Civil Engineering Materials Research Articles

Sustainability of Geosynthetics-Based Solutions

Sustainability emphasises the importance of increasing the resource efficiency of infrastructure. The usage of geosynthetic materials in civil and environmental engineering can significantly influence sustainability at the planning and design stages of infrastructure construction projects. They are used in many different applications in construction and environmental engineering, as they provide a better and longer performance and less costly solutions than traditional materials (such as sand, gravel, concrete and cement). Additional benefits can be achieved by combining geosynthetics with various recycled materials as substitutes for high-quality natural materials. In this paper, the importance of sustainability in geosynthetics-based solutions is discussed. The possibilities of using geosynthetics in sustainable development have been analysed and the benefits resulting from their application, such as the reduction in carbon footprint and release of greenhouse gases and saving water and other natural resources, have been assessed. Innovative solutions that support mitigation measures, adaptation to climate change and achievement of sustainable development goals have been presented.

Surface properties and de-polluting performance of a photocatalytic coating incorporating novel core@shell nanospheres for cementitious substrate

The surface of long-term exposed building materials usually shows serious deterioration under continuous environmental erosion, which can greatly shorten the service life of building structures. The application prospect of multifunctional photocatalytic materials in civil engineering is promising but the engineering application is still limited due to the inherent defects of traditional photocatalytic materials. In this paper, the ordinary Portland cement (OPC) and alkali activated slag (AAS) mortar samples were prepared with a photocatalytic coating incorporating novel core@shell nanospheres which feature with TiO2 core and CoAl-layered double hydroxide shell (TiO2@CoAl-LDH). The surface roughness, microhardness, contact angle and capillary water absorption of coated and uncoated mortars were analyzed and characterized to explore the effect of photocatalytic coating on surface properties. The photocatalytic activity and photo-induced hydrophilicity of the coated mortar were investigated by degrading methylene blue and contact angle tests. A simulated rainwater washing test was designed to evaluate the long-term stability of photocatalytic coatings on mortar substrate. The results show that compared with unwashed coated mortar, the coated mortar after rainwater washing can still maintain a higher photocatalytic activity, whereby the surface hydrophilicity was increased with the decrease of the surface roughness and capillary water absorption. As a newly developed protective coating material, TiO2@CoAl-LDH is expected to confer multifunctional properties to the cementitious materials.

Recycling of Contaminated Marine Sediment and Industrial By-Products through Combined Stabilization/Solidification and Granulation Treatment.

Stabilization/solidification (S/S) is becoming increasingly important, as it allows the remediation of contaminated sediments and their recovery into materials for civil engineering. This research proposes a cement-free cold granulation process for manufactured low-cost aggregates from marine sediments contaminated with organic compounds and metals. After the chemo-physical characterization of the study materials, two mix designs were prepared in a rotary plate granulator by adding two industrial by-products as geopolymer precursors, coal fly ash (CFA) and Blast Furnace Slag (BFS), but also alkaline activation solutions, water, and a fluidizer. The results indicated that sediments treated with mix 1 (i.e., with a higher percentage of water and fluidifier) represent the optimal solution in terms of metal leachability. The metal leachability was strictly influenced by aggregates' porosity, density, and microstructure. The technical performance (such as the aggregate impact value > 30%) suggested the use of granules as lightweight aggregates for pavement construction. The results indicated that cold granulation represents a sustainable solution to recycling contaminated marine sediments, CFA, and BFS into lightweight artificial aggregates.

Cyclic elastoplastic constitutive model for stainless steels compatible with multiple strengths

The application of stainless steel materials in civil engineering has begun to attract attention over the last decade. Nevertheless, most studies of stainless steel structures still use the oversimplified Chaboche model. Therefore a more accurate constitutive model is needed to describe the cyclic elastoplastic behavior of stainless steel. The model should be able to simulate stainless steel of varying strengths and should be easily calibrated for practical engineering purposes. This paper proposes a compatible constitutive model that meets these objectives. The constitutive model combines two forms of hardening, is dominated by isotropic and kinematic hardening, and accounts for the strain memory effect and the average stress relaxation effect. A complete numerical implementation scheme for the constitutive model is proposed and coded in the user material subroutine (UMAT) based on the implicit return mapping algorithm. Furthermore, simplified methods and recommendations for the calibration of material parameters are given. The simulation results of a detailed finite element model are compared with the results of the cyclic loading tests, and good agreements are obtained. The proposed constitutive model can be further used in seismic or other dynamic nonlinear analyses of stainless steel structures to correctly predict their strength, deformation, and energy dissipation capacity.

Effect of Addition of LD Slag Aggregate on Fresh and Hardened Properties of Cement Concrete

Cement concrete lends itself to a multitude of unique designs because of its many beneficial characteristics. Because of its inexpensive cost and desirable physical qualities, concrete is one of the most extensively utilised civil engineering materials. In this article, LD (Linz and Donawitz) slag is used to partially replace fine aggregate. This research mainly concentrates on partial replacement of natural fine aggregate with LD slag fine aggregate. Since the construction industry activity in India is gaining its momentum there is a scarcity of natural resources to overcome this problem substitute materials should be used to make the concrete and studies have to be conducted. In this study such an attempt is made where natural fine aggregate is partially replaced with LD slag fine aggregate. The purpose of this work is to investigate the fresh and hardened qualities of M-30 grade concrete in which LD slag has been partially replaced by the weight of natural fine aggregate in the ratios of 0%, 10%, 20%, 30%, 40%, and 50%. The slump test is used to investigate the features of workability. Compressive and split tensile strength tests are used to investigate the hardened characteristics of concrete. After 28 days of curing, the test is performed, and a mathematical regression model is constructed for the same.

Bond Characterization in Cementitious Material Binders Using Fourier-Transform Infrared Spectroscopy

Fourier-transform infrared (FTIR) spectroscopy is a fast and simple technique for functional group identification. This work provides a review and insight into the application and interpretation of FTIR spectroscopy for cementitious binders that comprise ordinary Portland cement, alkaline-activated binders, geopolymers, and material characterization for civil engineering material applications. This technique can be used to identify different compounds and a moiety of bond vibrations in inorganic molecules such as Si-O, -OH, H-O-H (water), C-O (carbonate or carbonation), aluminosilicate (Si-O-T, where T is Al or Si), and S-O (sulfate or gypsum) found in hydrated cement, alkaline binders, and geopolymers. The prominent bands include those representing carbonation (CO32− 1390–1475 cm−1), calcium carbonate (871, 1792–2516 cm−1), hydroxylation and water molecules (1607, 3400–3650 cm−1), strength skeletal framework compositions or Al-Si substitutions, silicate organization (C-A-S-H, N-A-S-H, or C-S-H (950–1055 cm−1), and sulfate (600–680, 1080–1100 cm−1). Some of the factors that could affect the spectra bands include elemental displacement due to changes in molar mass, activated temperature, pH, activator concentration, w/b ratio, Ca/Si ratio, Si/Al ratio, and the silica modulus (SiO2/Na2O) of the activators used in the binder synthesis. The method could be used for destructive and non-destructive testing on paste sample by using transmission and attenuated total reflectance methods, respectively.

3d imaging and analysis of cracks in loaded concrete samples

Concrete plays a central role as the standard building material in civil engineering. Experimental characterization of the concrete microstructure and a description of failure mechanisms are important to understand the concrete’s mechanical properties. Computed tomography is a powerful source of information as it yields 3d images of concrete specimens. However, complete visual inspection is often infeasible due to very large image sizes. Hence, automatic methods for crack detection and segmentation are needed. A region-growing algorithm and a 3d U-Net showed promising results in a previous study. Cracks in normal concrete and high-performance concrete that were initiated via tensile tests were investigated. Here, the methods are validated on a more diverse set of concrete types and crack characteristics. Adequate adaptions of the methods are necessary to deal with the complex crack structures. The segmentation results are assessed qualitatively and compared to those of a template matching algorithm which is well-established in industry.

Bamboo-Inspired Renewable, High-Strength, Vibration-Damping Composites for Structural Applications

Renewable structural materials derived from natural biological materials can potentially replace non-renewable synthetic materials for civil engineering and transportation applications. Here, inspired by the functional gradient structure of bamboo, we propose a simple and efficient two-step preparation strategy to convert natural bamboo into a lightweight, high-strength, damping, and sound-insulating structural engineering material called densified bundle-laminated veneer lumber (DBLVL). DBLVL was prepared by finely grading and thinning three layers of bamboo slices and removing the lignin and hemicelluloses from the surface of bamboo bundles. This was followed by penetrating the phenol formaldehyde resin and then solidifying and densifying it in situ. DBLVL had superior mechanical properties due to its bamboo-like gradient laminated structure, three-dimensional network distribution of adhesive under high temperature and high pressure, in situ curing, and solid interfacial bonding. It had a specific tensile strength of 297 MPa cm3 g–1, which was superior to those of many other construction materials. The tensile strength of DBLVL reached 363 MPa, and the bending strength reached 219 MPa, which were 97.28 and 92.11% higher than those of natural bamboo, respectively. The impact toughness reached 15.4 J/cm2. DBLVL also showed excellent damping and vibration reduction (the first three damping ratios were 2.35, 1.81, and 2.40%) and dimensional stability (the thickness expansion rate after 24 h of water absorption was 4.43%). Because of its excellent mechanical properties and hygrothermal stability, DBLVL is expected to replace non-renewable synthetic materials as a green and sustainable structural material for engineering applications.

Experiences and Challenges in Learning of Civil Engineering Materials (CEM) Course during the COVID-19 Pandemic among Civil Engineering Society (CES) Students

The COVID-19 disease has created the largest disruption in human history, affecting all sectors especially educational systems. Closure of schools, universities, and other educational premises due to pandemic has forced higher education and researchers to create a new alternative way on how to alleviate this problem. E-learning and online instructions is one of the most notable methods that is highly recommended during this pandemic. Thus, this paper aims to investigate the experiences and challenges in learning Civil Engineering Materials (CEM) during COVID-19 pandemic among Civil Engineering Studies (CES). This quantitative study data was conducted to 159 students who enrolled in the CEM course. The student’s experiences and challenges while undergoing online learning sessions and how the students can adapt to the CEM course with the new learning environment is the main concern of this study. The result showed that most of the students had a variety of problems such as internet access, discomfort, and inappropriate places to complete the required assessment. Whilst facing the risk of loss of enthusiasm in learning, lack of focus and lack of communication skills between the teaching staff and friends.

A review of recent developments in structural applications of natural fiber-Reinforced composites (NFRCs)

Natural fiber-reinforced composites (NFRCs) are expected to find growing applications in near future, especially in Europe where stringent environmental codes are being legislated and public pressure for their enforcement is increasing. Study has shown that NFRCs are also gaining recognition among civil engineers as a viable alternative to traditional materials for use as concrete reinforcement in load-bearing structural members as in building frames and bridge decks. The present review strives to provide a brief overview of NFRCs, state-of-the-art developments in their manufacture, and examples of their structural applications. Another aspect of the review involves investigation of the challenges facing the use of fiber composite materials in civil engineering. These include the high manufacturing costs, difficulties associated with appraisal of its potential benefits, uncertainties about their properties, lack of understanding among civil engineers of the material and its service life, and the relatively small battery of standards developed for the composite industry. Finally, the study will conclude with the prospects of bio-composite applications and the emerging trends in novel bio-composites for future structural applications.

Сумісність компонентів матеріалів в цивільній інженерії

The work highlights the problem of thermodynamic and kinetic compatibility of components in the creation of fire-resistant and strong composite materials in civil construction. The works of leading domestic and foreign scientists on this problem are analyzed. The kinetics of the interaction of temperature, pressure, structural features, the degree of compactness of the material and the external environment are considered. Areas of practical application of solid-phase reactions are indicated. Attention is paid to the protection of refractory materials from high-temperature gas corrosion. The compatibility of the boride coating with refractory metals was investigated. The interaction of titanium diboride with iron and its alloy was studied. It has been proven that iron alloys are promising for their use as a basis for composite materials. The laws of the compatibility process of components during the development and operation of high-temperature materials in civil engineering were studied. The main factors influencing the compatibility of components during thermodynamic solid-phase processes of creating composite materials are highlighted. Recommendations are given for the selection of the metal base and strengthening oxide, taking into account the affinity of the base metal and the oxide former for oxygen. The solid-phase interaction and solubility of materials at high temperatures were studied. Methods of obtaining composite materials using incompatible components are given. The results of the conducted experiments indicate that the strongest grafting of the coating with the base is achieved when an intermediate layer is formed between them, which is formed as a result of diffusion or chemical interaction. It should be noted that the chemical interaction is effective only if the new reaction products are accumulated in the transition layer and have properties that agree with the properties of the coating and the base, and also have high strength. Matching the properties of the coating and the base can be achieved by selecting the coating application mode, using activators or reaction retarders, and creating intermediate layers with similar properties.

An experimental study on smart-earth samples for structural applications

Concrete is the most widespread construction material in civil engineering because of its mechanical properties, durability, and versatility. However, its environmental impact is significant, due to the raw materials which constitute it, and its great ecological footprint. A possible solution to limit the energy consumption and the CO2 emissions during its production and use, stays in the development of more sustainable alternative mixes. Among eco-friendly ones, earth-based concretes, where cement is partially substituted by earth, allow an environmental advantage with respect to conventional concretes, keeping acceptable mechanical properties for smaller structural applications. The paper describes and comments the results of an experimental campaign carried out on samples with matrices of earth and cement, newly doped with carbon microfibers. These construction materials, developed by the authors, are able to exhibit self-monitoring capabilities. Such a multifunctional behavior results particularly effective for monitoring of structures during their service life and after critical events such as earthquakes. The characterization of fracture development occurred through three-point bending tests has been carried out through both electrical measurements and Digital Image Correlation. The influence of the carbon inclusions on the mechanical properties has been also evaluated and discussed.

Dynamic behavior of structural beams made of innovative smart concrete

The monitoring of structures and infrastructures is nowadays a pivotal activity for guaranteeing the safety of their users. Environmental conditions and exceptional events could affect their performance and integrity, shorten their service lives and even produce unexpected failures. The development of multifunctional smart structural materials with enhanced or novel properties could help to prevent or reduce damages and collapses. Among other building materials, concrete is particularly suitable for such improvements due to its composite nature. The authors have developed a smart concrete doped with carbon microfibers capable to sense variations of applied strains/stresses. The investigation started from the analysis of the performances of small samples, up to the manufacture of two full-scale RC beams. These applications at realistic scales are crucial for a diffuse use of such smart materials in civil engineering. The paper describes the novel characteristics of full-scale smart concrete beams, investigating their main physical, electrical, and monitoring capabilities. For this purpose, dynamic tests are carried out and discussed.

Influence of Micro-structure of selected components made from AISI 304 on the mechanical properties

Stainless steels, especially AISI 304, are increasingly used civil engineering materials in the last years because they have excellent properties. They are used for many civil engineering structures e.g. chemical, energy, bridges etc. The presented study brings results of the observation of micro-structure and results on basic mechanical properties of AISI 304 steel. This steel, supplied in different profiles by different suppliers, can vary considerably, which must be taken into account when designing structures.

Application of Fractal to Evaluate the Drying Shrinkage Behavior of Soil Composites from Recycled Waste Clay Brick

Soil drying cracking is the most common natural phenomenon affecting soil stability. Due to the complexity of the geometric shapes of soil cracks during the cracking process, it has become a major problem in engineering science. The extremely irregular and complex crack networks formed in civil engineering materials can be quantitatively investigated using fractal theory. In this paper, fractal dimension is proposed to characterize the drying cracking characteristics of composite soil by adding recycled waste brick micro-powder. At the same time, the concept of the probability entropy of cracking is introduced to quantify the ordered state of crack development. Correspondingly, the endpoint value of probability entropy was solved mathematically, and the meaning of the probability entropy of cracking was clarified. In this study, the fracture fractal characteristics of composite soil mixed with different materials were first investigated. Then, five groups of composite soil-saturated muds with added recycled waste brick micro-powder of different contents were prepared in the laboratory. Using the evaporation test under constant temperature and humidity, the change rules of the fractal dimensions, probability entropy, crack ratios, and water contents of cracks during the cracking process of the soil samples were obtained. The results show that: (1) on the whole, the fractal dimensions of the soil samples added with recycled waste brick micro-powder of different contents increased over time, and the fractal dimensions of the soil samples without recycled waste brick micro-powder were obviously larger than those of the soil samples with recycled waste brick micro-powder. With the increase in the content of recycled waste brick micro-powder, the maximum fractal dimension decreased in turn. The maximum fractal dimensions of the five groups of soil samples were 1.74, 1.68, 1.62, 1.57, and 1.45. (2) The change trends of the probability entropy and fractal dimensions were similar; both of them showed an upward trend over time, and the probability entropy of the soil samples without recycled waste brick micro-powder was greater than that of the soil samples with recycled waste brick micro-powder. With the increase in the contents of recycled waste brick micro-powder, the probability entropy decreased in turn. The maximum values of the crack probability entropy of the five groups of soil samples were 0.99, 0.92, 0.87, 0.83, and 0.80. (3) Under the action of continuous evaporation, the moisture contents of the soil samples gradually decreased over time, while the crack ratios increased over time. To sum up, both from the perspective of the development process of the cracks of the soil samples and from the perspective of the final stable crack networks of the soil samples, the geometric shapes of the cracks of the soil samples without recycled waste brick micro-powder were the most complex. With the increase in the content of recycled waste brick micro-powder, the fractal characteristics of the cracks gradually changed from complex to simple.

Effect of Biomass Ash on the Properties and Microstructure of Magnesium Phosphate Cement-Based Materials

The disposal of biomass ash (BA) will be of great importance for environmental protection and sustainability, and the aim of this study is to analyze the feasibility of the resourceful use of biomass ash in civil engineering materials. The effects of the content and type of biomass ash on the flowability, setting time, compressive strength, flexural strength, bonding strength, and drying shrinkage of magnesium phosphate cement (MPC) mortar were investigated. In addition, the effects of BA on the hydration and microstructure of MPC were investigated by X-ray diffraction (XRD), thermogravimetry, mercury intrusion porosimetry (MIP), and scanning electron microscope (SEM). The results showed that BA significantly affects the flowability and setting time of MPC mortar. The compressive and flexural strength of MPC mortars decreases with increasing amounts of BA. The drying shrinkage of MPC mortar specimens increases exponentially with the increase of BA content. The incorporation of BA will reduce the bonding strength of the MPC mortar, which is associated with increased drying shrinkage. The incorporation of BA into MPC results in low hydration product generation and poor pore structure. The incorporation of BA into MPC has a significant effect on the microstructure morphology and the hollow columnar-like hydration product may be formed by the reaction of BA with MgO in the paste.

Discrete element analysis of sand-tyre chips mixtures with different tyre chip orientations under triaxial compression tests

Sand-tyre chips (STCh) mixtures are emerging civil engineering materials that have been widely studied and applied. In the sand-tyre chips system, the mechanical behavior of sand matrix is improved attributed to the excellent property of tyres. However, the effect of tyre chip orientation for STCh mixtures is not fully appreciated, especially from the microscopic scale. In this paper, the microscopic behaviors of STCh mixtures with different orientation tyre chips were investigated employing the Discrete Element Method (DEM). The tyre chips model was constructed with sufficient consideration and the microscopic parameters of STCh model were confirmed by the calibration procedure. Simulation results illustrate that horizontal tyre chips more effectively enhance the mechanical properties of mixtures. The visualization of the specimen shows that the orientation of tyre chips can influence the evolution of system contact network, formation of shear band, and bulging deformation of specimen. The microscopic mechanism including the composition of strong contacts, coordination number, average normal contact force, sliding and rolling, energy storage and dissipation, and the tensile force in tyre chips were studied to evaluate the discrepancies of different orientation tyre chips. The mechanism of the reinforcement for tyre chips can receive further understanding from this study.

AN APPROACH TO SUBPIXEL ACCURACY WIDENING CRACK WIDTH DETERMINATION IN IMAGE SEQUENCES

Abstract. As an extension to existing work on crack detection and subpixel accuracy crack width determination as a tool for civil engineering material testing, the paper shows an algorithmic approach to handle widening cracks with relative rotations between related crack borders. In the first time step under zero-load, a set of points to be tracked through consecutive frames of an image sequence is defined. Then, subpixel-precise displacement fields are computed for the image data of the following time steps using an 8-parameter least-squares matching approach. The points are triangulated into a mesh, and the changes of the inner geometry of the triangles are considered with a mathematical model assuming a split of each triangle. With this model, subpixel-precise deformation vectors are derived. Crack candidates are determined by a thresholding applied to the vectors’ lengths. After an estimation of the crack normal, a decomposition of the deformation vectors is applied, allowing to compute crack widths and shear movements. As a novel contribution to the technique, a model extension is proposed for the case of a relative rotation between the crack borders in order to reduce systematic errors. The model includes two separate rigid transformations for each crack side.

Auxetics and Other Systems with Unusual Characteristics

Auxetics and Other Systems with Unusual Characteristics

Applications of wood ash as a construction material in civil engineering: a review

Applications of wood ash as a construction material in civil engineering: a review