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International Concrete Abstracts Portal

Showing 1-5 of 162 Abstracts search results

Document: 

SP-355_44

Date: 

July 1, 2022

Author(s):

Vigil de la Villa, R., García-Giménez, R., Frías, M., Martínez Ramírez, S., Fernández-Carrasco, L., Lahoz, E., Moreno-Juez, J., Vegas-Ramiro, I.

Publication:

Symposium Papers

Volume:

355

Abstract:

Sustainable development and circular economy policies currently prioritize the recovery of industrial waste and rubble as secondary raw materials. Concrete and demolition waste's (CDW) fine fractions of concrete nature are bringing special attention due to their accumulation, subject to weather conditions, and without any industrial application at present. These wastes have little pozzolanic activity, which is why it is necessary to combine them with other active additions for the ternary cements manufacture. At present, a laminar glass waste from the deconstruction has been selected to obtain the binary mixture. A binary mixture of pozzolan recycled concrete/glass with a 1:2 ratio has been prepared to evaluate the synergy of both wastes in the pozzolanic reaction, and its possible commercialization for future ternary cements that are more sustainable. The characterization of materials and reaction kinetics mainly in the ternary pastes have been characterized by XRF, ICP/MS, NMR, FTIR, XRD-Rietveld, and SEM/EDX, detecting calcite, quartz, mica, feldspar, and clay minerals and as hydrated phases ettringite, aluminates and C-S-H gels. According to these results, it can be highlighted that from the scientific point of view, this mixture of pozzolans from CDWs is viable for use as ecoefficient pozzolans for the more sustainable ternary cements.

DOI:

10.14359/51736056


Document: 

SP-355_08

Date: 

July 1, 2022

Author(s):

Franco Zunino, Karen L. Scrivener

Publication:

Symposium Papers

Volume:

355

Abstract:

The adoption of blended cements is the most feasible strategy to achieve a more sustainable industry. In this regard, reducing the clinker factor, while retaining performance, is the key parameter to address. Limestone calcined clays are a promising technology as they offer similar performance to OPC from 7 days onwards while enabling a reduction of the clinker content of 50%. In some regions of the world like South America, pozzolanic cements (i.e., blended cements that combine clinker with natural pozzolans) have been used for decades. Their clinker factors range from 80 down to 50%. However, their mechanical properties are in general lower as compared to OPC. In this study, we show that by using LC3-type formulations, cements with the same performance as commercial pozzolanic cements can be produced with clinker contents significantly below 50%. This is explained by the high reactivity of calcined clays and the synergetic reaction of metakaolin and limestone that allows offsetting the clinker reduction.

DOI:

10.14359/51736014


Document: 

SP-337_05

Date: 

January 23, 2020

Author(s):

Kjell Tore Fosså and Widianto

Publication:

Symposium Papers

Volume:

337

Abstract:

This paper describes the development in concrete technology for offshore concrete structures from the 1970’s until now and discusses some potential topics for future research which would result in more cost-effective offshore concrete structures.

Most of the offshore concrete structures constructed in the last 4 decades are still in operation, with no or only minor maintenance required, even though the average age for these structures in the North Sea is more than 25 years. The compressive strength in offshore structures has gradually increased from about 40MPa (5800 psi) in the 1970’s to more than 100MPa (14500 psi) in some of the latest concrete structures. Standards and concrete specifications have been revised several times during these years. In parallel, the knowledge from several research and development programs has been used to further improve the concrete properties and overcome the limitations. Focus has been primarily to improve the compressive strength of the concrete as well as the durability and concrete workability. The cement and admixture industry have been heavily involved in research programs to further adapt and develop these material properties. The result of the product developments in the concrete constituency has also improved cost-effectiveness and durability (including overall life-cycle cost-effectiveness) for offshore concrete structures.

With the new generation technology, the technical limitations we face today will be overcome. With more knowledge and improved technology, the quantity and size of cracks in concrete in service are expected to be reduced, which would also improve durability. In addition, the focus in the future will also be on sustainable and environmentally friendly materials.

DOI:

10.14359/51724548


Document: 

SP-320_11

Date: 

August 1, 2017

Author(s):

Yunusa A. Alhassan and Yunus Ballim

Publication:

Symposium Papers

Volume:

320

Abstract:

A detailed investigation on the properties of concrete made with fly ash (FA) blended cement were carried out by characterizing such concrete in terms of physical and chemical composition at early-age. In addition, the effects of inland exposure condition on the durability performance of the concrete were also monitored via the carbonation depth. Concrete cubes were made using various concrete mixtures of water-binder ratios (w/b) = 0.40, 0.50, 0.60, 0.75 and binder contents = 300, 350, 400, 450 kg/m3. Concrete cube of 100 mm size were cast and cured in water for 3, 7, or 28 days, then characterized at early-ages. Companion concrete samples were exposed indoors or outdoors to undergo carbonation under natural environment. The concrete cube samples were characterized at 6, 12, 18 and 24 months of exposure in terms of carbonation depths. The results of the concrete early-age properties and medium-term durability characterisation were analyzed. The results show that, increased knowledge of concrete materials and concrete early-age properties as well as its exposure conditions were vital in durability considerations for reinforced concrete structures.

DOI:

10.14359/51701049


Document: 

SP312-01

Date: 

October 1, 2016

Author(s):

Saamiya Seraj and Maria C.G. Juenger

Publication:

Symposium Papers

Volume:

312

Abstract:

Concerns about the future availability of traditional supplementary cementitious material (SCM) sources, like fly ash, have prompted the search for a wider variety of materials that could be used as SCMs in concrete. An important criterion for an SCM is pozzolanic reactivity, which is its ability to react with calcium hydroxide in the presence of water to form calcium silicate hydrate (C-S-H). ASTM criteria for SCMs address pozzolanic reactivity indirectly by measuring the compressive strength of SCM containing mortars, or more specifically the strength activity index (SAI). More direct methods of assessing pozzolanic reactivity include measuring the reduction of calcium hydroxide (CH) in cementitious pastes through methods like thermal gravimetric analysis (TGA). However, both direct and indirect tests to evaluate pozzolanic reactivity take a considerable amount of time due to the slow nature of certain pozzolanic reactions. Alternatively, the Chapelle test, which measures the amount of CH fixed by the SCM in solution at high temperatures, can serve as an accelerated test method for screening out potential SCMs. In this paper, the accuracy of the Chapelle test for measuring pozzolanic reactivity is evaluated for a variety of SCMs with different physical and chemical characteristics by comparing it with more traditional test methods like SAI and CH measurement through TGA.

DOI:

10.14359/51689364


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