Mohammadreza Izadifar

Technische Universität Darmstadt | TU · Department of Civil and Environmental Engineering Sciences (Dept.13)

The most prominent phase of hydrated cementpaste, as a model for calcium silicate hydrate (CSH) gel, istobermorite with varying Ca/Si ratios. In the present work, carbonmonoxide (CO) gas is introduced onto the surface of tobermoriteat 62 K. The experimental results from infrared spectroscopy reveala chemical reaction of CO with tobermorite, leading...

This work presents a 3D off-lattice coarse-grained Monte Carlo (CGMC) approach to simulate the nucleation of alkaline aluminosilicate gels, their nanostructure particle size, and their pore size distribution. In this model, four monomer species are coarse-grained with different particle sizes. The novelty is extending the previous on-lattice approa...

Metakaolin (MK) is a high-quality, reactive nanomaterial that holds promising potential for large-scale use in improving the sustainability of cement and concrete production. It can replace cement due to its pozzolanic reaction with calcium hydroxide and water to form cementi-tious compounds. Therefore, understanding the dissolution mechanism is cr...

Graphene-based materials are considered excellent candidates to implement cementitious nanocomposites due to their mechanical properties. This paper presents a comprehensive interface interaction that ends up with computing the elastic properties for four models of the C−S−H gel, taking tobermorite 14 Å as an example, with reduced graphene oxide (r...

Geopolymer nanocomposites incorporating carbon nanotube (CNT)/graphene-based nanomaterials have become an exciting area of research because of their exceptional interface compatibility, providing improved mechanical, electrical, and thermal properties for next-generation construction materials. Accordingly, geopolymers are superior candidates for t...

The major concern of the modern cement industry is to minimize the CO2 footprint. Thus cement based on belite, an impure clinker mineral (CaO)2SiO2 (C2S in cement chemistry notation), which forms at lower temperatures, is a promising solution to develop eco-efficient and sustainable cement-based materials, used in enormous quantities. However, the...

This study investigates the shear behavior of reinforced concrete (RC) beams that have been strengthened using carbon fiber reinforced polymer (CFRP) grids with engineered cementi-tious composite (ECC) through finite element (FE) analysis. The analysis includes twelve simply supported and continuous beams strengthened with different parameters such...

Cement clinkers containing mainly belite ( -C2S as a model crystal), replacing alite, offer a promising solution for the development of environmentally friendly solutions to reduce the high level of CO2 emissions in the production of Portland cement. However, the much lower reactivity of belite compared to alite limits the widespread use of belite...

The girder, abutment and pile of integral abutment jointless bridges (IAJB) are integrated. In IAJBs, the backfill soil behind abutments is directly subjected to the horizontal cyclic displacements originated by the expansion and contraction of girders under thermal loadings. Meanwhile, the monolithic behavior of the abutment and pile of IAJBs caus...

A major concern in the modern cement industry is considering how to minimize the CO2 footprint. Thus, cements based on belite, an impure clinker mineral (CaO)2SiO2 (C2S in cement chemistry notation), which forms at lower temperatures, is a promising solution to develop eco-efficient and sustainable cement-based materials, used in enormous quantitie...

Understanding the effect of crystallographic orientation on the twinnin/detwinning mechanisms in NiTi shape memory alloys at an atomistic scale can help to control and tune the mechanical properties and failure behavior of such materials. In this work, we employed classical molecular dynamics (MD) and density functional theory (DFT) computational m...

Portlandite, as a most soluble cement hydration reaction product, affects mechanical and durability properties of cementitious materials. In the present work, an atomistic kinetic Monte Carlo (KMC) upscaling approach is implemented in MATLAB code in order to investigate the dissolution time and morphology changes of a hexagonal platelet portlandite...

The current contribution proposes a multi-scale bridging modeling approach for the dissolution of crystals to connect the atomistic scale to the (sub-) micro-scale. This is demonstrated in the example of dissolution of portlandite, as a relatively simple benchmarking example for cementitious materials. Moreover, dissolution kinetics is also importa...

In this paper, we carried out molecular dynamic (MD) simulations to study the crack growth and its effects on the mechanical properties of carbon doped polycrystalline boron-nitride nanosheets. We also quantified the influence of the grain and crack size on the mechanical responses. Therefore, models of polycrystalline carbon-doped h-BN with primar...

Graphene is a two-dimensional material, with exceptional mechanical, electrical, and thermal properties. Graphene-based materials are, therefore, excellent candidates for use in nanocomposites. We investigated reduced graphene oxide (rGO), which is produced easily by oxidizing and exfoliating graphite in calcium silicate hydrate (CSHs) composites,...

A Correction to this paper has been published: https://doi.org/10.1007/s42860-020-00082-w

Kaolins and clays are important raw materials for production of supplementary cementitious materials and geopolymer precursors through thermal activation by calcination beyond dehydroxylation (DHX). Both types of clay contain different polytypes and disordered structures of kaolinite but little is known about the impact of the layer stacking of dio...

Strontium, calcium, and magnesium silicate hydrate phases are synthesized by the reaction between silica and solution of metal hydroxides. The kinetics of the reaction is recorded using a quartz crystal microbalance (QCM), continuously monitoring the change in frequency and dissipation energy. Based on QCM results, it is shown that properties of so...

This article investigates the effect of different initial crack sizes on the mechanical response of single-layer boron doped polycrystalline graphene nanosheets by Molecular Dynamics (MD) simulations. We study 1%, 3%, 6% and 10% of boron doped polycrystalline graphene nanosheets with grain sizes of 10 and 15 nm for eight different initial crack len...

This paper presents a systematic approach toward localized failure inspection of internally pressurized laminated ellipsoidal woven composite domes. The domes were made of thin glass fiber reinforced polymer (GFRP) woven composite layups [0,0,0], [0,30,0], [0,45,0], and [0,75,0]. The analytical results demonstrated that the circumferential regions...

Building and construction industries are at the same time the backbone and the driving force of our modern society. Nearly all our technical infrastructure today is based on cement-based materials. Detailed spectroscopic investigations of model reactions on well-defined mineral substrates under UHV conditions are largely lacking, thus prohibiting a...

In this paper, we study the mechanical behavior of carbon doped polycrystalline boron-nitride under uniaxial loading conditions by Molecular Dynamic (MD) simulations. We determine the influence of doping, grain size and temperature. Therefore, samples of polycrystalline (h-BN) with equivalent grain sizes ranging from 1 to 10 nm are generated, and t...

Macro Fiber Composite (MFC) actuators developed by the NASA have been increasingly used in engineering structures due to their high actuation power, compatibility, and flexibility. In this study, an efficient two dimensional (2D) quadratic multi-layer shell element by using first order shear deformation theory (FOSDT) is developed to predict the li...

Graphene is a promising material for nanopore-sequencing DNA technology. In the current study, we have utilized molecular dynamic simulation in order to fabricate nanopores in the four divergent locations with different properties in a single-layer graphene nanosheet by using clusters bombardment. Ten different kinetic energies have been applied to...

In this paper, molecular dynamic simulations have been performed to fabricate nanopores in a polycrystalline boron-nitride nanosheet applied to DNA sequencer devices by using Si clusters bombardment. Three different sizes of Si clusters with ten different kinetic energies and impacts at five different locations of the polycrystalline boron-nitride...

The purpose of this study is to investigate the mechanical properties of a new two-dimensional graphene like material, crystalline carbon nitride with the stoichiometry of C3N. The extraordinary properties of C3N make it an outstanding candidate for a wide variety of applications. In this work, the mechanical properties of C3N nanosheets have been...

Abstract In this paper, molecular dynamic simulations have been performed to fabricate nanopores in a polycrystalline boron-nitride nanosheet applied to DNA sequencer devices by using Si clusters bombardment. Three different sizes of Si clusters with ten different kinetic energies and impacts at five different locations of the polycrystalline boron...

In this paper, we investigate the effect of temperature and grain size on the mechanical response of ato- mistic polycrystalline structures through classical molecular dynamic (MD) simulations. Five samples with different grain sizes in the range of 2–20 nm are examined under different temperatures. In addi- tion, the effect of the crack size on th...

In this paper, molecular dynamic simulations are utilized to investigate the effect of temperature and topological defects on the mechanical response and tensile strength of grain boundaries in single-layer hexagonal boron-nitride (h-BN) nanosheets. Six different cases of grain boundaries are examined including four symmetric and two asymmetric mod...

Many failures such as those due to blast, impact, wind pressure and earthquakes can be caused by the progressive collapse in structures. This paper will discuss different mitigation methods for progressive collapse corresponding numerical analysis for a 9-storey reinforced concrete structure by SAP2000 following severe initial damage. After removin...

In our modern society, tall structures are an essential component of new civilization. These kinds of structures are sensitive to wind excitations due to their low damping and stiffness, and therefore large amplitude vibrations often happen under strong wind excitation. Focus of this study is a critical review of the research development on interac...