Post-Doctoral practical and scientific research would be carried out in the field of civil engineering, where waste of glass would be utilized in manufacture of ultra-high performance concrete. During the internship would be addressed two main problems: 1) how shard of glass, obtained from the municipal waste stream, properly utilize in useful construction products; 2) how to solve problems, related to insufficient and slow hydration processes and microstructure development of ultra-high performance concrete. In the research would be developing dispersion of waste glass technology, which could improve pozzolanic effect of glass powder and increase hydration intensity of Portland cement. This could significantly speed up setting and hardening processes, improve microstructure, mechanical and durability properties of ultra-high performance concrete. During the research would be concentrated not only in reducing shard of glass, obtained from municipal waste stream, but also would be developed new material with improved physical, mechanical and durability properties.
According to the European Statistics Department (Eurostat), Europeans annually produces about 38 million tonnes of glass products (such as: bottles, jars, porcelain, ceramics and etc.), and each year this amount significantly increases. Unfortunately, not all glass products can be successfully recycled. Most efficiently can be recycled glass waste (such as: glass bottles, jars, glass jars, glass scraps), which is disposed to specialized containers. Such type of waste annually is generated about 12 million tonnes, and averagely, in Europe, can be recycled up to 74 %. However, there are also generated significant proportion of glass waste (such as: porcelain, ceramic, mirrors, light bulbs, car windows, cut-glass) which is excessively contaminated and recycling process is too complex or too expensive for second reuse. Such types of waste glass, in Europe, averagely can be recycled up to 50 %. Unfortunately, between western and eastern European countries, the situation regarding collection and recycling of glass waste is significantly worse. Sweden manages to recycle over 95 %, Germany 81-85%, Italy 70-78 % of total glass production. However, Turkey, Greece, Cyprus, Malta are not always able to recycle even 50 % of waste glass, which is thrown into specialized containers. Although the recycling situation in Lithuania, during the last few years, has significantly improved. However still waste of glass is generated over 100 thousand tonnes per year, and the recycling rate is significantly below the European average (up to 40%). Such a gap arose due to the lack of people education, state policy and lack of incentives. Another problem arises, when unrecycled waste glass is dropped to landfills, where it can remain undisintegrated up to 900 years. Through this period, due to physical and chemical processes, waste glass can react with other waste in landfills to form harmful compounds, which pollutes the groundwater or forms harmful gases, which contribute to the negative greenhouse effect. If in the near future this problem will not be properly addressed, in several decades, it could become the problem not only in Lithuania, but in Europe as well. Unfortunately, the business is unable to properly focus and solve the problems associated with reducing of waste glass. Often, even if business able to offer appropriate solutions to the problem, the investment, which is dedicated in solving the problem, is limited to solve the specific local problem, which is not even always publicly available. Therefore, during this research, when solving similar problems, the results would be made public accessible to anyone, who is interested in solving similar problems.
The main idea of the project is to use non-recyclable glass shatters (which after initial cleaning is not suitable for second reuse) in manufacture process of ultra-high performance concrete. Glass is an amorphous material with a high amount of SiO2 (~60%), AlO3 (~3), CaO (~9%), Na2O (~10) and etc. Being amorphous and having a high content of SiO2, glass could be great pozzolanic material. Most pozzolanic materials has high content of amorphous SiO2, which in high alkaline pore solution can react with portlandite (lime), which is always produced during Portland cement hydration process. Similar pozzolanic materials such as fly ash, blast furnace slag; silica fume etc., for many years have been successfully utilized in various types of concrete. However, glass (in its structure) contains high level of CaO, which can lead to structure inhomogeneity, as well has Na2O, which can contribute to alkali silica reaction, as well can contain organic or other expansion impurities causing undesirable changes in concrete structure. Therefore, the utilization of glass waste in most type’s conventional concretes is not possible. However, there are made plenty of research, where after proper milling glass powder can be successfully utilized in concrete, manufacture process of artificial fillers (expanded glass) or glass wool. However, even finely grounded glass at room temperature acts as inert material and has no or very slight pozzolanic properties. Most researcher’s results are limited to simple experiments, where the main idea is to replace some micro filler or cement to waste glass powder. In this way, as inert micro filler, can be utilized considerable amount of waste glass, however such way is not very efficient. Utilization of glass powder would be more efficient, if on created samples, could be possible to apply thermal treatment. At higher temperature (>60 °C), the solubility of glass powder in high alkaline solution increases, and pozzolanicity properties becoming more intensive. Unfortunately, thermal treatment in many conventional concrete is not economically efficient. However, ultra-high performance concrete is completely different type of concrete, and thermal treatment for such type of concrete is even recommended. Ultra-high performance concrete is concrete which has compressive strength more than 100 MPa. Most specialists, who works with such type of concrete are able to achieve compressive strength between 150 MPa and 250 MPa, and this is about 3-5 times more comparing to conventional concrete. The durability properties of such type concrete could be more than several hundred times superior comparing to conventional concrete. Unfortunately, ultra-high performance concrete is not eco-friendly material. It has several times more of Portland cement (700-1200 kg/m3), which could be used to make the same structure several times if it was made from conventional concrete. It has very high amount of silica fume (up to 200 kg/m3), which is acts as micro filler and participates in pozzolanic reaction. During pozzolanic reaction, pore solution pH decreases. If construction has steel reinforcement, in longer time steel corrosion could occur. Ultra-high performance concrete, unlike conventional concrete, does not have a coarse aggregate (< 2 mm), thus such concrete requires a significantly higher amount of superplasticizer (up to 70 kg/m3), which significantly retards hydration processes. In order to achieve superior mechanical and durability properties, it is recommended not to make high water to cement ratio (0.25). In order to make effective mixing process, sophisticated mixer is needed. Additionally for more favorable hydration process, thermal treatment is needed. Despite the facts in hydrated ultra-high performance concrete remains more than 50% of unreacted clinker mineral, which later stays as expensive inert filler. Furthermore, during Portland cement hydration chemical processes, rate, kinetic and processes, formation of new hydration products goes not always according the same laws as in conventional concrete. How to make more intensive hydration process, how to make ultra-high performance concrete with lower binder quantity and simplifier technology equipment, without losing mechanical and durability properties is a challenge not only for European but as well for worldwide professionals.
The main aim of the research is to develop dispersion technology for glass powder, which could increase Portland cement hydration process and pozzolanic properties of glass powder without the use of thermal curing.
Main tasks of the research:
1) Investigate the effect of glass shatter, obtained from municipal waste, on Portland cement hydration process;
– Chemical analysis and suitability studies of glass shatter;
– Preparation of glass shatter, milling, neutralization research;
– Investigation of glass shatter application possibilities;
2) Develop dispersion and activating technology for glass powder and utilize it in production of ultra-high performance concrete;
– Mechanical, mechano-chemical, high frequency ultra-sonic dispersion of glass powder;
– Investigation of hydration kinetics, process parameters, hydration products, pozzolanic properties;
– Investigation of ultra-high performance concrete with glass powder waste hydration process, hardening processes, microstructure, mechanical properties, and resistance to frost damage;
Participating in this post-doctoral research would provide new competencies and practical skills.
This research project is funded by the European Social Fund according to the 2014–2020 Operational Programme for the European Union Funds’ Investments, under measure’s No. 09.3.3-LMT-K-712 activity “Promotion of postdoctoral fellowships studies”.
During the project, in addition to the final scientific report, it is planned to produce two scientific articles with Impact Factor in Clarivate analytics, Web of Science database. And to attend two international conferences, participate in foreign university or company for at least one month in a science internship. The results of the research could be applied in the future, solving relevant problems of a similar nature, preparing the topics of bachelor, master, and doctoral thesis.
Period of project implementation: 2020-09-01 - 2022-08-31
Project coordinator: Kaunas University of Technology