Ahmed S. Ouda

Bio: Ahmed S. Ouda is an academic researcher from University of Tabuk. The author has contributed to research in topics: Compressive strength & Medicine. The author has an hindex of 10, co-authored 21 publications receiving 319 citations.

Development of high- performance heavy density concrete using different aggregates for gamma-ray shielding

Abstract: The performance requirements of the concrete of containment structures are mainly radiological protection, structural integrity, durability, etc. For this purpose, high-performance heavy density concrete can be used. After extensive trials and errors, 15 concrete mixes were prepared by using coarse aggregates of barite, magnetite, goethite and serpentine with an addition of 10% silica fume (SF), 20% fly ash (FA) and 30% ground granulated blast furnace slag (GGBFS) to the total content of OPC. The compressive strength of hardened concrete was determined after 7, 28 and 90 days. In some concrete mixes, compressive strength was also tested up to 90 days upon replacing sand with the fine portions of magnetite, barite and goethite. The results revealed that, the concrete mixes containing magnetite coarse aggregate with 10% SF reaches the highest compressive strength values exceeding over the M60 requirement by 14% after 28 days. Whereas, the compressive strength of concrete containing barite aggregate was very close to M60 concrete and exceeds for 90 days. The results also indicated that, the compressive strength of the high-performance concrete incorporating magnetite as fine aggregate was significantly higher than that containing sand by 23%. Also, concrete made with magnetite fine aggregate has higher physico-mechanical properties than those containing barite and goethite. High-performance concrete incorporating magnetite as fine aggregate enhances the shielding efficiency against γ-rays.

Development the properties of brick geopolymer pastes using concrete waste incorporating dolomite aggregate

Abstract: This paper investigates the effects of dolomite-concrete powder (DCP) on the microstructure and strength development of alkali-activated brick waste. Raw DCP waste was used to replace alkali-activated brick waste at replacement ratios of 0%, 5%, 10%, 15%, 20% and 30% by mass. Similarly, raw DCP thermally treated at 800 °C for 2 h with a heating rate of 5 ° C/min was also used to replace alkali-activated brick waste at replacement ratios of 0%, 5%, 10%, 15%, 20% and 30% by mass. The water/binder ratio and compressive strength of the samples were measured. Laboratory techniques of Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric Analysis along with its derivatives (TGA/DTG) and Scanning Electron Microscopy (SEM) were utilized for studying molecular and microstructure of hardened samples. The experimental results obtained in the present procedure showed the feasibility of using DCP for enhancing the mechanical properties and the microstructure of alkali-activated brick waste-based geopolymer .

Properties Of Concrete

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The utilization of eco-friendly recycled powder from concrete and brick waste in new concrete: A critical review

Abstract: Recycled powder (RP) is the main by-product in the reclamation of construction and demolition (CD in addition, improvement methods and a benefit evaluation of RP concrete are further introduced. Based on statistical data that describe the activity index of RP and the compressive strength of RP concrete, the median diameter and replacement ratio of RP in concrete preparation should be below 30 μm and 30%, respectively. The use of RP improves the durability of concrete when the RP fineness is superior to the cement fineness. Increasing the RP fineness is an effective approach to improving the properties of RP concrete, and a CO2-curing treatment of RCP is an eco-friendly modification method. Furthermore, the use of RP in concrete has good economic and environmental benefits. Therefore, one expects that this review helps the further use of RP in concrete.

Microbially Induced Calcium Carbonate Precipitation (MICP) and Its Potential in Bioconcrete: Microbiological and Molecular Concepts

Abstract: In this review, microbiological and molecular concepts of Microbially induced Calcium Carbonate Precipitation (MICP) and their role in bioconcrete are discussed. MICP is a widespread biochemical process in soils, caves, freshwater, marine sediments and hypersaline habitats. MICP is an outcome of metabolic interactions between diverse microbial communities with organic and/or inorganic compounds present in environment. Some of the major metabolic processes involved in MICP at different levels are urea hydrolysis, denitrification, dissimilatory sulfate reduction and photosynthesis. Currently, MICP directed by urea hydrolysis, denitrification and dissimilatory sulfate reduction has been reported to aid in development of bioconcrete and demonstrated improvement in mechanical and structural properties of concrete. Bioconcrete is a promising sustainable technology in reducing the negative environmental impacts due to CO2 emission from construction sector and as well as in terms of economic benefits by way of promoting self-healing process of the concrete structures. Among the metabolic processes mentioned above, urea hydrolysis is the most applied in concrete repair mechanisms. MICP by urea hydrolysis is induced by a series of reactions driven by urease (Ur) and carbonic anhydrase (CA). Catalytic activity of these two enzymes depends on diverse parameters, which are currently being studied under laboratory conditions to understand the biochemical mechanisms involved and their regulation in microorganisms. It is clearly evident that microbiological and molecular components are essential to improve the process and performance of bioconcrete.

Review on concrete nanotechnology

Abstract: The study of the application of nanotechnology in the construction industry and building structures is one of the most prominent priorities of the research community. The outstanding chemical and physical properties of nanomaterials enable several applications ranging from structural reinforcement to environmental pollution remediation and production of self-cleaning materials. It is known that concrete is the leading material in structural applications, where stiffness, strength and cost play a key role in the high attributes of concrete. This paper reviews the literature on the application of nanotechnology in the construction industry, more particularly in concrete production. The paper first presents general information and definitions of nanotechnology. Then, it focuses on the most effective nanoadditives that readily improve concrete properties, such as (i) nanosilica and silica fume, (ii) nanotitanium dioxide, (iii) iron oxide, (iv) chromium oxide, (v) nanoclay, (vi) CaCO3, (vii) Al2O3, (viii) carb...

A review on the deterioration and approaches to enhance the durability of concrete in the marine environment

Abstract: This paper presents a review of the deterioration of concrete under seawater attack with particular interests in field exposure. The research reported in the literature has shown that salinity of seawater in different areas varies considerably but the type of ions and their proportion are similar. Because of this variation, laboratory studies should use specific artificial seawater to simulate on field environments. The phase changes induced by chloride, magnesium and sulfate ions contained in seawater are reviewed. The interaction between hydrates and chloride ion can lead to the formation Friedel's and Kuzel's salts. Magnesium ion can replace the calcium in Portlandite, and lowers the alkalinity of pore solution and eventually destabilizes C-S-H gel. The expansive ettringite is inhibited at the presence of chloride ions. At the tidal zone, the phase change mainly occurs on the surface of concrete, which weakens the structure and leads to spalling and delamination under the physical attack of the wave. Based on the existing deterioration mechanisms, the protocols to enhance the durability performance of marine concrete are also reviewed, such as using supplementary cementitious materials (SCMs) to mitigate rate of chloride penetration and, more promisingly, to use alternative binder systems. This paper also proposes a concept of designing a more durable concrete cover system by enhancing the chemical stability of cement hydrates, rapid self-healing and intelligent alkalinity control.