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International Concrete Abstracts Portal

Showing 1-5 of 1862 Abstracts search results

Document: 

SP-355_17

Date: 

July 1, 2022

Author(s):

E. Redaelli, M. Carsana, A. Filippi, F. Lollini

Publication:

Symposium Papers

Volume:

355

Abstract:

The use of recycled aggregates allows for reducing the environmental impact of concrete materials, by reducing the amount of waste and limiting the consumption of natural resources. Recycled asphalt pavement (RAP) is a granular material that comes from the milling of road pavements whose size and distribution make it suitable as aggregate for concrete. The environmental benefits of the replacement of natural aggregate with RAP need to be assessed with a better understanding of the long-term behavior of RAP concrete, considering the evolution of its performance in time and its ability to guarantee an adequate service life when exposed in operating conditions. This note presents the preliminary results of research on the effect of RAP on concrete properties. The addition of RAP aggregate affects concrete properties in a fresh and hardened state. Some parameters showed clear trends with the percentage of RAP, however, also other factors (e.g. w/c ratio and curing time) seem to play a role. Compressive strength and dynamic modulus of elasticity of RAP concrete were always lower compared to reference concrete, while the electrical resistivity did not show a clear trend. Further investigations will be carried out to clarify the role of RAP aggregate.


Document: 

SP-354_04

Date: 

July 1, 2022

Author(s):

Gilberto Artioli, Anna Bravo, Alberto Brocchi, Fabio Castiglioni, Maria Chiara Dalconi, Mikaela Decio, Giorgio Ferrari, Marco Mazzetti, Davide Salvioni, Luca Torelli, Luca Valentini

Publication:

Symposium Papers

Volume:

354

Abstract:

Supplementary cementitious materials (SCMs) can be effective levers to reduce the environmental impact of concrete. One of the major limitations for high substitution of clinker by SCMs in Portland cement is the loss of strength of the resulting concrete, particularly at early age, compared with similar concrete made with equivalent dosage of pure clinker Portland cement. Furthermore, the possibility to use larger fractions of SCMs requires strongly alkaline activators which pose environmental and safety problems and are not compatible with commercial PCE superplasticizers. A new hybrid additive was synthesized which works, at the same time, as seed for the clinker phase and as an activator for alkali-activated binders. The new product consists of an alkaline suspension of micro-sized particles containing nano-structured CSH seeds, amorphous portlandite, and AFm phases embedded in a polymeric matrix. The structure and the mechanism of action of the new product on slag cements have been investigated by Environmental Scanning Electron Microscopy, X-ray Powder Diffraction, Thermal Analysis, and Isothermal Calorimetry. The new product is fully compatible with PCE superplasticizers and can be used to produce alkali-activated concretes characterized by low-carbon impact.


Document: 

SP-355_40

Date: 

July 1, 2022

Author(s):

Christian Paglia, Michele Paderi, Cristina Mosca, Samuel Antonietti

Publication:

Symposium Papers

Volume:

355

Abstract:

The recycling of waste materials from the construction sector represents an opportunity for environmental protection, to save expensive landfill costs, and promote sustainability. The increased interest in the use of recycled materials is seen in several European countries with the production of concrete using granulates from demolition material. In Switzerland, the SIA 2030 standard defines recycled concrete based on a minimum percentage of 25% recycled aggregates to be added. This research focuses on the possibilities of producing high-quality recycled concrete, starting from high-quality cementitious material, i. e. concrete. The original material with known properties was demolished and used as aggregates to replace the natural aggregates. Fresh, hardened, and durable properties of concrete were evaluated on blends containing 25, 50, and 100% recycled aggregates. At early stage (2 days), the lowest value of compressive strength was already above 15 MPa for the blend with 100% recycled aggregates. Most of the recycled concrete satisfies the main mechanical and durability features, in particular with the addition of 25 respectively 50% of the recycled aggregate component.


Document: 

SP-355_22

Date: 

July 1, 2022

Author(s):

Ozlem Akalin, Ahmet Seven, Muhammed Marasli, Iskender A. Reyhancan, M. Hulusi Ozkul

Publication:

Symposium Papers

Volume:

355

Abstract:

Although radiation is used for many useful purposes today, it has properties that can cause serious harm to human health. Especially, the harmful effects of radiation come from radioactive sources used for diagnosis and treatment in hospitals. Armoring the environment that is used and preventing its effect from being transferred to the external environment is one of the most frequently used methods. For this purpose, lead plates (0.1-3 mm) and concrete (6-26 cm) are used in hospitals. The new building material to be produced is healthy compared to lead since it will have a thin section compared to concrete, and it will have the characteristics of lightness and workability. Precautions to be taken in concrete against radiation are available in the literature, but the concretes in the proposed solutions are both heavy, prone to cracking, and have low fire resistance. In this study different fine minerals are optimized to minimize pores and X-Ray, gamma, and neutron shielding effectiveness were measured. Different thicknesses 1-5 cm were molded after the preparation of glass fiber-reinforced concrete (GRC) to get an equivalent value of 2 mm lead.


Document: 

SP-355_02

Date: 

July 1, 2022

Author(s):

Ezio Cadoni, Deborah Briccola, Matteo Dotta, Daniele Forni

Publication:

Symposium Papers

Volume:

355

Abstract:

Understanding the dynamic response of cementitious materials is one of the key issues in the design and assessment of structures subjected to blast or impact loadings. The response of the material to these dynamic actions can be dramatically different and it must be carefully evaluated. The experimental response in direct tension of two ultra-high-performance concretes, tested in a wide range of stress-rate from 0.3 MPa/s (0.044 ksi/s) to 1.3 TPa/s (188’549 ksi/s), is presented in the paper. An electro-mechanic universal machine, a Hydro-Pneumatic Machine, and a Split Hopkinson Tensile Bar device were used to test low, medium, and high stress rates, respectively. The results showed a marked rate dependency of these materials. The resulting DIFs highlighted how Model Code 2010 underestimate the material dynamic strength both at medium and high stress-rate.


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