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Phosphorites (PF) have small particle sizes and interesting chemical compositions to be used as filler in asphalt mixtures. The present study assessed the performance that a hot-mix asphalt (HMA) displays when the natural filler (NF) is completely replaced by PF. X-ray diffractometry (XRD), X-ray fluorescence (XRF), and scanning electron microscope (SEM) tests were carried out on NF and PF particles. Asphalt mastic was manufactured using a weight ratio of filler (NF and PF) to asphalt binder of 1∶1.2. Penetration, softening point, viscosity, and linear amplitude sweep test were performed on the asphalt mastic. The following tests were carried out on mixes manufactured with NF (control) and PF (HMA-PF): Marshall, indirect tensile strength, Cantabro, resilient modulus, permanent deformation, and fatigue under stress-controlled mode. Additionally, moisture damage resistance was assessed through the tensile strength ratio (TSR) parameter. The HMA-PF mix displayed a better performance in all the evaluated properties, without increasing the optimum asphalt binder content. PF as fillers could be an interesting alternative in the manufacture of HMA mixtures subjected to high temperature climates. [ABSTRACT FROM AUTHOR]

The optimum asphalt content (OAC) in a hot-mix asphalt (HMA) is an important parameter that affects pavement performance and durability. To obtain it, it is essential to consider variables associated with the action of the climate and the rate of load application. The traditional way of obtaining the OAC through the Marshall test does not consider these variables. Additionally, this test is more appropriate to evaluate the performance of HMAs in high-temperature climates (mainly to evaluate rutting resistance) and does not consider the types of distresses that predominate in temperate and/or cold climates (e.g., fatigue cracking). This study analyzed the influence of asphalt binder content on the performance of an HMA by performing indirect tensile strength (ITS) and resilient modulus (RM) tests, considering temperatures of 10, 20, and 40 ºC, with load application rates of 10, 30 and 50 mm/min for the ITS test, and loading frequencies of 2.5, 5.0 and 10.0 Hz for the RM test. From the ITS test, the peak load (P), the slope at the inflection point (m), the stiffness (St), and the work of fracture (Wf) were obtained. The performance of the HMA based on these parameters was evaluated and an OAC was defined and compared with that obtained traditionally by the Marshall test. Additionally, these values were compared with the results obtained from resilient modulus (RM) tests. A mathematical correlation between the ITS and RM tests was reported. Temperature, speed of load application in the ITS test, and frequency of load in the RM test affected the performance of the HMA. P, ITS, St, Wf, and RM increased when temperature decreased and loading speed or frequency increased. The opposite was true for parameter m. For the HMA evaluated in the present study, the results show that the OAC obtained from ITS and RM tests is 0.5% higher than that obtained from the Marshall test. In other words, HMA design methods should include ITS and RM tests to help reduce susceptibility to cracking in temperate climates and rutting in high-temperature climates. It's suggested to conduct similar studies using different aggregates, asphalts, and gradations. • The effect of asphalt binder content, temperature, and loading rate on an HMA was studied by ITS and RM tests. • The fracture properties of an HMA were evaluated in the ITS test. • The OAC obtained from the Marshall test differs from the ITS and RM tests. • There is a mathematical correlation between the results of the ITS and RM tests. • For temperate climates, the design of HMAs is recommended by performing Marshall, ITS, and RM tests together. [ABSTRACT FROM AUTHOR]

Introduction. This study shows statistical information regarding COVID-19 in Colombia up to this date (March 1-2022). Specifically, the daily, monthly and cumulative evolution of infections and deaths, correlated with the distribution of the population according to age and gender. Objective. Show statistical information about COVID-19 that allows help to plan and design, in future Pandemics, public health policy strategies in Colombia. Methods. Daily information since the official declaration of Pandemic in Colombia (March 16 - 2020) was obtained by the National Health Institute (INS) and was organized in a database in order to conduct respective analysis. This information was compared to similar studies obtained based on the bibliographical review. Results and Conclusions. Results and conclusions are similar to those found in the reference literature: most part of those dead by COVID-19 are of senior age and male gender. Regarding Case Fatality Rate (CFR), it notoriously increases with age. The most vulnerable population displays an average age of = 52.8 years. The less vulnerable population are young persons under 30 years of age, but specifically, those within the age range of 10 and 20 years. Gompertz and Logistic models can mathematically simulate the evolution of deaths and the evolution of CFR according to age. [ABSTRACT FROM AUTHOR]

Introduction: This article shows an analysis of the evolution up until date (May 4-2021), of official coronavirus cases statistics (CC) and the total number of deaths (TND) due to SARS-CoV-2 in Colombia. Additionally, said information is shown in correlation to other variables such as Case Fatality Rate (CFR), age range of persons, their typical reported co-morbidities and the cities where there has been highest concentration of cases. Materials and Methods: From March 16 2020 until today, information regarding the daily number of new confirmed cases (DNC) and daily confirmed deaths (DD) was registered in a database with the purpose of estimating the evolution of CC, TND and CFR. The age of deceased was also registered, as well as their gender, prior co-morbidities and city of death. The evolution of TND with the time of other countries were compared to that of Colombia. A mathematical equation that represents the epidemiological curve of TND evolution of different countries across time was defined. Results: In Colombia, the average age of people who die due to COVID-19 is of 69.5±14.7 years (median and mode of 71 and 80 years, respectively), and the virus is less lethal amongst a population under the age of 40. The greater part of deaths have taken place in people with prior co-morbidities and of the male gender. Conclusion: Most of the persons that have deceased are those of senior age, mainly with prior co-morbidities, and predominantly of male gender. Epidemiological peaks of COVID-19 are consistent with the rainy and winter seasons, and with the traditional epidemiological peaks of flu or influenza. [ABSTRACT FROM AUTHOR]

The COVID-19 pandemic precipitated a unique period of social isolation, presenting an unprecedented opportunity to scrutinize the influence of human activities on urban air quality. This study employs ARIMA models to explore the impact of COVID-19 isolation measures on the PM10 and PM2.5 concentrations in a high-altitude Latin American megacity (Bogota, Colombia). Three isolation scenarios were examined: strict (5 months), sectorized (1 months), and flexible (2 months). Our findings indicate that strict isolation measures exert a more pronounced effect on the short-term simulated concentrations of PM10 and PM2.5 (PM10: −47.3%; PM2.5: −54%) compared to the long-term effects (PM10: −29.4%; PM2.5: −28.3%). The ARIMA models suggest that strict isolation measures tend to diminish the persistence of the PM10 and PM2.5 concentrations over time, both in the short and long term. In the short term, strict isolation measures appear to augment the variation in the PM10 and PM2.5 concentrations, with a more substantial increase observed for PM2.5. Conversely, in the long term, these measures seem to reduce the variations in the PM concentrations, indicating a more stable behavior that is less susceptible to abrupt peaks. The differences in the reduction in the PM10 and PM2.5 concentrations between the strict and flexible isolation scenarios were 23.8% and 12.8%, respectively. This research provides valuable insights into the potential for strategic isolation measures to improve the air quality in urban environments. [ABSTRACT FROM AUTHOR]

The generation and management of industrial solid waste is considered an environmental problem worldwide. Reason why, several studies have focused on the implementation of Construction and Demolition Waste (RCD) for pavement layers, focusing mainly on the use of Concrete Recycled Aggregates (RCA). The objective of this study was to determine the impact of the implementation of the RCA in hot asphalt mixture on its physical-mechanical properties, under three scenarios: i) replacement of the coarse fraction, ii) fine and iii) 100% of the aggregate granulometry conventional (AC). The monotonic load resistance of the mixtures (Marshall and Indirect Traction - IT tests) and the wear resistance Cántabro were evaluated. The substitution of the fine fraction of AC by RCA significantly reduces the resistance under monotonic load of the control mixture. When replacing the coarse fraction, the design criteria of the control asphalt mixture are met and the IT is increased, but it is necessary to slightly increase the asphalt content. By replacing all the aggregates with RCA, a satisfactory behavior was obtained in the face of the action of monotonic charges, but it is also necessary to significantly increase the asphalt content. An increase in RCA in the mixture increases the loss from Cántabro wear. [ABSTRACT FROM AUTHOR]

The behavior of the asphalt mixture is mainly attributed to the performance of the asphalt mastic. Several studies have been performed to evaluate the behavior of mastics made with different fillers. Most researchers have added the filler by mass within the bitumen; however, this comparison may be more appropriate by volume. An experimental program was designed to evaluate the behavior of mastics produced with five different fillers (natural limestone, LS; hydrated lime, HL; Portland cement, PC; Linz-Donawitz steel slag, LDSS; and blast furnace slag, BFS), and were dosed by mass and volume. Penetration, softening point, viscosity, multiple stress creep and recovery test, and linear amplitude sweep test were performed. Results showed that analyzed asphalt mastic properties depend on dosage type performed and test type. Furthermore, HL, PC, BFS and LDSS mastics showed better performance compared to control LS mastic. [ABSTRACT FROM AUTHOR]

Significant amounts of blast furnace slag (BFS) are generated daily as by-product from iron and steel industries. This waste material usually has interesting physical properties and mineralogical and chemical composition, which can be useful as granular aggregate in the production of hot mix asphalt (HMA). In this study, an experimental program was designed to evaluate the effect on the resistance of a HMA due to the replacement (in mass and volume) of the coarse fraction of a natural aggregate (type limestone; LS) by a BFS. Total aggregate replacement was also evaluated. The mechanical properties were evaluated by carrying out the following tests: Marshall stability, indirect tensile strength (ITS), Cantabro abrasion, resilient modulus, permanent deformation, and fatigue resistance. Water sensitivity or moisture damage was evaluated by determining the ratio of indirect tensile strength (TSR) in wet and dry conditions. X-ray diffractometry (XRD), X-ray fluorescence (XRF) tests, and imaging processing in a scanning electron microscope (SEM) were carried out on particles of LS and BFS. The results revealed a remarkable enhancement in the properties of the HMA mixture when the coarse fraction of the LS was replaced in volume by BFS. When such a replacement was made in mass, the adhesive properties of the asphalt-aggregate system worsened. Total replacement of the LS led to unsatisfactory mechanical behavior. [ABSTRACT FROM AUTHOR]

Large quantities of water are consumed during the washing of granular aggregates in laboratory tests. In this study, the volume of water used when is designed a hot mix asphalt - HMA was estimated. Besides, the effect of washing the aggregate in different quantities of mass and with two levels of water speed flow was evaluated. An analysis of variance (ANOVA) was performed to verify if the results obtained are significant or statically equal. As a general conclusion, it is reported that water consumption decreases significantly when larger amounts of material are washed at the same time and used to wash the particles, lower flow rates. [ABSTRACT FROM AUTHOR]

In the manufacture of asphalt mixtures, large quantities of natural stone aggregates are consumed, which has a negative impact on the environment. These aggregates can be partially or totally replaced by others that are disposed of in dumps and produced by steel companies, such as blast furnace slag (BFS) and steel (SS). These last two materials have chemical and physical properties that make them suitable for use in multiple applications such as road construction, maintenance and rehabilitation. The article presents a review of the state of knowledge of the use of BFS and SS in the production of asphalt mixtures, describes and defines both materials, presents the environmental problems, their toxicological risk of use, their chemical and physical properties, the advantages and limitations of use and the way they have been studied to be used as stone aggregates of asphalt mixtures. Based on the bibliographic review, the authors at the end of the article present some recommendations to continue the studies tending to substitute natural stone aggregates with BFS and SS in the manufacture of asphalt mixtures. [ABSTRACT FROM AUTHOR]

A relatively recent development in asphalt pavement technology, warm mix asphalt (WMA) offers a number of benefits. We present a comparison of some mechanical properties of warm mix asphalt (WMA) made in an asphalt plant batch with a traditional Hot Mix Asphalt (HMA). WMA mixture was made with asphalt cement CA 60-70 and a chemical additive that foams the asphalt at 80 °C. WAM was mixed and compacted at 120 °C and 110 °C, respectively. The control mixture (HMA) was a Dense Graded Mixture MDC-19 proposed by [1], was made with the same materials and mixed and compacted at 150 and 140 °C. Mechanical properties were evaluated under two loading modes: monotonic load (Marshall and indirect tensile test) and dynamic loads (resilient modulus, permanent deformation and fatigue). Results showed that mechanical properties of Warm Mixed Asphalts are better than control mixture. [ABSTRACT FROM AUTHOR]

One of the main forms of distress in asphalt mixtures is the moisture damage. This phenomenon occurs mainly when the asphalt binder is separated from the stone aggregate due to water presence. Many studies have been performed to describe and measure the moisture damage resistance in asphalt mixtures. Despite the high number of research projects performed, this phenomenon has not been fully understood yet. A laboratory study was initiated to investigate the influence of the asphalt binder on moisture damage, due to the effect of water only. Physical (softening point - ASTM D36, viscosity - ASTM D-2171, AASHTO T-316 and penetration - ASTM D-5), chemical (SARA - ASTM D-4124) and rheological (AASHTO T 315-05) properties of two asphalt binders (AC 60-70 and AC 80-100) immersed in water during 12 to 17 months were evaluated. Mechanical characteristics of a porous asphalt mixture immersed in water, and manufactured with asphalt binders also immersed in water were evaluated using Marshall (AASHTO T 245-97, 04) and Cantabro (NLT 352/86) tests. As concluding remark is reported that the interface asphalt binder-aggregate stone is affected for the change in the consistency that undergo the asphalt cements in presence of the water. Additionally, binders in presence of water undergo, inside the mixture, contraction, which may be one of the causes generating the stripping phenomenon. [ABSTRACT FROM AUTHOR]

A relatively recent development in asphalt pavement technology, warm mix asphalt (WMA) offers a number of benefits. Although its most important advantage is environmental in nature, it also shows technical and economic benefits. This paper presents and discusses results for the laboratory evaluation of a WMA, which were compared to traditional hot mix asphalts (HMA). Two samples of WMA and two samples of HMA with nominal maximum aggregate sizes of 10 mm and 19.0 mm were evaluated. A liquid chemical solution was used to make WMA (Patent pending for this additive). The purpose of this additive was to induce foaming of the asphalt binder AC 60-70 (PG 58-22). Moisture susceptibility and strength under monotonic and dynamic loading were studied. In addition, a set of tests were performed: Marshall, resilient modulus, permanent deformation and indirect tensile strength. The research led to the conclusion that the WMA chemical additive decreases mix temperatures by 30° C, which in turn, translates into better workability and volumetric composition. Furthermore, the WMA showed higher levels of resistance to both moisture damage and high service temperatures under monotonic and dynamic loading. [ABSTRACT FROM AUTHOR]

In tropical countries, roads built with asphalt layers must be made with bituminous mixtures containing asphalt that is reasonably stiff to increase resistance against permanent deformations, i.e., rutting. When the available asphalt is not stiff enough, an alternative is to modify it using Gilsonite. This article presents the laboratory results of tests performed on samples of Gilsonite-modified hot mix asphalts modified by wet and dry processes. Gilsonite increases the stiffness and improves the performance grade of a virgin binder at high temperatures of service. Additionally, Gilsonite-modified hot mix asphalts developed a greater strength and stiffness under monotonic and dynamic loading. [ABSTRACT FROM AUTHOR]

Population growth has led to the intensification of average daily traffic (ADT), highlighting vehicles as one of the major sources of heavy metal (HM) pollution in cities. The objective of this paper is to conduct a spatial analysis of the HM pollution associated with road-deposited sediments (RDSs), based on the ADT observed in the main roads of a Latin American megacity (Bogotá, Colombia). The following risk indices were considered: Geoaccumulation Index (Igeo), Integrated Pollution Index (IPI), Ecological Risk Index (ERI), Comprehensive Potential Ecological Risk Index (CERI), Hazard Index (HI), and Carcinogenic Risk Index (CRI). The findings confirm that a size fraction < 250 μm is the most suitable for studying the risk of HMs in the RDS from the indices considered. The best HMs indicative of the relationship with ADT are Ni, Cu, and Pb. The Pb is the HM of most attention, and Cr gains positions for its toxicity level during the evaluation of ecological, non-carcinogenic, and carcinogenic risks, respectively. Finally, the linear regression models developed between ADT and each of the risk indices considered have a better fit (R2 > 0.910) compared to the linear regression models developed between ADT and HM concentrations (R2 > 0.322). [ABSTRACT FROM AUTHOR]

Two grades of paving asphalt, AC 80-100 and AC 60-70, were studied to determine changes in their physical and chemical properties caused by exposure to water. This experimental study’s primary hypothesis is that the interaction between the water oxygen molecules and asphalt, known as oxidation, changes the asphalt properties, resulting in increased damage from mechanisms such as humidity and aging for mixtures in service. The chemical responses of both asphalts were measured, and the flow activation energy concept was used to understand the resulting changes in the physical and rheological properties after immersion in distilled water for one year. [ABSTRACT FROM AUTHOR]

High urbanization and a consequent change in land cover can lead to a deterioration in air quality and generate impacts on public health. The objective of this paper is to provide a multitemporal analysis of the influence of particulate matter ≤ 10 μm (PM10) on human mortality from the land cover variation in a Latin American megacity. Six monitoring stations (monitoring daily PM10 concentration, increases in daily mortality (IDM), and land cover) were established throughout the megacity. The results suggest that for every 10% increase in vegetation cover, the daily PM10 concentration and IDM decreases by 7.5 μg/m3 and 0.34%, respectively. Moreover, it is evident that the monitoring station with the lowest vegetation cover (8.96 times) shows an increase of 1.56 times and 4.8 times in the daily PM10 concentration and IDM, respectively, compared with the monitoring station with the highest vegetation cover (46.7%). It is also suggested that for each increase of 100 inhabitants/hectare in population density, the daily PM10 concentration and IDM increases by 9.99 µg/m3 and 0.45%, respectively. Finally, the population densification of the megacity possibly implies a loss of vegetation cover and contributes to the increase in PM10 and IDM. [ABSTRACT FROM AUTHOR]

This article studies the relationship between atmospheric condition (AC) and human mortality rate associated with coarse particulate matter (PM10) in a high-altitude mega-city (Bogotá-Colombia). Information was collected from three automatic monitoring stations equipped with measuring instruments for PM10, temperature, solar radiation and wind speed. The sampling period lasted six years. The results showed the best possible scenario for the maximum hourly concentrations of PM10 (52.3-135 µg/m3). These events occurred during daytime periods where the predominant AC was between unstable and very unstable. The risk from exposure to PM10 showed that February>March>January were the highest risks. These months showed PM10 concentrations 35.9% higher than those observed during the months of lower risk (August>June>July). A higher mortality rate (+2.0%) was suggested in urban sectors with less atmospheric instability (AI) and predominance of impervious cover compared to sectors with higher AI and predominance of vegetated cover. [ABSTRACT FROM AUTHOR]

An experimental program was devised to evaluate the effect on the resistance of a hot mix asphalt, due to the total replacement of a natural aggregate (limestone — LS) by a recycled concrete aggregate (RCA). Two asphalt binders were used: conventional AC 50-70 (penetration grade) and AC 50-70 modified with crumb rubber (CRM). The mechanical properties investigated were the stability and flow ratio (Marshall test), indirect tensile strength, resistance to abrasion (Cantabro test), resilient modulus, resistance to permanent deformation, to fatigue and to moisture damage (modified Lottman test). When the LS is completely replaced by RCA, the resistance under monotonic loading, moisture damage and permanent deformation improved, the mass loss in the Cantabro test and the resilient modulus shows appropriate values, however, the fatigue resistance decreases. Besides, mixtures with RCA using CRM binder showed lower fatigue life under stress controlled tests, but much better rutting resistance. [ABSTRACT FROM AUTHOR]

In recent years, there has been a significant increase in construction projects in the city of Barranquilla, leading to contamination in soils and water sources due to the inadequate generation and disposal of Construction and Demolition Waste (CDW). It is clear that this is not a local problem alone but that it involves trends present at a global level, which have led several countries to design measures for an adequate management of waste generated on building sites. Some examples of this adequate management are: reincorporation of CDW in construction processes, reuse or use of CDW as raw materials, processing of CDW to be converted into mineral aggregates for concrete and asphalt and the use of CDW as mineral fillers. In this work we present results of a study carried out in 75 construction sites located at different areas of the city of Barranquilla. We have carried out a detailed survey to assess the management, treatment and final disposal procedures, thus leading to a clear identification of relevant issues to deal with in this field, as well as improvements in the knowledge in the local legislation for the management of CDW. Based on the results obtained here, we have identified that the CDW management practices that the construction guild is currently carrying out are not adequate to solve these problems and that a more practical and long term solution needs to include a proposal to improve the management model (involving use and transformation) and its posterior implementation in the city of Barranquilla. [ABSTRACT FROM AUTHOR]

• HMA containing several contents of RCA from different sources were studied. • Results showed that the mixes with RCA exhibited a similar behavior to that of conventional HMA. • HMA mix-design with coarse RCA fraction satisfied the requirements of national specifications. • Performance of mixes with RCA was found to be highly dependent on the source and dosage of RCA. The waste generated by the construction industry generally has an undesired negative impact on both human and animal life as well as the environment. Among these wastes, recycled concrete aggregate (RCA), due to its good residual physical, mechanical, mineralogical, and chemical properties, has attracted promising potential for re-use and incorporation in the construction of new infrastructural elements. These infrastructure applications include construction of sidewalks, curb and gutters, subbase/base layers, and/or as a partial replacement of natural aggregates (NA) in the production of hot mix asphalt (HMA) mixtures. In this laboratory study, experimental research work was conducted to evaluate the influence of RCA on the mechanical properties and performance of RCA modified HMA mixtures against a control HMA mixture without any RCA. RCAs were obtained from two different concrete sources, namely: (a) one from the demolition of a building (RCAB), and (b) another one from the rehabilitation of a Portland cement concrete pavement (RCAP). Both NA and RCA were characterized taking into account physical and mechanical properties. HMA mixtures were produced using the Marshall mix-design method by replacing 0.0% (control), 15%, 30%, and 45%, respectively, of the coarse NA fraction with RCA. Thereafter, laboratory testing (i.e., Scanning Electron Microscopy [SEM], resilient modulus, indirect tensile strength, etc.) including material property characterization and performance evaluation were conducted on HMA samples. Overall, the laboratory test results showed that the RCA modified mixtures exhibited a similar behavior to conventional HMA mixtures, but with greater environmental benefits and potential cost savings through the recycling and reuse of waste concrete aggregates. However, it was observed that the laboratory performance of RCA modified mixtures is strongly dependent on the RCA source and dosage, with RCAP exhibiting superior performance over RCAB. HMA mixtures produced with RCA provided higher optimum asphalt-binder content (OAC) than that of mixes with NA. [ABSTRACT FROM AUTHOR]