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International Concrete Abstracts Portal

Showing 1-10 of 51 Abstracts search results

Document: 

SP320

Date: 

September 1, 2017

Author(s):

Arezki Tagnit-Hamou

Publication:

Special Publication

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.


Document: 

SP-320_50

Date: 

August 1, 2017

Author(s):

Kamilia Abahri, Chady El Hachem, Fares Bennai, Ngoc Toan, and Rafik Belarbi

Publication:

Special Publication

Volume:

320

Abstract:

This study presents experimental and 3D correlation results of the microstructural hygrothermal behavior of hemp concrete. The experimental procedure was performed using non-destructive method’s X-ray tomography and digital microscopy. Hemp concrete specimens were scanned and examined at different relative humidity levels through a specifically developed processing protocol. The material response to temperature in the range of 25°C to 110°C where also analyzed via the 3D topology post-processing. After that, 3D correlation is performed on the reconstructed volumes, with fined resolution of 17μm/voxel, in order to quantify the various displacements due to the hygric load. The imaging data and the 3D correlation results allowed having access to the displacement field caused by the relative humidity and temperature solicitations on real structure of hemp concrete. These results provide reliable data on the microstructural evolution when studying aging or the material durability.


Document: 

SP-320_49

Date: 

August 1, 2017

Author(s):

Laurent Steger, Bernard Salesses, Cédric Patapy, Mohend Chaouche, Laurent Frouin, and Martin Cyr

Publication:

Special Publication

Volume:

320

Abstract:

Ordinary portland cement (OPC) substitution by high contents of ground granulated blast furnace slags (GGBS) reduces the early hydration kinetics, causing a slower development of mechanical properties. Chloride are well known for their accelerating effect on OPC but are mostly used for specific applications, such as non-reinforced concrete, due to their detrimental effects regarding steel bars corrosion. However, GGBS-based concretes are known for their ability to resist chloride ingress due to their capacity to fix more chlorides in hydrates, hence reducing the free chloride available for corrosion. This paper aims to present a link between strength development and in-situ formation of aluminate based hydrates at early age in the presence of chloride salts. Isothermal calorimetry is coupled with XRD investigations to gather insights on the accelerating mechanisms and on the potential impact of GGBS on durability. SEM-EDS observations were conducted to determine the spatial distribution of products formation and anhydrous grains dissolution in the presence of chlorides. The resistance to corrosion of chlorides/GGBS blends is then studied by electrochemical tests.


Document: 

SP-320_48

Date: 

August 1, 2017

Author(s):

Reda Jaafri, Abdelilah Aboulayt, Syed-Yasir Alam, Emmanuel Roziere, and Ahmed Loukili

Publication:

Special Publication

Volume:

320

Abstract:

Slabs are subjected to many important drying effects due to their large exchange surface area, particularly plastic and drying shrinkage. The use of suitable mineral additions with shrinkage reducing properties is necessary to improve cement-based materials behavior. The aim of the experimental work carried out is to investigate the influence of natural hydraulic lime (NHL) and aerial lime (AL) on the properties of cement mortars at fresh and hardened state. A reference mortar was designed with a water-to-cement ratio of 0.6. At a constant paste volume, cement was replaced with increasing mass proportions of 12.5%, 25% and 50% of NHL. The approach used shows that the substitution of cement by either type of lime reduces plastic and drying shrinkage, but negatively affected rheological behavior and compressive strength. The findings of this paper highlight the benefits of lime/cement substitution on the volume changes in cement mixtures at early age and long-term.


Document: 

SP-320_47

Date: 

August 1, 2017

Author(s):

Peter G. Gaunt, Mathew K.R. Versfeld, André Ferreira and Stephen O. Ekolu

Publication:

Special Publication

Volume:

320

Abstract:

In this paper, it is shown that Class F fly ash can be effectively used in high volumes as a supplementary cementitious material. High Volume Fly Ash (HVFA) use is of interest in promoting the development and application of green materials. In South Africa, there is little or no literature on high volume incorporation of locally available fly ash in concrete. In this investigation, six different concrete mixtures with water/cementitious ratios of 0.3 and 0.45, were used. The mixtures consisted of 0, 30, 50 and 70% fly ash. Tests carried out were workability, compressive strength and heat of hydration. Large 300 mm cubes were used to study hydration heat development in fresh concrete. As expected, concrete strength decreased as fly ash content increased owing to the slower rate of strength development in fly ash mixtures. It was found that heat of hydration generated in HVFA mixtures gave lower peak temperatures compared to mixtures without fly ash, producing reductions of 27% to 43.5% in peak temperatures for mixtures containing 50% and 70% fly ash respectively. Temperature simulation using ConcreteWorks gave predictions correctly depicting the measured temperature profiles but with slight under-estimation of peak temperatures.


Document: 

SP-320_46

Date: 

August 1, 2017

Author(s):

Hayder Alghazali, John J. Myers

Publication:

Special Publication

Volume:

320

Abstract:

As is known, more sustainable concrete has become the desired aim of many transportation departments. To produce more sustainable concrete, the emphasis has been placed on replacing cement with more sustainable materials and taken into account, materials cost and CO2 footprint. High volume fly ash with hydrated lime mixtures have been proposed as one potential approach for achieving durable and sustainable concrete. In this first phase study, performance ranking analysis approach is presented to optimize the performance of high volume fly ash mortars. A total of 15 mortar mixtures were prepared at different replacement levels (up to 75 percent). Hydrated lime was incorporated with ASTM Class C fly ash to increase hydration reaction at different dosage levels (between 0-15 percentages). Fresh properties and semi Adiabatic temperature tests were conducted for each mixture. Compressive strength, drying shrinkage, bulk electric conductivity, and electric resistivity (surface) were measured and monitored until the age of 90 days. Cost efficiency was also evaluated. Based on performance ranking approach, five different binder compositions were selected to conduct the second phase of this study.


Document: 

SP-320_45

Date: 

August 1, 2017

Author(s):

Isabelle Fily-Paré, Benoît Fournier, Josée Duchesne, Arezki Tagnit-Hamou

Publication:

Special Publication

Volume:

320

Abstract:

Finely ground glass produced from recycling facilities is an alternative supplementary cementing material that is often considered for eco-friendly concrete mix designs. However, documentation on its behaviour in concrete is limited or somewhat contradictory. Many studies suggest that glass powder can suppress the expansion of concrete due to alkali-silica reaction (ASR), while others suggest that its high alkali content maintains the expansive potential in concrete due to ASR and consequently limits its preventive character. The present work seeks to clarify the overall availability of alkalis in the pore solution of cementitious matrices incorporating glass powder. For this purpose, pore solution extraction had been conducted, on pastes containing 0%, 20% and 40% of Glass Powder and cements of alkali levels of 0.25%, 0.63%, 0.94% and 1.25% Na2Oe. The concentration of alkalis available in the pore solution was analysed after 28 and 91 days. Results showed that the effect of GP on the hydroxyl concentration of the pore solution is limited for cement of high alkali content and important for low alkali cement. Also GP tends to reduce the potassium concentration and increase the sodium concentration of the pore solution.


Document: 

SP-320_44

Date: 

August 1, 2017

Author(s):

Daniela Hesselbarth, Thomas Moser, and Juerg Sturzenegger

Publication:

Special Publication

Volume:

320

Abstract:

Cement production is an energy-intensive process, responsible for a significant amount of the world’s carbon dioxide emissions. Over the last years, geopolymers have been often promoted as an ecologically friendly alternative with low CO2 footprint. The presented work proposes curing of geopolymers at ambient temperature for application as construction materials. Different aluminosilicates like fly ash, metakaolin, slag and combinations thereof are evaluated as binders. Furthermore, the influence of alkali silicate activator (water glass), with respect to type and molar ratio, on the resulting geopolymer properties is investigated. This paper discusses characteristics of ambient temperature cured geopolymers, such as workability, mechanical, and physical properties. The achieved mechanical properties represent medium performance as well as high performance.


Document: 

SP-320_43

Date: 

August 1, 2017

Author(s):

Mohammad A. Aqel, and Daman K. Panesar

Publication:

Special Publication

Volume:

320

Abstract:

The focus of this paper is to evaluate the effect of replacing 15% (by weight) of the cement by limestone filler on the concrete expansion due to delayed ettringite formation. The freeze-thaw testing and microstructural analysis were conducted to further assess the damage caused by the expansion due to delayed ettringite formation. This study also evaluates the interplay between cement type (Type GU and Type HS), limestone filler content (0 and 15% by weight), and steam curing temperature (55°C [131°F] and 82°C [180°F]). The results showed that replacing 15% of the cement reduced the expansion of concrete due to delayed ettringite formation. However, this reduction in the concrete expansion was insignificant compared to the reduction in concrete expansion when the steam curing temperature was reduced from 82°C [180°F] to 55°C [131°F] or when cement with low sulfate and alkali contents (i.e., HS cement) was used instead of GU cement.


Document: 

SP-320_42

Date: 

August 1, 2017

Author(s):

Théau Conte and Mohend Chaouche

Publication:

Special Publication

Volume:

320

Abstract:

Cement pastes exhibit virtually all the rheological features of complex fluids. Thus, several rheological methods and setups have been used in the literature to characterize these materials. In the present investigation Large Amplitude Oscillatory Shear (LAOS) is for the first time exploited for cement pastes. LAOS can be used to characterize all the rheological properties within a single procedure. This technique is tested in the case of three different cement mixes: a Portland cement paste, nanoclay blended cement paste and a cement paste containing a hydro-soluble polymer. These mixes were selected in order to get rheological properties that are different both quantitatively and qualitatively. Indeed, addition of a low amount of nanoclay increased significantly the yield stress and the shear-thinning/thixotropic aspects of the cement paste, whereas addition of cellulose ether led to the decrease of yield stress and thixotropy. These non-linear rheological properties are discussed within the framework of LAOS.


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