Torsional Behavior of Waste Fiber-Reinforced Concrete.

Factory made steel fiber and steel fiber derived from worn tires was used to develop cement concrete, which was subjected to torsional forces. A dedicated stand for torsion tests, allowing for the measurement of force, deflection, and torsion angle, was used. The test results showed that both the factory-made fiber and the waste steel fiber significantly improved torsional properties of the concrete matrix. The test results of specimens made with waste fiber were characterized by slightly worse results compared to factory-made fibers, but there was a significant improvement in torsional properties compared to samples without fibers. Taking into account the financial and environmental benefits, the application of waste steel fiber recovered from car tires could be an interesting alternative to using commercially sold steel fiber applied for the production of construction elements subjected to torsional forces.

Modifying Water-Frost Resistance and Mechanical Properties of Lime Mortar Using Siliceous and Fluidised Bed Fly Combusted Ashes Activated with Cement.

The research focuses on pozzolanic additives, which are compatible with traditional lime mortars, and enable the modification of the rheological, physical and mechanical properties of tested composites. It was noted that lime mortars with fluidised bed fly ash require sand without impurities to avoid possible ettringite crystallisation. The work presents siliceous fly ash and fluidised bed combustion fly ash to modify the frost resistance and mechanical properties of traditional lime mortars with and without the addition of cement. The results show better effects using fluidised bed ash. Traditional Portland cement CEM I 42.5R was used to activate ash and increase the results. The possibility of a significant improvement of properties is indicated with a hybrid addition to the lime binder of 15-30% ash (siliceous or fluidised bed ash) and 15-30% cement. Changing the class and type of cement provides an additional opportunity to alter the properties of the composites. For architectural reasons relating to colour, the suitability of lighter fluidised bed ash instead of darker siliceous ash and of white Portland cement instead of the traditional grey cement can be used. The proposed mortars can be the basis for future modifications with admixtures and additives, e.g., metakaolin, polymers, fibres, slag, glass powder and impregnating agents.

A Statistical Model of Fibre Distribution in a Steel Fibre Reinforced Concrete.

The aim of the research was to create a model of steel fibre distribution in a Steel Fibre Reinforced Concrete space using statistical probability means. The model was created in order to better understand the behaviour of the composite under operating conditions. Four statistical distributions (Beta, Kumaraswamy, Three Parameter Beta and Generalised Transmuted Kumaraswamy) were examined to find the distribution that best described fibre settling phenomenon caused by manufacturing process conditions. In the next stage the chosen statistical distribution was adapted to create the model of steel fibre distribution in a Steel Fibre Reinforced Concrete space. The model took into account technological conditions such as vibrating time and properties such as consistency of the tested concrete. The model showed a good agreement with the real fibre distribution.

Investigation of Hybrid Methods for Elimination of Brilliant Blue Dye from Water Phase Using Various Nanomaterials Combined with Activated Sludge and Duckweed.

The main goal of this experimental work is screening of different natural and synthetic nanomaterials and biopolymers that may improve elimination of stable micropollutants from water phase. In this work, as a target chemical acting as the micropollutant molecule, the Brilliant Blue (BB) dye was selected. We tested different active matrices dispersed in water phase including activated carbon (AC), lyophilized graphene oxide (GO), ß-cyclodextrin (CD), raw dandelion pappus (DP), microcrystalline cellulose(MC), and raw pine pollen (PP), as well as two types of Egyptian Blue mineral pigments (EB1 and EB2). Graphene oxide and Egyptian Blue nanomaterials were synthesized in our laboratory. We investigated potential application of such nanoparticles and biopolymer conglomerates as additives that may tune the activated sludge (AS) microorganisms or duckweed water plant (DW) and increase efficiency of micropollutants removal from wastewater. Studied nanomaterials/biopolymers were used in two different experimental modes involving real activated sludge microorganisms (24 h experiment) as well as duckweed plant (16 day experiment). Quantitative data of BB were obtained using microfluidic type device based on micro-TLC plate. This approach enabled direct determination of target component without sample pre-treatment like pre-concentration or pre-purification. Within single analytical run calibration line, retention standard spots (methyl red) and multiple samples were analyzed simultaneously. Due to the multivariate nature of these experiments, quantitative data were explored with chemometric tools including AHC (agglomerative hierarchical clustering), PCA (principal component analysis), and FA (factor analysis). Experimental data and multivariate calculations revealed that BB is strongly resistant on biodegradation, however, inclusion complexes formation with ß-cyclodextrinmay induce degradation of this dye in the presence of duckweed. It is hoped that results of our experimental work can be used for designing of future experiments for fast screening of different additives and improvement of technological processes, focusing on purification of sewage and water from micropollutants.

Principal Component Analysis as a Statistical Tool for Concrete Mix Design.

With the recent and rapid development of concrete technologies and the ever-increasing use of concrete, adapting concrete to the specific needs and applications of civil engineering is necessary. Due to economic considerations and care for the natural environment, improving the methods currently used in concrete design is also necessary. In this study, the author used principal component analysis as a statistical tool in the concrete mix design process. Using a combination of PCA variables and 2D and 3D factors has made it possible to refine concrete recipes. Thirty-eight concrete mixes of different aggregate grades were analyzed using this method. The applied statistical analysis showed many interesting relationships between the properties of concrete and the content of its components such as the clustering of certain properties, showing dependence between the properties and the quantities of certain ingredients in concrete, and reducing noise in the data, which most importantly simplifies interpretation. This method of analysis can be used as an aid for concrete mix design.

Influence of Crimped Steel Fibre on Properties of Concrete Based on an Aggregate Mix of Waste and Natural Aggregates.

This research was inspired by the growing global shortage of natural aggregates. Different types of waste ceramics (apart from recycled concrete) are the most popular materials for the production of waste aggregates as possible substitutes for natural ones. The aim of this research was to analyse the efficiency of different aggregate mixes composed of waste and natural materials focusing on two waste ceramic aggregates, which were prepared concrete mixes based on specifically composed aggregates (blend of natural aggregate, porous and iron oxide-rich (red) waste ceramic aggregate, and dense, kaolin-based (white) waste ceramic aggregate). All aggregates were thoroughly tested before utilisation for concrete mix creation. Altogether, four blends of aggregates were prepared in order to prepare concrete mixes using a simplex experiment design. The mixes were then modified by adding various amounts of crimped steel fibre. Such properties of hardened steel fibre-reinforced concrete (SFRC) such as density, compressive strength, shear strength, ultrasound propagation velocity, dynamic modulus of elasticity, and limit of proportionality during flexural testing were of special interest. Tests were conducted according to European and Japanese standards. The achieved fibre-reinforced concretes were characterised by satisfactory strength characteristics, thereby enabling the substitution of traditional reinforcement. Strength classes according to the fib Model Code 2010 were assigned.

Lightweight SFRC Benefitting from a Pre-Soaking and Internal Curing Process.

The presented research program is focused on the design of a structural lightweight fiber-reinforced concrete harnessing an internal curing process. Pre-soaked waste red ceramic fine aggregate and pre-soaked artificial clay expanded coarse aggregate were utilized for the creation of the mix. Copper-coated steel fiber was added to the mix by volume in amounts of 0.0%, 0.5%, 1.0%, and 1.5%. Test specimens in forms of cubes, cylinders, and beams were tested to specify the concrete characteristics. Such properties as consistency, compressive strength, splitting tensile strength, static and dynamic modulus of elasticity, flexural characteristics, and shear strength were of special interest. The achieved concrete can be classified as LC12/13. A strength class, according to fib Model Code, was also assigned to the concretes in question. The proposed method of preparation of concrete mix using only pre-soaked aggregate (with no extra water) proved to be feasible.

A Combined Electromagnetic Induction and Radar-Based Test for Quality Control of Steel Fibre Reinforced Concrete.

In this paper, the authors made an attempt to detect the fibre content and fibre spacing in a steel fibre reinforced concrete (SFRC) industrial floor. Two non-destructive testing (NDT) methods, an electromagnetic induction technique and a radar-based technique, were applied. The first method allowed us to detect the spacing in subsequent layers located in the thickness of the slab. The result of the second method was a 3D visualization of the detected fibre in the volume of concrete slab. The conducted tests showed aptitude and limitations of the applied methods in estimating fibre volume and spacing. The two techniques also allowed us to locate the areas with relatively low fibre concentration, which are very likely to be characterized by low mechanical properties.

Pilbara Craton Soil as A Possible Lunar Soil Simulant for Civil Engineering Applications.

Recent fast development in lunar exploration exposed a lack of lunar soil simulant (LSS) fit for civil engineering applications. Permanent human presence on the Moon will be associated with significant construction efforts. Adequate technologies and building materials have to be developed and tested prior to setting the actual building site on the Moon. Current LSSs were created for non-civil engineering purposes, thus they are very expensive and available in limited amounts. In the paper, the authors proved that Pilbara Craton soil is a suitable material for the creation of an affordable LSS for civil engineering applications. The main tool of the conducted study was principal component analysis (PCA).