Girts Bumanis

Alkaline Activated Material for pH Control in Biotechnologies

By using industrial aluminium recycling waste, recycled silicate glass from outworn fluorescence lamp recycling plant, calcined kaolinite clay supplemented with alkali activator with different silicate modulus the new type of porous material for biotechnologic processes without the need for additional equipment for pH control was researched. This controlled-release system contains an alkali activated matrix in which NaOH crystals are encased. In this study ability to release NaOH per time in water according to material composition and structure were investigated. Three alkaline activated materials AAM 7.5, 10 and 12.5, with different alkali activator content were characterized.

The Effect of Activator on the Properties of Low-Calcium Alkali-Activated Mortars

Properties of the low-calcium alkali-activated materials (AAMs) made from the metakaolin, waste glass and sand were tested in this research. Specimens with dimensions 40x40x160mm were prepared. The correlation between development of microstructure and concentration of NaOH solution used for preparing of the AAMs was observed. Structure investigation with SEM and FTIR was performed to describe the formation of microstructure in low-calcium AAMs. The research results aimed that the improvement of physical and mechanical properties of the AAMs with increasing the activator’s concentration from 2 to 10 mol/kg H2O were in concordance with the structure development of AAM. The 28 days old AAMs with a compressive strength up to 31MPa and water absorption lower than 2% were obtained by using activator with concentration 10 mol/kg H2O.

Effect of Ground Glass Fineness on Physical and Mechanical Properties of Concrete

This research is focused on the development of concrete mix by using borosilicate glass micro-filler obtained from the waste of outworn fluorescent lamps. The task of the research is to find the optimal fineness of glass particles, which can improve packing of microparticles in cement matrix to increase the strength properties of concrete. Previous research as well as chemical composition of glass proved that ground glass can be used as an effective concrete component. Borosilicate glass micro-fillers with different grinding degree were used in experiments. Particle grading was determined by using the laser diffraction method. The morphology of microparticles was investigated. The effect of glass powder on cement setting time was checked. It was determined that fine glass particles powder produces a long-term hardening effect. Experimental work includes preparation of samples from standard concrete and concrete with borosilicate glass micro-filler (with particles of different sizes and mixed in different proportions) and testing after the ageing period of 7 and 28 days. The long-term hardened samples were also tested. The compressive strength of concrete samples is decreasing when rough glass powder is used as cement replacement. At the same time fine glass filler with particle size up to 0.1–10 μm allows improvement in mechanical properties of concrete and makes it possible to replace up to 25% of the cement without impairing the strength characteristics of concrete. As a result, concrete with improved water resistance and durability was obtained.

Durability of High Strength Self Compacting Concrete with Metakaolin Containing Waste

Metakaolin is considered as one of most promising pozzolanic microfiller material in concrete industry. Metakaolin is a high value product obtained from kaolin clay calcined at high temperatures which also can be effectively used in ceramic industry therefore its application in concrete industry is rather limited. In present research metakaolin containing waste (MKW) by-product was studied as a partial cement replacement in high strength self compacting concrete (SCC). Obtained waste material derives from the foam glass granule production plant where kaolin clay is used as releasing agent during heating process and in the end metakaolin with glass impurities is obtained as by-product. In present research 5 to 15 wt.% of cement was replaced by MKW. A constant water amount was used for all mixtures and workability (>600 mm by cone flow) was ensured by changing the amount of superplasticizer. Compressive strength was tested at the age of 7, 28 and 180 days. To determine durability of SCC the chloride penetration was tested according to NT BUILD 492, freeze-thaw test according to LVS 156-1:2009 annex C and alkali-silica reactivity test according to RILEM TC 106-AAR-2. The results indicate that cement replacement by MKW did not affect the strength of SCC significantly. At the age of 28 days SCC with 15 wt.% of MKW reached compressive strength of 70 MPa comparing to 68 MPa to reference mixture. The chloride penetration test results indicated that the non-steady-state migration coefficient of reference samples was reduced 3.7 times and it was concluded that SCC resistance to chloride penetration can be increased by incorporation of MKW in mixture composition. Freeze-thaw test results indicated that obtained SCC can withstand at least 500 freeze-thaw cycles without surface damage and weight loss. It was concluded that up to 15 wt.% of cement can be replaced by metakaolin containing waste without strength loss and the durability of SCC could be increased.

Utilisation of Borosilicate Glass Waste as a Micro-Filler for Concrete

Glass from a light bulb is a waste product that cannot be utilised in a traditional way. This study looks into the possibilities of using lamp borosilicate glass powder as a cement replacing admixture in conventional concrete. Experimental work provides preparation of standard concrete samples and sample testing after seven and 28-day ageing periods in standard conditions. The following glass materials were used for cement replacement: rough ground glass powder, glass dust from filters (both materials were obtained from a glass treatment plant) and additionally ground glass powder. The effect of glass powder on cement setting time was studied. The experimental results indicate that replacement of cement by rough glass powder decreases the compressive strength. Fine glass particles make it possible to replace up to 20% of cement without the loss in strength characteristics. Fine glass powder offers a long-term hardening effect. The best compressive strength results were achieved by using the glass that was additionally ground for 60 minutes. Glass dust obtained from filters shows a less significant effect. Summarising the research findings it may be concluded that ground borosilicate lamp glass may be successfully applied as a micro-filler for concrete as cement replacing material.

Influence of fillers on the alkali activated chamotte

Alkali-activated materials (AAM) exhibit remarkable high-temperature resistance which makes them perspective materials for high-temperature applications, for instance as fire protecting and insulating materials in industrial furnaces. Series of experiments were carried out to develop optimum mix proportions of AAM based on chamotte with quartz sand (Q), olivine sand (OL) and firebrick sawing residues (K26) as fillers. Aluminium scrap recycling waste was considered as a pore forming agent and 6M NaOH alkali activation solution has been used. Lightweight porous AAM have been obtained with density in range from 600 to 880 kg/m3 and compressive strength from 0.8 to 2.7 MPa. The XRD and high temperature optical microscopy was used to characterize the performance of AAM. The mechanical, physical and structural properties of the AAM were determined after the exposure to elevated temperatures at 800 and 1000°C. The results indicate that most promising results for AAM were with K26 filler where strength increase was observed while Q and OL filler reduced mechanical properties due to structure deterioration caused by expansive nature of selected filler.

Structural Investigation of Alkali Activated Clay Minerals for Application in Water Treatment Systems

Alkali activation technology can be applied for a wide range of alumo-silicates to produce innovative materials with various areas of application. Most researches focuse on the application of alumo-silicate materials in building industry as cement binder replacement to produce mortar and concrete [1]. However, alkali activation technology offers high potential also in biotechnologies [2]. In the processes where certain pH level, especially alkaline environment, must be ensured, alkali activated materials can be applied. One of such fields is water treatment systems where high level pH (up to pH 10.5) ensures efficient removal of water pollutants such as manganese [3]. Previous investigations had shown that alkali activation technology can be applied to calcined clay powder and aluminium scrap recycling waste as a foam forming agent to create porous alkali activated materials. This investigation focuses on the structural investigation of calcined kaolin and illite clay alkali activation processes. Chemical and mineralogical composition of both clays were determined and structural investigation of alkali activated materials was made by using XRD, DTA, FTIR analysis; the microstructure of hardened specimens was observed by SEM. Physical properties of the obtained material were determined. Investigation indicates the essential role of chemical composition of the clay used in the alkali activation process, and potential use of the obtained material in water treatment systems.

Microstructural Investigations of Ultra-High Performance Concrete Obtained by Pressure Application within the First 24 Hours of Hardening

Abstract In this study, the effect of pressure application (0-50 MPa) to fresh concrete right after casting and during the first 24 hours of hardening has been examined. Supplementary cementitious materials in a form of silica fume, nanosilica and ground quartz sand were used. The aim of pressure application was to reduce porosity, thus improving concrete mechanical properties. Considerable reduction in porosity and a subsequent increase in compressive strength reaching the level of Ultra-High Performance Concrete (UHPC) were achieved. Mechanical and physical properties were tested and gas sorption porosimetry, mercury intrusion porosimetry (MIP), X-ray diffraction (XRD), as well as scanning electron microscopy (SEM) were used for material characterization.

Effect of the Ratio SiO 2 /Al 2 O 3 on the Structure, Properties, and Thermal Stability of Geopolymer Refractory Materials

The properties of lightweight geopolymer materials (GM) based on refractory technogenic aluminosilicate wastes were studied. The effect of the ratio of the oxides SiO2 and Al2O3 in the compositions of GM on the physical and mechanical properties of GM was investigated. It was found that SiO2/Al2O3 reduction in the GM composition results in higher density and strength and lower water absorption of the samples after a keeping period. After firing at temperatures 800 and 1000°C the strength of the samples becomes all the higher the lower the ratio SiO2/Al2O3 in the composition. The heat resistance of the samples comprises four thermal cycles for high and more than seven cycles low ratio SiO2/Al2O3.

The effect of curing conditions on the durability of high performance concrete

This study researches compressive strength and durability of the high strength self-compacting concrete (SCC) impacted at early stage by the curing conditions. The mixture compositions of metakaolin containing waste and cenospheres as partial cement replacement (15 wt%) were compared to reference SCC with 100% cement. The specimens prepared in advance were demoulded 24h after casting of the SCC and the specific curing conditions were applied for up to 28 days: standard water curing at 20°C (i); indoor curing at 20°C, RH 60% (ii) and low temperature air curing (2°C) at RH 60% (iii). Results indicate that at early stage (14 days) indoor curing conditions increase compressive strength of the SCC whilst no strength loss has been detected even at a low temperature curing. The further strength gain has been substantially reduced for samples cured indoor and at a low temperature with significant variation observed for long term compressive strength (180 days). The metakaolin containing waste has proved to be an effective partial cement replacement and it has improved strength gain even at a low temperature curing. Meanwhile cenospheres have reduced the SCC strength and with no positive effect on strength observed within the standard term. Freeze-thaw durability and resistance to the chloride penetration have been improved for the SCC cured at low temperature. The SCC with metakaolin containing waste has proved to be the most durable thus demonstrating importance of effective micro filler use.