Rihards Gailitis
@rtu.lv
Department of Structural Engineering / Faculty of Civil Engineering
Institute of Structural Engineering and Reconstruction / Riga Technical University
2018 – 2020 Latvian Council of Science Fund (LZP-2018/2-0249) „Long-term properties of innovative cement composites in various stress-strain conditions”; researcher
EDUCATION
2018 – present PhD in Construction Materials and Technology, Structural Engineering, Faculty of Civil Engineering, Riga Technical University, Riga, Latvia
2017 – 2018 Professional Master's degree in Civil Engineering, Riga Technical University, Riga, Latvia
2012 – 2017 Professional Bachelor's degree in Civil Engineering and Civil Engineer's qualification, Riga Technical University, Riga, Latvia
RESEARCH INTERESTS
Alkali activated cement composites, geopolymer composites, cement composites, creep and shrinkage strains, long - term deformations, Image analysis of polished and thin sections, polished section analysis using SEM
Scopus Publications
Scholar Citations
Scholar h-index
Scholar i10-index
Scopus Publications
Rihards Gailitis, Andina Sprince, Michał Łach, Pavels Gavrilovs, and Leonids Pakrastins
MDPI AG
This study investigates the cyclic load application impact on fly-ash-based geopolymer composites that are reinforced with a low amount of fibre reinforcement. For reinforcement purposes, polyvinyl alcohol and steel fibres are used. For testing purposes, four geopolymer composite mixes were made, three of which had fibre reinforcement. Simultaneously, specimens were tested for shrinkage, static-load-induced creep, and cyclic-load-induced creep. For static and cyclic creep testing, specimens were loaded with 20% of their strength. For cyclic creep testing, load application and release cycles were seven days long. When each cycle was introduced, the load was applied in steps. Necessary load application or unloading lasted for 5 min and consisted of four steps, each 25% of the necessary load. From the long-term static and cyclic creep tests, it was seen that only the plain specimens showed that static creep strains are within cyclic creep strains. For all the other specimens, the static load was higher than the cyclic-load-induced creep amplitude. Also, 1% polyvinyl alcohol fibre-reinforced specimens showed the most elastic characteristics under cyclic load, and 1% steel fibre-reinforced specimens appeared to be the most resistant to the cyclic load introduction.
L Radina, A Sprince, L Pakrastins, R Gailitis, and G Sakale
IOP Publishing
Abstract Undoubtedly, current environmental trends force scientists to search for a way to reduce carbon dioxide emissions in the production process of building materials. Geopolymers have been called as a potential alternative to traditional concrete for decades, allowing us to obtain more sustainable and durable materials with good thermal and reasonable mechanical properties and solve the problems related to waste materials utilization. Despite the great interest of scientists and the many advantages both in the production process of geopolymers and in terms of material properties, this idea looks unattainable in the near future, so it is worth investigating alternative ways of geopolymer applications. Thereby this review paper summarizes the recent progress in the field of foamed geopolymer concrete, focusing on the different preparation methods, material base, as well as information about the obstacles and challenges that hinder the transition of foamed geopolymers from research laboratories to real application in the civil engineering. This report also describes the density, compressive strength, thermal conductivity, pore size and distribution. A random sampling method and descriptive analysis were used in the preparation of a review, taking into account the year of publication, used materials, availability and the number of citations.
Rihards Gailitis, Andina Sprince, Tomass Kozlovksis, Leonids Pakrastins, and Viktorija Volkova
IOP Publishing
Abstract For the last 40 years, there has been increased interest in geopolymer composite development and its mechanical properties. In the last decades, there have been cases when geopolymer composites have been used for civil engineering purposes, such as buildings and infrastructure projects. The main benefit of geopolymer binder usage is that it has a smaller impact on the environment than the Portland cement binder. Emissions caused by geopolymer manufacturing are at least two times less than emissions caused by Portland cement manufacturing. As geopolymer polymerization requires elevated temperature, it also has a significant moisture evaporation effect that further increases shrinkage. It can lead to increased cracking and reduced service life of the structures. Due to this concern, for long-term strain reduction, such as plastic and drying shrinkage and creep, fibre reinforcement is added to constrain the development of stresses in the material. This research aims to determine how different fibre reinforcements would impact geopolymer composites creep and shrinkage strains. Specimens for long-term property testing purposes were prepared with 1% of steel fibres, 1% polypropylene fibres (PP), 0.5% steel and 0.5% polyvinyl alcohol fibres, 5% PP fibres, and without fibres (plain geopolymer). The lowest creep strains are 5% PP fibre specimens, followed by 1% PP fibre, plain, 0.5% steel fibre and 0.5% PVA fibre, and 1% steel fibre specimens. The lowest specific creep is to 5% PP fibre reinforced specimens closely followed by 1% PP fibre followed by 0.5% steel and 0.5% PVA fibre, plain and 1% steel fibre reinforced composites. Specimens with 0.5% steel and 0.5 PVA fibre showed the highest compressive strength, followed by 1% PP fibre specimens, plain specimens, 1% steel fibre, and 5% PP fibre reinforced specimens. Only specimens with 1% PP fibre and 0.5% steel, and a 0.5% PVA fibre inclusion showed improved mechanical properties. Geopolymer concrete mix with 1% PP fibre inclusion and 0.5% steel and 0.5% PVA fibre inclusion have a 4.7% and 11.3% higher compressive strength. All the other fibre inclusion into mixes showed significant decreases in mechanical properties.
Rihards Gailitis, Leonids Pakrastins, Andina Sprince, Liga Radina, Gita Sakale, and Krzysztof Miernik
MDPI AG
This study investigated the effect of a low amount of polyvinyl alcohol (PVA) and steel fiber reinforcement on fly ash-based geopolymer composite long-term deflection and its microstructure. For testing purposes, specimens with different amounts and types of fiber reinforcement as well as plain (reference) were prepared. The long-term deflection test was performed by loading specimens with 40% of the ultimate flexural strength. A microstructure analysis was performed using polished section specimens, and images were acquired at 25-times magnification on a scanning electron microscope. The results of the flexural strength test show that all geopolymer composites with fiber reinforcement have lower flexural strength than plain geopolymer composites. The long-term deflection tests show that the highest deflections exhibit 1% PVA fiber-reinforced specimens. The lowest amount of deflection is for 1% steel fiber-reinforced specimens. Specific creep shows similar results to plain, and 1% steel fiber-reinforced specimens, while 1% PVA and 0.5% PVA/0.5% steel fiber-reinforced specimen exhibits the same properties. The quantitative microanalysis of the polished section further confirms the deflection results. Specimens with 1% PVA fiber reinforcement have significantly higher porosity than all other specimens. They are followed by plain specimens and 1% steel fiber, and 0.5% PVA/0.5 steel fiber-reinforced specimens have almost the same porosity level.
Rihards Gailitis, Beata Figiela, Kalvis Abelkalns, Andina Sprince, Genadijs Sahmenko, Marta Choinska, and Martin Duarte Guigou
MDPI AG
One way to prevent cement from ending up in landfills after its shelf life is to regain its activity and reuse it as a binder. As has been discovered, milling by planetary ball mill is not effective. Grinding by collision is considered a more efficient way to refine brittle material and, in the case of cement, to regain its activity. There has been considerable research regarding the partial replacement of cement using disintegrated cement in mortar or concrete in the past few decades. This article determines and compares the creep and shrinkage properties of cement mortar specimens made from old disintegrated, old non-disintegrated, and new non-disintegrated Portland cement. The tests show that the creep strains for old disintegrated and old non-disintegrated cement mortars are close, within a 2% margin of each other. However, the creep strains for new non-disintegrated cement mortar are 30% lower. Shrinkage for old disintegrated and non-disintegrated cement mortar is 20% lower than for new non-disintegrated cement mortar. The research shows that disintegration is a viable procedure to make old cement suitable for structural application from a long-term property standpoint. Additionally, it increases cement mortar compressive strength by 49% if the cement is disintegrated together with sand.
Andina Sprince, Tomass Kozlovskis, Rihards Gailitis, Juozas Valivonis, Kinga Korniejenko, and Arnaud Castel
MDPI AG
Creep and shrinkage of Cement and Concrete Composites (CCC) are significant properties that need to be considered to use these materials in practice. Many previous scientific studies revealed CCC creep characteristics under sustained compression and shrinkage, using traditional test methods from design standards. Because of the complexity of experimental procedures, CCC creep in tension has not been studied as close. Furthermore, there is no unified standard that proposes applicable testing methods or specific testing apparatus. This study examines the suitability of 2D—Digital Image Correlation (DIC) to observe the creep deformations of specimens under tension. Ordinary Portland cement (OPC) mortar with 1% polyvinyl alcohol (PVA) fibres has been investigated in the research. Compact tension (CT) specimens 150 × 150 × 12 mm (with a notch) were used. Creep deformations under sustained uniaxial tension (applied loading corresponding to 60% of the ultimate strength) were measured. DIC images were captured using an entry/mid-level DSLR camera. Results show that DIC is suitable for studying uniaxial tensile creep of cement and concrete composites. Deformation of specimens in tension was similar to that measured using the conventional method (using surface-attached gauges).
Barbara Kozub, Patrycja Bazan, Rihards Gailitis, Kinga Korniejenko, and Dariusz Mierzwiński
MDPI AG
This study examines foamed geopolymer composites based on fly ash from the Skawina coal-fired power plant in Poland. The paper presents the effect of adding 3% and 5% by weight of glass wool waste on selected properties of foamed geopolymers. The scope of the tests carried out included density measurements, compressive and bending strength tests, measurements of the heat conduction coefficient, and the results of measurements of changes in thermal radiation in samples subjected to a temperature of 800 °C. The obtained results indicate that glass wool waste can be successfully used to lower the density and heat conduction coefficient of foamed geopolymer composites with a fly ash matrix. In addition, the results of changes in thermal radiation in the samples subjected to the temperature of 800 °C showed a positive effect of the addition of glass wool waste. Moreover, the introduction of the addition of glass wool waste made it possible to increase the compressive strength of the examined foamed geopolymers. For the material modified with 3% by weight of mineral wool, the increase in compressive strength was about 10%, and the increase in fibers in the amount of 5% by weight resulted in an increase of 20% concerning the base material. The obtained results seem promising for future applications. Such materials can be used in technical constructions as thermal insulation materials.
N. Vatin, A. Sprince, R. Gailitis, L. Pakrastins and T. Kozlovskis
Cement composite long-term property assessment usually is limited to the compression strain state due to the difficulty of performing long-term tests in tension and 3-point bending. This paper shows the difference in long-term properties in compression, tension, and 3-point bending for plain ordinary Portland cement mortar (OPC). The obtained results were compared to reinforced specimen results to determine whether the PVA refibres improve the long-term properties of OPC mortar in various stress-strain conditions. Cylinders, compact tension specimens (CT), and beams – plates were prepared to evaluate material properties and the role of fibre reinforcement in these different stress states. Additionally, to conventional surface-attached strain gauges, 2D-DIC was employed to observe the creep strain of specimens in tension. This paper aim to determine long-term property differences in compression, tension and 3-point bending and, also, to see if low amount PVA fibre incorporation improve long-term properties in previously stated stress-strain states. It was determined that the usage of 1 % of PVA fibres increases creep strains in compression on average by 15 % and reduced by 7 % in tension. It reduces shrinkage strain by 18 % in compression and 8 % in tension. The long-term deflection for the PVA fibre-reinforced specimens are, on average by 55 % higher than for plain OPC mortar specimens in 3-point bending.
Rihards Gailītis, Andina Sprince, Leonids Pakrastins, Patrycja Bazan, and Kinga Koniejenko
Rezekne Academy of Technologies
For more than 40 years, low calcium alkali-activated cement composite, or in other words, geopolymer, has been around. In recent years there has been increased interest in this material and its properties. It is mainly due to the claim that geopolymer is the cement of the future. This claim is based on environmental factors. For instance, the CO2 emissions for geopolymer binder can be up to 6 less than for Portland cement binder. Most of the researches regarding geopolymer composite properties examine only mechanical and long-term properties in compression. There has been a lack of long-term tests in tension due to difficulties in performing them. As the tensile stresses are an essential part of structure assessment, it is necessary to evaluate new material properties as thoroughly as possible. Due to the nature of geopolymer specimen hardening (polymerisation), there is a difference in modulus of elasticity development and shrinkage caused by binding that could have factors that regular Portland cement specimens do not.This article aims to evaluate the surface composition of plain and 1% PVA reinforced geopolymer compact tension specimens that have been subjected to creep and shrinkage tests. Specimen cross-section images were acquired using the scanning electron microscope (SEM). Using the quantitative image analysis method, amounts of cross-section composition elements are determined. Furthermore, the amount of cracks is determined and compared between plain and PVA fiber-reinforced specimens.It has been determined that even though 1% of PVA fibre-reinforced specimens have lower tensile strength, their creep and shrinkage strains are lower, and the number of microcracks at the notch base of the specimen. Still, it has to be acknowledged that the amount of air voids in all analysed specimens is relatively high.
Rihards Gailitis, Andina Sprince, Leonids Pakrastins, Kinga Korniejenko, and Tomass Kozlovskis
Springer International Publishing
Rihards Gailitis, Kinga Korniejenko, Andina Sprince, and Leonids Pakrastins
AIP Publishing
R. Gailitis, J. Sliseris, K. Korniejenko, J. Mikuła, M. Łach, L. Pakrastins, and A. Sprince
Springer Science and Business Media LLC
Andina Sprince, Leonids Pakrastins, and Rihards Gailitis
Springer International Publishing
R Gailitis, K Korniejenko, M Łach, J Sliseris, J Morán, E Rodriguez, and J Mikuła
IOP Publishing
R Gailitis, A Sprince, L Pakrastins, G Sahmenko, and T Kozlovskis
IOP Publishing
Rihards Gailitis, Andina Sprince, Leonids Pakrastins, Genadijs Shakhmenko, Tomass Kozlovskis, and Liga Radina
Vilnius Gediminas Technical University
Foamed concrete has been used as a building material since the early 1920s. In the beginning, it was used as an insulation material with very low density. Since then there have been attempts to improve the structural properties in order to increase materials load-bearing capacity. In the present-day foamed concrete is being used in soil reinforcement, manufacturing of building blocks and other sorts of construction materials (Mugahed Amran, Farzadnia, & Abang Ali, 2015). The aim of this article is to determine the behaviour and long-term properties of foamed concrete. Cylindrical specimens (Ø46×190 mm) were used for creep and shrinkage testing. The creep properties of the specimens were determined by loading them with 20% and 60% of the ultimate compressive stress value (Sprince, 2015). The compressive strength, creep, shrinkage and specific creep of the material were examined. It was determined that during 90 days of creep testing the non-linear creep deformations (specimens loaded with 60% of the ultimate stress) are 4 times larger than linear creep deformations (specimens loaded with 20% of the ultimate stress). Also, changes in the modulus of elasticity of foamed concrete were researched over time. Foamed concrete modulus of elasticity reached 12.21 GPa on the 28th day, 12.49 GPa on the 62nd and 14.23 GPa on the 144th day since the specimens were made.
Rihards Gailītis, Andina Sprince, Leonids Pakrastins, Genadijs Shakhmenko, and Tomass Kozlovskis
Rezekne Academy of Technologies
Foamed concrete has been used as a building material since the early 1920s. In the beginning, it was used as an insulation material with very low density. Since then there have been attempts to make this material more load-bearing and structural. In the present-day foamed concrete is being used in soil reinforcement, manufacturing of building blocks and other sorts of construction materials. [1] The aim of this article is to determine long-term properties and strength of foamed concrete specimens as well as compare the results between two differently sized foamed concrete specimens. The size of creep and shrinkage specimens were Ø46x190 mm and Ø75x180 mm. The creep properties of the specimens were determined by loading them with 20% of the ultimate stress value. [2] The compressive strength, creep and specific creep of specimens were determined as well as specimen size factor to creep deformations.
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2018 – 2020 Latvian Council of Science Fund (LZP-2018/2-0249) „Long-term properties of innovative cement composites in various stress-strain conditions”; senior researcher, chief executor