance in global development. As we stand at the crossroads of environmental awareness and the imperative to advance our societies, the sustainability of concrete production and utilization is becoming a new engineering paradigm. The immense demand for concrete, driven by urbanization and infrastructure development, has prompted a critical examination of its environmental impact. One of the most pressing concerns is the substantial carbon footprint associated with traditional concrete production. The production of cement, a key ingredient in concrete, is a notably energy-intensive process that releases a significant amount of carbon dioxide (CO2) into the atmosphere. As concrete remains unparalleled in its ability to provide structural functionality, disaster resilience, and containment of hazardous materials, the demand for concrete production is increasing, while at the same time, the industry is facing the urgency to mitigate its ecological consequences. This special publication investigates the multi-faceted realm of concrete sustainability, exploring the interplay between its engineering properties, environmental implications, and novel solutions, striving to provide an innovative and holistic perspective. In recent years, the concrete industry has witnessed a surge of innovation and research aimed at revolutionizing its sustainability. An array of cutting-edge technologies and methodologies has emerged, each offering promise in mitigating the environmental footprint of concrete. Notably, the integration of supplementary cementitious materials, such as calcined clays and other industrial byproducts, has gained traction to reduce cement content while enhancing concrete performance. Mix design optimization, coupled with advanced admixtures, further elevates the potential for creating durable, strong, and eco-friendly concrete mixtures. Concrete practitioners will gain an advanced understanding of a wide variety of strategies that are readily implementable and oftentimes associated with economic savings and durability enhancement from reading these manuscripts. The incorporation of recycled materials, such as crushed concrete and reclaimed aggregates, not only reduces waste but also lessens the demand for virgin resources. Furthermore, the adoption of efficient production techniques, along with the exploration of carbon capture and utilization technologies, presents an optimistic path forward for the industry. This special publication aspires to contribute to the ongoing discourse on concrete sustainability, offering insights, perspectives, and actionable pathways toward a more environmentally conscious future.

DOI:

10.14359/51740669


Document: 

SP-355_01

Date: 

July 1, 2022

Author(s):

Gilberto Artioli, Anna Bravo, Stefano Broggio, Giorgio Ferrari, Francesco Santonicola, Francesco Surico, Luca Torelli, Luca Valentini, Andrea Zecchini

Publication:

Symposium Papers

Volume:

355

Abstract:

The new San Giorgio bridge replaced the Polcevera viaduct, built between 1963 and 1967 and collapsed during a storm in summer 2018. The new bridge was designed by Renzo Piano and is made by 19 steel spans supported by 18 concrete pillars. Beside the architectural aspects, special attention was devoted to the mix-design of the pillars, to ensure the production of durable concrete in the marine environment. The use of slag cement combined with limestone filler and polycarboxylate superplasticizers allowed to cast flowable concrete associated with low water to cement ratio and high final compressive strength. A new generation accelerating admixtures, working on the homogeneous nucleation technology, was used to accelerate the cement hydration and gain early compressive strength to speed-up the elevation of the pillars. In the present paper, the advantage of using the new admixture is discussed both in terms of early strength development and microstructure of the cement paste. Beside the improvement of the early strength development, the new admixture reduced the water permeability and the chloride diffusion and improved the resistance to carbonation of the concrete used for the pillars, with further advantages for the durability of this structure.

DOI:

10.14359/51736007


Document: 

SP-354_29

Date: 

July 1, 2022

Author(s):

Mario Collepardi, Silvia Collepardi, Giuseppe Marchese and Roberto Troli

Publication:

Symposium Papers

Volume:

354

Abstract:

A special concrete was used to erect the MAXXI building in Rome designed by Zaha Hadid and her team with long, inclined, curvilinear walls. Due to the very congested reinforcements, the original concrete issued by Zaha Hadid and her team was self-compacting concrete (SCC). However, irregular cracks -caused by the restrained drying shrinkage- appeared on the surface of this concrete a few days after removing the formworks. On the other hand, due to aesthetic reasons, neither saw cuts in the hardened concrete to produce regular contraction joints -carried out to avoid the irregular cracks caused by a restrained drying shrinkage- were accepted by the Architects. Therefore, a special 3-SC mixture was developed and used; it is characterized to be: - a self-compacting concrete based on the use of an acrylic superplasticizer, a viscosity modifier to avoid the bleeding risk, and a special particle size distribution of the aggregates; - a self-compressive concrete due to the use of a CaO-based expansive agent; - a self-curing concrete based on the use of a shrinkage-reducing admixture (SRA). This concrete called 3-SC, because it is 3 times “self”, was very successful in producing a crack-free concrete surface even in the very long, curvilinear, and inclined walls: after 18 years of building the long, inclined, curvilinear walls of the MAXXI museum have been carefully examined and during the last inspection their surface resulted to be still sound and crack-free. However, just before the building’s inauguration in 2009, in very few areas some micro-cracks were observed on the concrete surface and considered to be dangerous for the future of the building. Therefore, the concrete surface was treated with a transparent varnish in order to avoid the ingress of the aggressive humid air to protect the steel reinforcements from the corrosion promoted by the carbonation process.

DOI:

10.14359/51736085


Document: 

SP-354_24

Date: 

July 1, 2022

Author(s):

Vyacheslav R. Falikman, Valery L. Ugolkov, Pavel N. Vasilyev, Ivan V. Bondarenko

Publication:

Symposium Papers

Volume:

354

Abstract:

Polycarboxylate superplasticizers are increasingly being used in nuclear power plant construction including the dry shielding concrete containment, which directly surrounds the reactor pressure vessel. The problems of their thermal and radiation stability are brought to the fore. Tests were performed based on the simultaneous thermal analysis of admixtures based on HPEG-type polycarboxylate ethers. Scanning calorimetry (DSC) and thermogravimetry (TG) measurements were employed in this study. Both measurements were performed on a Netzsch STA 429 CD Simultaneous Thermal Analysis Apparatus. For analysis of degradation products, Netzsch aQMS 403 C quadrupole mass-spectrometer was used that allows performing analysis (IC curves) of thermal degradation products within the range from 1 to 121 atom-charge units. The aluminum oxide tablets impregnated with superplasticizers were used. The comprehensive analysis of superplasticizers has proven their quite high thermal stability. During heating up to 250°С and thermal degradation of polycarboxylate ethers, there is no emission of explosive and toxic gases.

DOI:

10.14359/51736080


Document: 

SP-354_19

Date: 

July 1, 2022

Author(s):

Franco Zunino, Karen L. Scrivener

Publication:

Symposium Papers

Volume:

354

Abstract:

The optimization of the production process and mixture design using blended cements is an important step to achieving widespread adoption of these new technologies. In particular, grinding is an important step to ensure good reactivity at early ages and adequate flowability. Grinding aids are normally used to reduce the electrostatic forces between particles and increase the yield of the process. Alkanolamines is a family of molecules that are commonly used for this purpose. In this study, the effect of alkanolamines on LC3 hydration was studied. It was observed that alkanolamines influence the hydration of the aluminate phases in clinker, particularly ferrite. This leads to enhanced precipitation of carboaluminates. An increase in early age strength was seen for LC3 systems incorporating TIPA (triisopropanolamine).

DOI:

10.14359/51736075


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