New doctoral dissertation

June 14, 2024

VILNIUS TECH Library invites you to follow the published new dissertations. The dissertation „Development of alkali-activated materials using biomass fly ash, phosphogypsum, and recycled concrete aggregates“ prepared by VILNIUS TECH, Chengjie Zhu. The dissertation was prepared in 2020–2024. Supervisor – Dr Ina Pundienė.

The dissertation will be defended at the public meeting of the Dissertation Defence Council of the Scientific Field of Materials Engineering in the SRA-I Hall of Vilnius Gediminas Technical University at 9 a. m. on 14 June 2024.

Cement production is responsible for 9–11% of total CO2 emissions worldwide, so it is essential to develop low-energy materials, avoiding using Port-land cement. Using waste materials in developing new cement-free binders, such as alkali-activated materials (AAMs), is a promising method for creating novel building materials. This study aims to develop a cement-free AAM binder based on high-carbon biomass fly ash (BFA), calcined phosphogypsum (CPG), and the low-alkalinity activator Na2CO3/Na2SiO3. The created AAM binder was used to develop a lightweight AAM concrete containing recycled concrete aggregate (RCA). The dissertation consists of an introduction, three chapters, general conclusions, recommendations, lists of references and the author’s publications on the dissertation topic, and a summary in Lithuanian. The first chapter reviews the state-of-the-art investigations on AAM, especially the application of BFA and CPG in AAM technologies. The literature states that BFA can be used as an aluminosilicate precursor with NaOH/Na2SiO3 in geopolymerisation technology. CPG participates as a calcium source, creating new minerals in the AAM and significantly enhancing its early strength. The second chapter describes the characteristics of the raw materials used, the mix design, and the sample preparation for each part of the research. It also describes the techniques and methods that were tested to fully evaluate the effect of each parameter on the rheological properties, physical-mechanical properties and reaction products of AAM samples based on BFA, CPG, and RCA. The third chapter presents the results and analysis of the research. It determines the effect of the Na2CO3/Na2SiO3 ratio and temperature on the properties and reaction products of BFA-based AAM. Also, it investigates the influence of the CPG content and Na2CO3/Na2SiO3 ratio on the properties and reaction products of BFA-CPG-based AAM. Furthermore, it reveals the effect of the RCA content on the physical-mechanical properties of AAM concretes based on BFA, CPG, and RCA. The lightweight AAM concrete can be applied to non-structural components with low strength requirements. Five scientific papers were published on the dissertation topic: three in scientific journals included in the Clarivate Analytics Web of Science database with an impact factor, and two in conference proceedings included in the Clarivate Analytics Web of Science and Scopus databases. Eight reports, including the dissertation results, were presented at national and international scientific conferences.

Doctoral dissertation readers can search via VILNIUS TECH Virtual Library.
 

Related news

€75,000 Funding Opportunity for Women-Led Deep Tech Startups
€75,000 Funding Opportunity for Women-Led Deep Tech Startups
Women-led deep tech startups are invited to apply for the European Union-funded "Women TechEU 2" program. This initiative aims to strengthen women's entrepreneurship in the technology sector, foster innovation, and help promising startups prepare for further growth and attract additional funding. Selected participants will receive a €75,000 grant and the opportunity to take part in a six-month tailored business development program. During this period, startups will be provided with mentoring, consulting, and training services designed to accelerate business growth and enhance competitiveness in the international market. The total budget for the "Women TechEU 2" program is €12 million. The plan is to fund 160 women-led startups from across Europe. Application Process The application process for the new call consists of two stages. First, applicants must submit an application for the Eligibility Strand to verify whether the startup meets the program's requirements. Applicants deemed eligible will then be invited to submit a Full Proposal. The eligibility assessment stage began on June 1, 2026. Applications are accepted on a rolling basis, with evaluations conducted weekly – the weekly submission deadline is every Tuesday by 18:00 (17:00 CEST). The first deadline is June 30, 2026, and the final deadline is July 13, 2027. Applicants will receive their eligibility assessment results no later than one week after the respective submission deadline. Who Can Apply? The program is designed for women-led, early-stage deep tech startups. To be eligible for funding, the following conditions must be met: At least one founder or co-founder of the startup is a woman; A woman holds a top-level executive position (CEO, CTO, or equivalent); Women hold at least 25% of the company's shares. Program Objectives The "Women TechEU 2" program aims to: Promote women's entrepreneurship in the deep tech sector; Help innovative startups scale up and attract additional European Union funding; Strengthen European innovation ecosystems; Support the development and commercialization of new technologies. Potential applicants are encouraged to review the application guidelines in advance and avoid waiting until the final deadline to submit their proposals. More information can be found here: https://womentecheurope.eu/active-calls/
More
New doctoral dissertation
New doctoral dissertation
VILNIUS TECH Library invites you to follow the published new dissertations. The dissertation „Performance investigation of a hybrid car engine fuelled with gasoline and gaseous mixtures“ („Benziną ir dujų mišinius naudojančio hibridinio automobilio variklio efektyvumo tyrimas“) prepared at VILNIUS TECH by Tadas Vipartas. The dissertation was prepared in 2021–2026. Scientific consultant – Prof. Dr Alfredas Rimkus. The dissertation was defended at the public meeting of the Dissertation Defence Council of the Scientific Field of Transport Engineering in the Aula Doctoralis Meeting Hall of Vilnius Gediminas Technical University at 9 a.m. on 12 June 2026. This dissertation investigates the use of alternative fuels (natural gas and hydrogen) to increase the efficiency of a spark-ignition engine. The impact of different fuels and engine control algorithms on the combustion process and on energy and ecological indicators was determined and evaluated by analysing the emerging technological constraints within the context of a power-split (series-parallel) hybrid powertrain. The dissertation presents a review of scientific literature, analysing the directions for internal combustion engine improvement, the properties of gaseous fuels and the challenges of their application, along with the operating principles of automotive hybrid powertrains. Bench tests were conducted to investigate the effect of late intake valve closing timing on an engine operating on natural gas, and the influence of hydrogen additives on the combustion process and knock control. The numerical analysis of the engine’s combustion process was performed using AVL BOOST™ software, while the energy and ecological indicators of the hybrid vehicle were evaluated through experimental research and numerical simulation in the AVL CRUISE™ software. The following main results were obtained in the dissertation: retarding the intake valve closing timing increased the brake thermal efficiency and NOx emissions while reducing carbon dioxide emissions when the engine operates on natural gas. It was determined that a hydrogen additive in the fuel improves the engine’s energy indicators, but increases nitrogen oxides emissions and the risk of engine knock. Engine knock is effectively managed by retarding the ignition advance angle. Numerical simulation results confirmed that these trends persist during the Worldwide Harmonized Light-duty Vehicles Test Cycle: the use of hydrogen reduces fuel consumption and carbon dioxide emissions, but increases nitrogen oxides emissions. The dissertation results revealed the potential of these technologies and strategies for their application. The obtained data can be applied in the development and selection of advanced engine control algorithms and in the formulation of technologically sound environmental standards. Nine scientific articles have been published on the topic of the dissertation: six in scientific journals indexed in the Clarivate Analytics Web of Science database with an impact factor, one in a scientific journal indexed in the Clarivate Analytics Web of Science database without an impact factor, one in conference proceedings indexed in the Clarivate Analytics Web of Science Conference Proceedings Citation Index, and one in peer-reviewed conference proceedings not indexed in international databases. The research results were presented at three scientific conferences in Lithuania and Poland. Doctoral dissertation readers can search via VILNIUS TECH Virtual Library.
More