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Posts Tagged ‘geopolymer building’

Ultra-High Performance Concrete

Ultra-High Performance Concrete


“According to a recent article in the Economist, Iran happens to be good, very good, at developing what is known as “ultra-high performance concrete” (UHPC). Because of its geographical position, the county is under constant threat of earthquakes. The most devastating earthquake in recent memory occurred in the city of Bam, located in southern Iran, and claimed the lives of 30,000 people. As a result, Iranian engineers have developed – out of necessity – some of the toughest and most rigid building materials in the world.

So how does Iranian concrete standout? Well, unlike conventional concrete, Iranian concrete is mixed with quartz powder and special fibers – transforming it into high performance concrete that can withstand higher pressure with increased rigidity. What this all translates to is excellent building material given the environment that has found peaceful applications like the construction of safer bridges, dams, tunnels, increasing the strength of sewage pipes, and even absorbing pollution.”

Read the full article at the source: Digital Trends.com

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Abstract
Concrete is the most common building material in the world and its use has been increasing during the last century as the need for construction projects has escalated. Traditionally, concrete uses Ordinary Portland Cement (OPC) as binder, water as the activator of cement and aggregate. Finding an appropriate replacement for traditional concrete is a desirable solution to obviate the environmental problems caused by cement production. The use of fly ash as a partial replacement for Portland cement is a method to maintain the properties of concrete and reduce the need for cement. Fly ash is a by-product from coal-fired power plants and is abundantly available. The percentage of cement replacement can be varied according to application and mix design. One of the potential materials to substitute for conventional concrete is geopolymer concrete (introduced by Davidovits in 1979). Geopolymer concrete is an inorganic alumino-silicate polymer synthesized from predominantly silicon, aluminum and byproduct materials such as fly ash. Geopolymer properties have been investigated for several years and it is still a major area of interest among researchers and industry partners as it does not contain cement and uses fly ash and alkali liquids as binders to produce a paste to consolidate aggregates. Furthermore, the aggregate comprises a substantial portion of concrete. Including coarse and fine aggregates it is normally obtained from natural sources. Fine aggregate in Australia is usually mined from sand quarries. As the demand for concrete production increases, more natural sand is needed. The need for fine aggregate should be addressed in an environmentally friendly manner, considering the diminishing sources of natural sand. Red sand is a by-product generated from the manufacture of alumina from bauxite by the Bayer process.

Previous studies on properties of red sand have shown that it has the potential to be used in concrete as a fine aggregate. While the use of red sand in traditional concrete has been investigated by some researchers, no research has been reported regarding the use of this by-product in manufacturing geopolymer concrete. This research looks into the replacement of natural sand fine aggregates with red sand in geopolymer concrete. Initially, an extensive series of mixtures was prepared and tested. The objective of the research was to identify the salient parameters affecting the properties of geopolymer concrete when natural sand is replaced by red sand. At the next stage, attempts were made to enhance the mechanical and durability features of red sand geopolymer concrete. The final stage consisted of testing red sand geopolymer concrete to find out the various properties of this novel construction material.

Source: Espace Library at Curtin.edu

http://espace.library.curtin.edu.au/R/?func=dbin-jump-full&object_id=115093&local_base=GEN01-ERA02

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Easy Chanvre hemp block building system

Easy Chanvre hemp block building system


To meet 21st century environmental, economic, and social constraints, the construction sector has to focus on new materials that meet:
* climate demands (fighting CO2 releases),
* saving of fossil fuel resources,
* use of renewable raw materials,
* conservation of water resources,
* respect for biodiversity.

Use of these ecomaterials allows:
Reduced costs of use,
Creation of new jobs,
Waste-free job site management,
A healthy habitat (air quality, water).
Blocks and slabs made of hemp concrete are molded industrially and dried naturally in our factory.

Source: Easy Chanvre

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Geopolymers – Alkali Activated Composites for Encapsulation of Intermediate Level Wastes

Geopolymers – Alkali Activated Composites for Encapsulation of Intermediate Level Wastes


Source: Immobilization Science Laboratory

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Abstract
“Geopolymer cements offer an alternative to, and potential replacement for, ordinary Portland cement (OPC). Geopolymer technology also has the potential to reduce global greenhouse emissions caused by OPC production. There is already a considerable amount of work and research conducted on geopolymers in the past decades, and it is now possible to implement this technology commercially. However, to ensure that geopolymer becomes commercially available and able to be used in the world, further understanding of its ability to provide durable and long lasting materials is required. One main property which is still relatively unexplored compared to other properties is its shrinkage properties. The objective of this thesis is therefore to examine the shrinkage of geopolymers and factors which might influence it.

The factors which influence geopolymer strength were investigated as being the factors which may influence shrinkage. The selection of the activating solution is an important factor in forming the final product of a geopolymer. Activating solution SiO2/Na2O ratio is determined to be an important influence on the shrinkage of geopolymer. SEM images of the samples enable observation of the sample topology and microstructure. An important observation was the existence of a ‘knee point’ which also occurs in OPC shrinkage. The ‘knee point’ is the point where the shrinkage goes from rapid shrinkage to slow shrinkage. From SEMs it is noted that the samples past the knee point are shown to have a smoother topology which means it is more reacted.”

Source: Melbourne University Library

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I prefer low tech, low cost approaches, but it’s fun to consider larger scale solutions and what could happen in the future.

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Abstract
This paper presents the findings of an experimental investigation to study the effect of alkali content in geopolymer mortar specimens exposed to sulphuric acid. Geopolymer mortar specimens were manufactured from Class F fly ash by activation with a mixture of sodium hydroxide and sodium silicate solution containing 5% to 8% Na2O. Durability of specimens were assessed by immersing them in 10% sulphuric acid solution and periodically monitoring surface deterioration and depth of dealkalization, changes in weight and residual compressive strength over a period of 24 weeks. Microstructural changes in the specimens were studied with Scanning electron microscopy (SEM) and EDAX. Alkali content in the activator solution significantly affects the durability of fly ash based geopolymer mortars in sulphuric acid. Specimens manufactured with higher alkali content performed better than those manufactured with lower alkali content. After 24 weeks in sulphuric acid, specimen with 8% alkali still recorded a residual strength as high as 55%.

Source: Waset.org

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