Influence of Silica Fume on SCC Concrete Properties

The use of recycled materials or waste increases sustainability in the construction sector. Likewise, the self-compacting concrete (SCC) has shown improvement in mechanical properties, when made with some waste pozzolanic materials. The differences in the compressive strength of the SCC concrete sample in the case of 5% by mass share of silica fume compared to samples with 7% were explored. The results shown that optimal replacement of Ordinary Portland Cement by silica fume is 5%, under applied experimental conditions

Recycled Coarse Aggregate and Fly Ash Effect on Compressive Strength of Self-Compacting Concrete

The paper presents experimental results of the tests conducted on Self-Compacting Concrete (SCC) with recycled coarse aggregate, and fly ash as filler component. A fine fraction of aggregate originated from a riverbed, while coarse aggregate was obtained either from a riverbed or by crushing laboratory concrete cubes as recycled concrete aggregate. The larger coarse aggregate grains than typical for SCC were used, to highlight the possibility of application in structure elements with sparse reinforcement bars. Four mixtures of concrete were made, in order to compressive strength as the dominant property of any concrete. All of the fresh concrete mixtures displayed proper behavior for this kind of concrete, whereas recycled concrete aggregate induced several challenges. Hardened concrete mixtures showed that beyond the use of natural coarse aggregate, there is the possibility to obtain proper mechanical behavior needed for structural concrete, with moderate amounts of cement. Such an approach paves a way for a cleaner and more sustainable civil engineering practice

Cathode Ray Tube Waste Glass in Concrete Preparation - Increasing Sustainability

The construction sector is responsible for approximately 39% of energy use and process-related carbon dioxide emissions. Mixing waste materials into concrete, as a substitute for cement and/or aggregate, increases energy efficiency and sustainability in general. Additionally, pressure on the environment is decreasing by reducing the amount of exploitation of natural raw materials. On the other hand, the rapid progress of the electronic industry has led to the generation of a large amount of electrical waste before the end of its useful life. Disposal of old monitors and TV screens, i.e. their cathode-ray tubes (CRT), represents a major problem for the environment because CRT waste is classified as hazardous due to its high lead content. This paper deals with an overview of investigations on CRT waste utilization in cement materials in order to increase sustainability and encourage a circular economy in the construction sector

Utilization of Waste In Geopolimerization A Review

The aim of this article is to review the utilization of various types of waste in geopolimerization technology processes. The geopolymerization represents a process comprising of the dissolution of aluminosilicate solids in a strongly alkaline medium followed by condensation of free alumina-silica oligomers to form a tetrahedral polymeric structure. Advantage of this technology represents the possibility of utilization of any silica and alumina-containing waste material that could be dissolved in an alkaline solution. Production of geopolymers from waste not only provides less raw material consumption but also addresses issues regarding the disposal of wastes. Fly ash, red mud, construction and demolition waste (C&DW), slags, or mine waste are the most utilized waste types in combination with supplementary waste materials according to their characteristics. Conducted investigations showed that the use of various waste materials leads to the production of geopolymers with a broad range of final properties. Despite a high number of published Publications and patents, the large-scale utilization of waste is still missing

Reuse of Solid Brick Waste Mix in Geopolymerization – a Preliminary Investigation

The applicability of solid bricks waste in geopolymerization technique was considered. Waste samples were characterized in terms of mineralogical composition by XRD prior to mechanical testing. XRD analysis showed that both brick samples contained anorthite, wollastonite, and mullite as the main components. The compressive strength investigation was carried out by screening method with three geopolymer mixtures. Geopolymer mixtures were prepared with alkaline activators; the mixtures were poured into molds and air-dried for 28 days. The compressive strength of samples was measured according to the standard SRPS EN 12390-3:2010 for cubic samples. The compressive strength values ranged from 9.8 MPa for the newer solid brick, 10.2 MPa for the older solid brick, and 10.5 MPa for the solid brick mix waste geopolymer sample. The most likely underlying reason for the higher compressive strength results of the older solid brick and the mixed sample is their mineral composition, i.e. higher proportion of aluminosilicate. However, all samples showed satisfactory compressive strengths, and it represents an excellent basis for further research

Energy Efficiency and Sustainability of Biofibres-Based Thermal Insulation

Energy efficiency of residential and commercial buildings is acutely important as this sector is responsible for approximately 40% of overall energy consumption and around 35% of CO2 emissions (in the European Union). The construction sector has intense environmental footprint due to exploitation of non-renewable material and energy resources, land use and generation of waste materials during construction and demolition. It is therefore important to develop sustainable building structures, practices and materials with minimal resources and energy use. Utilization of energy efficient, sustainable and resource-saving building materials is of particular importance. The study is carried out to investigate possibilities and evaluate effects of application of biofibres-based structures as non-constructive and/or insulating materials in current building practice. Focus is on natural, dominantly cellulose, fibres, traditionally used in the past (hemp, reed, straw, flax, rice hulls, cotton stalks, sunflower, cattail, bagasse, etc) as well as on some promising grass/reed cultures, such as Miscanthus x Giganteus. The experimental examinations of thermal and mechanical properties decisive for the performance of thermal insulation have been undertaken. Expectedly, the thermal conductivity, as the material characteristic primarily responsible for Operational Energy Consumption, has been found mostly worse than in commonly used, mass produced, thermal insulation materials such as expanded or extruded polystyrene, glass or mineral wool, etc. On the other hand, conclusions of Life Cycle Analysis and examination of Embodied Energy advocates the utilization of designated natural biofibres-based thermal insulation as more sustainable and in the long run (Cradle to Grave) energy efficient alternative to the conventional insulation materials

Analysis of factors influencing Cu(II) sorption by clinoptiolite

Experimental design methodology represents a powerful tool for the analysis and optimization of various processes. Immobilization of toxic substances by sorption onto low-cost materials has gained a lot of attention in the last decade. Fundamental knowledge about sorption processes and their practical use can be improved by experimental planning and statistical analysis. In this study, the effects of initial metal concentration and pH, as well as the sorbent mass and particle size, on Cu(II) sorption by natural clinoptilolite were evaluated and compared. Full factorial experimental design at two levels was applied. Statistically significant factors were determined considering residual Cu(II) concentrations as a system response. The Pareto graphs of standardized effects, Main effect plots and Interaction plots were created using statistical software. Initial sorbate concentration, sorbent mass and their interaction were recognized as statistically significant, at 95% confidence level. Main effect plot approved that sorbent mass increase and initial Cu(II) concentration decrease caused reduction of residual Cu(II) concentration in solution. On the other hand, the change of initial solution pH and sorbent particle size didnt provoke significant response changes. Bearing in mind that pH is a factor with high effect on heavy metal sorption, the insignificant influence of initial pH detected in this study can be explained by buffering properties of the applied clinoptilolite and relatively narrow pH range chosen in order to prevent sorbent dissolution on one side and sorbate precipitation on the other. By regression analysis, the mathematical model for process description was derived. The correlation between predicted and experimental values was high (R-2 GT 0.99). In the investigated ranges of parameters, the obtained empirical equation can be applied for the prediction of system response

Speciation of Sr-90 and other metal cations in artificially contaminated soils: the influence of bone sorbent addition

The influence of bone sorbent addition onto distribution of Sr-90 in artificially contaminated soil was preliminary studied to assess the possibility of biogenic apatite utilization for reduction of Sr-90 mobility and availability. Simultaneously, the disruption of soil micro- (Cd, Zn, Co, Cu, Cr, and Ni,) and macroelements (Al, Fe, Mn, K, Mg, and Ca) upon Sr contamination and sorbent addition was monitored. The model soil was contaminated by inactive Sr, in the form of Sr(NO3)(2) solution. As a soil additive, sorbent obtained by annealing bovine bones at 400 A degrees C (B400) was applied. Both the uncontaminated and Sr-contaminated soils were mixed with 1, 3, 5, and 10 % of sorbent, suspended in distilled water (initial pH 5; solid/solution ratio, 1:2), and equilibrated for 15 days on a rotary shaker. Solid residues were subjected to modified Tessier five-step sequential extraction analysis, and the amounts of chosen metals in each fraction were determined by inductively coupled plasma-optical emission spectroscopy. In the original soil, Sr was mainly found in exchangeable (61 %) and carbonate phase (16 %), whereas after contamination, the content of Sr in exchangeable phase raised to 94 %. With the addition of B400, the decrease in Sr amounts in exchangeable fraction was detected, whereas increase occurred mainly in operationally defined carbonate phase and in the residual. High level of Sr contamination caused the increase in Zn, Ni, Co, Cu, Cd, and Mn and decrease in Ca content in exchangeable phase. Sorbent addition resulted in a migration of these cations to less soluble fractions. This effect was observed even for major soil elements such as Fe, Al, and Mn, regardless of the excessive amounts of Sr in the soil. Mixing the soil with B400 resulted in reduced Sr mobility and bioavailability. B400 acted as a stabilizing agent for heavy metals, as well. Apatite distinguished selectivity towards heavy metals may interfere with the Sr immobilization and disrupt original cation distribution. Further studies should include more realistic (lower) Sr concentrations in the soil, different soil types, pH, and longer incubation times