International Journal of Sustainable Built Environment最新文献

The increase outdoor temperature acts directly on the indoor climate of buildings. In Cameroon, the energy consumption demand in the buildings sector has been rapidly increasing in recent years; so well that energy supply does not always satisfy demand. Thermal insulation technology can be one of the leading methods for reducing energy consumption in these new buildings. However, choosing the thickness of the insulation material often causes high insulation costs. In the present study, the optimum insulation thickness, energy saving and payback period were calculated for buildings in Yaoundé and Garoua cities, located in two climatic regions in Cameroon. The economic model including the cost of insulation material and the present value of energy consumption and the cost over a life time of 22 years of the building, were used to find the optimum insulation thickness, energy saving, and payback period. Materials that extruded polystyrene were chosen and used for two typical wall structures (concrete block (HCB) and compressed stabilized earth block wall (CSEB)). The early cooling transmission loads, according to wall orientations and percentage of radiation blocked were calculated using the explicit finite-difference method under steady periodic conditions. As a result, it was found that the west- and east-facing walls are the least favourite in the cooling season, whereas the south and north orientations are the most economical. Although wall orientation had a significant effect on the optimum insulation thickness, it had a more significant effect on energy savings. In equatorial region (Yaoundé), for south orientation, the optimum insulation thickness was 0.08 m for an energy savings of 51.69 $/m2. Meanwhile, in tropical region (Garoua), for north orientation, the optimum insulation thickness was 0.11 m for an energy savings of 97.82 $/m2.

Ground granulated blast-furnace slag (designated as GGBS) has been utilized as building material due to the environmental, economic and technical benefits. In this study, the possibility of improving compressive strength of high-volume GGBS (HVS) paste before and after being exposed to elevated temperatures using metakaolin (MK) in micro-size (mMK) has been investigated. Portland cement (PC) has been partially substituted with GGBS at level of 70%, by weight, to produce HVS paste. Afterword, GGBS was partially substituted with mMK at levels ranging from 2% to 10% with an increment of 2%, by weight. After curing, the specimens were subjected to elevated temperatures ranging from 400 °C to 1000 °C with an interval of 200 °C for 2 h. Weight and compressive strength before and after being exposed to elevated temperatures have been thoroughly explored. The various decomposition phases formed were identified using X-ray diffraction (XRD) and thermogravimetric (TGA) analyses. The morphology of the formed hydrates was studied using scanning electron microscopy (SEM). The results showed that the compressive strength before and after being exposed to elevated temperatures increased with increasing mMK content. For all mixtures, the residual compressive strength at 400 °C reached its maximum peak value.

Improving the mechanical properties of lightweight concrete using waste material is the goal of this work to get both structural and environmental advantage besides cost saving. Porcelanite aggregate was used as lightweight aggregate. First plastic bottles were cut into slices and used as fibers with these percentages: 0.0%, 0.5%, 0.75%, 1.0%, 1.25% and 1.5% by volume. The results of tests under compression and tensile stress showed that mix 1% plastic fiber (PF) gave the best results when compared to reference mix without PF. Eggshell (rich with CaO) and glass wastes (rich of silca) were crashed and powdered to desired size and used as partial replacement of cement with these percentage: 0%, 5%, 10%, 15% and 20%. Compressive strength, flexural strength, density, absorption and modulus of elasticity were tested. Comparison was made with reference mix (without waste powder) to figure the efficiency of using these waste in lightweight Porcelanite concrete. The results of tests showed that mixes with 1% PF and 5% eggshell powder (ESP) gave results so close to reference mix. Using more than 5% ESP made no improvement in lightweight concrete, while the mix with 1% PF with any glass powder (GP) percentages used in this research gave good improvement in the tested properties especially at 20% GP.

Customer involvement in infrastructure maintenance activities is a complex process due to various decision-making parameters surrounding maintenance. Compared to manufacturing and other disciplines where QFD is widely used, expectations of the infrastructure user as a customer are truly dynamic given the changing economic conditions, technologies, environmental regulations, etc. While such dynamic or changing customer expectations can be addressed by repeated surveys and constant communication, having indicators to predict customer response would be a valuable tool and aid the QFD decision-making process. In this study, a framework that utilizes hidden Markov model (HMM) is proposed for evaluating customer expectation by using probabilities of focus areas that are of interest to the infrastructure user as hidden parameters. The focus areas are based on sustainability parameters and include economic, social, technological, maintenance efficiency, safety and environmental conditions. Probabilities that represent the probability of transition from current state (of the focus area) to next possible state were generated based on expert opinion of the authors. Using the 2005 customer survey by California Transportation, a case study is presented in order to demonstrate the application which concludes that the proposed methodology can be successfully implemented for infrastructure maintenance.

Fez is the most ancient of the imperial cities of Morocco. In Fez the rate of population growth has been spectacular in recent times (484,300 inhabitants in 1982 and 1,129,768 in 2014). The accelerated rate of population growth has generated a large urban sprawl in all its forms and serious environmental problems. In this research, we have analyzed the relationship between urbanization and land use changes and their impact on cityscape in Fez and the importance of the increase in impervious surface areas. Satellite imageries and census data have been used to identify different patterns of land use change and growth of the city for the period 1984–2013. Classification and analysis of the satellite imageries were performed using Erdas imagine and ArcGIS Software. Urban sprawl in Fez was assessed over 29 years (1984–2013). The overall accuracy of land cover change maps, generated from post-classification change detection methods and evaluated using several approaches, ranged from 78% to 87%. The maps showed that between 1984 and 2013 the amount of urban or developed land increased by about 121%, while rural cover by agriculture and forest decreased respectively by 11% and 3%.

In recent years, rainfall induced ‘urban storm water-logging’ (USWL) events are experiencing in Chittagong city like other urbanized parts of Bangladesh. To mitigate this there is an urgent need to predict the USWL beforehand and a numerical model could help. Thus, this paper aimed to use a hydrological model i.e. HEC-HMS through field survey during 2013–2014 and a questionnaire survey. With the support of secondary data source viz. daily newspaper, intensive questionnaire survey and field visits identified 13 most vulnerable USWL locations and based on these a USWL depth–duration–frequency curve was developed. This showed during water logging (i.e. May–July), the depth of logged water rises 0.3–1.27 m causing adjacent dwellers sufferings upto 13 times per year and the inundation period is up to 48 h. Using these, HEC-HMS model was setup and the correlation obtained with the field measurement as R² values 0.83 and 0.77 during calibration and verification period respectively. Once a real time hydrological dataset is available, the validated model supposed to provide useful information in the decision support system.

This paper aims at investigating the effect of crumb rubber size and content on hardened characteristics of self-compacting concrete. To this end, different self-compacting concrete mixtures were designed at constant water-to-binder ratio of 0.35 and 520 kg/m³ of binder content. The class F fly ash was replaced with cement as 30% by weight. Six designated crumb rubber contents of 5%, 10%, 15%, 20%, and 25% and three different sized crumb rubbers (No. 18, No. 5, and mixed crumb rubber) were considered as experimental parameters. According to the obtained results, the use of crumb rubber had a negative effect on the hardened properties of self-compacting concretes and the significant improvement was achieved with addition of all tire wastes types, for ductility.