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International Concrete Abstracts Portal

Showing 1-5 of 51 Abstracts search results

Document: 

SP320

Date: 

September 1, 2017

Author(s):

Arezki Tagnit-Hamou

Publication:

Symposium Papers

Volume:

320

Abstract:

The purpose of this international conference is to present the latest scientific and technical information in the field of supplementary cementitious materials and novel binders for use in concrete. The new aspect of this conference is to highlight advances in the field of alternative and sustainable binders and supplementary cementitious materials, which are receiving increasing attention from the research community. The conference was held in Montréal, Canada from October 2 to 4, 2017. The conference proceedings, containing 50 refereed papers from more than 33 countries, were published as ACI SP-320.

DOI:

10.14359/51701166


Document: 

SP-320_23

Date: 

August 1, 2017

Author(s):

Siva Uppalapati and Özlem Cizer

Publication:

Symposium Papers

Volume:

320

Abstract:

The purpose of this study is to investigate the autogenous shrinkage of alkali-activated slag/fly ash (AASF) mortar blends. A series of tests was performed to determine the effect of type and dosage of activators on autogenous shrinkage deformation. Heat progression in AASF systems was characterized by means of isothermal calorimetry. The reaction products of alkali-activated slag/fly ash (Class F) blends was characterized using X-ray diffraction (XRD). From those results, two main phases (C-A-S-H and N-A-S-H gels) are detected in slag/fly ash blended systems and with increase in fly ash content, the amount of the C-A-S-H gel decreases and the amount of N-A-S-H gel increases. Test results show that the slag/fly ash mass ratio, type and dosage of activator are the significant factors influencing the autogenous shrinkage and rate of reaction in AASF system. With increasing fly ash content and decrease in activator-to-cementitious materials ratio, the autogenous shrinkage (up to 7 days) of the AASF system decreases.

DOI:

10.14359/51701061


Document: 

SP-320_26

Date: 

August 1, 2017

Author(s):

Rolf Andreas Lauten

Publication:

Symposium Papers

Volume:

320

Abstract:

Characteristics of a sodium carbonate-activated slag concrete in presence of different plasticizers are presented and discussed. Inclusion of a calcined clay in the activator system allows for a more rapid curing in a system that is known to cure slowly. Depending upon the plasticizer (lignosulfonate, polycarboxylate or naphthalene sulfonate), slump retention is either improved relative to the control or inferior. Compressive strength of concrete prisms can be recorded after 24 hours, but set times determined from temperature as a function of curing time indicate longer set times. The longest slump retention is obtained with lignosulfonate, and the compressive strength at 28 days is comparable among the three plasticizers. Surprisingly, lignosulfonate appears to be as efficient as the other plasticizers when it comes to fluidization of the concrete mixes.

DOI:

10.14359/51701064


Document: 

SP-320_01

Date: 

August 1, 2017

Author(s):

Diego Velandia, Cyril Lynsdale, John L. Provis and Fernando Ramirez

Publication:

Symposium Papers

Volume:

320

Abstract:

Concretes made with blended portland cement containing high volumes of fly ash provide an alternative to conventional portland cement concrete for reducing CO2 emissions. This study evaluates mechanical and chemical activation of four fly ashes by assessing their effects on hydration and compressive strength. Results show the importance of the amorphous content in terms of compressive strength. The composition of fly ash is changed by a sieving process where certain particle sizes are retained; the amorphous silica and loss on ignition (LOI) contents varied depending on the fineness, hence affecting the performance of the fly ash in concrete. Reduction in particle size and LOI do not always lead to improvement in compressive strength. The effect of sodium sulfate, as activator, was significant at early ages for two of the fly ashes studied; the amount of portlandite consumption is reflected in the compressive strength evolution observed. However, sodium sulfate does not have the same effect on fly ashes with high amount of Fe2O3, where portlandite consumption is much lower.

DOI:

10.14359/51701039


Document: 

SP-320_06

Date: 

August 1, 2017

Author(s):

Francisca Puertas, María del Mar Alonso, Manuel Torres-Carrasco, Belen González Fonteboa, Iris González Taboada, Gemma Rojo, and Fernando Martínez-Abella

Publication:

Symposium Papers

Volume:

320

Abstract:

This study compared waterglass- and NaOH-activated slag concrete (AASC) rheology to the behaviour in OPCC concrete. The effect of mixing time on fresh concrete rheology was also assessed. A rotational rheometer was used to apply shear stress to the materials to determine static and dynamic yield stress at 15, 30, 45 and 60 min of age. Concrete strength and porosimetry were determined to relate rheology to hardened concrete behaviour. The results indicate that slump and rheological behaviour of OPCC and AASC are different, scpecially when the alkaline activator is waterglas (AAS WG). The mixing protocol appeared to affect concrete rheology (fresh behaviour) more than its strength (hardened behaviour). In AASC WG, both rheological and mechanical behaviour improved at longer mixing times.

DOI:

10.14359/51701044


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