Diana Bajare - Academia.edu (original) (raw)

Papers by Diana Bajare

Journal of Composites Science

Additive manufacturing by 3D printing has emerged as a promising construction method offering num... more Additive manufacturing by 3D printing has emerged as a promising construction method offering numerous advantages, including reduced material usage and construction waste, faster build times, and optimized architectural forms. One area where 3D printing’s potential remains largely unexplored is in combination with lightweight materials, especially lightweight gypsum. This research paper explores the potential of combining 3D printing technology with lightweight gypsum-based composites to extend the relatively limited gypsum application possibilities in the construction industry. The study investigates the use of expanded polystyrene (EPS) beads as an aggregate in gypsum composites, focusing on the printability of the mixture and hardened state mechanical properties in various print directions. Mechanical tests reveal that 3D printing can reduce the compressive strength of the EPS–gypsum composite by between 3% and 32%, and the flexural strength by up to 22%, depending on testing dir...

Construction technologies and architecture, Jan 6, 2022

Hemp concrete is a well-known bio-based building material, but due to its relatively low compress... more Hemp concrete is a well-known bio-based building material, but due to its relatively low compressive strength is mainly used as an insulation material with a load-bearing wooden frame. There are possibilities to expand hemp concrete application in construction by substituting traditional lime with magnesium cement. Magnesium oxychloride cement is a material already known for some time and nowadays used in building board production. Strength, lightweight, ease of use are advantages that highlight relatively new magnesium oxychloride type boards compared to traditional sheeting materials such as plywood, gypsum plasterboard and fibre-cement board. Therefore, similar parameters are thought to be reached by producing magnesium oxychloride hemp board. In this work, magnesium cement water resistance was studied and possibilities to improve it was examined by adding fly ash and nanosilica. Among the nanomaterials used in building materials, nanosilica has gained significant interest by performing a beneficial effect in improving the mechanical properties of concretes. In addition, due to its ultrafine size and high chemical reactivity, the performance of nanosilica is much better with a lower amount of admixture required. Results show that applied nanosilica slightly reduced the compressive strength of magnesium cement in a dry state, but at the same time significantly increased its water resistance. Hemp magnesium oxychloride cement board prototype samples were produced and demonstrate promising results for further manufacturing of hemp composite boards.

Civil Engineering, 2013

Modern high and ultra-high performance concretes (HPC) and (UHPC) are demonstrating very good mec... more Modern high and ultra-high performance concretes (HPC) and (UHPC) are demonstrating very good mechanical properties and durability, however these properties can be compromised by early age cracking caused by autogenous shrinkage

: Advanced properties of ultrahigh performance concrete (UHPC), such as high compressive strength... more : Advanced properties of ultrahigh performance concrete (UHPC), such as high compressive strength, high modulus of elasticity, low permeability and excellent durability, can be achieved taking into account some basic principles and processing methods. Following tasks should be solved by reaching these properties: minimising defect occurrence in concrete matrix and obtaining maximum density by optimizing particle size distribution; minimising water/cement ratio by the use of water reducing admixtures and using pozzolanic materials. Improvement of microstructural packing and enhancing formation of secondary calcium silicate hydrate can be achieved by fill voids between larger particles. Since pozzolanic activity depends basically on content of amorphous silica dioxide, particle specific surface area and particle size distribution, different investigation and tests have been performed. Used silica dioxide particles have wide range of particle grading ranging from 20 nm to 100 m. Conventional non-modified concrete can be defined as a porous media with high capillary porosity, especially in the aggregate–hydrated cement paste transition zone. Two different ways to reach denser matrix have considered and implemented in the investigations. The first one is the applying of pressure to a fresh concrete with aim to reduce porosity and therefore improving concrete mechanical properties and durability. By applying pressure in initial phase of concrete hardening, increase of compressive strength in 1.5 times and decrease porosity in 4.5 times with effect of reducing capillary water have been reached. The second way is use special nano-sized particles synthesised by Sol-gel method, that characterised by extremely high specific surface area and very high pozzolanic reactivity. The properties of the fresh and hardened cement compositions have been tested in the framework of the research

The main challenge of this work is using dolomite filler in concrete production. A method for ins... more The main challenge of this work is using dolomite filler in concrete production. A method for inspecting a fine dolomite group has been developed for evaluation of the possibility of using this dolomite as filler in concrete. The concrete composition has been created, where the traditional sand are replaced totally or partly by the dolomite sand used as a filler. The practical recommendations have been elaborated for using the dolomite processing byproducts for producing concrete and reinforced concret

Technology of high efficiency concrete provides for use of ultra-fine micro and nano-sized admixt... more Technology of high efficiency concrete provides for use of ultra-fine micro and nano-sized admixtures which considerably improve properties of fresh and hardened concrete. In the frame of this study the concept of high efficiency concrete provides for two basic directions: 1. Creating ecologically effective concrete mixes with low cement content (<330 kg/m3) for conventional application (mass concrete etc). 2. Creating concrete having high compressive strength (>100MPa) and high performance characteristics allowing producing thin light-weight bearing elements. (HPC –High Performance Concrete, UHPC –Ultra High Performance Concrete). The basic principles for obtaining high performance properties are low water/cement ratio and dense micro structural packing achieved by using special pozzolanic admixtures which chemically react with calcium hydroxide and form calcium silicate-hydrate. Silica fume is the most popular commercially available pozzolanic micro filler based on silicium dioxide. Pyrogenic silica having nano-sized particles (<100 nm), has been elaborated recently

The importance of the environmental issues on the agenda of our society has been increasing const... more The importance of the environmental issues on the agenda of our society has been increasing constantly during last few decades in the society. Growing demand for Earth resources has led to serious environmental pollution. The most important resource, with countinuously growing demand, is the energy

... Pētījumu gaitā tika izgatavoti paraugi un veiktas pārbaudes, lai salīdzinātu tradicionāla bet... more ... Pētījumu gaitā tika izgatavoti paraugi un veiktas pārbaudes, lai salīdzinātu tradicionāla betona un tāda betona īpašības, kur kompozīcijas izveidei kvarca smiltis daļēji vai pilnībā aizvietotas ar dolomīta izstrādes atkritumiem. ...

Energies

The evolution of bio-based composites in the building industry is strongly linked with the growin... more The evolution of bio-based composites in the building industry is strongly linked with the growing demand for sustainable development, which is relevant nowadays. Hemp shives are a large group of organic residues that are obtained in the process of oil extraction as well as straw processing. These residues could be utilized along with a binder as constituents in the manufacture of bio-based building composites. This study is focused on the impact of density and relative humidity on the effective thermal conductivity of hemp shive-based bio-composites with a magnesium binder. For this reason, a series of samples with variable densities was manufactured and subjected to conditioning in a climatic chamber at a constant temperature and different relative humidity settings. As soon as samples were stabilized, the guarded hot plate method was applied to determine their thermal conductivities. Before each measurement, great care was taken during sample preparation to ensure minimum moistur...

Energies

The share of bio-based materials in modern construction needs to grow more rapidly due to increas... more The share of bio-based materials in modern construction needs to grow more rapidly due to increasingly stringent environmental requirements as a direct result of the climate emergency. This research aims to expand the use of hemp concrete in construction by replacing traditional lime binder with magnesium oxychloride cement, which provides a faster setting and higher strength, opening the door for industrial production. However, the negative feature of this binder is its low water resistance. In this work, the water resistance of magnesium cement was studied, and the possibilities of improving it by adding fly ash, various acids and nano-silica were considered. Nano-silica and citric acid showed the most significant impact, increasing the binder water resistance up to four times, reaching softening coefficient of 0.80 while reducing the compressive strength of the magnesium cement in a dry state by only 2–10%. On the downside, citric and phosphoric acid significantly extended the se...

Minerals

The search for efficient waste source precursors for geopolymer production is active in scientifi... more The search for efficient waste source precursors for geopolymer production is active in scientific society. The feasibility of using calcined kaolin clay and fly ash as suitable precursors for the production of geopolymers is widely described and acknowledged. The availability and energy input required to produce such precursors hinders their competing with traditional binders, however. Therefore, new by-product source precursors are sought in different industries. In this research, three industrial origin secondary raw materials are examined as precursors for the production of porous geopolymers. Calcined illite or kaolin clay in combination with salt cake from the aluminium scrap recycling industry after alkali activation gives lightweight material from 540–675 kg/m3. A comparison of the two precursors was made, and the physical and mechanical properties were determined. Freeze-thaw resistance and sulfate attack were used to characterize durability. Results indicate the role of wa...

Energies

Thermal insulation bio-composites made of plant origin by-products as bio-aggregates are one of t... more Thermal insulation bio-composites made of plant origin by-products as bio-aggregates are one of the ways to decrease the impact of the building and construction sector on CO2 emissions. In this study, three bio-aggregates were analysed for their potential use in the production of bio-composites with potato starch binder. Technologically important properties, such as particle size, shape and compacted bulk density, as well as properties of the resulting bio-composites were identified. The main characteristics of the aggregates are relatively similar: density of 80–100 kg/m3, thermal conductivity of 0.042–0.045 W/m∙K, specific heat capacity of 1240–1330 J/g∙K, kinetic water absorption from 456–584%. This leads to similar basic properties of the produced bio-composites: density around 200 kg/m3, thermal conductivity 0.053–0.062 W/m∙K, specific heat capacity 1250–1450 J/kg∙K, with a difference in compressive strength ranging from 0.2 to 0.8 MPa. Created starch binder and agricultural by...

Recycling

The waste amount coming from construction and demolition (CDW) has significant volume and potenti... more The waste amount coming from construction and demolition (CDW) has significant volume and potential to provide the backbone of a secondary material bank. Up to now, little attention is paid to waste gypsum recycling from CDW while a shift in global attitude toward waste management brings motivation to use CDW gypsum as secondary raw material. The present research investigates the properties of gypsum binder obtained from secondary raw materials originating from CDW. Three types of drywall boards and cast monolithic gypsum from interior walls, treated in the laboratory, and a gypsum binder was obtained. Comparison has been studied and the most effective solutions regarding CDW treatment are represented. Separation, crushing, and milling were done. DTA/TG, XRD, SEM, and particle size distribution were characterized by CDW gypsum. The heat treatment temperature was selected at 130 °C for 4 or 24 h and 180 °C for 4 h. Consistency, set time, and mechanical properties were characterized. ...

The EU directive 2010/31/EU – sets goals to reduce CO2 emission levels by 20% until year 2020. As... more The EU directive 2010/31/EU – sets goals to reduce CO2 emission levels by 20% until year 2020. As primary energy for households and construction industry both are among the largest manufacturers of CO2, a building material that can positively impact both these industries is topical. A lime-hemp concrete (LHC) is a material with negative CO2 balance, but to achieve the goals set in EU directive a more industrialized product, that can also be used in insulation of existing buildings is needed, so methods of LHC slab and block manufacture are tested in this paper. Eight different types of hemp shives are taken and twelve LHC mixes are prepared to assess the importance of hemp granulometrical distribution. To measure the effect of different preparation techniques mixes in two different mixers – gravity and forced action – were prepared to test the superiority of the latter as it is widely used in LHC production. Also different drying methods – natural, forced with temperature at various...

Construction Technologies and Architecture, 2022

Hemp concrete is a well-known bio-based building material, but due to its relatively low compress... more Hemp concrete is a well-known bio-based building material, but due to its relatively low compressive strength is mainly used as an insulation material with a load-bearing wooden frame. There are possibilities to expand hemp concrete application in construction by substituting traditional lime with magnesium cement. Magnesium oxychloride cement is a material already known for some time and nowadays used in building board production. Strength, lightweight, ease of use are advantages that highlight relatively new magnesium oxychloride type boards compared to traditional sheeting materials such as plywood, gypsum plasterboard and fibre-cement board. Therefore, similar parameters are thought to be reached by producing magnesium oxychloride hemp board. In this work, magnesium cement water resistance was studied and possibilities to improve it was examined by adding fly ash and nanosilica. Among the nanomaterials used in building materials, nanosilica has gained significant interest by per...

The main purpose of concrete mixing is homogenous distribution of different types of particles wi... more The main purpose of concrete mixing is homogenous distribution of different types of particles within the system. Failure in particle blending can result in poor concrete workability in the fresh state, low performance in hardened state and inefficient use of materials

Journal of Composites Science

Additive manufacturing by 3D printing has emerged as a promising construction method offering num... more Additive manufacturing by 3D printing has emerged as a promising construction method offering numerous advantages, including reduced material usage and construction waste, faster build times, and optimized architectural forms. One area where 3D printing’s potential remains largely unexplored is in combination with lightweight materials, especially lightweight gypsum. This research paper explores the potential of combining 3D printing technology with lightweight gypsum-based composites to extend the relatively limited gypsum application possibilities in the construction industry. The study investigates the use of expanded polystyrene (EPS) beads as an aggregate in gypsum composites, focusing on the printability of the mixture and hardened state mechanical properties in various print directions. Mechanical tests reveal that 3D printing can reduce the compressive strength of the EPS–gypsum composite by between 3% and 32%, and the flexural strength by up to 22%, depending on testing dir...

Construction technologies and architecture, Jan 6, 2022

Hemp concrete is a well-known bio-based building material, but due to its relatively low compress... more Hemp concrete is a well-known bio-based building material, but due to its relatively low compressive strength is mainly used as an insulation material with a load-bearing wooden frame. There are possibilities to expand hemp concrete application in construction by substituting traditional lime with magnesium cement. Magnesium oxychloride cement is a material already known for some time and nowadays used in building board production. Strength, lightweight, ease of use are advantages that highlight relatively new magnesium oxychloride type boards compared to traditional sheeting materials such as plywood, gypsum plasterboard and fibre-cement board. Therefore, similar parameters are thought to be reached by producing magnesium oxychloride hemp board. In this work, magnesium cement water resistance was studied and possibilities to improve it was examined by adding fly ash and nanosilica. Among the nanomaterials used in building materials, nanosilica has gained significant interest by performing a beneficial effect in improving the mechanical properties of concretes. In addition, due to its ultrafine size and high chemical reactivity, the performance of nanosilica is much better with a lower amount of admixture required. Results show that applied nanosilica slightly reduced the compressive strength of magnesium cement in a dry state, but at the same time significantly increased its water resistance. Hemp magnesium oxychloride cement board prototype samples were produced and demonstrate promising results for further manufacturing of hemp composite boards.

Civil Engineering, 2013

Modern high and ultra-high performance concretes (HPC) and (UHPC) are demonstrating very good mec... more Modern high and ultra-high performance concretes (HPC) and (UHPC) are demonstrating very good mechanical properties and durability, however these properties can be compromised by early age cracking caused by autogenous shrinkage

: Advanced properties of ultrahigh performance concrete (UHPC), such as high compressive strength... more : Advanced properties of ultrahigh performance concrete (UHPC), such as high compressive strength, high modulus of elasticity, low permeability and excellent durability, can be achieved taking into account some basic principles and processing methods. Following tasks should be solved by reaching these properties: minimising defect occurrence in concrete matrix and obtaining maximum density by optimizing particle size distribution; minimising water/cement ratio by the use of water reducing admixtures and using pozzolanic materials. Improvement of microstructural packing and enhancing formation of secondary calcium silicate hydrate can be achieved by fill voids between larger particles. Since pozzolanic activity depends basically on content of amorphous silica dioxide, particle specific surface area and particle size distribution, different investigation and tests have been performed. Used silica dioxide particles have wide range of particle grading ranging from 20 nm to 100 m. Conventional non-modified concrete can be defined as a porous media with high capillary porosity, especially in the aggregate–hydrated cement paste transition zone. Two different ways to reach denser matrix have considered and implemented in the investigations. The first one is the applying of pressure to a fresh concrete with aim to reduce porosity and therefore improving concrete mechanical properties and durability. By applying pressure in initial phase of concrete hardening, increase of compressive strength in 1.5 times and decrease porosity in 4.5 times with effect of reducing capillary water have been reached. The second way is use special nano-sized particles synthesised by Sol-gel method, that characterised by extremely high specific surface area and very high pozzolanic reactivity. The properties of the fresh and hardened cement compositions have been tested in the framework of the research

The main challenge of this work is using dolomite filler in concrete production. A method for ins... more The main challenge of this work is using dolomite filler in concrete production. A method for inspecting a fine dolomite group has been developed for evaluation of the possibility of using this dolomite as filler in concrete. The concrete composition has been created, where the traditional sand are replaced totally or partly by the dolomite sand used as a filler. The practical recommendations have been elaborated for using the dolomite processing byproducts for producing concrete and reinforced concret

Technology of high efficiency concrete provides for use of ultra-fine micro and nano-sized admixt... more Technology of high efficiency concrete provides for use of ultra-fine micro and nano-sized admixtures which considerably improve properties of fresh and hardened concrete. In the frame of this study the concept of high efficiency concrete provides for two basic directions: 1. Creating ecologically effective concrete mixes with low cement content (<330 kg/m3) for conventional application (mass concrete etc). 2. Creating concrete having high compressive strength (>100MPa) and high performance characteristics allowing producing thin light-weight bearing elements. (HPC –High Performance Concrete, UHPC –Ultra High Performance Concrete). The basic principles for obtaining high performance properties are low water/cement ratio and dense micro structural packing achieved by using special pozzolanic admixtures which chemically react with calcium hydroxide and form calcium silicate-hydrate. Silica fume is the most popular commercially available pozzolanic micro filler based on silicium dioxide. Pyrogenic silica having nano-sized particles (<100 nm), has been elaborated recently

The importance of the environmental issues on the agenda of our society has been increasing const... more The importance of the environmental issues on the agenda of our society has been increasing constantly during last few decades in the society. Growing demand for Earth resources has led to serious environmental pollution. The most important resource, with countinuously growing demand, is the energy

... Pētījumu gaitā tika izgatavoti paraugi un veiktas pārbaudes, lai salīdzinātu tradicionāla bet... more ... Pētījumu gaitā tika izgatavoti paraugi un veiktas pārbaudes, lai salīdzinātu tradicionāla betona un tāda betona īpašības, kur kompozīcijas izveidei kvarca smiltis daļēji vai pilnībā aizvietotas ar dolomīta izstrādes atkritumiem. ...

Energies

The evolution of bio-based composites in the building industry is strongly linked with the growin... more The evolution of bio-based composites in the building industry is strongly linked with the growing demand for sustainable development, which is relevant nowadays. Hemp shives are a large group of organic residues that are obtained in the process of oil extraction as well as straw processing. These residues could be utilized along with a binder as constituents in the manufacture of bio-based building composites. This study is focused on the impact of density and relative humidity on the effective thermal conductivity of hemp shive-based bio-composites with a magnesium binder. For this reason, a series of samples with variable densities was manufactured and subjected to conditioning in a climatic chamber at a constant temperature and different relative humidity settings. As soon as samples were stabilized, the guarded hot plate method was applied to determine their thermal conductivities. Before each measurement, great care was taken during sample preparation to ensure minimum moistur...

Energies

The share of bio-based materials in modern construction needs to grow more rapidly due to increas... more The share of bio-based materials in modern construction needs to grow more rapidly due to increasingly stringent environmental requirements as a direct result of the climate emergency. This research aims to expand the use of hemp concrete in construction by replacing traditional lime binder with magnesium oxychloride cement, which provides a faster setting and higher strength, opening the door for industrial production. However, the negative feature of this binder is its low water resistance. In this work, the water resistance of magnesium cement was studied, and the possibilities of improving it by adding fly ash, various acids and nano-silica were considered. Nano-silica and citric acid showed the most significant impact, increasing the binder water resistance up to four times, reaching softening coefficient of 0.80 while reducing the compressive strength of the magnesium cement in a dry state by only 2–10%. On the downside, citric and phosphoric acid significantly extended the se...

Minerals

The search for efficient waste source precursors for geopolymer production is active in scientifi... more The search for efficient waste source precursors for geopolymer production is active in scientific society. The feasibility of using calcined kaolin clay and fly ash as suitable precursors for the production of geopolymers is widely described and acknowledged. The availability and energy input required to produce such precursors hinders their competing with traditional binders, however. Therefore, new by-product source precursors are sought in different industries. In this research, three industrial origin secondary raw materials are examined as precursors for the production of porous geopolymers. Calcined illite or kaolin clay in combination with salt cake from the aluminium scrap recycling industry after alkali activation gives lightweight material from 540–675 kg/m3. A comparison of the two precursors was made, and the physical and mechanical properties were determined. Freeze-thaw resistance and sulfate attack were used to characterize durability. Results indicate the role of wa...

Energies

Thermal insulation bio-composites made of plant origin by-products as bio-aggregates are one of t... more Thermal insulation bio-composites made of plant origin by-products as bio-aggregates are one of the ways to decrease the impact of the building and construction sector on CO2 emissions. In this study, three bio-aggregates were analysed for their potential use in the production of bio-composites with potato starch binder. Technologically important properties, such as particle size, shape and compacted bulk density, as well as properties of the resulting bio-composites were identified. The main characteristics of the aggregates are relatively similar: density of 80–100 kg/m3, thermal conductivity of 0.042–0.045 W/m∙K, specific heat capacity of 1240–1330 J/g∙K, kinetic water absorption from 456–584%. This leads to similar basic properties of the produced bio-composites: density around 200 kg/m3, thermal conductivity 0.053–0.062 W/m∙K, specific heat capacity 1250–1450 J/kg∙K, with a difference in compressive strength ranging from 0.2 to 0.8 MPa. Created starch binder and agricultural by...

Recycling

The waste amount coming from construction and demolition (CDW) has significant volume and potenti... more The waste amount coming from construction and demolition (CDW) has significant volume and potential to provide the backbone of a secondary material bank. Up to now, little attention is paid to waste gypsum recycling from CDW while a shift in global attitude toward waste management brings motivation to use CDW gypsum as secondary raw material. The present research investigates the properties of gypsum binder obtained from secondary raw materials originating from CDW. Three types of drywall boards and cast monolithic gypsum from interior walls, treated in the laboratory, and a gypsum binder was obtained. Comparison has been studied and the most effective solutions regarding CDW treatment are represented. Separation, crushing, and milling were done. DTA/TG, XRD, SEM, and particle size distribution were characterized by CDW gypsum. The heat treatment temperature was selected at 130 °C for 4 or 24 h and 180 °C for 4 h. Consistency, set time, and mechanical properties were characterized. ...

The EU directive 2010/31/EU – sets goals to reduce CO2 emission levels by 20% until year 2020. As... more The EU directive 2010/31/EU – sets goals to reduce CO2 emission levels by 20% until year 2020. As primary energy for households and construction industry both are among the largest manufacturers of CO2, a building material that can positively impact both these industries is topical. A lime-hemp concrete (LHC) is a material with negative CO2 balance, but to achieve the goals set in EU directive a more industrialized product, that can also be used in insulation of existing buildings is needed, so methods of LHC slab and block manufacture are tested in this paper. Eight different types of hemp shives are taken and twelve LHC mixes are prepared to assess the importance of hemp granulometrical distribution. To measure the effect of different preparation techniques mixes in two different mixers – gravity and forced action – were prepared to test the superiority of the latter as it is widely used in LHC production. Also different drying methods – natural, forced with temperature at various...

Construction Technologies and Architecture, 2022

Hemp concrete is a well-known bio-based building material, but due to its relatively low compress... more Hemp concrete is a well-known bio-based building material, but due to its relatively low compressive strength is mainly used as an insulation material with a load-bearing wooden frame. There are possibilities to expand hemp concrete application in construction by substituting traditional lime with magnesium cement. Magnesium oxychloride cement is a material already known for some time and nowadays used in building board production. Strength, lightweight, ease of use are advantages that highlight relatively new magnesium oxychloride type boards compared to traditional sheeting materials such as plywood, gypsum plasterboard and fibre-cement board. Therefore, similar parameters are thought to be reached by producing magnesium oxychloride hemp board. In this work, magnesium cement water resistance was studied and possibilities to improve it was examined by adding fly ash and nanosilica. Among the nanomaterials used in building materials, nanosilica has gained significant interest by per...

The main purpose of concrete mixing is homogenous distribution of different types of particles wi... more The main purpose of concrete mixing is homogenous distribution of different types of particles within the system. Failure in particle blending can result in poor concrete workability in the fresh state, low performance in hardened state and inefficient use of materials