scholarly journals Correlating the Cellular Network, in Foamed Concrete containing Ash, with their Physical Properties

2020 ◽  
Author(s):  
Jonathan Stolz ◽  
Yaman Boluk ◽  
Vivek S Bindiganavile
Keyword(s):  
Fractal Dimension ◽  
Portland Cement ◽  
Physical Properties ◽  
Cellular Network ◽  
Sound Absorption ◽  
Cell Structure ◽  
Thermal Constants ◽  
Foamed Concrete ◽  
Alkali Activated ◽  
Cellular Concrete

Cellular concrete is a lightweight solid cementitious foam that is used mainly for thermal insulation and sound absorption. Either partially or wholly, when the Portland cement in the binder is replaced with ash, the environmental impact of the material is reduced. However, the resulting changes in the cell structure and their subsequent impact upon the physical properties of the material have not been well examined. In this study, cellular concrete was prepared from alkali activated fly ash binders and separately, from Portland cement binders blended with wood ash. The cell structure was photographed using laser confocal microscopy and the images were analyzed to quantify the cellular network in terms of the porosity and the fractal dimension of the porous phase. Alongside, the cellular concrete specimens were tested for their thermal constants and sound absorption. The results show that there was an increase in the fractal dimension and an associated drop in thermal conductivity for an increase in the porosity.

Effect of AlF3 production waste on the processes of hydration and hardening of the alkali-activated Portland cement with sodium silicate hydrate

2019 ◽  
Vol 138 (2) ◽  
pp. 879-887
Author(s):  
Pavel Krivenko ◽  
Danutė Vaičiukynienė ◽  
Aras Kantautas ◽  
Vitoldas Vaitkevičius ◽  
Evaldas Šerelis
Keyword(s):  
Portland Cement ◽  
Sodium Silicate ◽  
Production Waste ◽  
Alkali Activated

scholarly journals A Review of the Mechanical Properties and Durability of Ecological Concretes in a Cold Climate in Comparison to Standard Ordinary Portland Cement-Based Concrete

Materials ◽  
2020 ◽  
Vol 13 (16) ◽  
pp. 3467
Author(s):  
Ankit Kothari ◽  
Karin Habermehl-Cwirzen ◽  
Hans Hedlund ◽  
Andrzej Cwirzen
Keyword(s):  
Carbon Dioxide ◽  
Portland Cement ◽  
Ordinary Portland Cement ◽  
Cementitious Materials ◽  
Cold Climate ◽  
Supplementary Cementitious Materials ◽  
Short Exposure ◽  
Chemical Admixtures ◽  
Composite Cements ◽  
Alkali Activated

Most of the currently used concretes are based on ordinary Portland cement (OPC) which results in a high carbon dioxide footprint and thus has a negative environmental impact. Replacing OPCs, partially or fully by ecological binders, i.e., supplementary cementitious materials (SCMs) or alternative binders, aims to decrease the carbon dioxide footprint. Both solutions introduced a number of technological problems, including their performance, when exposed to low, subfreezing temperatures during casting operations and the hardening stage. This review indicates that the present knowledge enables the production of OPC-based concretes at temperatures as low as −10 °C, without the need of any additional measures such as, e.g., heating. Conversely, composite cements containing SCMs or alkali-activated binders (AACs) showed mixed performances, ranging from inferior to superior in comparison with OPC. Most concretes based on composite cements require pre/post heat curing or only a short exposure to sub-zero temperatures. At the same time, certain alkali-activated systems performed very well even at −20 °C without the need for additional curing. Chemical admixtures developed for OPC do not always perform well in other binder systems. This review showed that there is only a limited knowledge on how chemical admixtures work in ecological concretes at low temperatures and how to accelerate the hydration rate of composite cements containing high amounts of SCMs or AACs, when these are cured at subfreezing temperatures.

scholarly journals Complex multifunctional additive for anchoring grout based on alkali-activated portland cement

2020 ◽  
Vol 907 ◽  
pp. 012055
Author(s):  
P V Krivenko ◽  
O M Petropavlovskyi ◽  
I I Rudenko ◽  
O P Konstantynovskyi ◽  
A V Kovalchuk
Keyword(s):  
Portland Cement ◽  
Multifunctional Additive ◽  
Alkali Activated

scholarly journals Volcanic Ash as a Sustainable Binder Material: An Extensive Review

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1302
Author(s):  
Andrés Játiva ◽  
Evelyn Ruales ◽  
Miren Etxeberria
Keyword(s):  
Chemical Composition ◽  
Portland Cement ◽  
Urban Areas ◽  
Volcanic Ash ◽  
Mechanical Performance ◽  
Cement Clinker ◽  
Alkali Activation ◽  
Cement Production ◽  
Sustainable Solutions ◽  
Alkali Activated

The construction industry is affected by the constant growth in the populations of urban areas. The demand for cement production has an increasing environmental impact, and there are urgent demands for alternative sustainable solutions. Volcanic ash (VA) is an abundant low-cost material that, because of its chemical composition and amorphous atomic structure, has been considered as a suitable material to replace Portland cement clinker for use as a binder in cement production. In the last decade, there has been interest in using alkali-activated VA material as an alternative material to replace ordinary Portland cement. In this way, a valuable product may be derived from a currently under-utilized material. Additionally, alkali-activated VA-based materials may be suitable for building applications because of their good densification behaviour, mechanical properties and low porosity. This article describes the most relevant findings from researchers around the world on the role of the chemical composition and mineral contents of VA on reactivity during the alkali-activation reaction; the effect of synthesis factors, which include the concentration of the alkaline activator, the solution-to-binder ratio and the curing conditions, on the properties of alkali-activated VA-based materials; and the mechanical performance and durability properties of these materials.

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