Sharif Digital Repository

This study seeks to compare the effect of curing conditions in the sea, coast, and middle of the island environment on five mix designs of alkali-activated concrete (AAC) based on ground granulated blast furnace slag (GGBFS) and fly ash (FA) and the effect of the ratio of sodium silicate (SS) to sodium hydroxide (SH) and alkali activated solutions (AAMS) to the binder on mechanical properties. The compressive strength and load-deflection test was conducted to obtain uniaxial compressive strengths (UCS), modulus of elasticity ("E" _"S" ), elastic and ultimate strain, and dissipated energy. The most significant decrease in strength was observed in the coastal area and the sea. Also, the... 

In some concrete projects, the consolidation of concrete is quite challenging due to the congestion of rebar and the complex concrete placement. Self-compacting concrete (SCC) can overcome these problems. On the other hand, nanomaterials in concrete can be used to improve the engineering properties of concrete and adverse environmental effects. This study uses aluminum-nano oxide and carbon-nano tubes (by replacing 1, 3, and 5% by weight of cementitious materials) to enhance the physical and mechanical properties of SCC. Additionally, adverse environmental effects of SCC improve by replacing 35% of cement with combustion furnace slag. Experimental results showed that with increasing... 

The interface behavior of rock-concrete joints and between concrete layers influence the behavior of concrete dam structures. In this study, a modified direct shear test (DST) was implemented in the laboratory to evaluate the interface behavior between 1) rock and conventional vibrated concrete (CVC), 2) rock and roller compacted concrete (RCC), 3) CVC and RCC and 4) two layers of RCC. Two series of in-situ shear tests were also carried out on rock-concrete joints. The friction angle and adhesion for all tested interfaces were determined and analyzed. The effect of uniaxial compressive strength (UCS) of concrete on the interface behavior was determined. Additionally, the effect of surface... 

Schools are known as the educational infrastructure of countries. Most people in the community spend more than 12 years of their education in schools. The organization for development, renovation, and equipping of in Iran, as the custodian of school construction in the country, has moved towards using new technologies due to the problems encountered in schools' construction. Among these tools, BIM is selected to help project management and control. For BIM implementation on the macro scale, readiness assessment plays a significant role. In this dissertation, an attempt has been made to provide a model for evaluating the needs, use BIM, and evaluate the organization by having a strategic... 

This study has investigated the effects of different environmental conditions on the bond at the interface between two fiber reinforced polymer (FRP) layers. A total of 945 single lap splice coupons with three bond length were made using wet lay-up technic. There were used three unidirectional fabrics and one type of epoxy resin. A Uniaxial tensile test was performed on samples after 2, 4, 12, 20, 28, 36 and 48 weeks of exposure. Also series of test were conducted in order to determine the minimum lap splice length of single splice FRP samples. The experimental results indicated reduction of bond strength in glass specimens that was 17 % after 48 weeks of exposure while for same amount of... 

Most of the investigations during the two past decades focused on the effect of moisture and temperature on the bond at the interface of carbon or glass-fabrics and concrete, masonry or timber. Few investigations have studied the effect of chemical solutions, dry heat exposure and ultravilolent (UV) radiation on the bond at the interface of other types of fiber reinforced-polymers (FRPs) and masonry, timber and concrete in the short and long terms. Therefore, this research aims to investigate the effect of five chemical solutions with pH of 2.5±0.1, 7±0.1, 7.25±0.1, 10±0.1 and 12.5±0.1 on the interfacial bond strength between seven types of FRPs (unidirectional, bidirectional and hybrids)... 

The repair of pipes that deteriorate over time or due to various factors is a critical issue in engineering. Consequently, effective and novel repair methods, especially using FRP (Fiber-Reinforced Polymer) composites, have gained significant importance. In this research, the repair and connection of pipes using FRP are examined. In the pipe repair section, through hydrostatic testing, various factors such as the damaged area, the number of sharp corner points, the width of the sheets, the number of layers, and the pre- stress condition of the FRP are studied for their impact on the pipe's ultimate pressure tolerance. Also, in the pipe connection section, with hydrostatic tests, the ultimate... 

In recent years, machine learning techniques have been available to predict and interpret the structural behavior of dams. The main goal of this research is to predict structural behavior through modeling with data read by accurate instruments of dams. This requires the selection of several machine learning methods such as Random Forests (RF), Boosted Regression Trees (BRT), Artificial Neural Networks (ANN), Support Vector Regression (SVR), and Decision Tree Regression (DTR) algorithms. In this research, considering the 24 target variables defined from the detailed instrumentations studied, the behavior of the dam is modeled using selected machine learning models. These precision instruments... 

Concrete, a versatile construction material, combines cement, aggregates, and water to form a composite known for its durability and adaptability in various architectural and engineering applications. Its widespread use stems from its ability to efficiently bear heavy loads while maintaining longevity. However, producing concrete's key ingredient, cement, contributes significantly to environmental harm by emitting substantial carbon dioxide during its manufacturing process. This carbon footprint underscores the urgent need for sustainable alternatives and innovative practices in the construction industry to mitigate the detrimental effects on our planet. On the other hand, understanding the... 

Fracture Toughness of Geopolymer Concrete Containing Blast Furnace Slag in Corrosive Environments  

The goal of this research is to study the effect of local microcracking due to step by step pressure loading on the durability properties of geopolymer concrete. To better understand the behavior of GGBS-based GPC under different pressure stress levels, some experiments such as water permeability and water absorption conducted on the samples at each state of damage. Also, non-destructive tests such as ultrasonic waveform and pulse velocity (UPV) was used to quantify the extent of damage at each step. GGBFS and a blend of sodium silicate solution and 10 molar sodium hydroxide solution with SSSH⁄ ratio of 2 were used for production of GPC samples. GPC, OGPC and OPC samples with water to binder... 

The environmental friendliness and sustainable development of rammed earth structures has attracted the attention of numerous researchers in recent years. Obviously, a better understanding of the structural and mechanical performance of rammed earth is the way to use rammed earth as a sustainable building material. Structural fire safety is one of the primary considerations in the design of structures. Several experiments and investigations had been conducted to investigate the behavior of materials at high temperatures. Base on author knowledge at present, few studies are available on thermomechanical properties of earthen construction materials at temperatures higher than 100°C and even... 

This study aims to evaluate the seismic behavior of geotextile-reinforced soil retaining walls by using incremental dynamic analysis and endurance time analysis methods. Five different wall models with variables of length and the modulus of elasticity of reinforcements have been constructed in the ABAQUS finite element software. In this study, the soil behavior and the interaction between the soil and reinforcement are modeled using a fully plastic linear elastic behavior model based on the Mohr-Coulomb yield criterion. Despite reinforced retaining walls' numerous benefits and extensive use, there is an obvious need for more precise design and a better knowledge of these structures' static... 

In this thesis, supervised and unsupervised deep learning-based frameworks were proposed for distributed damage detection and quantification in concrete using sinusoidal ultrasonic response signals. Before the main study on ultrasonic-based concrete damage assessment, a preliminary study was performed on deep learning-based concrete compressive strength prediction. In this study, convolutional neural networks were utilized to predict the compressive strength of concrete through its mix proportions. The Genetic algorithm was employed to find the optimum number of filters in each convolutional layer of the convolutional neural networks. The proposed framework demonstrated high accuracy in... 

Selecting a suitable material is crucial for repairing the old concrete structures and joining precast panels of bridges, especially the bond strength between the substrate concrete and the overlay material. In this regard, this research focused on high-performance alkali-activated slag concrete (HPASC) as a new concrete used as an overlay on ordinary Portland cement concrete (OPCC) as a block of old concrete. Approximately four hundred bi-surface shear (BSS) tests were performed to evaluate the interface properties of OPCC and HPASC. HPASC specimens were designed with different NaOH molarity, silica fume (SF) content, steel fiber content, age of repair material, and proportion of grooved... 

Fiber-reinforced polymer (FRP) composites have been used tremendously to repair and rehabilitate timber structures due to their formability, ease of use, and high specific strength. The quality of the bond between FRP and timber substrate is critical for having complete composite action. In this paper, a comprehensive set of linear and nonlinear ultrasonic methods was performed to investigate the bond between carbon-FRP (CFRP) and timber. For this purpose, one hundred and twenty-six specimens of reinforced timber were prepared. Two techniques were considered to bond CFRP and timber: 1) externally bonded reinforcement (EBR) and 2) externally bonded reinforcement on the groove (EBROG). The... 

Material durability is quite critical in corrosive environments. In this study, two hundred and seventy geopolymer concrete specimens with different mix designs were prepared and then wrapped with two different fiber reinforced polymer (FRP) materials. For 12960 hrs (eighteen months), the specimens were exposed to four different pHs (2.5, 7, 7.25, 12.5). The reliability and SEM analysis were performed after modeling the compressive strength over time. Based on the results, the reduction of the compressive strength was up to 22% in an acidic environment. The compressive strength of the specimens was increased up to 11 percent after alkaline solution exposure. The ductility of all specimens... 

The behavior of construction materials at high temperatures has been an important aspect of researches in recent years. The first part of the current research aims to non-destructively monitor the formation and growth of damage at geopolymer concrete (GPC) after being exposed to high temperatures using linear and nonlinear ultrasonic techniques. Ultrasonic waveform and pulse velocity (UPV) tests were conducted on the specimens before and after exposure to the temperatures. Nonlinear wave signals were processed in phase-space domain for qualitative health monitoring of GPC. Furthermore, feature extraction was applied to phase-plane attractors using fractal dimension for quantitative... 

Nowadays, construction with earthen materials has become more widespread due to their advantages: low construction cost, low embodied energy, application of green materials, and recyclability. Rammed earth (RE) as a sustainable construction has been used worldwide for decades. They are built in many countries such as Australia, China, India, and many parts of Africa and Europe. The rammed earth materials are cheap, accessible, and green and provide good thermal buffering. Stabilizers such as cement and lime with high embodied energy are frequently used in rammed earth construction to enhance materials' mechanical properties and durability. Stabilizers in RE materials could affect the energy... 

Alkali-activated fly ash-slag (AAFS) is a new type of sustainable construction material widely studied in recent years for its desirable mechanical properties and low environmental impacts. In this study, the effects of the slag incorporation from 10 to 30% of fly ash are investigated on the strength, pore structure, and transport properties of the AAFS with various levels of fly ash replacements with slag. The unconfined compression and ultrasonic pulse velocity tests were performed to evaluate the mechanical properties of the AAFS concrete. Microstructural and mineralogical changes were studied by porosity, N2-adsorption/desorption, and SEM/EDX tests. Additionally, transport properties...