Measuring fuel transport through fluorocarbon and fluorine-free firefighting foams

A flux chamber was designed to measure the transient fuel transport through a foam layer before significant degradation of foam occurred. The fuel transport rate through AFFF (fluorinated foam) was much slower than through RF6 (fluorine-free foam) with break-through times being 820 s and 276 s respectively over n-heptane. The fuel flux through AFFF covering three fuel pools (n-heptane, iso-octane, and methyl-cyclohexane) was also measured. AFFF had the smallest flux over iso-octane with a break-through time over 1900 s and the highest flux over methyl-cyclohexane with a break-through time under 80 s even though the fuels have similar vapor pressures at room temperature. Despite the lack of aqueous film formation on an iso-octane fuel pool, the fuel vapor flux through AFFF was much smaller relative to the methyl-cyclohexane pool, which enables film formation due to its higher surface tension than iso-octane. Our measurements of transient fuel flux show that the foam layer is a significant barrier to fuel vapor transport. The data suggest a transient mechanism based on the suppression of fuel adsorption onto bubble lamellae surfaces due to the oleophobicity of fluorocarbon surfactants, which is consistent with fuel solubility data. This suggests that surfactants that suppress fuel adsorption and solubility into bubble lamellae surfaces may reduce fuel transport through foams.     

Effect of alkali-silica reaction and freezing and thawing action on concrete–steel bond

An experimental program was conducted to investigate the effect of stresses and cracks, caused by alkali-silica reaction (ASR) and freezing and thawing (F/T), on bond between reinforcing steel and concrete. Pullout test cylinders, reinforced with 18 mm steel bars, were used to evaluate bond behavior. Concrete prisms (50 × 50 × 300 mm) were also cast to evaluate expansion and reduction in ultrasonic velocity due to ASR and F/T cycles, respectively. Specimens were cured for 40 days before being either immersed in sodium hydroxide solution of 0.5 normality in order to accelerate ASR, or subjected to different cycles of F/T. Bond behavior, expansion, and ultrasonic pulse velocity tests were carried out as ASR progressed or under F/T cycles.The progress of ASR resulted in significant losses in critical bond stress and ultimate bond strength capacity reaching as high as 44% and 24%, respectively, accompanied by a significant increase in free-end slip at failure. The loss in bond due to ASR was higher for specimens prepared using concrete with lower concrete strength and higher percentage of reactive aggregate. F/T action caused a significant reduction in critical bond stress and ultimate bond strength that reached as high as 100% and 55%, respectively, and an increase in free-end slip at failure. Neither ASR nor F/T cycles affected trends in the behavior of bond stress versus free end slip curves.     

Applications of glaze and decor on dimensioned andesites used in construction sector

This report presents initial results of the development process of a new product using andesites obtained from Afyon/Iscehisar region as an alternative to traditional ceramic wall and floor tiles used in construction sector. The series of characterization tests were conducted on andesite samples. Then, the samples were applied glaze for trial purposes. Analysis indicated that the andesite samples consisted of sanidine, mica and pyroxene minerals and its apparent porosity, density, water absorption and compressive strength values were 15.75%, 2610 g/cm³, 7.43% and 40.7 MPa, respectively. In heat microscope measurements, maximum sintering was recorded at 1138 °C. Linear expansion coefficient (α) of the andesite at 400 °C was 3.26 × 10^?6 K^?1. Firing performed by using the prepared glaze recipe at approximately 1160 °C produced good results in terms of body-glaze harmony. In addition, different decorative surface finishes to be used in indoor and outdoor spaces were obtained via under glaze decorative technique.     

Development and characterization of an inorganic foam obtained by using sodium bicarbonate as a gas generator

In the construction industry almost all of the insulating and expansive materials are organic foams. In this work, the production of an inorganic foam is described. Sodium bicarbonate is used as a gas generator. CO₂ gas is released when water is added to the mixture of sodium bicarbonate and β-hemihydrate gypsum powder (CaSO₄ · 1/2H₂O). Hence, stabilization of the foam is achieved when CO₂ gas is released and water is absorbed by β-hemihydrate gypsum powder, which subsequently is converted into calcium sulphate dihydrate (gypsum matrix). The bulk density and mechanical properties (compressive and flexural strength) of the inorganic foam and gypsum were determined. Microstructural characterization has been carried out by SEM and XRD, and a new sodium sulphate phase was identified in the gypsum foam due to this chemical reaction. Finally, thermal properties such as thermal conductivity and diffusivity were measured and it was observed how for the same heat flux, the thickness of an inorganic foam slab is 73.4% less than that of a concrete slab.     

Air leakage measurement and analysis in duct systems

Air ducts and related equipments are used in a large number of buildings having thermal comfort. In this study, energy loss related with air leakage is studied. The leakage measurement setup was produced according to NEN-EN standards and the evaluation of data have been conducted by using power law model. The measurements were made on 300 and 1000 mm diameter single circular ducts, 300 mm × 250 mm and 1000 mm × 500 mm flanged joint rectangular ducts, 300 and 630 mm diameter circular beaded slip joint ducts, 300 mm × 200 mm and 500 mm × 300 mm rectangular flanged and drive slip joint ducts, and an branched air distribution system having different diameters for positive internal pressures. Test results have showed that the most of air leakage is from the joints. The seam contribution to air leakage is relatively lower than the joints. Using sealing gaskets help to improve the air leakage by about 50%.     

Development of titania coatings on glass foams

TiO₂ coatings on glass foam substrates were produced by electrophoretic deposition (EPD) and sol–gel method with the aim to impart surface functional properties to glass foam such as antibacterial and photocatalytic effects. Starting with charged TiO₂ nanoparticles (21 nm) suspended in acetylacetone, EPD was shown to be a useful method to obtain TiO₂ coating on the glass foam substrates placed close to the deposition electrodes in the EPD cell. Best results were obtained by applying 25 V for 4 min and a subsequent thermal treatment (450 °C for 1 h). In the second approach, multilayer sol–gel TiO₂ coatings on glass foam were fabricated, which were heat-treated at 450 °C for 1 h to obtain pure anatase structure. Both techniques led to partially microcracked coatings which were however well adhered to the glass foam substrate (qualitatively assessed). The presence of microcracks was not considered to be a disadvantage as they increase the surface area of the coating, which is required to maximise the interaction of the titania layers with the environment for their antibacterial and photocatalytic function.     

Application ranges of EPB shields in coarse ground based on laboratory research

Earth Pressure Balance (EPB-) Shields were originally used in fine-grained soils as well as in mixed-grained soils with a content of fines (d < 0.06 mm) of at least 30 M%. In these soils, if an adequate consistency is given, an EPB-Shield can be used without additional ground conditioning. Further, the application ranges of EPB-Shields have successfully been extended to mixed-grained and coarse-grained soils by ground conditioning, see Herrenknecht et al. (2011). In these soils, foams, if required also foams with polymers, polymer suspensions or high density slurries, are applied to change the properties of the soil in the excavation chamber. So far, the application ranges of EPB-Shields in mixed-grained and coarse-grained soils were based on experience with former tunnelling projects with different hydro-geological boundaries and different conditioning agents. First investigations on the properties of soil–foam-mixtures were done in different laboratories (Mair et al., 2003; Borio et al., 2011; Bezuijen, 2011). In these investigations, the focus was on the determination of special properties of the conditioning agents and conditioned soils. These laboratory investigations were the basis for further examination. Laboratory research was carried out at the Institute for Tunnelling and Construction Management at the Ruhr-University Bochum, Germany, using selected methods for the reproducible determination of essential properties of foams, foams with polymer additives, polymer suspensions and high density slurries. The results are summarised in a doctoral thesis (Budach, 2012). These methods were tested systematically regarding their workability. Furthermore, coarse-grained soils were mixed with the selected conditioning agents and methods to determine the essential properties of the conditioned soils were developed and tested on their suitability as well. Based on the results of this research, application ranges for EPB-Shields were developed based on extensive laboratory research considering varying hydro-geological ground conditions and conditioning agents.     

Transient free convection in passive buildings using 2D air-filled parallelogram-shaped enclosures with discrete isothermal heat sources

This work evaluates the transient convective exchanges taking place in a building wall made up of air-filled inclined cells. Each cell is formed by two vertical active walls connected by a channel of insulating material. The active hot wall is composed by alternated isothermal and adiabatic bands and is opposite to the active cold wall. Both walls are vertical and separated by a distance equal to their height. The channel connecting these walls is inclined at an angle α with respect to the horizontal, being the values considered in the present work 0° (square cell), ±15°, ±30°, ±45° and ±60°. Two-dimensional temperature fields and streamlines are presented at some representative instants. The temporal evolution of the average Nusselt number at each band of the hot wall is determined for all the treated configurations. Numerical results are validated by comparison with other experimental and numerical studies for cavities with isothermal hot wall in steady state. The maximum deviation found is about 9% for the Nusselt number. This can be considered as very satisfactory for this type of studies characterized by high Rayleigh numbers varying between 1 × 10⁵ and 3 × 10⁸, representative of real building installations.     

Strength correlation between individual block,prism and basic wall panel for load bearing interlocking mortarless hollow block masonry

This paper focuses on the development of the compressive strength correlation between the individual block, prism and basic wall panel for load bearing interlocking hollow mortarless blocks. The interlocking blocks used were developed by the Housing Research Centre at Universiti Putra Malaysia. The blocks consisted of stretcher, corner and half blocks. Forty individual block units from each type were tested under compression. The compressive strengths of 10 prisms assembled by stacking two stretcher blocks and two half blocks were evaluated. In addition, four wall panels each having a dimension of 1.2 × 1.2 m were assembled and tested under axial compressive loads. The results obtained were compared with those found in bonded masonry. BS 5628 Part 1:1992 were used for predicting of the compressive capacity of the bonded masonry. The interlocking mechanism, crack patterns and failure mechanism of the interlocking masonry specimens are highlighted and discussed.The correlations between the compressive strength of the interlocking masonry individual block (f_cb), prism (f_cp) and standard panel (f_cw) found in this analysis were f_cp = 0.47f_cb, f_cw = 0.83f_cp and f_cw = 0.39f_cb. Test results indicate that the interlocking mechanism and strength of the block in the load-bearing wall was satisfactory.     

Predicting the structural response of a compartment fire using full-field heat transfer measurements

Inverse heat transfer analysis (IHT) was used to measure the full-field heat fluxes on a small scale (0.9 m×0.9 m×0.9 m) stainless steel SS304 compartment exposed to a 100 kW diffusion flame. The measured heat fluxes were then used in a thermo-mechanical finite element model in Abaqus to predict the response of an aluminum 6061-T6 compartment to the same exposure. Coupled measurements of deflection and temperature using Thermographic Digital Image Correlation (TDIC) were obtained of an aluminum compartment tested until collapse. Two convective heat transfer coefficients, h =35 W/m²-K and h =10 W/m²-K were examined for the thermal model using the experimentally measured heat fluxes. Predictions of the thermal and structural response of the same compartment were generated by coupling Fire Dynamics Simulator (FDS) and Abaqus using the two values for h, h =35 W/m²-K and h from convection correlations. Predictions of deflection and temperature using heat fluxes from IHT and FDS with h=35 W/m²-K agreed with experimental measurements along the back wall. The temperature predictions from the IHT-Abaqus model were independent of h, whereas the temperature predictions from the FDS-Abaqus model were dependent on h.     

Correlations among mechanical properties of steel fiber reinforced concrete

In this paper, applicability of previously published empirical relations among compressive strength, splitting tensile strength and flexural strength of normal concrete, polypropylene fiber reinforced concrete (PFRC) and glass fiber reinforced concrete (GFRC) to steel fiber reinforced concrete (SFRC) was evaluated; moreover, correlations among these mechanical properties of SFRC were analyzed. For the investigation, a large number of experimental data were collected from published literature, where water/binder ratio (w/b), steel fiber aspect ratio and volume fraction were reported in the general range of 0.25–0.5, 55–80 and 0.5–2.0%, respectively, and specimens were cylinders with size of Φ 150 × 300 mm and prisms with size of 150 × 150 × 500 mm. Results of evaluation on these published empirical relations indicate the inapplicability to SFRC, also confirm the necessity of determination on correlations among mechanical properties of SFRC. Through the regression analysis on the experimental data collected, power relations with coefficients of determination of 0.94 and 0.90 are obtained for SFRC between compressive strength and splitting tensile strength, and between splitting tensile strength and flexural strength, respectively.     

Sulphate resistance of fibre reinforced cement-based foams

This paper describes the results of an investigation on the resistance of plain and fibre reinforced cement-based foams to sulphate exposure. A synthetic foaming agent was used to produce foamed cementitious composites with essentially a closed cellular structure at 1200 kg/m³, 750 kg/m³, and 475 kg/m³. Polymeric microfibres were introduced at 0% and 0.2% volume fraction to result in 6 mixes. Prismatic specimens were immersed in a sodium sulphate solution to be tested in flexure, after specific intervals of exposure, according to ASTM C1609. A comparison with the response of unexposed specimens reveals that the heavier cement-based foams are more susceptible to sulphate attack and perform poorly with an increase in the duration of exposure. On the other hand, the lightest of the mixes—at 475 kg/m³—registered higher flexural strength and toughness factors up to 30 days of exposure before succumbing to sulphate attack. This self-healing response was attributed to the space available in such highly porous composites that allows for the unhindered growth of ettringite without attendant cracking. The presence of microfibres facilitated self-healing, as evident from the flexural toughness factor.     

Confidence intervals of prediction and synthesis of prediction estimates for deformability of expanded polystyrene in long-term compression

The paper presents an experimental and numerical study of expanded polystyrene (EPS) with density ranging from 14.5 to 33 kg/m³, which was subjected to long-term compression of σ_c = 0.35σ_10% to verify the suggested methods of predicting compressive strain development in EPS products. The total time of testing was 608 days. Interval prediction of creep strain development for the period of 50 years was made by extrapolation based on power and exponential regression equations applied to approximate creep formation. These equations were reduced to a linear form by using logarithms. An additional factor K, depending on the number of retrospective test results and non-dimensional intervals in the range of prediction is used for a linear trend to correct for the expansion of confidence interval due to discounting of prediction information. Predictions obtained by using power and exponential equations were synthesised and the results were discussed.     

Comparison of fibrous insulations – Cellulose and stone wool in terms of moisture properties resulting from condensation and ice formation

Cellulose fibres are often used as thermal insulation in buildings. The organic nature of cellulose fibres, however, makes the insulation sensitive to high moisture content. This study investigates the moisture performance of cellulose insulation when exposed to a subzero environment. The paper is focused on the condensation and freezing in the material and includes comparison with the authors previous studies on stone-wool insulation. While the used stone-wool samples were water-repellent due to resin binders, cellulose is a typical representative for hydrophilic thermal insulation to which any contact with water condensate can be crucial.Test specimens of loose-fill cellulose were placed in a special laboratory device providing high moisture load. During a period of 100 h the specimens were subjected to a continuous load of moisture at atmospheric conditions on one side while the other side of the specimen faced a surrounding temperature of 0, −10 and −20 °C and the laboratory tests were repeated three times for each set of the specific thermal conditions (T_i = +20 °C, T_e = 0, −10 and −20 °C). The results indicate that there are minor changes in the water vapour permeability of the specimens. The experimental data from the investigation is compared with a mathematical model that simulates moisture diffusivity of cellulose together with accumulation due to sorption and freezing, using the actual climatic data.     

On the fracture possibility of thin-walled tubes under axial crushing

Thin-walled tubes are widely used as energy absorption components in vehicle crashworthiness design where axial crushing is one of the most typical loading conditions. Lightweight materials such as high-strength steel, aluminum and magnesium have been applied for thin-walled tubes for weight reduction. Meanwhile, most of these lightweight materials are more brittle and easily fractured than traditional steel. Distribution and history of stress triaxiality and equivalent strain in the thin-walled tubes under axial crushing have been analyzed in this article with finite element simulation, as these two parameters of stress and strain states are commonly used for constructing fracture locus of materials. It is observed that both stress triaxiality and equivalent strain are transferring along the tube length like waves. Analysis results show that fracture is more likely to take place on the edge than the other positions of square thin-walled tubes. For identical axial crushing stroke, there is little difference of stress and strain states inside the square thin-walled tubes with initial impact velocity varying from 6 m/s to 24 m/s. Influence of geometrical parameters on the stress and strain states have also been analyzed, including the shape of cross-section corner, the wall thickness and the shape of cross-section, respectively. Analysis results in this article may offer references for design of thin-walled tubes and the necessary experimental characterization of mechanical properties for lightweight materials.     

Experimental study and implementation of a novel internal foam spraying system for roadheaders

Foam technology utilizes the good coverage of foam to form a closed space around dust sources. The foam then wets the dust particles, causing them to adhere before they spread into the air, resulting in better dust control than with water sprays. In the process of foam dust control at a heading face, the foam spray trajectory is highly influenced by the wind, making it difficult to focus foam on the dust sources, which wastes the foam and reduces dust control efficiency. To resolve this problem, the idea of transporting foam to the cutting head through the roadheader’s inner pipeline is proposed. To adapt to the high resistance of foam delivery in the roadheader’s inner pipeline, according to the water and air supply of the heading face, a table water-jet suction device and porous spiral coupling foaming device were designed, and the working conditions were tested using a self-designed experiment system in the laboratory. The results showed that the foaming agent could be automatically added into the device at a working water flow rate of 1–1.6 m³/h at a ratio of 1%. The optimum air flow was 45–50 m³/h, in which range the foam expansion ratio reached the maximum and the outlet pressure demand was satisfied. Field application showed that the new foam method had a better dust control efficiencies than traditional foam methods.     

The impact of the exterior painted thin-layer render’s water vapour and liquid water permeability on the moisture state of the wall insulating system

The paper aims at the determination of the possible limits of vapour resistance and liquid water permeability alteration in the case of the exterior painted thin-layer render finish of the building walls from outside insulated with the mineral wool slabs when exploited in the area of cold and humid climate that could guarantee a normal moisture state of the wall insulating system. The moisture testing of the insulating system’s fragments was carried out in the climatic chamber, where the climatic parameters were modelled on the basis of the climatic typical of Lithuania. Thin-layer render was coated with acrylic paints. When the thickness of the paint coating on thin-layer render was increased from 0.08 mm to 0.24 mm, the liquid water absorption coefficient decreased by 59% and vapour resistance increased by 43%. It has also been determined that in the double-layer system paint coating – thin-layer render condensation moisture will be accumulated when the thickness of the air layer s_d equivalent to the material’s water vapour permeability is higher than 0.6 m. Rain will have an impact on the wall’s moisture state, when the liquid water absorption coefficient w of the double-layer system paint coating – thin-layer render is higher than 0.025 kg/(m² h^0.5). The micro-lens discovered in the areas of moisture accumulation by the thermographic analysis should be considered as the rudiments of the defect formation in the exterior insulating system.     

Composite tubes as an alternative to steel spirals for concrete members in bending and shear

Glass fibre-reinforced polymer (GFRP) tubes are compared to steel spiral reinforcement in circular concrete members with longitudinal reinforcement and prestressing, using six beam tests. Two 324 mm diameter and 4.2 m long prestressed specimens were tested in bending. Four 219 mm diameter reinforced specimens were also tested, including two 2.43 m long beams tested in bending and two 0.6 m long beams tested in shear. In each set, one specimen was essentially a concrete-filled GFRP tube, while the other control specimen included steel spiral reinforcement of comparable hoop stiffness to that of GFRP tube. The strength of control specimens was governed by crushing and spalling of concrete cover. Unlike spiral reinforcement, GFRP tubes confined larger concrete areas and also contributed as longitudinal reinforcement, leading to increases in flexural and shear strengths, up to 113% and 69%, respectively.