Hot Climate Regions Research Articles

Holistic Approach to Ecological Design Parameters of Building and Landscape Design on Outdoor Thermal Comfort in Hot, Humid Climate

In this study, academic staff residential buildings were studied as part of a university campus located in a hot and humid climate zone in Türkiye. Within the scope of the study, the energy efficient architectural and landscape design decisions of the buildings built in 1976 were examined. The aim was to determine the energy performance of buildings built about 50 years ago and to quantify the effect of changing landscape conditions on thermal comfort. In this aim, the outdoor thermal comfort level was determined by creating microclimate simulations for the hottest day and time of the year. Microclimatic analyses were performed with ENVI-met software and thermal comfort was evaluated with two metrics, average PMV and ASHRAE scale. The energy performance of the buildings was determined using ecological design parameters. An approach to global environmental problems is the use of ecological design principles, including architectural and landscape design principles. It is important to consider both architectural design criteria and landscape design criteria when discussing ecological design in the built environment. Architectural and landscape design decisions for hot and humid climate regions together increased energy efficiency by 51.1% to 75.5%. It was found that although the plant design improves energy performance in buildings by that range value, it improved outdoor thermal comfort by 15% to 22%. As a result, the study evaluated climate-balanced plant design with building energy performance in order to improve outdoor thermal comfort.

Создание комфортных условий эксплуатации выставочных комплексов в жарком климате

Purpose: To consider the possibility of using modern innovative coating materials, and in particular ETFE film, in the enclosure structures when designing public buildings in different natural and climatic conditions, with the example of regions with hot climates. Method: Generalization of design principles, including those for hot climates. Analysis of climatic parameters of hot climate regions which have a significant impact on comfortable conditions of people staying in public buildings, characterized by multifunctionality, large spatial dimensions, high occupancy rates, and other factor s. To show the possibility of providing favorable conditions for people staying in such buildings in different ways: through planning and design; improvement of adjacent areas; the location of the building. To carry out the analysis of domestic and foreign experience of application of means of sun protection of buildings. To develop space-planning and structural solutions of the exhibition complex. To evaluate the effectiveness of the proposed solution through a computational study. Results: The results of the research of a range of measures aimed at improving the conditions for comfortable stay of people in the exhibition complexes are presented. The constructive solution of sun protection of the exhibition complex taking into account physical and mechanical properties of the membrane system and climatic conditions of the construction areas has been proposed. Practical significance: The versatility of using dome structures as enclosures is demonstrated. The advantage of using innovative covering materials as an alternative to traditional materials is shown.

Urban microclimate and climate change impact on the thermal performance and ventilation of multi-family residential buildings

Urban settings and climate change both impact on energy use and thermal comfort inside buildings. This paper first presents a study of changes in energy demand in residential buildings considering the overlapping effect of climate change and urban heat island intensity in two European locations; Cadiz (Spain) and London (United Kingdom), representing temperate and hot European climates and moderate and dense urban settings. Future-urban weather files were generated and simulations were run considering energy demand and indoor thermal comfort. In hot climate regions such as the one of Cadiz, future climate will increase the cooling demand and the additional impact of the UHI leads to a further increase of up to +28% of total energy demand compared to the current climate without considering urban effects. Future-urban weather conditions will be detrimental also for buildings in London, where the annual energy demand is predicted to increase by up to the 16% if future climate and urban effects are included. This is due to a higher increase in cooling demand compared to the reduction for the heating need. The paper also presents a method to take into account microclimatic conditions in naturally ventilated buildings, especially the effect of wind variations around the building which impacts natural ventilation rates. Air and surface temperature and wind speeds were studied using ENVImet and the resulting microclimatic conditions were used as inputs to the EnergyPlus Airflow Network model for the calculation of the building ventilation rates. It was found that ventilation rates are reduced (in comparison to meteorological weather files) and this reduction impacts negatively on internal operative temperatures. A thermal comfort analysis was carried out indicating that the selection of a suitable weather file and microclimatic conditions is essential for more accurate predictions of internal thermal comfort and will assist in the sizing of passive and active systems to avoid overheating.

Using Cement as Filler to Enhance Asphalt Mixes Performance in Hot Climate Regions

This paper investigates the addition of different percentages of ordinary Portland cement as a filler in conventional asphalt concrete for a range of heavy traffic. Road pavement agencies in hot areas face the daunting challenge of preserving their pavements in a fair to good condition to increase their lifespan. This challenge is due to the high occurrence of permanent pavement deformation via rutting, which is one of the major distress factors influencing pavements. This is a particularly serious issue in hot and arid countries which are closely associated with various aggravating factors. These aggravating factors include the choice of bitumen binder viscosity, the type of bitumen, the available low-quality materials, and the high environmental temperatures. Ultimately, poor performance will show within the first few years of service as permanent deformations such as rutting, shoving, and depressions. The examined properties include the resilient modulus and the resistance to rutting. Findings indicate that the resistance to rutting and the rigidity of the asphalt concrete are both substantially increased as the cement content is increased. Moreover, to meet the heavy traffic spectrum requirements, increasing the embedded cement content in the asphalt concrete improves pavement structural capacity. Finally, based on the rigidity expected for different cement levels, design curves are provided for pavement design in hot climates using low quality aggregate materials.

Human tolerance to extreme heat: evidence from a desert climate population.

Ambient temperatures exceeding 40 °C are projected to become common in many temperate climatic zones due to global warming. Therefore, understanding the health effects of continuous exposure to high ambient temperatures on populations living in hot climatic regions can help identify the limits of human tolerance. We studied the relationship between ambient temperature and non-accidental mortality in the hot desert city of Mecca, Saudi Arabia, between 2006 and 2015. We used a distributed lag nonlinear model to estimate the mortality-temperature association over 25 days of lag. We determined the minimum mortality temperature (MMT) and the deaths that are attributable to heat and cold. We analyzed 37,178 non-accidental deaths reported in the ten-year study period among Mecca residents. The median average daily temperature was 32 °C (19-42 °C) during the same study period. We observed a U-shaped relationship between daily temperature and mortality with an MMT of 31.8 °C. The total temperature-attributable mortality of Mecca residents was 6.9% (-3.2; 14.8) without reaching statistical significance. However, extreme heat, higher than 38 °C, was significantly associated with increased risk of mortality. The lag structure effect of the temperature showed an immediate impact, followed by a decline in mortality over many days of heat. No effect of cold on mortality was observed. High ambient temperatures are projected to become future norms in temperate climates. Studying populations familiar with desert climates for generations with access to air-conditioning would inform on the mitigation measures to protect other populations from heat and on the limits of human tolerance to extreme temperatures. We studied the relationship between ambient temperature and all-cause mortality in the hot desert city of Mecca. We found that Mecca population is adapted to high temperatures, although there was a limit to tolerance to extreme heat. This implies that mitigation measures should be directed to accelerate individual adaptation to heat and societal reorganization.

Thermal performance of solar photovoltaic panel in hot climatic regions: Applicability and optimization analysis of PCM materials

A numerical modeling methodology based on the finite element method is utilized in this investigation to predict the impact of the PCM characteristics on the system cooling performance and the solar module output power. The thermal analysis considers the transient nature and the nonlinearity of the problem. The boundary conditions include the cyclic variation with time of solar irradiance and ambient temperature in a hot climatic region, with peak temperatures close to 50 °C. Under these circumstances and owing to the various influencing parameters, choosing an appropriate PCM is a challenging task. By allowing the PCM characteristics to vary continuously over the applicable domains and not just by giving specified discrete values, a systematic approach is adopted in this work. This technique is applied to explore the relationships between system input parameters, as defined by the PCM properties, and output variables, as described by cell temperature and module efficiency. Due to the harsh boundary conditions, the obtained results demonstrated that PCM with high thermal conductivity is required to achieve efficient thermal regulation. The enhanced material characteristics can only be provided by composite PCMs with graphite or metal additives. The resulting optimized design variables of the suitable PCM, melting temperature, thermal conductivity, and thickness, can reduce the cell temperature to 57 °C (20% reduction). The corresponding efficiency and power output are raised by around 8%. The power output was found to increase from 125 W (reference case) to 135 W for the optimized case. The results suggest that using a passive cooling system based on PCM is a viable method for enhancing the power output of a solar PV module. The created coupled model predicts the thermal behavior of the PV module and significantly facilitates the PCM selection procedure to ensure its applicability.

Multi-Objective Optimization of Ultra-Low Energy Housing in Hot Summer Cold Winter Climate Zone of China Based on a Probabilistic Behavioral Model

Occupant behavior has an important impact on building energy consumption, and the accuracy of an occupant behavior model directly affects the reliability of energy consumption simulation results. Ultra-low energy buildings are crucial to achieving building energy conservation and carbon dioxide reduction in China. In order to effectively promote the development of ultra-low energy buildings in Hot Summer and Cold Winter Climate Zones. where most residents adopt a “part-time, part-space” pattern of intermittent energy use behavior, and to solve the problem of poor indoor thermal environments and the high incremental cost of ultra-low energy, the study described in this paper takes Changsha as an example to carry out a multi-objective optimization study on ultra-low energy housing using a probabilistic behavioral model. On the basis of a probability model representing the residents’ actual behavior in Changsha, the optimization objective indicators, key variables and the technology benchmarks for ultra-low energy building were determined, then multi-objective optimization was carried out for a range of energy efficient technologies to obtain the Pareto optimal solutions. The results showed that the set of optimal solutions could reduce energy demand by 50.2 to 60.2% and reduce indoor thermal discomfort time by 3.52–11.09% compared with those of a reference base case, which just meets the requirements of the current design standard for energy efficient domestic buildings. An optimum solution for energy savings and indoor thermal comfort, along with economic costs, was identified, which can assist in decision-making by providing different preferences and provide useful reference for the design of ultra-low energy buildings in Hot Summer and Cold Winter Climate regions.

Detecting the Impact of Micro and Nano Size Additives on Deformation of Asphalt Concrete

Permanent deformation is considered as one of the major distress type of asphalt concrete pavement in the hot climate region. It can be controlled by the use of additives either for asphalt binder or for the asphalt concrete mixture. In the present assessment, the impact of micro and Nano size additives (fly ash and silica fumes) on the deformation behaviour of asphalt concrete mixtures was assessed. Such additives were implemented as partial substitute of mineral filler. Asphalt concrete slab samples were prepared in the laboratory with the aid of roller compaction. The optimum percentages of the additives are (2 and 4) % of silica fumes and coal fly ash respectively by the weight of the binder. Beam specimens were obtained from the slab samples and tested for fatigue life under three constant strain levels using four point bending beam technique. It was observed that for mixture treated with Nano additive (silica fumes), the reduction in the permanent deformation starts at 0.0001 MJ/m3 loss in energy for 750 microstrain level. However, for mixture treated with Micro size additive (fly ash), as the dissipated energy vanishes, the permanent deformation was in the range of (3 - 4.5) microstrain. It was concluded that as the dissipated energy vanishes, the permanent deformation was lower by (29.4 and 11.7) % for mixtures treated with silica fumes and fly ash additives respectively as compared with the control mixture.

The Effect of Solar Control Elements on Building Energy Consumption in Hot Dry Climate Regions The Case of Diyarbakır

The Effect of Solar Control Elements on Building Energy Consumption in Hot Dry Climate Regions The Case of Diyarbakır

Gas turbine suitable for the ambient conditions prevailing in Arab Gulf countries: A prognostic analysis

The present study conducted a prognostic analysis with the aim of understanding the problems associated with the operation of gas turbines in hot climatic regions like the Middle Eastern region. In addition to the hot and dry climatic condition, the region experiences frequent dust storms which can result in operational problems, shorter life span and very high maintenance costs, making air filtration a mandatory operation. Due to this condition and taking into consideration the high humidity of the coastline region, for better effective operation, longer useful life and reduced operating cost the gas turbines have to be located away from the coastline region. To get better power output from the gas turbines, the ambient air has to be cooled. Among the different options available for cooling, evaporative cooling system was found to be more suitable and cost effective for the region. Analyzing the performance of the gas turbine, it was found that adopting the cooling system will result in enhancing the output power up to 7.12%.

Projection of temperature extremes of Egypt using CMIP6 GCMs under multiple shared socioeconomic pathways.

Global warming has amplified the frequency of temperature extremes, especially in hot dry countries, which could have serious consequences for the natural and built environments. Egypt is one of the hot desert climate regions that are more susceptible to climate change and associated hazards. This study attempted to project the changes in temperature extremes for three Shared Socioeconomic Pathways (SSPs), namely, SSP1-2.6, SSP2-4.5, and SSP5-8.5 and two future periods (early future: 2020-2059 and late future: 2060-2099) by using daily maximum (Tmax) and minimum temperature (Tmin) of general circulation model (GCMs) of Coupled Model Inter-comparison Project phase 6 (CMIP6). The findings showed that most temperature extreme indices would increase especially by the end of the century. In the late future, the change in the mean Tmin (4.3°C) was projected to be higher than the mean Tmax (3.7°C). Annual maximum Tmax, temperature above 95th percentile of Tmax, and the number of hot days above 40°C and 45°C were projected to increase in the range 3.0‒5.4°C, 1.5‒4.8°C, 20‒95days, and 10‒52days, respectively. In contrast, the annual minimum of Tmin, temperature below the 5th percentile, and the annual percentage of cold nights were projected to change in the range of 2.95‒5.0°C, 1.4‒3.6°C, and - 0.1‒0.1%, respectively. In all the cases, the lowest changes would be for SSP1-2.6 in the early period and the greatest changes for SSP5-8.5 in the late period. The study indicates that the country is likely to experience a rise in hot extremes and a decline in cold extremes. Therefore, Egypt should take long-term adaptation plans to build social resiliency to rising hot extremes.

Temperate with Maritime Climatic Regions: Hub of Technology and Production with Auspiciousness of Habita to Temperate & Maritime Climate Countries

Climatic elements affected extremely human activities, health, and structure of body & colour which may be negative or positive. In the gross, temperate maritime climatic regions are the main centre of technology, economy as well as famous for high quality industrial production and food processing commodities. Notwithstanding, equatorial, tropical, polar and subpolar regions lack technology, skills & industrial production as a consequence of climatic barriers. They live conflicted with nature or climatic barriers and expend time for food collection and other requirement elements. Otherwise, temperate & maritime climatic countries are extremely advanced at science, excellence skill, high quality industrial production, excellence infrastructure etc than equatorial, tropical and sub-polar countries. Although a lot of factors are responsible for development of a country or region such as racial group, availability of resources (mineral & fuel), large area, good location, leadership etc however climatic factors are extremely effective for the improvement of a region. A person can work harder in temperate climatic regions than extremely hot or cold climatic regions. Although, the climate is changeable with enhancement time or era. For instance, during the Pleistocene era Europe and North America were covered by glaciers and after a long time these glaciers melted with increasing time, utmost it converted suitable land for excellent comfortable climate and recently it is hub of technology, industrial commodities and economy. Ordinarily, ocean currents (warm & cold currents) influence rainfall, temperature, moisture in air, wind velocity and other climatic elements. As well as oceanic influence, it keeps balance between the range of temperature (diurnal and annual range) and humidity, and it can’t increase temperature during summer season. And it can’t decrease temperature during the winter season. The temperate climate with maritime climatic regions is extremely healthy and humans face less disease, and it has an appropriately mature brain and body structure. Even in this climatic zone flourished sufficiently fishing, cattle, various farming, ecosystem and others. Further, men’s thinking power increased, numerous major and minor industries including agriculture base industries improved extensively throughout the temperate with maritime climatic zone. All major and advanced racial groups (British, Spanish, Central Asian, French, German, Turkish, Japanese etc) originated and developed in this predominantly suitable and appropriate climate. Although, several suitable climatic regions converted into uncomfortable climatic regions. For instance, northern Africa, especially Egypt and the Middle-East, especially Iran, were extremely suitable habitats as Western Europe and Northeast USA. However, it is converted into deserts for climate change. Ordinarily, temperate with maritime climatic regions are the greatest suitable & perfect place in the world and all of fisheries, agriculture, infrastructure, softwood forest, soft grass lands, cattle, poultry farming etc exhibited spectacularly to temperate with maritime climate regions or countries with predominantly favourable climatic conditions. These peoples are many times more creative & skilled than equatorial, tropical, polar and subpolar peoples. Henceforward, temperate with maritime climatic regions are divided into two categories based on suitability, comfortability and perfectibility. These categories are given below- Major Regions: A). Western Europe a) Entire United Kingdom b) Entire Germany c) Entire France d) Entire Spain e) Entire Portugal f) Entire Belgium g) Entire Netherland h) Entire Denmark i) Entire Switzerland j) Entire Austria k) south-western Norway l) Southern Sweden m) Northern part of Italy B) Middle-eastern North America a) North-eastern USA b) South-eastern Canada C) Central Asia a) Entire Kazakhstan b) Entire Uzbekistan c) Entire Kyrgyzstan d) Entire Turkmenistan e) Entire Tajikistan f) Several part of northern Iran D) Eastern Asia a) North-eastern China b) Entire Japan c) south-eastern Russia d) Entire North Korea e) Entire South Korea E) South-eastern Oceania a) south-eastern Australia b) Entire New Zealand Minor regions: A) Remaining Europe (Included western part of Russia) B) Middle part of North America a) Remaining USA b) Southern Canada c) Northern Mexico d) Entire Cuba C) Southern South America a) Southern Argentina b) Southern Chile D) Middle part of Asia a) Northern, western and eastern China b) Southern Russia E) Northern Africa a) Northern Morocco b) Northern Algeria c) Entire Tunisia d) Northern Libya e) Northern & eastern Egypt F) Western Asia a) Entire Turkey b) Entire Syria c) middle-western Iran G) Southern Africa a) Entire South Africa b) Southern Namibia c) Southern Botswana H) Southern and western Australia

Lifetime of forage grasses submitted to different water regimes using survival analysis

Forage plants are considered one of the main factors for livestock development, for they present perennial growth, resistance to drought, adaptation to hot climate regions, and wide soil diversity. The water deficit causes changes in their anatomy, physiology, and biochemistry, which can affect all stages of development and productivity. For these reasons, it is necessary to evaluate the lifetime of forage plants under water stress conditions. The design used was a factorial scheme, consisting of two types of grasses, and five levels of water replacement, with ten replications. During the experimental period, grasses were evaluated daily, with more than 70% of leaf area in senescence being considered a dead plant the one with more than 70% of leaf area in senescence. Urochloa mosambicensis lifetime was of 61 days for grasses that were not irrigated, 131 and 195 days for those that received 25% and 50% of field capacity, and greater than 240 days for those that were irrigated with 75 and 100% of field capacity. Digitaria pentzii lifetime was of 54 days for grasses that were not irrigated, 117 and 152 days for those that received 25 and 50% of field capacity, and greater than 240 days for those that were subjected to water regime 75 and 100% of field capacity. Irrigation with 25 and 50% of field capacity doubles and triplicates, respectively, the lifetime of grasses when compared to plants that did not receive irrigation. Irrigations with 75% or more of field capacity do not promote grass mortality.

Impact of high temperature on PV productivity in hot desert climates

Hot dry climate regions enjoy high solar irradiation, albeit with high ambient temperatures. These two factors have a contradictory effect on the power generated from PV systems. This work studies the combined effect of high ambient temperature and high irradiation on the net performance of PV systems. The study is based on monitoring a grid-connected 5 kW PV system installed on the rooftop of the Energy Research Center of the University of Khartoum, Sudan. The performance was monitored by meteorological and power measurement equipment from April 2017 to March 2018. The results showed stable power output from the PV system with an average final yield of 4.57 kWh/kWp and a 0.21 standard deviation from this average value. The stability in power output is due to the compensation of the efficiency degradation due to high temperature by high irradiation in summer. This is combined with the relatively low irradiation in winter compensated by the low temperature effect in winter. The annual deviation of the temperature and irradiation is small in Khartoum due to its proximity to the equator. The semi desert climate, offers Khartoum notably few annual cloudy hours. These characteristics were compared with the annual performance of other countries with different climates. The conclusion from this work on hot dry regions is that despite the negative effect of temperature, the annual output power from the system tends to be stable due to the substitution contributed by the regionally high radiation and the relatively cool winter climate.

Modelling and analysis of a renewable energy-driven climate-controlled sustainable greenhouse for hot and arid climates

Population growth and improved living standards led to increased demand for food and crops, of which cultivation is heavily affected by average ambient temperature increase resulting from global warming. Hot and arid climate regions with high average summer temperatures suffer further as agricultural greenhouse indoor temperature reaches levels much higher than the ambient, causing severe dehydration and eventual death of crops. This research proposes an innovative, resilient and sustainable integrated greenhouse system to control greenhouse indoor climate within the cultivation range. This system consists of concentrating photovoltaic thermal system utilizing nucleate boiling heat transfer, thermal energy storage based on phase change material, lithium bromide absorption cooling system and dehumidifier, borehole ground heat exchanger, and spectrum selective roof for a greenhouse. The system is driven by renewable energy sources: Solar irradiation, ambient air, and geothermal cooling to provide electricity, space cooling, air-conditioning, and irrigation water. A comprehensive thermodynamic analysis of the sustainable integrated greenhouse system was done to obtain the energy and exergy efficiencies of the subsystems and overall system. The analysis shows overall energy and exergy efficiencies of 43.36 % and 19.19 %, respectively. Compared to the conventional greenhouse roof, the spectrum selective roof efficiently reduced the maximum cooling load by 29.2 %. Under the investigated hot and arid climate conditions, the system produced 33.28 kW of cooling, 29.3 kW of electricity, 8.36 L/h of dehumidified irrigation water, and 250 m3/h of dry ventilation air. An economic analysis based on the life cycle cost was executed to determine the economic feasibility of the integrated system. The recorded levelized cost of cooling, electricity, and water are 0.021 USD/kWhc, 0.0366 USD/kWhele, and 8.8 USD/m3, respectively, presenting a cost-competitive standalone integrated system.

Energy Retrofitting Assessment of Public Building Envelopes in China’s Hot Summer and Cold Winter Climate Region

The retrofitting of existing public buildings to save energy and reduce carbon emissions is a priority for China’s building sector. Accordingly, the Chinese government requires all public buildings to be energy retrofitted based on the Design Standard for Energy Efficiency of Public Buildings GB50189-2015. However, few studies have been conducted to assess the energy efficiency of this design standard in the hot summer and cold winter (HSCW) climate region of China. The aim of this study was therefore to provide sensitivity analysis for the thermal properties of the envelope of a typical public building energy retrofit in China’s HSCW climate region. The results show that the thermal performance of the existing envelope of the sample building was very poor, with heating and cooling energy consumption 18.94% higher than the GB90189-2015 baseline model. It was found that better optimized parameters could reduce the heating and cooling energy load by 28.26% compared with the parameters of the sample building. The findings from this study provide valuable references for local governments and practitioners eager to improve the energy efficiency of existing public buildings in China’s HSCW region.

Effects of cashew nutshell ash on the thermal and sustainability properties of cement concrete

The present study valorizes cashew nutshell ash (CNA) and uses it at 5–20 wt. % of cement for concrete production. The concrete grades of 25–40 MPa were used as mix design proportions. The thermal and mechanical properties of the concrete samples were determined on day 28 of curing. Regression models were used to predict the thermophysical properties of the concrete specimens. Also, the concrete's sustainability was estimated via the inventory of carbon and energy (ICE). The results revealed that CNA enhanced the thermal insulating characteristics of the concrete produced. Maximum compressive strength was obtained at 15 wt. % of CNA content, while the developed models yielded high precision. Compared with the control concrete, the sustainability index decreased as CNA content in the mix increased, indicating that incorporating CNA in concrete production improves the sustainability of such concrete. Therefore, the outcome of this work can be beneficial, especially in hot or arid climate regions, and at the same time, achieve a cleaner environment.

Experimental investigations on thermal performance of spray cooling double skin façade in hot humid climate region

Thermal performance of the spray cooling double skin façade in hot and humid climate region are experimentally investigated in this study. Two identical double skin facades are constructed for the comparative analysis. Thermal performance of the spray cooling double skin façade is evaluated by the indicators of cavity air temperature, glass surface temperature, the U-value, and solar heat gain coefficient. The influences of the ventilation mode (open conditions of the top and bottom vents in the double skin façade system), operation time (spray and interval time of the spray system), and spray direction on the cooling effect of the spray cooling double skin façade are experimentally compared and analyzed, and the operation mode of the spray cooling double skin façade with the best thermal performance is obtained. The results demonstrate that the appropriate operation mode of the spray cooling double skin façade is that the top and bottom vents are opened, and the spray direction is from up to down with the operation time of 10/15 min (spray/interval time). The average temperature of the cavity and inner glass decreased by 8.1 °C and 3.7 °C, respectively. The mean U-value and SHGC of the spray cooling double skin façade are 2.13 W/(m2·K) and 0.25, respectively, which are smaller than the most stringent limit values of the current national standard. The spray cooling double skin façade has good thermal performance in hot humid climate region in China.

Characterization and rheological properties of asphalt binder with a novel tall oil-based boron additive to enhance asphalt performance

Many researchers have recently turned to making studies based on asphalt modification by adding polymeric type additives to different rheological properties to asphalt. However, because of the cost of these additives, requiring special mixing plants and causing environmental pollution, it is necessary to increase the asphalt coating performance by producing low-cost additives equivalent to the additives in the market and environmentally friendly additives. In this study, a new additive not previously described in the literature was produced in the laboratory by chemically synthesizing tall oil, a by-product of the paper manufacturing, with boron oxide. FTIR, TG/DTG and SEM analyses were used to determine the microstructural characteristics of the produced modifier. FTIR analysis showed that a chemical synthesis had occured. While TG/DTG analysis determined the thermal structure characterization, the SEM analysis showed that the new modifier was distributed homogeneously the asphalt matrix. The rheological properties of the modified asphalts were investigated by conducting penetration, softening point, ductility, flash point test, rotational viscosity (RV), Dynamic Shear Rheometer (DSR), Bending Beam Rheometer (BBR) tests. The experimental results showed that the workability of the asphalt binder increased while the temperature sensitivity decreased. In addition, the rutting and fatigue resistance of the asphalt binder increased, but the low temperature performance was badly affected after a certain additive ratio. As a result, it appears that this new additive may be better suited to hot climate regions. Finally, it is thought that this new tall oil based boron additive (TOBO) obtained in the laboratory will be important for road pavement construction because it is easy to produce and environmentally friendly.

Aggregate Gradation Variation on the Properties of Asphalt Mixtures

National highway projects present a crucial role in economic growth, as they have a great influence on the national income. Therefore, the decision makers plan to construct these projects at a rapid rate. To achieve the just aforesaid, the utilization of asphalt of adequate quality and gradation is essential. The key problem which lies in recent decades is that many types of asphalt mixtures are rejected and reconstructed in the site due to the gradation variation of aggregates in the asphalt mixture which waste raw materials, cost and time. Thus, this research seeks to assess the possibility of accepting asphalt mixes with aggregates gradation variation (within the range from +4% above the upper specification limit to −2% below the lower specification limit). A wearing surface mix with gradation 3B was prepared according to the Egyptian code. The gradation variation was presented as the aggregate gradation is out of the specification limits during Hot Mix Asphalt (HMA) production. The aggregate gradations lie above and below the upper and lower specification limits, respectively, by ±2%, ±4% and ±6%. The design gradation of the control mix was included as a reference case. The different mix properties were measured using the Marshall Mix design method. Then, the performance of HMA mixes was evaluated under the effects of high temperature and water cycles through applying wheel loading tracking and Indirect Tensile Strength (ITS) tests. The results show that the 3B mixes with a gradation within a range of +4% to −2% of the upper and lower specification limits recorded the lowest rutting depth and the highest water damage resistance in hot regions compared to ordinary asphalt mixes. In summary, the new aggregate gradation limits will provide a reference for the design of asphalt mixture in hot climate regions.