Digital Repository for Department of Civil Engineering

—Predicting the groundwater level has recently become very important research topic especially with the rise of population density and consequently increasing the water demand. This paper uses the Random Forest and linear regression neural network models to predict the groundwater level of Wadi-Alshaty district in the South West part of Libya. The results are compared with that obtained using the hydrologic long-term forecasting graphical approach. One of the most important findings of this study is the effectiveness of the neural network models to investigate the fluctuation of the groundwater levels over time (20 years)
Amna Elhawil, Alarabi Naji, Malak Nuesry, Almabruk Sanossi(12-2021)

Building and infrastructure damages, such as tunnels, have become a more important issue because of the continuous expansion of rural and urban constructions. It is well-known that when high-strength concretes (HSCs) are exposed to high temperatures; it is more likely to experience explosive fire-induced spalling than conventional strength concrete. Spalling might result in catastrophic loss of life and damage to nearby critical infrastructure. The exposure of reinforcement bars to elevated temperature, decreased permeability, higher density, moisture transfer, and brittleness of the HSC contribute to spalling. The concrete on a structural member's surface may be violently ripped apart by a high and fast rising temperature during a fire. Despite being a non-combustible material, the physics-chemo-mechanical properties of concrete deteriorate when subject to high temperatures. The magnitude and duration of a fire in a concrete structure define the severity of the fire. The resistance to fire spalling of HSCs under different fire conditions, extremes, and tendencies must be explored urgently. Cementitious materials exhibited a positive impact as an alternative to cement in HSC because they are known as environmentally friendly concrete materials with superior fire-resistant properties. In addition, the inclusion of fibers as an additive reinforcement is adopted to prevent and mitigate fire spalling in HSCs. Therefore, the establishment of appropriate fire-safety measures is a fundamental requirement in building design to ensure the safety of its inhabitants. While the process of fire spalling for HSC during a fire has not yet been completely understood. For this reason, a critical literature study on recent developments in HSC fire-resistance performance should be conducted to determine the present fire spalling behavior of HSC in the event of high temperatures and/or a fire. This article systematically reviews the mechanisms, influential factors, and types of fire spalling. This literature also reviews the behavior, fire spalling modelling, and strategies to prevent spalling in HSC applications. Given the advantages of the research subject, several hotspot research topics for scientific investigations are also suggested to facilitate the widespread use of HSCs in advanced construction applications.
Hakim S. Abdelgader (5-2022)

Concrete is a material that is widely used in the construction market due to its availability and cost, although it is prone to fracture formation. Therefore, there has been a surge in interest in self-healing materials, particularly self-healing capabilities in green and sustainable concrete materials, with a focus on different techniques offered by dozens of researchers worldwide in the last two decades. However, it is difficult to choose the most effective approach because each research institute employs its own test techniques to assess healing efficiency. Self-healing concrete (SHC) has the capacity to heal and lowers the requirement to locate and repair internal damage (e.g., cracks) without the need for external intervention. This limits reinforcement corrosion and concrete deterioration, as well as lowering costs and increasing durability. Given the merits of SHCs, this article presents a thorough review on the subject, considering the strategies, influential factors, mechanisms, and efficiency of self-healing. This literature review also provides critical synopses on the properties, performance, and evaluation of the self-healing efficiency of SHC composites. In addition, we review trends of development in research toward a broad understanding of the potential application of SHC as a superior concrete candidate and a turning point for developing sustainable and durable concrete composites for modern construction today. Further, it can be imagined that SHC will enable builders to construct buildings without fear of damage or extensive maintenance. Based on this comprehensive review, it is evident that SHC is a truly interdisciplinary hotspot research topic integrating chemistry, microbiology, civil engineering, material science, etc. Furthermore, limitations and future prospects of SHC, as well as the hotspot research topics for future investigations, are also successfully highlighted.
Hakim S. Abdelgader (4-2022)

For decades, lightweight concrete has been used in various civil engineering applications. Cellular concrete is a type of lighweight concrete that is an emerging composite in materials engineering still. However, due to its low weight, it can be integrated with industrial by-products to develop more advanced composites such as ultra-lightweight cellular concrete (ULCC). ULCC is sustainable and regarded as a potential candidate due to its simplicity of use and other benefits. A systematic review of the potential applications of ULCC in geotechnical construction are presented in this review article. Due to technological breakthroughs and changes in environmental conditions, and their material property is one of the variables that influence the degradation of roadway. Several investigations have been conducted by incorporating different materials into pavement structures to achieve longer-lasting and better pavement infrastructures than those at present. Sustainability benefits, workability, low prices, time, and structural capacity are factors that have been widely focused. This study focuses on the raw materials, production techniques, types, and properties of the ULCCs. The boundary densities of the ULCCs were considered from 400 to 1600 kg/m3. Structures all across the globe have benefited from the usage of cellular concrete in some form or another. However, much work in this field should be focused on, particularly in geotechnical applications. Geotechnical applications need specific attention to develop this kind of concrete with enhanced qualities. In order to address this need, this review paper has extensively focused on raw materials, manufacturing procedures, cellular concrete characteristics, types and uses of ULCC, particularly in geotechnical applications. Furthermore, several limitations and gaps in ULCC application in highway construction are highlighted, and recommendations on further improving its use and performance are provided.
Hakim S. Abdelgader(6-2022)

Two-stage concrete (TSC) is known by various names such as colcrete, Polcrete, preplaced aggregate concrete and prepacked concrete. It is different from traditional concrete in two fundamental ways, namely method of construction and mix proportion. Two-stage concrete (TSC) is defined as firstly, coarse aggregates are placed into the formwork and grout is applied to fill in the between coarse aggregate particles voids. Secondly, the percentage of coarse aggregates in the mix proportion of TSC is higher than that in normal concrete. The typical value is about 60% as compared with 40% in traditional concrete. As coarse aggregates are preplaced first, they can occupy up to 60–70% of the total volume. As coarse aggregates are not involved in the mixing process, TSC is environmentally friendly with lesser consumption of energy. With a higher content of aggregates, TSC reduces the use of cement by 20–30% and may minimize the temperature rise. Engineering properties of TSC, including its stress–strain relationship, is mainly governed by the properties of coarse aggregates as stress is transferred from the skeleton of aggregates to hardened grout. Main advantages of TSC include a higher volume of coarse aggregates and the ability to use larger size coarse aggregates. The latter also reduces the cost of crushing. TSC has beneficial properties such as low drying shrinkage, high bonding strength, high modulus of elasticity, and excellent durability. The method of TSC has proved particularly useful in a number of applications like underwater construction, and masonry repair, where placement by conventional methods is extremely difficult. The method is also applicable in case of massive concrete where low heat of hydration is required. It is studied the feasibility of casting two stage concrete with 100% steel slag as coarse aggregate. In term of formulation, to adopt two stage concreting method we could minimize the risk of concrete bleeding and segregation due to high water absorption and quite high density of slag aggregate. The effect of slag coal ash and foamed glass on the mechanical properties of two-stage concrete has rarely been reported. Thus, the development of an eco-efficient alkali-activated grout for two-stage concrete is a new research topic that has no robust results to draw solid conclusions and it should blaze the track towards a cleaner production of building materials with outstanding sustainability.
Hakim S. Abdelgader(1-2022)

The construction sector has embraced digitalization and industrialization to boost production, reduce material consumption, and improve workmanship. The 3D-printed concrete technology (3DPCT), more broadly recognized as the design of a 3D object via a computer-aided design (CAD) model or a digital 3D model, has accelerated considerable progress in these areas in other industries. Although 3DPCT has advanced remarkably in recent years, producing an appropriate 3D printing material that improves performance while reducing material consumption, which is really important for CO2 reduction, is urgently needed. The present 3DPCT faces many obstacles, one of which is the limited range of printable concretes. To tackle this limitation, extensive studies on developing creative approaches for formulating alkali-activated materials (AAMs) for 3DPCT for modern building applications have been conducted. AAMs are maintainable substitutive binders to ordinary Portland cement. Therefore, the need to undertake a comprehensive literature review on the current status of AAM performance on 3D-printable concretes for building applications is substantial. This article comprehensively reviews the quality requirements, advantages, disadvantages, common techniques, delivery, and placement of 3DCP. This literature also delivers indepth reviews on the behaviors and the properties of AAM-based concrete composites used in 3D-printed construction. Moreover, research trends are moving toward a wide-ranging understanding concerning the economic benefits and the environmental footprints of 3DCP for building applications with AAMs as suitable concrete materials for the emerging robust eco-friendly concrete composite for digital construction constructions nowadays. Given the merits of the study, several hotspot research topics for future investigations are also provided for facilitating the wide use of 3DPCT in real applications to address rapidly the gap between demand and supply for smart and cost-effective homes for upcoming generations.
Hakim S. Abdelgader(2-2022)

The number of deteriorating bridges due to chloride-induced corrosion increases annually as does the cost of inspection, maintenance, repair and where necessary replacement. Meanwhile, budgets made available to bridge owners/managers for repair and maintenance of these bridges are reducing. To optimise and manage their budget spend, bridge owners/mangers need to rely more on rational decision making methods rather than on subjective engineering judgment. In this thesis, the author has developed a probabilistic- based model which aims to predict the lifetime performance of Reinforced Concrete (RC) structures exposed to chloride corrosive environment and consequently to optimise their lifetime management.
Omran Kenshel(11-2009)

Estimating the Reliability (Probability of Failure) of Reinforced Concrete (RC) structures in marine environments has been of major concern among researchers in recent years. While General (uniform) corrosion affects the reinforcement by causing a uniform loss of its cross-sectional area, Pitting (localized) corrosion concentrates over small areas of the reinforcement. Many studies have focused on the effect of general corrosion, the effect of pitting corrosion on the structure reliability has not been fully investigated. Furthermore, due to the variability associated with the parameters involved in the reliability estimation of the corroded structure, this paper focuses on the effect of variability of pitting corrosion on the structure reliability. The analysis also takes into consideration the Spatial Variability (SV) of key deterioration parameters often neglected in previous studies. The authors have used their experimental data in modeling SV parameters of a specific deterioration parameter. The analysis adopted here used Monte Carlo (MC) simulation technique to construct a Spatial-Time Dependent model to estimate the girder reliability. The results showed that pitting corrosion potentially has a far more aggressive effect on the structure reliability than general corrosion and that pitting corrosion affects shear resistance far more severely than it would affect flexure resistance. The analysis showed that after 50 years of service, the reduction in the beam reliability due to pitting corrosion was 51% higher than that caused by general corrosion and that considering SV has caused the reliability predicted in terms of pitting corrosion to decrease by 12%. In the case of general corrosion, the decrease in beam reliability was only about 2% for the SV scenario.
Omran Kenshel, Mohamed Sulieman (12-2021)