The Influence of the Waste Foundry Sand on the Microstructure and the Physico-Mechanical Properties of Autoclaved Aerated Concrete

2020 ◽  
Vol 998 ◽  
pp. 293-298
Author(s):  
Jindřich Melichar ◽  
Vit Černý ◽  
Rostislav Drochytka
Keyword(s):  
Mechanical Properties ◽  
Porous Structure ◽  
X Ray Diffraction ◽  
Hydrothermal Conditions ◽  
Foundry Sand ◽  
Autoclaved Aerated Concrete ◽  
Calcium Hydrosilicates ◽  
Waste Foundry Sand ◽  
Aerated Concrete ◽  
Positive Effect

Thanks to its porous structure the autoclaved aerated concrete has excellent thermal insulation properties. The production of this building material is carried out in two main steps. At first calcium hydroxide reacts with aluminum powder. This reaction releases hydrogen which creates the porous structure. Secondly lime reacts with siliceous components under hydrothermal conditions. This reaction forms crystalline calcium hydrosilicates which represent a binder component in the material. Focus of this paper is to study the degree of crystallization of calcium hydrosilicates depending on the quantity and fineness of the admixture of the waste foundry sand. This material was tested in three different values of specific surface. The influence of granularity of the waste foundry sand on the microstructure and physical-mechanical properties of the autoclaved aerated concrete was monitored. At the same time, the influence primary filler substitution by foundry sand was also observed. The substitution was realized in amounts of 10%, 30% and 50%. As the final step the influence of the waste foundry sand admixture on the autoclaved aerated concrete porous structure was evaluated. The microstructure was analyzed by X-ray diffraction. Obtained values show that admixture of waste foundry sand has positive effect on the crystallisation of calcium hydosilicate phases. Substitution of primary filler by waste foundry sand is possible up to 50%. With a higher amount of substitution, the higher values of compressive strength of autoclaved aerated concrete were monitored.

scholarly journals The influence of the fireclay waste on the microstructure and the physico-mechanical properties of autoclaved aerated concrete

2019 ◽  
Author(s):  
Pavlína Šebestová ◽  
Vít Černý ◽  
Rostislav Drochytka
Keyword(s):  
Mechanical Properties ◽  
Porous Structure ◽  
X Ray Diffraction ◽  
Hydrothermal Conditions ◽  
Second Stage ◽  
Autoclaved Aerated Concrete ◽  
Calcium Hydrosilicates ◽  
Aerated Concrete ◽  
Two Phases ◽  
Positive Effect

Autoclaved aerated concrete is a building material with good thermal insulation properties, which it receives through the pore structure. The production of autoclaved aerated concrete consists of two phases. In the first stage, a porous structure is formed by the reaction of calcium hydroxide and aluminum powder to form hydrogen. In the second stage, the lime and siliceous components react under hydrothermal conditions to form crystalline calcium hydrosilicates which form a binder component in the material. In this paper, the degree of crystallization of calcium hydrosilicates is studied depending on the quantity and fineness of the admixture of the fireclay waste. The effect of three different sizes of the specific surface of the fireclay waste on the microstructure and physico-mechanical properties of the autoclaved aerated concrete was monitored. At the same time, the influence of sand substitute for waste was monitored. The amount of the substitute was 10%, 30% and 50%. Finally, the influence of the fireclay waste admixture on the autoclaved aerated concrete porous structure was assessed. The microstructure was analyzed by X-ray diffraction. Based on the achieved values, it can be said that the admixutre of fireclay waste has a positive effect on the crystallisation of calcium hydosilicate phases. Fireclay waste substitution is possible up to 50%. With a higher amount of substitution, the increasing pressure of autoclaved aerated concrete compression is monitored.

Content of Aluminium Hydroxide in Lime-Silica Composite and its Influence on Tobermorite Formation

2018 ◽  
Vol 916 ◽  
pp. 195-199 ◽  
Author(s):  
Jindrich Melichar ◽  
Vit Cerný ◽  
Jan Fleischhacker ◽  
Rostislav Drochytka
Keyword(s):  
Mechanical Properties ◽  
Aluminium Hydroxide ◽  
Raw Materials ◽  
Mineralogical Composition ◽  
Silica Sand ◽  
Chemical Formula ◽  
Hydrothermal Conditions ◽  
Silicon Oxides ◽  
Calcium Hydrosilicates ◽  
Aerated Concrete

Aerated concrete is lightweight building material with excellent thermos-technical properties compared to its strengths, easy workability and economic efficiency. It is material with long tradition of manufacturing since 1924 but its potential is yet possible to be extended. Since the beginning pure ingredients such as lime and silica sand has been used. Nowadays we are looking for ways to replace these expensive raw materials with cheaper alternatives. One of the most important mechanical properties of each material is its strength. In case of aerated concrete the bearer of strength is mineral tobermorite. It is created by reaction of silicon oxides and lime at hydrothermal conditions. It belongs to the group of calcium hydrosilicates with chemical formula Ca5Si6O16(OH)2·4H2O. Main goal of this paper is proposal for modification of the raw materials composition and autoclave regime of aerated concrete using aluminium hydroxide in order to improve final mechanical properties and mineralogical composition.

Improving Mechanical Properties of Autoclaved Aerated Concrete by Sugar Sediment

2013 ◽  
Vol 807-809 ◽  
pp. 1266-1269 ◽  
Author(s):  
Atthakorn Thongtha ◽  
Somchai Maneewan ◽  
Chantana Punlek ◽  
Yothin Ungkoon
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Flexural Strength ◽  
Crystalline Morphology ◽  
X Ray Diffraction ◽  
Quality Class ◽  
X Ray ◽  
Autoclaved Aerated Concrete ◽  
Aerated Concrete ◽  
Scanning Electron

The comparison of microstructure and mechanical properties between the autoclaved aerated concrete (AAC) and the autoclaved aerated concrete consist of sugar sediment (AAC-SS) was investigated in this work. The microstructure of AAC and AAC-SS was analyzed by the scanning electron microscopy (SEM). The mechanical properties of AAC and AAC-SS were focused on the compressive strength, the density, the water absorption and the flexural strength. To comfirm the tobermorite phase, the phase formation of the samples was tested using X-ray diffraction (XRD). It was found that the microstructure of AAC and AAC-SS surface was the finer needle-like crystalline morphology. The compressive strength (5.9 N/mm2) and flexural strength (1.82 N/mm2) of AAC-SS were higher than that of the AAC (5.0 N/mm2 and 1.64 N/mm2). While, the value of density (0.60 g/cm3) and humidity (23.59%) of AAC-SS had little less than that of the AAC (0.61 g/cm3 and 24.11%). The increasing of the tobermorite phase, which was added by the sugar sediment, had affected to the improvement of the mechanical properties. The specimens of both AAC and AAC-SS were claimed in quality class of 4, which based on the Thai Industrial Standard 1505-1998.

scholarly journals Study of the influence of the secondary raw materials on microstructure and properties of calcium silicate composite

2019 ◽  
Author(s):  
Jana Húšťavová ◽  
Vít Černý ◽  
Rostislav Drochytka
Keyword(s):  
Calcium Silicate ◽  
Raw Materials ◽  
Molar Ratio ◽  
X Ray Diffraction ◽  
X Ray ◽  
Autoclaved Aerated Concrete ◽  
Secondary Raw Materials ◽  
Aerated Concrete ◽  
The Difference ◽  
Positive Effect

Calcium silicate composites are a widely used building material, especially autoclaved aerated concrete or sand-lime bricks. The physico-mechanical properties of these materials depend on their microstructure. Microstructure is characterized by the content of crystalline calcium silicate compounds that arise during autoclaving. This is in particular the tobermorite mineral, which carries the mechanical strength of the composite. This paper focuses on the influence of secondary raw materials on properties and microstructure of the calcium silicate composite. Secondary raw materials were selected as slag from the combustion of lignite and ground glass. Mixtures of composites were selected with respect to the required C/S molar ratio of 0.73. The hydrothermal treatment was carried out at a temperature of 190 °C and a residence time of 4, 8 and 16 hours. The microstructure of calcium silicate composites and autoclaved aerated concrete was studied. The use of slag resulted in an increase in the intensity of the diffraction line of tobermorite by X-ray diffraction analysis as well as the use of glass. The difference was particularly evident in the shape of the tobermorite crystals. Long strong crystals were detected in the sample with slag, while the sample with glass exhibited low tobermorite leaves. Porous structure of autoclaved aerated concrete with slag was uniform, unlike samples with glass. Both materials have a positive effect on the increase in compressive strengths of the samples.

scholarly journals In situ monitoring of hydrothermal reactions by X-ray diffraction with Bragg–Brentano geometry

2020 ◽  
Vol 53 (4) ◽  
pp. 1163-1166
Author(s):  
Karsten Mesecke ◽  
Winfried Malorny ◽  
Laurence N. Warr
Keyword(s):  
Quantitative Information ◽  
In Situ Monitoring ◽  
X Ray Diffraction ◽  
Hydrothermal Conditions ◽  
X Ray ◽  
Saturated Vapour Pressure ◽  
Concrete Production ◽  
Aerated Concrete ◽  
Kinetics Of

This note describes an autoclave chamber developed and constructed by Anton Paar and its application for in situ experiments under hydrothermal conditions. Reactions of crystalline phases can be studied by successive in situ measurements on a conventional laboratory X-ray diffractometer with Bragg–Brentano geometry at temperatures <483 K and saturated vapour pressure <2 MPa. Variations in the intensity of X-ray diffraction reflections of both reactants and products provide quantitative information for studying the reaction kinetics of both dissolution and crystal growth. Feasibility is demonstrated by studying a cementitious mixture used for autoclaved aerated concrete production. During a period of 5.7 h at 466 K and 1.35 MPa, the crystallization of torbermorite and the partial consumption of quartz were monitored.

Influence of Fluidized Fly Ash on the Selected Physical-Mechanical Properties of the Autoclaved Aerated Concrete

2014 ◽  
Vol 899 ◽  
pp. 409-414 ◽  
Author(s):  
Alena Struhárová ◽  
Stanislav Unčík ◽  
Svetozár Balkovic ◽  
Mária Hlavinková
Keyword(s):  
Mechanical Properties ◽  
Fly Ash ◽  
Chemical Properties ◽  
Physical And Chemical Properties ◽  
Amorphous Phases ◽  
Autoclaved Aerated Concrete ◽  
Aerated Concrete ◽  
Free Cao ◽  
Physical And Chemical ◽  
And Chemical Properties

Fluidized fly ash has different physical and chemical properties compared to fly ash emerging from classic combustion. It contains amorphous phases resulting from a dehydration of clay minerals as well as unreacted sorbent of CaCO3, free CaO and anhydrite (CaSO4). Work targets the possibilities of production of an autoclaved aerated concrete (AAC) from fluidized fly ash, and its influence on particular physical-mechanical properties of autoclaved aerated concrete.

scholarly journals Processes of structure and phase formation of aerated concrete of non-autoclave hardening containing ferrosilicon as a gasifier

2021 ◽  
pp. 45-50
Author(s):  
A.O. Musina ◽  
◽  
O.O. Sihunov ◽  
O.P. Ryzhova ◽  
O.S. Sverdlikovska ◽  
...  
Keyword(s):  
Thermal Analysis ◽  
Differential Thermal Analysis ◽  
Phase Composition ◽  
Porous Structure ◽  
Dicalcium Silicate ◽  
X Ray ◽  
Calcium Hydrosilicates ◽  
Aerated Concrete ◽  
Differential Thermal Analysis Analysis ◽  
Ray Patterns

The paper deals with the structure and phase composition of non-autoclave aerated concrete with a density of 600–800 kg m–3 using ferrosilicon as a gasifier. The conditions of formation of porous structure of aerated concrete and preparation of calcium hydrosilicates were considered. Phase composition of the samples was investigated by means of X-ray phase analysis and differential thermal analysis. Analysis of X-ray patterns showed that the test samples contained tobermorite 11.3 Å (5CaO6SiO25.5H2O), xonotlite (6CaO6SiO2H2O) and -dicalcium silicate hydrate (2CaOSiO2H2O) as a binder. It was established that there is an increase in the content of hydrosilicate phases with an increase in the content of gasifier in the vast majority of cases. The obtained data were confirmed by the results of differential thermal analysis.

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