Sharif Digital Repository

Rammed earth (RE) structures are getting popular due to sustainability, environmental-friendly and economic advantages. Various studies have investigated the mechanical behavior and the energy performance of RE materials. However, little is known about the fracture behavior of RE materials. In this research, the fracture properties of RE materials containing different percentages of various stabilizers were investigated using a modified wedge splitting test. The stabilizers were cement, pozzolan, microsilica, glass-fiber, guar-gum and phase change material. In addition, the effect of stabilizers on the microstructure and the phase composition was inspected using scanning electron microscope... 

This study investigates the reliability analysis of mechanically stabilized earth (MSE) wall and takes into account the uncertainty associated in the mechanical properties of soil and geogrid, the magnetude of surcharge load and the soil-geosynthetic interface friction angle. In addition, the effect of number, length and place of the geogrid layers on the performance of this wall has been evaluated. The failure modes related to external stability, internal stability and horizontal displacement of the wall were considerd. In order to determine the probabilistic characteristics and the probability distribution function of soil and soil-geosynthetic interface friction angle, direct shear test... 

Usage of masonry materials in a country like Iran is still significantly high. As most of the failures during an earthquake in this system is failure caused by low ductility of cement mortars and also the high rate of carbon dioxide produced by cement. Experiences of Kermanshah earthquake in 2017 in Iran has doubled the importance of this issue. Hence, in the present investigation, an attempt to enhance the shear bond characteristics of structures constructed by masonry using green materials has been made. “Taftan” natural Pozzolan and two types of rice husk ash (RHA) was used in mix design of used mortars as a green material. In this investigation, a direct shear test (DST) device is... 

The high rate of energy consumption in the building sector has led the designers towards the construction methods that consume less energy during construction up to serviceability. One of these methods is rammed-earth (RE) structures due to the availability of its materials, ease of preparation, considerable decrease in energy consumption and environmentally-destructive consequences. Improving the thermal characteristics besides the mechanical parameters of RE structures develops the application of this method. In the current study, the dynamic thermal parameters of RE wall specimens were experimentally measured under simulated conditions and compared to those of masonry walls. Thereby, a... 

Ultrasonic wave attenuation is an effective descriptor of distributed damage in inhomogeneous materials. Methods developed to measure wave attenuation have the potential to provide an in-site evaluation of existing concrete structures insofar as they are accurate and time-efficient. In this study, material classification and distributed damage evaluation were investigated based on the sinusoidal modeling of the response from the through-transmission ultrasonic tests on polymer concrete specimens. The response signal was modeled as single or the sum of damping sinusoids. Due to the inhomogeneous nature of concrete materials, model parameters may vary from one specimen to another. Therefore,... 

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... 

Understanding and defining mechanical behavior of engineering materials play an important role in the prediction of material response as well as analysis and design of engineering structures. In this investigation, polymer concrete (PC) with three different epoxy resin contents, ordinary cement concrete (OCC), lightweight concrete (LWC) and lime-mortar soil (LMS) have been studied under uniaxial and triaxial compression tests to determine their mechanical behavior by measuring axial stress-strain and volumetric strain versus axial strain curves. According to the results, PC showed higher strength, ductility and energy absorption than that of OCC and LWC. Nowadays, waste tire rubber is used... 

In order to enhance the behavior of structures during an earthquake, various system have been proposed and used in recent years. The main purpose of these systems is to provide enough deuctility to dissipate the input energy of the earthquake. Buckling restrained braces are used extensively in seismic-restraint structures due to their sutiable cyclic behavior. They consist of a core energy dissipation and external restraining component. The purpose of this study is to improve the behavior of BRBs using FRP strips as a restraining component. In this study ABAQUS is used to model analyze the structure. Concrete Damage Plasticity (CPD) is used to model concrete, Hashin model used for FRP strips... 

Understanding mechanical behavior of engineering materials plays an important role in prediction of material response and helps to analysis and design of engineering structures. In this thesis, behavior of polymer concrete (PC) with three different epoxy resin ratios, ordinary cement concrete (OCC), lightweight concrete (LWC), lime mortar soil (LMS), four various types of sandstone and granite was investigated under uniaxial and triaxial compression. In order to predict the mechanical behavior of aforementioned brittle materials, their behavior was simulated in terms of axial stress and volumetric strain versus axial strain. For computation of volumetric deformation and softening behavior,... 

The understanding of the mechanical behavior of engineering materials and their interfaces plays an important role in the prediction, analysis, and desing of engineering systems. Considering the important role of understanding and describing the behavior of materials and systems, this thesis is devided into three sections: 1) Modeling the behavior of polymer concrete under uniaxial compression, 2) Modeling the behavior of various light- and normal- weight concretes under uniaxial and triaxial compression, and 3) Modeling the behaivor of interfaces between polymer concrete and normal concrete with sand. In this context, various constitutive models were investigated and compared together,... 

The behavior of soil-structure interface plays an important role in the static and dynamic analysis of soil-structure systems. Development of new materials such as polymer concrete requires an understanding of the behavior and their interaction with other materials. In this investigation, the interface behavior between polymer concrete and ordinary concrete with sand was studied using interface direct shear tests. In order to find optimum content of epoxy resin for polymer concrete, a series of tensile and compressive tests were conducted. To study the mechanical properties of concretes-sand interfaces behavior two series of interface direct shear tests were conducted at three different... 

Rammed earth structures have attracted the attention of engineers and researchers in recent years due to their economic advantages, sustainable development, and environmental sustainability. One of the main concerns for public opinion for acceptance of Rammed Earth as a reliable construction material is their durability. Previous studies have investigated the durability of rammed earth materials by conducting wet and dry cycle test, accelerated erosion test, and rain simulation in the laboratory environment. This research studied the durability of cement stabilized rammed earth (CSRE) for one year under the aggressive environments. Three cement contents were considered for preparing the CSRE... 

Geopolymer concrete is one of the most environmentally friendly concretes that does not have any pollutants harmful to the environment. By-products that are normally harmful to the environment can be used in manufacturing this product, therefore, the use of this concrete is known as the first concrete replacement in the world. In order to use geopolymer concrete, it is necessary to an essential to know the mechanical information of these materials.In this study, the mechanical behavior of geopolymer concrete for fly ash and slag in terms of its stress and strain uniaxial loading and triaxial loading at , and15MPa pressures for three concrete mixing design are investigated.Then the... 

Rammed earth (RE) is an eco-friendly building material and has been capturing special attention among researchers. Many of the recently studied RE additives are extremely resource- and energy-consuming. On the other hand, the usage of fly ash (FA), which is a sustainable replacement for cement, has been scarcely investigated in RE construction. In this paper, an experimental investigation was performed on the physical and mechanical properties of RE materials stabilized with the combination of cement and alkali-activated FA. This scrutiny consists of density measurements, pulse velocity tests, unconfined compression tests, and direct shear tests. Additionally, the carbon dioxide emission and... 

Polymer concrete is well-known for the quick repair of concrete structures and pavement. Many concrete structures such as bridges, offshore, and pavements are under cyclic loads when they are exposed to different environmental conditions during their lifespan. However, there are relatively few studies on the durability of Polymer concrete. The durability and fatigue performance of these structures are significant issues that should be considered. This study aims to investigate the long-term environmental effects on the mechanical properties of Polymer concrete. Therefore, polymer and ordinary cement concrete specimens were prepared and exposed to four chemical solutions with pH values of... 

In recent decades, particle composite materials have a wide range of applications in engineering. Particle composites are a group of heterogeneous materials with different length scales and are characterized by particles that are randomly distributed in a matrix phase. Geopolymer concrete is a special type of concrete that its binder is made by reacting alumina and silicate carriers with an activating agent and in recent years with the expansion of its use has reduced the amount of cement consumption. In addition to the many advantages of geopolymer concrete, it has disadvantages in terms of setting time. That is why the use of cement has been proposed as a solution to the problem. This... 

Ground granulated blast furnace slag (GGBFS) based alkali-activated concrete (GAAC) is one of the eco-friendly alternatives of traditional concrete, which uses industrial byproducts instead of ordinary Portland cement (OPC). Besides environmental benefits, substituting OPC concrete with GAAC has some economic advantages, while it successfully meets the concrete structural requirements in both mechanical and durability characteristics. Despite this fact, employing GAAC in the construction industry has been limited due to a lack of standard mix design code.This study aims to develop an accurate prediction model for the compressive strength of GAAC by employing the most appropriate machine... 

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... 

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... 

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...