Micromechanical Models for FDM 3D-Printed Polymers: A Review.

Due to its large number of advantages compared to traditional subtractive manufacturing techniques, additive manufacturing (AM) has gained increasing attention and popularity. Among the most common AM techniques is fused filament fabrication (FFF), usually referred to by its trademarked name: fused deposition modeling (FDM). This is the most efficient technique for manufacturing physical three-dimensional thermoplastics, such that FDM machines are nowadays the most common.

Influence of Fiber Orientation on the Water and Ions Transportation of Engineered Cementitious Composite (ECC).

An engineered cementitious composite (ECC) belongs to a type of high-performance fiber-reinforced materials. Fiber alignment causes the anisotropy of such materials. Herein, the influence of the fiber orientation on water and ion penetration into an ECC was studied.

Behavior of Engineered Cementitious Composites (ECCs) Subjected to Coupled Sustained Flexural Load and Salt Frost.

The performance of engineered cementitious composites (ECCs) under coupled salt freezing and loaded conditions is important for its application on the transportation infrastructure. However, in most of the studies, the specimens were generally loaded prior to the freezing. The influence of sustained load was merely considered.

Carbonation Behavior of Engineered Cementitious Composites under Coupled Sustained Flexural Load and Accelerated Carbonation.

Engineered cementitious composites (ECCs) belong to a broad class of fibre-reinforced concrete. They incorporate synthetic polyvinyl alcohol (PVA) fibres, cement, fly ash and fine aggregates, and are designed to have a tensile strain capacity typically beyond 3%. This paper presents an investigation on the carbonation behaviour of engineered cementitious composites (ECCs) under coupled sustained flexural load and accelerated carbonation.

Thermomechanical Performance Analysis of Novel Cement-Based Building Envelopes with Enhanced Passive Insulation Properties.

The design of new insulating envelopes is a direct route towards energy efficient buildings. The combinations of novel materials, such as phase-change (PCM), and advanced manufacturing techniques, such as additive manufacturing, may harness important changes in the designing of building envelopes. In this work we propose a novel methodology for the design of cement-based building envelopes.

Microbiologically Induced Concrete Corrosion: A Concise Review of Assessment Methods, Effects, and Corrosion-Resistant Coating Materials.

Microbiologically induced concrete corrosion (in wastewater pipes) occurs mainly because of the diffusion of aggressive solutions and in situ production of sulfuric acid by microorganisms. The prevention of concrete biocorrosion usually requires modification of the mix design or the application of corrosion-resistant coatings, which requires a fundamental understanding of the corrosion process. In this regard, a state-of-the-art review on the subject is presented in this paper, which firstly details the mechanism of microbial deterioration, followed by assessment methods to characterize biocorrosion and its effects on concrete properties.

Mechanical Properties of Lightweight Cementitious Cellular Composites Incorporating Micro-Encapsulated Phase Change Material.

This work focuses on combining digitally architected cellular structures with cementitious mortar incorporating micro-encapsulated phase change material (mPCM) to fabricated lightweight cementitious cellular composites (LCCCs). Voronoi structures with different randomness are designed for the LCCCs. Aided by the indirect 3D printing technique, the LCCCs were prepared with a reference mortar (REF) and a mortar incorporating mPCM.

Determination of Loss of Reinforcement Due to Corrosion through X-ray Computer Micro-Tomography.

X-ray computer scanning tomography (CT scan) is an increasingly more available technique, which has been applied to material sciences for years. Although most of its use is qualitative for gaining insights on material behavior, quantitative analysis for estimations of deterioration rates is possible. This paper describes an unbiased, straightforward method to determine the amount of reinforcement lost to corrosion through the use of X-ray tomography without the need to remove the concrete cover.

On the Use of Machine Learning Models for Prediction of Compressive Strength of Concrete: Influence of Dimensionality Reduction on the Model Performance.

Compressive strength is the most significant metric to evaluate the mechanical properties of concrete. Machine learning (ML) methods have shown promising results for predicting compressive strength of concrete. However, at present, no in-depth studies have been devoted to the influence of dimensionality reduction on the performance of different ML models for this application.

Effect of Fibers on Durability of Concrete: A Practical Review.

This article reviews the literature related to the performance of fiber reinforced concrete (FRC) in the context of the durability of concrete infrastructures. The durability of a concrete infrastructure is defined by its ability to sustain reliable levels of serviceability and structural integrity in environmental exposure which may be harsh without any major need for repair intervention throughout the design service life. Conventional concrete has relatively low tensile capacity and ductility, and thus is susceptible to cracking.

Influence of Micro-Pore Connectivity and Micro-Fractures on Calcium Leaching of Cement Pastes-A Coupled Simulation Approach.

A coupled numerical approach is used to evaluate the influence of pore connectivity and microcracks on leaching kinetics in fully saturated cement paste. The unique advantage of the numerical model is the ability to construct and evaluate a material with controlled properties, which is very difficult under experimental conditions. Our analysis is based on two virtual microstructures, which are different in terms of pore connectivity but the same in terms of porosity and the amount of solid phases.

Elucidating the Effect of Accelerated Carbonation on Porosity and Mechanical Properties of Hydrated Portland Cement Paste Using X-Ray Tomography and Advanced Micromechanical Testing.

Carbonation of hydrated cement paste (HCP) causes numerous chemo-mechanical changes in the microstructure, e.g., porosity, strength, elastic modulus, and permeability, which have a significant influence on the durability of concrete structures.

Effect of Recycled Iron Powder as Fine Aggregate on the Mechanical, Durability, and High Temperature Behavior of Mortars.

This study evaluates the mechanical, durability, and residual compressive strength (after being exposed to 20, 120, 250, 400 and 600 °C) of mortar that uses recycled iron powder (RIP) as a fine aggregate. Within this context, mechanical strength, shrinkage, durability, and residual strength tests were performed on mortar made with seven different percentages (0%, 5%, 10%, 15%, 20%, 30% and 50%) of replacement of natural sand (NS) by RIP. It was found that the mechanical strength of mortar increased when replaced with up to 30% NS by RIP.

Development of Nano-SiO and Bentonite-Based Mortars for Corrosion Protection of Reinforcing Steel.

In this study, the use of nano-silica (nano-SiO) and bentonite as mortar additives for combating reinforcement corrosion is reported. More specifically, these materials were used as additives in ordinary Portland cement (OPC)/fly ash blended mortars in different amounts. The effects of nano-silica and bentonite addition on compressive strength of mortars at different ages was tested.

The Effect of Material Fresh Properties and Process Parameters on Buildability and Interlayer Adhesion of 3D Printed Concrete.

The advent of digital concrete fabrication calls for advancing our understanding of the interaction of 3D printing with material rheology and print parameters, in addition to developing new measurement and control techniques. Thixotropy is the main challenge associated with printable material, which offers high yield strength and low viscosity. The higher the thixotropy, the better the shape stability and the higher buildability.

Agricultural Solid Waste as Source of Supplementary Cementitious Materials in Developing Countries.

Concrete production utilizes cement as its major ingredient. Cement production is an important consumer of natural resources and energy. Furthermore, the cement industry is a significant CO₂ producer.

Static and Fatigue Tests on Cementitious Cantilever Beams Using Nanoindenter.

Cement paste is the main binding component in concrete and thus its fundamental properties are of great significance for understanding the fracture behaviour as well as the ageing process of concrete. One major aim of this paper is to characterize the micromechanical properties of cement paste with the aid of a nanoindenter. Besides, this paper also presents a preliminary study on the fatigue behaviour of cement paste at the micrometer level.

Smart Crack Control in Concrete through Use of Phase Change Materials (PCMs): A Review.

Cracks in concrete structures present a threat to their durability. Therefore, numerous research studies have been devoted to reducing concrete cracking. In recent years, a new approach has been proposed for controlling temperature related cracking—utilization of phase change materials (PCMs) in concrete.

Microscale Testing and Modelling of Cement Paste as Basis for Multi-Scale Modelling.

This work aims to provide a method for numerically and experimentally investigating the fracture mechanism of cement paste at the microscale. For this purpose, a new procedure was proposed to prepare micro cement paste cubes (100 × 100 × 100 µm³) and beams with a square cross section of 400 × 400 µm². By loading the cubes to failure with a Berkovich indenter, the global mechanical properties of cement paste were obtained with the aid of a nano-indenter.

A 3D Lattice Modelling Study of Drying Shrinkage Damage in Concrete Repair Systems.

Differential shrinkage between repair material and concrete substrate is considered to be the main cause of premature failure of repair systems. The magnitude of induced stresses depends on many factors, for example the degree of restraint, moisture gradients caused by curing and drying conditions, type of repair material, etc. Numerical simulations combined with experimental observations can be of great use when determining the influence of these parameters on the performance of repair systems.

Influence of Microencapsulated Phase Change Material (PCM) Addition on (Micro) Mechanical Properties of Cement Paste.

Excessive cracking can be a serious durability problem for reinforced concrete structures. In recent years, addition of microencapsulated phase change materials (PCMs) to concrete has been proposed as a possible solution to crack formation related to temperature gradients. However, the addition of PCM microcapsules to cementitious materials can have some drawbacks, mainly related to strength reduction.

Simulation-Aided Design of Tubular Polymeric Capsules for Self-Healing Concrete.

Polymeric capsules can have an advantage over glass capsules used up to now as proof-of-concept carriers in self-healing concrete. They allow easier processing and afford the possibility to fine tune their mechanical properties. Out of the multiple requirements for capsules used in this context, the capability of rupturing when crossed by a crack in concrete of a typical size is one of the most relevant, as without it no healing agent is released into the crack.

Towards understanding the influence of porosity on mechanical and fracture behaviour of quasi-brittle materials: experiments and modelling.

In this work, porosity-property relationships of quasi-brittle materials are explored through a combined experimental and numerical approach. In the experimental part, hemihyrate gypsum plaster powder ( ) and expanded spherical polystyrene beads (1.5-2.