Assesment of clay bricks compressive strength using quantitative values of colour components

This study was conducted to assess the relationships among firing temperature, colour components and compressive strength of bricks. Lightness (L*) and chromaticity (a* and b*) of 10 replicated brick samples fired at temperatures 700–1050 °C in steps of 25 °C under free access of air, were measured with a colorimeter, which uses an L* a* b* colour space. Increasing firing temperature significantly increased the compressive strength of bricks. The values of L* slightly increased with firing temperature up to around 800 °C then decreased as temperature increased further. The values of b* and a* increased with increasing firing temperature up to around 900 °C then rapidly decreased with further increases in firing temperature. A negative relationship occurred between each of L*, a*, and b* and compressive strength. Compressive strength was adequately described by colour components of L* and b* by linear regression equations (R² = 0.87 for L*, and R² = 77 for b*). However, the relationship occurred between a* and compressive strength was quite poor. It was concluded that the numerical values of colour components of L* and b* may be used to predict and judge the compressive strength of bricks. However, the method can not be generalized before its calibrated with different raw materials under different firing conditions.     

Evaluation of the mechanical properties of Brazilian lumber (Goupia glabra) by nondestructive techniques

The purpose of this work was to ascertain the accuracy of the ultrasonic and transverse vibration techniques in comparison with the values obtained from static tests on structural lumber, thereby contributing to the body of knowledge about nondestructive testing of timber. The experimental methodology involved studies on pieces of structural dimensions of the species Goupia glabra, a Brazilian hardwood, which were classified mechanically using the nondestructive ultrasonic and transverse vibration techniques to determine the dynamic modulus of elasticity (E_d). Concomitantly to the nondestructive tests, static bending tests were conducted to determine the static modulus of elasticity (MOE) and compare it with the values of dynamic modulus of elasticity. The values of the coefficient of determination for the ultrasonic technique (R² = 0.88) and for the transverse vibration technique (R² = 0.88) obtained for the species G. glabra were significant, demonstrating that the ultrasonic and transverse vibration techniques are important tools for the nondestructive inference of the modulus of elasticity of timber.     

Rutting evaluation of hydrated lime and SBS modified asphalt mixtures for laboratory and field compacted samples

The purpose of this study is to evaluate permanent deformation for hydrated lime and SBS modified asphalt mixtures. Control (C), 2% hydrated lime (2L), 5% SBS polymer mixtures and 2%hydrated lime–5%SBS (2L5SBS) mixtures were prepared. The Laboratoire Central des Ponts et Chaussées (LCPC) wheel tracker, also known as French Rutting Tester were realized with two different stages. Same LCPC slabs were produced. Original LCPC compactors and also field cylinder were used separately. LCPC rutting values were determined with left and right wheel loadings. Also averages were obtained with calculation. Repeated creep tests were used for these mixtures and permanent deformations were plotted for two different moisture conditioning that water immersion and freeze and thaw cycles. Diameter samples (100 mm and 150 mm) were studied in repeated creep tests. In the result that LCPC tracking values were compared with repeated creep tests in terms of sample diameters. LCPC wheel-tracking test results show that 2L5SBS mixtures reveal utmost performance according to the other mixtures types. Polymer modification increased rutting resistance of lime modified ones. Both original LCPC compactor and field cylinder compaction showed resemble results. 150 mm samples showed highest correlation (higher than R² = 0.80) between LCPC test and repeated creep test for different compaction types and different moisture conditionings.     

Improved parameterization of dust emission (PM10) fluxes by the gradient method using the Naiman tower data at the Horqin desert in China

Dust emission/deposition flux has been estimated using the gradient method with the two-level (3 and 15 m high) measured PM₁₀ concentrations and the sonic anemometer measured momentum and kinematic heat fluxes at 8 m high from a 20-m monitoring tower located at Naiman (Horqin desert) in the Asian dust source region in China for the winter of November 2007 to March 2008. The time series of measured PM₁₀ concentration at 3 m high is used to identify the dust event and the non-dust event periods. It is found that the dust emission/deposition flux (F_C) shows a significant diurnal variation with the maximum emission flux of 5.8 kg km^? 2 h^? 1 at noon and the minimum of ? 1.6 kg km^? 2 h^? 1 in the afternoon for the non-dust event cases. Whereas for the dust event cases, the dust emission flux is found to occur when the prevailing winds are westerlies to northerlies with the maximum flux of 1275 kg km^? 2 d^? 1, while the maximum dust deposition flux of 148 kg km^? 2 d^? 1 occurs with the prevailing winds of southerlies to easterlies without any diurnal variation. The optimal regression equation between F_C and the friction velocity (u_*) for the dust emission cases is found to be F_C = 9.55 u_*^3.13 with the R² value of 0.73. However, this regression equation can be improved by taking into account the convective velocity (w_*). The resulting optimal regression equation is found to be F_C = 9.3(u_* ? 0.1w_*)^3.19 for the stable stratification (w_* < 0) with the R² value of 0.77 and F_C = 10.5(u_* + 0.34w_*)^4.11 for the unstable stratification (w_* > 0) with the R² value of 0.78, suggesting the importance of the convective velocity on the dust emission flux.     

The effect of fuel area size on behavior of fires in a reduced-scale single-track railway tunnel

A set of experiments was carried out in a 1/9 reduced-scale single-track railway tunnel to investigate the effect of fuel area size on the temperature distribution and behavior of fires in a tunnel with natural ventilation. Methanol pool fires with four different fuel areas 0.6 × 0.3 m² (1 pan), 1.2 × 0.3 m² (2 pans), 2.4 × 0.3 m² (4 pans) and 3.6 × 0.3 m² (6 pans), were used in these experiments. Data were collected on temperatures, radiative heat flux and mass loss rates. The temperature distribution and smoke layer in the tunnel, along with overflow dimensions and radiant heat at the tunnel entrance were analyzed. The results show that as the fuel area enlarges, the fire gradually becomes ventilation-controlled and the ceiling temperature over the center of fire source declines. Burning at the central region of fire source is depressed due to lack of oxygen. This makes the temperature distribution along the tunnel ceiling change from a typical inverted V-shape to an M-shape. As observed in the experiments, a jet flame appeared at tunnel entrances and both the size and temperature of the flame increased with the enlargement of fuel area leading to a great threat to firefighters and evacuees in actual tunnel fires.     

Investigating alien plant invasion in urban riparian forests in a hot and semi-arid region

In this paper, we examined twelve riparian forests along urban–rural gradients in Austin, TX (USA), on the relationship among watershed urbanization and the invasion of alien woody species. We assessed the degree of biological invasion by measuring relative alien cover (RAC) of the riparian forests. We also measured environmental variables (15 in total) that characterize the study forests, including impervious surface percentage of corresponding watersheds, stream hydrology of adjacent streams, species diversity, canopy gap percentage, and soil nutrient contents of the riparian forests. Stream hydrology was quantified by the transfer function model. The results indicate that impervious surface percentage was related to stream hydrology: the more the impervious surface in a watershed, the faster streamflow recedes after the storm, and the longer dry period the riparian forest experienced (R² = 0.722). Impervious surface percentage was also related to RAC (R² = 0.498). Nonmetric multidimensional scaling (NMDS) grouped the 15 environmental variables into five dimensions. Multiple regression analysis of RAC on the five NMDS dimensions shows that RAC was related only to the dimension related to hydrological drought. Based on these results, we concluded that watershed urbanization facilitates the invasion of alien species in riparian forests by causing hydrologic drought, particularly in hot and semi-arid regions.     

Numerical simulation of air ventilation in super-large underground developments

Recent advancements in engineering technology have enabled the construction of super-large underground engineering projects in China. Currently, the ventilation requirements and standards of normal-size underground spaces are used for super-large underground excavating engineering projects in China. For example, the minimum air velocity of 0.15 m/s is the standard velocity for normal-size underground spaces; however, this value is also used as the required air velocity for diluting underground contaminants in super-large underground developments. This paper aims to examine the minimum ventilation requirements for super-large underground developments (S > 100 m²). A three-dimensional computational domain representing a full-scale underground space has been developed. The pertinent parameters such as dust concentration, smoke density, oxygen concentration and air temperature have been simulated. The results show that at some specific underground conditions, the ventilation air velocity of 0.15 m/s is sufficient to control the dust level, provide required oxygen concentration and maintain the air temperature at acceptable levels during development; however, it is not sufficient to bring the CO concentration below an acceptable safe limit. This must be considered by the ventilation system designers of super-large underground developments.     

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.     

An empirical radon emanation model for residential premises

Based on an averaging technique, a methodology has been established to estimate an effective radon emanation factor M for residential premises. The model shows that the new term M and the ventilation rate are the essential parameters in estimating the level of indoor radon. M includes two components: the radon emanation rates of internal surface materials and the ratio of surface areas of applicable materials to premises volume. The value of M can be determined from on-site measurements. Different ventilation modes of a sampled residential unit during daytime and nighttime, with air conditioner on, window-open, and window-closed were included in site measurements. Each ventilation mode was measured twice during daytime and twice at night. During the investigation, air exchange rate, and indoor and outdoor radon levels were monitored simultaneously. The results of measurements were then used to verify the model. The value of M was found to be 31.7 Bq m⁻³ h⁻¹. The model is valid if the air exchange rate is larger than 0.2 h⁻¹.     

Year round performance and potential of a natural circulation type of solar water heater in India

The system consists of a flat-plate collector and a storage tank. Flat-plate collector is made of galvanised steel tube and aluminium plate, with MAXORB selective surface, encased in a mild steel tray with top single glass cover, bottom has been provided with glass wool insulation. It is kept facing equator and at λ+15° tilt (λ latitude of the place).The double walled storage tank is of 100 l capacity. The inner drum is made of 18 gauge galvanised steel and outer of mild steel. Space (100 mm) between them is filled with glass wool insulation.Performance and testing of solar water heater has been carried out extensively. It has been found that the heater can provide 100 l of hot water at an average temperature of 60.6 °C at 16:00 h when tap water temperature was 23.6 °C, it can retain hot water till next day morning at an average temperature of 51.6 °C. The overall efficiency of the heater is 57%.Based on performance at Jodhpur, a model has been developed by using ambient temperature and solar radiation for the prediction of its performance at various Indian stations. The predicted performance at various Indian stations revealed that hot water is required at most places for domestic use only during winter season and it can provide 100 l of hot water at an average temperature of 50–70 °C that can be retained to 40–60 °C till next day morning use.     

Flammability limits of iso-butanol/iso-octane/n-heptane blends

A set of experiments was carried out to determine the flammability limits (FL) of blends of iso-butanol and a surrogate fuel for gasoline at 154±11 °C and ≈91.4 kPa. The surrogate gasoline was a binary PRF mixture of 87% iso-octane and 13% n-heptane (PRF 87). The volumetric fraction of iso-butanol in the liquid fuel was varied from 0 to 0.25 at a step of 0.05. Flammability tests with pure fuels were also performed to confirm the reliability of the applied experimental procedure. The homogeneous air/fuel mixtures were defined as flammable when formed a self-sustained flame able to travel upward a 0.3 m long open combustion tube. The lower FL of the blends of iso-butanol and PRF 87 (0.80−0.98%) were estimated correctly with the mixing rule of Le Chatelier, but the same simplified model failed to reproduce the measured upper flammability limits (5.10−5.61%).     

Monitoring the energy-use effects of cool roofs on California commercial buildings

Solar-reflective roofs stay cooler in the sun than solar-absorptive roofs. Such “cool” roofs achieve lower surface temperatures that reduce heat conduction into the building and the building's cooling load. We monitored the effects of cool roofs on energy use and environmental parameters in six California buildings at three different sites: a retail store in Sacramento; an elementary school in San Marcos (near San Diego); and a four-building cold storage facility in Reedley (near Fresno). The latter included a cold storage building, a conditioning and fruit-palletizing area, a conditioned packing area, and two unconditioned packing areas.Results showed that installing a cool roof reduced the daily peak roof surface temperature of each building by 33–42 K. In the retail store building in Sacramento, for the monitored period of 8 August–30 September 2002, the estimated savings in average air conditioning energy use was about 72 Wh/m²/day (52%). On hot days when the afternoon temperature exceeded 38 °C, the measured savings in average peak demand for peak hours (noon–5 p.m.) was about 10 W/m² of conditioned area. In the school building in San Marcos, for the monitored period of 8 July–20 August 2002, the estimated savings in average air conditioning energy use was about 42–48 Wh/m²/day (17–18%). On hot days, when the afternoon temperature exceeded 32 °C, the measured savings in average peak demand for hours 10 a.m.–4 p.m. was about 5 W/m² of conditioned area. In the cold storage facility in Reedley, for the monitored period of 11 July–14 September 2002, and 11 July–18 August 2003, the estimated savings in average chiller energy use was about 57–81 Wh/m²/day (3–4%). On hot days when the afternoon temperature exceeded 38 °C, the measured savings in average peak-period demand (average cooling-power demand during peak demand hours, typically noon–6 p.m.) was about 5–6 W/m² of conditioned area.Using the measured data and calibrated simulations, we estimated savings for similar buildings installing cool roofs in retrofit applications for all 16 California climate zones. For similar retail stores in climate zones 2 and 4–16, installing a cool roof can save about 6–15 kWh/m²/year of conditioned area. In climate zones 2–16, estimates of average peak demand savings for hours noon–5 p.m. range from 2.9 to 5.8 W/m². For similar school buildings in climate zones 2–16, installing a cool roof can save from 3 to 6 kWh/m²/year of conditioned roof area. For all 16 climate zones estimates of average peak demand savings for hours noon–5 p.m. range from 2.6 to 3.8 W/m². In similar cold storage buildings in all 16 climate zones, installing a cool roof can save about 4.5–7.4 kWh/m²/year of conditioned roof area. In all 16 climate zones, estimates of average peak demand savings for hours noon–5 p.m. range from 3.9 to 6.6 W/m².     

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.     

Modelling the cleaning performance of rotating brush in duct cleaning

The bristle of a rotating duct cleaning brush was modelled using large deformation elastic theory. In addition to contact and centrifugal forces, especially the effect of air drag was studied in the article. The dependence of the drag coefficient on air speed was simulated for numerical computations by fitting a fourth degree polynomial in logarithmic co-ordinates on point-wise data for a cylindrical body from literature.The results show that the effect of air drag on the deflection of the single bristle (L=1 mm, d=1 mm, ρ_b=1140 m³/kg, EI=2 GPa) is negligible at normal rotating speeds of the brush (300−1000 rpm). However, air drag may affect considerably the deflection of a bristle, which has a large diameter and low density. As to be expected, air drag decreases the contact force between the single bristle tip and duct surface even at low rotation speed of bristle (<50 rpm). Thicker or stiffer bristle decreases the deflection of the rotating bristle and increases the magnitude of the contact normal force between the bristle tip and the duct surface. The model presented combined with the Mathcad software seems to be a useful tool in the cleaning brush design work.     

Numerical study of heat transfer by laminar and turbulent natural convection in tall cavities of façade elements

Laminar and turbulent natural convection flow in a two-dimensional tall rectangular cavity heated from the vertical side has been investigated numerically for aspect ratios of 20, 40 and 80. The finite volume method was used to solve the conservation equations of mass, momentum and energy for Rayleigh numbers from 10² to 10⁸, the flow was considered either laminar or turbulent. For turbulent flow, four different turbulence models κ−ɛ were compared along with their experimental results for a cavity with an aspect ratio of 30, it was found that the better approach was with the one reported by Ince and Launder turbulent model [N. Ince, B. Launder, On the computation of buoyancy-driven turbulent flows in rectangular enclosures, Int. J. Heat Fluid Flow 10 (1989) 110–117]. The average Nusselt numbers as a function of Rayleigh numbers for the aspect ratios range of 20–80 were calculated and compared with five convective Nusselt number correlations reported from the literature. Convective Nusselt number correlations for laminar flow in the range of 10² ≤ Ra ≤ 10⁶ and for turbulent flow in the range of 10⁴ ≤ Ra ≤ 10⁸ were presented. This study will help to have more accurate heat transfer parameters for applications such as façade elements, insulating units, double-skin façades, etc.     

Thermal analysis for a double glazing unit with and without a solar control film (SnS–CuxS) for using in hot climates

In this paper the thermal analysis by natural convection of a double glazing unit (DGU) is presented. One of the sheet glasses may or may not have a solar control film (SnS–Cu_xS) on its surface. Solar radiation falls on the outside surface of the DGU at 32 °C, the opposite sheet glass interacts with the inside environment at 24 °C. The governing equations of mass, momentum and energy of the air enclosed between the two sheet glasses are solved, as well as the heat conduction equation for both sheet glasses. The effect of varying the separation distance between the glasses (1.0 ≤ b (cm) ≤ 10.0) and the incident solar radiation is analyzed (500.0 ≤ G (W/m²) ≤ 800.0). From the results, it was found that in order to reduce heat gains towards the inside environment, the optimal separation distance between the sheet glasses was b ≥ 6.0 cm. It was also observed that, the use of a solar control film in this type of system (double glazing unit) is highly recommended; due to energy gain was reduced by 55% compared to the traditional DGU without solar control film.     

Properties of Portland cement-modified asphalt binder using Superpave tests

This study investigates the effect of cement additive on some properties of asphalt binder using Superpave testing methods. Six cement-to-asphalt (C/A) ratios were considered in the study: 0.05, 0.10, 0.15, 0.20, 0.25 and 0.30 by volume of asphalt binder. The experimental tests that were conducted in the study included the Superpave rotational viscosity (RV) test and the dynamic shear rheometer (DSR) test. The RV test was conducted at the Superpave-specified high temperature of 135 °C that represents the average mixing and laydown temperature, and at seven different rotational speeds of 5, 10, 20, 30, 50, 60, and 100 rpm. On the other hand, the DSR test was conducted at four test temperatures of 58, 64, 70, and 76 °C; one lower and two higher than the Superpave high performance grade (PG) temperature of the asphalt binder used in the study (PG 64). The loading frequency used in the DSR test was 10 rad/s (1.59 Hz) as specified by the Superpave system. Results of the study showed that the addition of Portland cement to asphalt binders increased the rotational viscosity (RV) of asphalt binders at 135 °C and different rotational speeds. The C/A ratio of 0.15 was found to be the optimum ratio that achieved a balanced increase in the rotational viscosity and the value of the DSR G^*/sin δ rutting parameter of asphalt binders. The C/A ratio had insignificant effects on the Newtonian behavior, the phase angle (δ), and the elastic behavior of asphalt binders. The increase in C/A ratio increased the stiffness of asphalt binders represented by the complex shear modulus (G^*) value. The increase in the C/A ratio improved the rutting parameter, G^*/sin δ value, at all temperatures. The increase in C/A ratio improved the Superpave high PG temperature (the high temperature at which the asphalt binder passed the Superpave criteria for G^*/sin δ value). It was also shown that the best function that described the relationship between each of RV, G^*, and G^*/sin δ and the C/A ratio was the exponential function with high coefficient of determination (R²).     

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.     

Study of a floor supply air conditioning system using granular phase change material to augment building mass thermal storage—Heat response in small scale experiments

We have proposed a new floor supply air conditioning system, using phase change material to augment building mass thermal storage. A scale model was constructed for such a system. Granules containing phase change material (PCM), with a phase change temperature of about 20 °C, were made from foamed glass beads and paraffin waxes. Results from measurements simulating an air conditioning schedule in office buildings indicate that 89% of daily cooling load could be stored each night in a system that used a 30 mm thick packed bed of the granular PCM.