Recent Submissions

  • Mechanical Engineering Design, Learning from the Past to Design a Better Future

    Sole, Martin; Barber, Patrick; Turner, Ian; The University of Derby (Loughborough University, 2021-11-07)
    The economic importance of design, and design engineers to the success of a company has led to the exponential growth in the demand for qualified design engineers. To fill this demand, colleges and universities provide the best training available so that, after graduation these engineers will provide significant input from the first day of work. We live in a time known as industry 4.0 or the 4th Industrial Revolution, where computer power rules and takes on greater tasks, freeing up time for the design engineer to design more and more complex designs. Sometimes, it is good to stop, and take a breath to review our practices and remind ourselves of things we may have forgotten. It is true that we can design complex mechanisms and systems, in times past many of these would not be possible. But can we learn or be reminded of good practice by taking a journey through some of the design methods from the past. This paper will travel back to the 2nd century BC and look at cutting edge water pump design and the importance of a good literature review. It will highlight a serious gap in knowledge when comparing full-time and part-time students in our modern age. Airship design will be reviewed, the R100, R38 and R101 to remind us of the need to cross check design calculations. Looking at the beauty of Concorde design will remind us of the requirement in any design of good planning and regular meetings. This journey will finish by looking at the design process of the Boeing 777 commercial airliner, one of the first designs to use Computer Aided Design (CAD) and Computer Aided Manufacture (CAM). The use of Design Build Teams (DBT) with cross-disciplinary experts who can reside anywhere in the world will be considered. The reviewed historical examples may at first glance appear happen-stance but are in fact linked, and demonstrate a continuing growth in the ability, knowledge, complexity, and techniques of engineering design. This step back in time will remind teachers of some basic principles when teaching design to future design engineers. Designs have become more complex in this modern age, but it would be incorrect to say that complex design did not exist in times past. Before the internet, aircraft were built, global communication systems existed, men went to the moon.
  • Experimental investigation on the quasi-static crush performance of resin-infused thermoplastic 3D fibre-reinforced composites

    Shah, S. Z. H; Megat-Yusoff, P.S.M; Choudhry, R.S; Sajid, Zubair; Din, I.U; Universiti Teknologi PETRONAS, 32610, Bandar Seri Iskandar, Perak, Malaysia; University of Derby; National University of Sciences and Technology (NUST), Sector H-12, Islamabad, Pakistan (Elsevier, 2021-09-01)
    This paper presents the quasi-static crush performance of newer resin-infused thermoplastic 3D fibre reinforced composites (FRC) under axial load. The main objective is to make an assessment of the energy absorption capability of novel 3D composites for improved energy absorbing applications. Flat specimens of resin-infused thermoplastic (TP) and thermoset (TS) 3D composites with three trigger angles, i.e., 15°, 30° and 45° were tested under quasi-static crush loads. The thermoplastic 3D-FRC at 45° trigger angle demonstrated 31% higher specific energy absorption (SEA), and 17% higher average crushing stress. This improved performance is attributed to higher fragmentation failure mechanisms, which absorbed more energy. These results elucidate that the resin-infused thermoplastic composites are suitable for higher energy absorption and lightweight design for automotive and sports applications.
  • Multiscale damage modelling of 3D woven composites under static and impact loads

    Shah, S. Z. H; Megat-Yusoff, P.S.M; Karuppanan, S; Choudhry, R.S; Sajid, Z; Universiti Teknologi PETRONAS, Bandar Seri Iskandar, Perak 32610, Malaysia; University of Derby (Elsevier, 2021-09-24)
    A multiscale progressive damage modelling methodology for 3-dimensional (3D) woven composites is presented. The proposed methodology is generic and can be implemented in most finite element software to create a digital twin for simulation of damage response. It uses 3D solid element (reduced integration) representation of the part for global analysis, while the local damage response, as well as matrix nonlinearity is modelled using a mesoscale constitutive unit-cell model of 3D woven composite consisting of idealised regions of polymer matrix and impregnated yarns. The idealised unit-cell model is defined based on realistic input from X-ray tomography of the 3D woven composite part and the micro-level constituent properties of the matrix and fibres. The damage model has been validated using quasi-static tensile/compression tests as well as dynamic drop-weight impact tests for both thermoset (epoxy) and thermoplastic (Elium) 3D woven composites. These simulations successfully demonstrate the accuracy and efficiency of the model for both 3D-textile composites.
  • Influence of Yawed Wind Flow on the Blade Forces/Bending Moments and Blade Elastic Torsion for an Axial-Flow Wind Turbine

    Ahmadi, Mohammad H. B.; Yang, Zhiyin; University of Derby (American Society of Mechanical Engineers, 2021-09-16)
    Effects of yawed incoming flow on wind turbine blades forces and root bending moments (RBMs) are not fully understood. To advance our current understanding, numerical studies of a small-scale three-bladed horizontal axis wind turbine at TSR = 6.7 with yaw angles of zero and 45° have been carried out to examine the variations of blade and rotor loading due to the yawed incoming flow. An approach combining Large Eddy Simulation (LES) with Actuator Line Modelling (ALM) has been employed in the present study. The predicted phase-averaged blade forces reveal that the blade tangential force, in-plane RBM and power coefficient are much more sensitive to the upstream streamwise velocity variations and are much more strongly affected than the blade axial force, out-of-plane RBM and thrust coefficient. It also shows that for yawed incoming flows the blade axial force to the blade tangential force ratio fluctuates significantly during one rotor revolution, resulting in large variations of the blade elastic torsion and that the total blade force (magnitude and direction) undergoes a non-linear change in the circumferential and radial directions, which will likely lead to the reduction in the turbine operational life significantly, especially for long lightweight blades of large size wind turbines.
  • Regulating Product Sustainability

    Takhar, Raj; Takhar, Sukhraj; University of Derby (The Parliamentary Office of Science and Technology, 2021-06-10)
    Interview, written review and feedback on UK government proposals on the future of regulating product for sustainability.
  • Transforming product labels using digital technologies to enable enhanced traceability and management of hazardous chemicals

    Takhar, Sukhraj; Liyanage, Kapila; University of Derby (Inderscience, 2021-06-08)
    Manufacturers that produce, distribute or market physical products are likely to be impacted by numerous chemical and product regulations. Manufacturers must identify chemical substances which appear within mixtures, materials, formulations, raw materials, components, assemblies and finished products. This results in a very manual and resource intensive process of collection of chemical substances in products data, where definitions arise from internal, industry standards, supplier and customer requirements and often sourced from multiple supply chain actors. This paper contributes to existing literature by identifying a research gap in transforming current manual state data collection tasks via the utilisation of digital technologies, leveraging real-time data collection using smart labels to identify chemicals contained within products. The proposed design enables manufacturers to identify the use of chemicals consumed in a automated manner and enabling appropriate risks to be identified and managed accordingly. The design can be further expanded in the proposed collaborative data sharing network.
  • Realignment of Product Stewardship towards Chemical Regulations, the Circular Economy and Corporate Social Responsibility – a Delphi Study

    Liyanage, Kapila; Takhar, Sukhraj; University of Derby (Sepuluh Nopember Institute of Technology (ITS), 2021-07)
    Chemical regulations exist to limit and control the amount of hazardous chemical substances being used by industry. Increasing awareness of diminishing natural resources, increasing pollution, and reducing the amounts of harmful waste, has led towards increasing societal and regulatory pressure on industry to change from the traditional closed-loop manufacturing towards the adoption of sustainable materials and open-loop manufacturing systems as part of the Circular Economy. Corporate Social Responsibility (CSR) extends the relationship between industry and society. Product Stewardship (PS) provides a platform for organizations to assess impacts to manufacturing systems ensuring adequate measures are in place to understand, control or limit any impact(s) from manufacturing and using products. The research question answered in this paper relates to understanding the impacts on PS. This paper has been written based on a literature review and Delphi study. The outcomes from this paper will attempt to outline a framework for PS to align with Chemical Regulations, the Circular Economy and CSR.
  • Mechanical Engineering Design, Does the Past Hold the key to the Future?

    Sole, Martin; Ian, Turner; Barber, Patrick; University of Derby (The Design Society, 2021)
    Industry design of a complex product has always required a cross-disciplinary team of experts. Is it possible to mimic these teams in academia when training the design engineers of the future, and what disciplinary skills will they possess? The exceptional collaboration potential provided by the internet means industry experts can work as a team, and at the same time, reside anywhere in the world. What are the capabilities of teamwork when the team members may never see each other for real? Though a physical prototype is sometimes required, most prototypes are designed and created in the virtual world using 3D modelling. The model can be tested, checked for accuracy, have materials applied, and be created parametrically which allows the products geometry to be reset to different sizes by the designer. Collaboration, effective communication and 3D modelling make it possible to design intricate and complex designs remotely. While we rightly congratulate ourselves on the complexity of modern design and how clever we have become, we must not lose sight of past achievements. Design has become more complex in this modern age, but it would be incorrect to say that complex design did not exist in times past. Before the internet, aircraft were built, global communication systems existed, men went to the moon. What can we learn, if anything, by looking at the methods used to design complex products in the past? How can we apply what we learnt from the past to the future?
  • Design Education - A Reversed Method to Fill and Information and Knowledge Gap Between Full-Time and Part-Time Students

    Sole, Martin; Barber, Patrick; Ian, Turner; University of Derby (The Design Society, 2021-08)
    Teachers in schools, tutors in colleges, and lecturers in universities are all required to have specific teaching qualifications. As part of the qualification, it is normal to study tried and tested pedological theories. Some examples are Bloom’s Taxonomy, Constructivism, and Experiential Learning. This paper identifies a gap in the information and knowledge required of student design engineers studying on a full-time course, when compared to part-time students. To redress this gap, it is suggested that no new theories are required but just a new method of applying an old theory, the application of Bloom’s Taxonomy in reverse alongside reverse engineering. An example of applying this method to a class of design engineers in their final year of a BEng (Hons) Mechanical Engineering is provided.
  • The effect of fine droplets on laminar propagation speed of a strained acetone-methane flame: Experiment and simulations

    Fan, Luming; Tian, Bo; Chong, Cheng Tung; Jaafar, Mohammad Nazri Mohd; Tanno, Kenji; McGrath, Dante; Oliveira, Pedro M.de; Rogg, Bernd; Hochgreb, Simone; University of Derby; et al. (Elsevier, 2021-07-31)
    In this study, we investigate the effect of the presence of fuel droplets, their size and concentration, on stretched laminar flame speeds. We consider premixed strained methane/air mixtures, with the addition of small acetone droplets, and compare the flame velocity field behaviour to that of the fully vaporized mixture. An impinging stagnation flame configuration is used, to which a narrowly distributed polydisperse mist of acetone droplets is added. Total acetone molar concentrations between 9% and 20% per mole of methane are used, corresponding to 18.6% and 41.4% of the total fuel energy. The Sauter Mean Diameter (SMD) of acetone droplets is varied from 1.0 to 4.7 μm by carefully tuning the air flow rate passing through an atomizer. The droplet size distribution is characterized by a Phase Doppler Anamometry (PDA) system at the outlet of the burner. The flame propagation speed is measured using Particle Image Velocimetry (PIV) for overall equivalence ratios ranging from 0.8 to 1.4 at various strain rates, and the result is compared with a reference case in which acetone was fully vaporized. Unlike the fully vaporized flame, a two-stage reaction flame structure is observed for all droplet cases: a blue premixed flame front followed by a reddish luminous zone. Comparison of the results between gas-only and droplet-laden cases shows that the mean reference burning velocity of the mixture is significantly enhanced when droplets are present under rich cases, whereas the opposite is true for stoichiometric and lean cases. The mean droplet size also changes the relationship between flame speed and strain rate, especially for rich cases. The result suggests that with typical conditions found in laminar strained flames, even for the finest droplets that may have been vaporized before reaching the flame front, the resulting inhomogeneities may lead the flame to behaves differently from the well-premixed gaseous counterpart. Simulations at similar conditions are performed using a two-phase counterflow flame model to compare with experimental data. Model results of reference velocities do not compare well with observations, and the possible reasons for this behaviour are discussed, including the difficulties in determining the pre-vaporization process and thus the boundary conditions, as well as the fidelity of the current point-source based 1D model.
  • Thermal Fatigue Life of Ball Grid Array (BGA) Solder Joints Made From Different Alloy Compositions

    Depiver, Joshua Adeniyi; Sabuj, Mallik; Amalu, Emeka H; University of Derby; Teeside University (Elsevier, 2021-04-27)
    As temperature cycling drives fatigue failure of solder joints in electronic modules, characterisation of the thermal fatigue response of different solder alloy formulations in BGA solder joints functioning in mission-critical systems has become crucial. Four different lead-free and one eutectic lead-based solder alloys in BGA solder joints are characterised against their thermal fatigue lives (TFLs) to predict their mean-time-to-failure for preventive maintenance advice. Five finite elements (FE) models of the assemblies of the BGAs with the different solder alloy compositions are created with SolidWorks. The models are subjected to standard IEC 60749-25 temperature cycling in ANSYS mechanical package environment. Plastic strain, shear strain, plastic shear strain, and accumulated creep energy density responses of the solder joints are obtained and inputted into established life prediction models – Coffin Manson, Engelmaier, Solomon and Syed – to determine the lives of the models. SAC405 joints have the highest predicted TFL of circa 13.2 years, while SAC387 joints have the least life of circa 1.4 years. The predicted lives are inversely proportional to the magnitude of the areas of stress-strain hysteresis loops of the BGA solder joints. The prediction models are significantly not consistent in predicted magnitudes of TFLs across the solder joints. With circa 838% variation in the magnitudes of TFL predicted for Sn63Pb37, the damage parameters used in the models played a critical role and justifies that a combination of several failure modes drives solder joints damage. This research provides a technique for determining the preventive maintenance time of BGA components in mission-critical systems. It proposes developing a new life prediction model based on a combination of the damage parameters for improved prediction.
  • Detection of Cover Collapse Doline and Other Epikarst Features by Multiple Geophysical Techniques, Case Study of Tarimba Cave, Brazil

    Hussain, Yawar; Uagoda, Rogerio; Borges, Welitom; Prado, Renato; Hamza, Omar; Cárdenas-Soto, Martín; Havenith, Hans-Balder; Dou, Jie; Clemson University, Clemson, SC 29634, USA; University of Brasilia, Brasilia 70910-900, Brazil; et al. (MDPI, 2020-10-12)
    Reliable characterization of the karst system is essential for risk assessment where many associated hazards (e.g., cover-collapse dolines and groundwater pollution) can affect natural and built environments, threatening public safety. The use of multiple geophysical approaches may offer an improved way to investigate such cover-collapse sinkholes and aid in geohazard risk assessments. In this paper, covered karst, which has two types of shallow caves (vadose and fluvial) located in Tarimba (Goias, Brazil), was investigated using various geophysical methods to evaluate their efficiency in the delineation of the geometry of sediments filled sinkhole. The methods used for the investigation were Electrical Resistivity Tomography (ERT), Seismic Refraction Survey (SRS), Seismic Refraction Tomography (SRT) and the Very Low-Frequency Electromagnetic (VLF-EM) method. The study developed several (2D) sections of the measured physical properties, including P-wave velocity and electrical resistivity, as well as the induced current (because of local bodies). For the analysis and processing of the data obtained from these methods, the following approaches were adopted: ERT inversion using a least-square scheme, Karous-Hjelt filter for VLF-EM data and time-distance curves and Vp cross-sections for the SRS. The refraction data analysis showed three-layered stratigraphy topsoil, claystone and carbonate bedrock, respectively. The findings obtained from ERT (three-layered stratigraphy and sediment-filled doline), as well as VLF-EM (fractured or filled caves as a positive anomaly), were found to be consistent with the actual field conditions. However, the SRS and SRT methods did not show the collapsed material and reached the limited depth because of shorter profile lengths. The study provides a reasonable basis for the development of an integrated geophysical approach for site characterization of karst systems, particularly the perched tank and collapse doline.
  • On wind turbine power fluctuations induced by large-scale motions

    Ahmadi, Mohammad; Yang, Zhiyin; University of Derby (Elsevier, 2021-04-21)
    Our current understanding on the dynamic interaction between large-scale motions in the approaching turbulent flow and wind turbine power is very limited. To address this, numerical studies of a small-scale three-bladed horizontal axis wind turbine with cylinders placed in front of it to produce energetic coherent structures of varying scale relative to the turbine size have been carried out to examine the temporary variations of the turbine power. The predicted spectra reveal a strong interaction between large-scale turbulent motions generated by cylinders and the instantaneous turbine power. More specifically, it shows how the large dominant turbulent scales of incoming flow affect the spectral characteristics of turbine power, i.e, determining the level and trend of the turbine power spectrum. Comparisons reveal that there are two critical frequencies recognisable in the turbine power spectrum: the first one, close to the turbine rotational frequency, above which the coupling of upstream flow and turbine power disappears; the second one, identified for the first time and related to the dominant large-scale motions which dictate the level and trend of the turbine power spectrum. This study also shows that the strong scale-to-scale interaction between the upstream flow and turbine power reported previously does not appear at high Reynolds numbers.
  • Biodiesel sustainability: The global impact of potential biodiesel production on the energy–water–food (EWF) nexus

    Chong, Cheng Tung; Loe, Ting Yu; Wong, Kang Yao; Ashokkumar, Veeramuthu; Lam, Su Shiung; Chong, Wen Tong; Borrion, Aiduan; Tian, Bo; Ng, Jo-Han; Shanghai Jiao Tong University, Lingang, Shanghai 201306, China; et al. (Elsevier, 2021-02-01)
    A data-driven model is used to analyse the global effects of biodiesel on the energy–water–food (EWF) nexus, and to understand the complex environmental correlation. Several criteria to measure the sustainability of biodiesel and four main limiting factors for biodiesel production are discussed in this paper. The limiting factors includes water stress, food stress, feedstock quantity and crude oil price. The 155-country model covers crude oil prices ranging from USD10/bbl to USD160/bbl, biodiesel refinery costs ranging from -USD0.30/L to USD0.30/L and 45 multi-generation biodiesel feedstocks. The model is capable of ascertaining changes arising from biodiesel adoption in terms of light-duty diesel engine emissions (NO, CO, UHC and smoke opacity), water stress index (WSI), dietary energy supply (DES), Herfindahl–Hirschman index (HHI) and short-term energy security. With the addition of potential biodiesel production, the renewable energy sector of global primary energy profile can increase by 0.43%, with maximum increment up to 10.97% for Malaysia. At current crude oil price of USD75/bbl and refinery cost of USD0.1/L, only Benin, Ireland and Togo can produce biodiesel profitably. The model also shows that water requirement varies non-linearly with multi-feedstock biodiesel production as blending ratio increases. Out of the 155 countries, biodiesel production is limited by feedstock quantity for 82 countries, 47 are limited by crude oil price, 20 by water stress and 6 by food stress. The results provide insights for governments to set up environmental policy guidelines, in implementing biodiesel technology as a cleaner alternative to diesel.
  • Self-healing of bio-cementitious mortar incubated within neutral and acidic soil

    Esaker, Mohamed; Hamza, Omar; Souid, Adam; Elliott, David; University of Derby (Springer Science and Business Media LLC, 2021-04-14)
    The efficiency of bio self-healing of pre-cracked mortar specimens incubated in sand was investigated. The investigation examined the effect of soil pH representing industrially recognised classes of exposure, ranging from no risk of chemical attack (neutral pH≈7) to very high risk (pH≈4.5). Simultaneously, the soil was subjected to fully and partially saturated cycles for 120 days to resemble groundwater-level fluctuation. Bacillus Subtilis with nutrients were impregnated into perlite and utilised as a bacterial healing agent. The healing agent was added to half of the mortar specimens for comparison purposes. Mineral precipitations were observed in both control and bio-mortar specimens, and the healing products were examined by SEM-EDX scanning. The healing ratio was evaluated by comparing (i) the repair rate of the crack area and (ii) by capillary water absorption and sorptivity index - before and after incubation. The results indicated that bacteria-doped specimens (bio-mortar) exhibited the most efficient crack-healing in all incubation conditions i.e. different chemical exposure classes. In the pH neutral soil, the average healing ratios for the control and bio-mortar specimens were 38% and 82%, respectively. However, the healing ratio decreased by 43% for specimens incubated in acidic soil (pH≈4) compared with specimens incubated in neutral soil (pH≈7). The study implies that bio self-healing is generally beneficial for concrete embedded within the soil; however, aggressive ground conditions can inhibit the healing process.
  • The cradle to gate life-cycle assessment of thermoelectric materials: A comparison of inorganic, organic and hybrid types

    Soleimani, Zohreh; Zoras, Stamatis; Ceranic, Boris; Shahzad, Sally; Cui, Yuanlong; University of Derby; Sheffield University (Elsevier, 2021-02-18)
    Using thermoelectric generators to convert waste heat into electricity is a renewable alternative to fossil energy sources. As thermoelectric materials are the main element of thermoelectric generators, so far numerous studies have attempted to optimize their energy conversion efficiency. However, no single study to date has examined their life cycle impacts, whilst it is the most important feature of any renewable technology. Accordingly, the aim of the present study is to assess the life cycle impacts of thermoelectric materials at their production stage (cradle to gate) using a life cycle assessment tool called GaBi v.4.4. Thus, the thermoelectric materials were categorized into inorganic, organic, and hybrid types. The five investigated impact categories were resource consumption, emission, waste, primary energy demand, and global warming potential. The results confirmed that the inorganic type caused significantly greater environmental impacts than the other two types. The only inorganic exception was Bi 2 Te 3 that its environmental impact was by far the lowest among all the studied thermoelectric materials. Notably, the inorganic type caused major harm to the environment due to its extremely energy-intensive manufacturing process. However, the core environmental drawback of the organic and hybrid types was driven from their raw materials supply.
  • Seismic signature of mudflow tremor resulted from Brumadinho (Brazil) tailings dam failure

    Hussain, Yawar; Hamza, Omar; Huang, Xinghui; Silva, André Carlos; Condori, Cristobal; Uagoda, Rogério; Cavalcante, André Luís Brasil; University of Derby; University of Liège; University of Brasília; et al. (Fundação Gorceix, Brazil, 2020-06-22)
    Mudflow is often associated with seismic activities. The present study applied a seismic based detection of the surface waves generated by the mudflow of Brumadinho dam collapse using records of Brazilian Seismographic Network. The signal envelope and time-frequency spectrograms of the mudflow signals were used in the analysis. As a result, the mudflow signals were successfully detected from the data recorded at a nearby seismic station. The findings of this study provide a good basis for future research to develop a flood early warning system based on cost-effective, remote and contentious seismic monitoring approaches.
  • Blockchain application in supply chain chemical substance reporting - a Delphi study

    Takhar, Sukhraj Singh; Liyanage, Kapila; University of Derby (Inderscience, 2021-02-08)
    Blockchains utilise digital ledger technology to enable data to be traced in a more efficient manner than traditional paper-based systems. Smart contracts extend the capabilities of a blockchain by defining specific obligations. Chemical regulations impose the need on industry to record and report the use of hazardous chemicals within products. The process of collating supply chain chemical substance reporting information is a manually intensive and lengthy process in order to identify potential business risks and reporting of information to employees, consumers and chemical regulators. The research question answered in this paper relates to use of a blockchain with a smart contract to enable the automated collation of supply chain chemical substance information. This paper presents the findings from a Delphi study and a proposed 'supply chain chemical substance reporting' (SCCSR) blockchain. The SCCSR blockchain enables industry to implement greater efficiencies in collecting the required chemical substance information.
  • Compression and buckling after impact response of resin-infused thermoplastic and thermoset 3D woven composites

    Shah, S.Z.H; Megat-Yusoff, P.S.M; Karuppanan, S; Choudhry, Rizwan Saeed; Din, I.U; Othman, A.R; Sharp, K; Gerard, P; Universiti Teknologi PETRONAS, 32610, Bandar Seri Iskandar, Perak, Malaysia; University of Derby; et al. (Elsevier, 2020-12-29)
    Damage tolerance of a unique resin-infused thermoplastic (Elium) 3D fibre-reinforced composite (3D-FRC) is compared with the conventional resin-infused thermoset (Epoxy) 3D-FRC using compression after impact (CAI) tests and finite element simulations. Higher damage tolerance is demonstrated for the thermoplastic 3D-FRC as its CAI failure strength and CAI stiffness is nearly insensitive to the impact energy levels and subsequent damage, while in contrast, both these properties for the thermoset 3D-FRC get compromised significantly. The buckling performance shows a gradual, almost linear, reduction in critical buckling (44.5% reduction in 0–100 J) for the thermoplastic 3D-FRC. In comparison, the thermoset 3D-FRC shows a much steeper drop in critical buckling, which becomes more pronounced for the higher impact energy cases (84.5% reduction in 0–100 J). It is postulated that the local plastic deformation of the thermoplastic matrix at the impact site as well as better interfacial adhesion is responsible for its better damage tolerance.
  • The effect of soil incubation on bio self-healing of cementitious mortar

    Hamza, Omar; Esaker, Mohamed; Elliott, David; Souid, Adam; University of Derby (Elsevier, 2020-02-07)
    Successful implementation of bacteria-based self-healing in cracked cementitious materials requires the provision of a suitable incubation environment, which can activate the bacteria to produce e.g. calcium carbonate sealing the cracks. Research to date has focused on the self-healing process in humid air and water. However, almost all structures are built on or in the ground, thus, significant amounts of concrete are exposed to ground conditions. To investigate the effect of soil incubation on the self-healing process, laboratory experiments were conducted on mortar impregnated with Bacillus subtilis (encapsulated in calcium alginate). The mortar specimens were initially cracked and subdivided into three groups and each group was incubated for 28 days within different incubation environments, namely, partially-saturated soil, full-saturated soil, and water. Supported by Scanning Electron Microscope (SEM) and Energy Dispersive X-Ray Spectrometry (EDX), the results revealed that the bio self-healing can be activated within the cracks under the saturated regime of soil as far as the matric suction is smaller than the capillary pressure of the cracks. Moreover, the results indicated there was no evidence suggesting the influence of naturally existing bacteria in the soil on the self-healing process within the considered incubation period.

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