Review of geopolymer concrete: a structural integrity evaluation

Acids attack concrete by dissolving both hydrated and unhydrated cement compounds as well as calcareous aggregates and the subsequent chemical reaction forms water soluble calcium compounds which are then leached away. The aggressiveness of the reaction depends on the pH of the acidic medium and the types of salts formed. Concrete pipes made of ordinary portland cement (OPC) carrying sewage water have always the presence acidic solutions in it. They deteriorate and service life of the pipes is affected along with the increased maintenance costs and that process cause environmental impacts. Geopolymer binders are novel binders that relies on alumina silicate rather calcium silicate bonds for structural integrity so they have been reported as being acid resistant. Those could be produced by the chemical action between alumino-silicate material such as fly ash(FA), granulated blast furnaces slag (GGBS), metakaoline or silica fume with alkaline solutions like sodium silicate or sodium hydroxide. Geopolymers show superior performance in terms of corrosion and fire resistance due to the absence of water and calcium in their structure.Utilisation of waste materials like FA and GGBS makes geopolymer concrete (GPC) an environment friendly construction material. This review paper looks in to the effect of various acids such as sulphuric acid, acetic acid, nitric acids on durability properties of OPC specimens, GPC specimens and GPC composite specimens when immersed in acidic solutions for certain period. The performance of geopolymer is analysed by the visual inspection and studying the parameters like weight loss, loss in compressive strength and maximum depth of penetration. Keywords- Geopolymer concrete, Sodium hydroxide, sodium silicate, metakaoline, silica fume, alumina silicate

Download Full-text

Review of geopolymer concrete: a structural integrity evaluation

International Journal of Forensic Engineering ◽

10.1504/ijfe.2021.10040669 ◽

2021 ◽

Vol 5 (1) ◽

pp. 59

Author(s):

Sara Gharehbaghi ◽

Kong Fah Tee ◽

Koorosh Gharehbaghi

Keyword(s):

Structural Integrity ◽

Geopolymer Concrete

Download Full-text

EFFECT OF CURING TEMPERATURE ON THE PROPERTIES OF 100% CLAY-BASED GEOPOLYMER CONCRETE

Proceedings of International Structural Engineering and Construction ◽

10.14455/isec.res.2017.98 ◽

2017 ◽

Vol 4 (1) ◽

Author(s):

Muhammad Mukhlesur Rahman ◽

David w. Law ◽

Indubhushan Patnaikuni

Keyword(s):

Structural Integrity ◽

Curing Temperature ◽

Superior Performance ◽

Clay Material ◽

Geopolymer Concrete ◽

X Ray Diffraction ◽

X Ray ◽

Binder Material ◽

Alkali Activated Binders ◽

Alkali Activated

Substantial researches have already been carried out on alkali-activated binders for the production of geopolymer concrete but studies on clay-based geopolymer concrete is still insufficient. The aim of this paper is to identify the effect of curing temperature on the properties of 100% clay-based geopolymer concrete. Clay pre-treated at 80°C and 120°C for 24 hours were selected as the source binder material. Four Activator Modulus (AM); 1.0, 1.25, 1.5 and 1.75 for each of two Sodium Oxide (Na2O) dosages of 10% and 15% were selected as the activator material for this investigation. X-ray diffraction (XRF) was applied to characterize the clay material. Specimens were cured at 80°C and 120°C for 24 hours. Specimens were tested under compression at seven, 14, 28 and 40 days. Specimens cured at 80°C took a longer duration (>28 days) to achieve structural integrity while the specimens cured at 120°C achieved structural integrity within seven days. Compressive strength of specimens prepared with AM of 1.0 for both of the Na2O dosage of 10% and 15% exhibited superior performance to other AMs investigated.

Download Full-text

Effect of Heating Duration at High Temperature on the Strength and Integrity of Fly Ash-Based Geopolymer Concrete

IOP Conference Series Earth and Environmental Science ◽

10.1088/1755-1315/945/1/012063 ◽

2021 ◽

Vol 945 (1) ◽

pp. 012063

Author(s):

Siti Nooriza Abd Razak ◽

Nasir Shafiq ◽

Laurent Guillaumat ◽

Mohamed Mubarak Abdul Wahab ◽

Syed Ahmad Farhan ◽

...

Keyword(s):

Compressive Strength ◽

High Temperature ◽

Fly Ash ◽

Structural Integrity ◽

Colour Change ◽

Free Water ◽

High Strength ◽

Visual Observation ◽

Geopolymer Concrete ◽

Heating Duration

Abstract Fire is one of the most severe environmental conditions that concrete structures might be subjected to, especially in closed conduct structures, such as tunnels. Concrete in general can withstand fire but its properties degrade when exposed to fire at high temperatures. The effect of heating duration, at a high temperature, on the performance of fly ash-based geopolymer concrete is presented. Cubes of low, medium and high strength grades of geopolymer concrete that had been cured for 28 days, were exposed to a fire flame at 1000 °C for 30, 60, 90, 120, 150 and 180 min. After the fire exposure, the cubes were cooled to the ambient temperature before further testing. A visual observation was performed on the cubes to detect any colour change, cracking and spalling. The losses of mass and residual compressive strength of the cubes were recorded. The results showed that as the heating duration increased from 30 to 90 min, the compressive strength of the cubes also increased. Contrarily, the compressive strength decreased as the heating duration increased beyond 90 min indicating that the extended heating duration induced the loss of free water and decomposition of aluminosilicate products in geopolymer concrete. The evaporation of water by virtue of the heating for the extended duration, at high temperature, led to a loss in the mass of concrete. The findings suggest that geopolymer concrete was able to sustain its structural integrity without any noticeable spalling and hence, it can be classified as a fire-resistant material.

Download Full-text

Fire Performance of Fly Ash-Based Geopolymer Concrete: Effect of Burning Temperature

IOP Conference Series Earth and Environmental Science ◽

10.1088/1755-1315/945/1/012062 ◽

2021 ◽

Vol 945 (1) ◽

pp. 012062

Author(s):

Siti Nooriza Abd Razak ◽

Nasir Shafiq ◽

Laurent Guillaumat ◽

Mohamed Mubarak Abdul Wahab ◽

Syed Ahmad Farhan ◽

...

Keyword(s):

Fly Ash ◽

Structural Integrity ◽

Green Building ◽

Geopolymer Concrete ◽

Fire Performance ◽

Fire Event ◽

Rich Material ◽

Loss Of Mass ◽

Reference Specimens ◽

Fire Flame

Abstract Geopolymer concrete (GEO) is a cementless concrete produced from the reaction of an aluminosilica-rich material, in particular, fly ash, with an alkaline solution, which can either be sodium or potassium-based. In light of the potential of fly ash-based GPC as an alternative to Ordinary Portland Cement (OPC)-based concrete as a green building material, an investigation on the fire performance of GEO, in comparison to OPC-based concrete, is essential. The results of an experimental study on the fire performance of fly ash-based GEO that was subjected to a flame test using a methane burner torch, after 28 days of curing, to simulate a real fire event, are presented. Concrete specimens were exposed to a fire flame at 500 °C and 1200 °C for two hours and subsequently cooled to the ambient temperature, prior to testing. Visual inspection was performed on the specimens to observe for any cracking, spalling and change in colour. Losses of mass and residual compressive strength were measured. The results were compared with those of OPC-based reference specimens. The findings revealed that, in contrast to OPC-based concrete, the strength of GPC increased when exposed to fire at 500 °C. GEO also suffered a smaller loss of mass as compared to OPC-based concrete due to the smaller amount of loss in moisture from burning. It was also observed that no spalling had occurred on the GEO, with less cracking on the exposed surface in relation to OPC-based concrete, hence indicating that the structural integrity of GEO was successfully maintained.

Download Full-text

Electron Beam Damage of Biomolecules Assessed by Energy Loss Spectroscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100069855 ◽

1978 ◽

Vol 36 (3) ◽

pp. 61-69

Author(s):

M. Isaacson ◽

M.L. Collins ◽

M. Listvan

Keyword(s):

Electron Microscopy ◽

Radiation Damage ◽

Structural Integrity ◽

Analytical Electron Microscopy ◽

High Dose ◽

Dose Rates ◽

Special Cases ◽

Analytical Electron ◽

Atom Migration ◽

Beam Damage

Over the past five years it has become evident that radiation damage provides the fundamental limit to the study of blomolecular structure by electron microscopy. In some special cases structural determinations at very low doses can be achieved through superposition techniques to study periodic (Unwin & Henderson, 1975) and nonperiodic (Saxton & Frank, 1977) specimens. In addition, protection methods such as glucose embedding (Unwin & Henderson, 1975) and maintenance of specimen hydration at low temperatures (Taylor & Glaeser, 1976) have also shown promise. Despite these successes, the basic nature of radiation damage in the electron microscope is far from clear. In general we cannot predict exactly how different structures will behave during electron Irradiation at high dose rates. Moreover, with the rapid rise of analytical electron microscopy over the last few years, nvicroscopists are becoming concerned with questions of compositional as well as structural integrity. It is important to measure changes in elemental composition arising from atom migration in or loss from the specimen as a result of electron bombardment.

Download Full-text

Structural integrity after cold storage of human epidermal model in hypothermosol: A correlative ultrastructural and fluorescent assay

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100169080 ◽

1994 ◽

Vol 52 ◽

pp. 270-271

Author(s):

Henry H. Eichelberger ◽

John G. Baust ◽

Robert G. Van Buskirk

Keyword(s):

Cold Storage ◽

Structural Integrity ◽

Culture Media ◽

Cell Structure ◽

Natural State ◽

Sodium Cacodylate ◽

Ruthenium Tetroxide ◽

Cacodylate Buffer ◽

Before And After

For research in cell differentiation and in vitro toxicology it is essential to provide a natural state of cell structure as a benchmark for interpreting results. Hypothermosol (Cryomedical Sciences, Rockville, MD) has proven useful in insuring the viability of synthetic human epidermis during cold-storage and in maintaining the epidermis’ ability to continue to differentiate following warming.Human epidermal equivalent, EpiDerm (MatTek Corporation, Ashland, MA) consisting of fully differentiated stratified human epidermal cells were grown on a microporous membrane. EpiDerm samples were fixed before and after cold-storage (4°C) for 5 days in Hypothermosol or skin culture media (MatTek Corporation) and allowed to recover for 7 days at 37°C. EpiDerm samples were fixed 1 hour in 2.5% glutaraldehyde in sodium cacodylate buffer (pH 7.2). A secondary fixation with 0.2% ruthenium tetroxide (Polysciences, Inc., Warrington, PA) in sodium cacodylate was carried out for 3 hours at 4°C. Other samples were similarly fixed, but with 1% Osmium tetroxide in place of ruthenium tetroxide. Samples were dehydrated through a graded acetone series, infiltrated with Spurrs resin (Polysciences Inc.) and polymerized at 70°C.

Download Full-text

High-Resolution electron crystallography of the light-harvesting chlorophyll-a/b protein complex from chloroplast membranes

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100181816 ◽

1990 ◽

Vol 48 (1) ◽

pp. 610-610

Author(s):

Werner Kühlbrandt ◽

Da Neng Wang ◽

K.H. Downing

Keyword(s):

High Resolution ◽

Electron Diffraction ◽

Chlorophyll A ◽

Protein Complex ◽

Structural Integrity ◽

Light Harvesting ◽

Lhc Ii ◽

Diffraction Patterns ◽

Difference Fourier ◽

2D Crystals

The light-harvesting chlorophyll-a/b protein complex (LHC-II) is the most abundant membrane protein in the chloroplasts of green plants where it functions as a molecular antenna of solar energy for photosynthesis. We have grown two-dimensional (2d) crystals of the purified, detergent-solubilized LHC-II . The crystals which measured 5 to 10 μm in diameter were stabilized for electron microscopy by washing with a 0.5% solution of tannin. Electron diffraction patterns of untilted 2d crystals cooled to 130 K showed sharp spots to 3.1 Å resolution. Spot-scan images of 2d crystals were recorded at 160 K with the Berkeley microscope . Images of untilted crystals were processed, using the unbending procedure by Henderson et al . A projection map of the complex at 3.7Å resolution was generated from electron diffraction amplitudes and high-resolution phases obtained by image processing .A difference Fourier analysis with the same image phases and electron diffraction amplitudes recorded of frozen, hydrated specimens showed no significant differences in the 3.7Å projection map. Our tannin treatment therefore does not affect the structural integrity of the complex.

Download Full-text