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A recently used material that shows environmental and technical advantages for use as an asphalt binder modifier is biochar (BC). Different biomasses can be converted into BC by pyrolysis. One agro-industrial biomass that is abundant in copious quantities is oil palm mesocarp fiber (OPMF) obtained from African palm cultivation. In the present study, the use of a BC obtained from OPMF (BC-OPMF) as a modifier of asphalt binder (AC type) to produce a hot mix asphalt (HMA) was evaluated. This type of BC has not been investigated or reported in the reference literature as a binder and/or asphalt mix modifier. Initially, AC was modified with BC in three ratios (BC/AC = 5, 10, and 15%, with respect to mass) to perform penetration, softening point, and rotational viscosity tests; rheological characterization at high and intermediate temperatures; and scanning electron microscope (SEM) visualization. Based on this experimental phase, BC/AC = 10% was chosen to manufacture the modified HMA. Resistance parameters under monotonic loading (stability—S, flow—F, S/F ratio of the Marshall test, and indirect tensile strength in dry—ITSD and wet—ITSC conditions) and cyclic loading (resilient modulus, permanent deformation, and fatigue resistance under stress-controlled conditions) were evaluated on the control HMA (AC unmodified) and the modified HMA. Additionally, the tensile strength ratio (TSR) was calculated to evaluate the resistance to moisture damage. Abrasion and raveling resistance were evaluated by performing Cantabro tests. BC-OPMF is shown to be a sustainable and promising material for modifying asphalt binders for those seeking to increase stiffness and rutting resistance in high-temperature climates, resistance to moisture damage, raveling, and fatigue without increasing the optimum asphalt binder content (OAC), changing the volumetric composition of the HMA or increasing the manufacturing and construction temperatures.

A correlation between economic development and road freight is demonstrated in the literature review provided in this paper. This relationship was studied in relation to the global gross domestic product (GDP) of the countries under review. Therefore, this paper presents the validation of this correlation in the Colombian case, based not only on global GDP, but also on the GDP for each of the main economic sectors of the country. The correlation was analyzed using several of the following statistical methods: correlation using the non-parametric method (Spearman), the causality relationship using the Granger test, the relationship between variables using Principal Component Analysis (PCA), and multivariate correlation to establish the level of significance of each economic sector by means of the p-value. The study concludes that the best correlation is between the GDP of some economic sectors and the amount of freight transported one year later.

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.

The phenomenon of the oxidation and aging of asphalt binders affects the strength and durability of asphalt mixtures in pavements. Several studies are trying to improve the resistance to this phenomenon by modifying the properties of the binders with nano-particles. One material that shows promise in this field is zinc oxide (ZnO), especially in improving ultraviolet (UV) aging resistance. Few studies have evaluated the effect of these nano-particles on the thermo-oxidative resistance of asphalt binders, and, on hot-mix asphalt (HMA), studies are even more scarce and limited. Therefore, in the present study, the resistance to thermo-oxidative aging of an HMA manufactured with an asphalt binder modified with ZnO was evaluated. An asphalt cement (AC 60–70) was initially modified with 0, 1, 3, 5, 7.5, and 10% ZnO (percentage by weight of asphalt binder; ZnO/AC in wt%), and then exposed to aging in Rolling Thin-Film Oven tests (RTFOT) and a Pressure Aging Vessel (PAV). Penetration, viscosity, and softening point tests were performed on these binders, and aging indices were calculated and evaluated. Samples of HMAs were then manufactured using these binders and designed by the Marshall method, determining the optimum asphalt binder content (OAC) and the optimum ZnO/AC ratio. Control (unmodified) and modified HMA were subjected to short-term oven aging (STOA) and long-term oven aging (LTOA) procedures. Marshall, Indirect Tensile Strength (ITS), and resilient modulus (RM) tests were performed on these mixtures. LTOA/STOA results of the parameters measured in these tests were used as aging indices. In this study, ZnO was shown to increase the thermo-oxidative aging resistance of the asphalt binder and HMA. It also contributed to an increase in the resistance under monotonic loading in the Marshall and ITS tests, and under repeated loading in RM test. Likewise, it contributed to a slightly increasing resistance to moisture damage. The best performance is achieved using ZnO/AC = 5 wt%.

Large quantities of natural aggregates (NA) are required in the manufacturing of asphalt mixtures for pavements. The extraction of NA generates high environmental impacts that negatively affect environmental preservation and conservation. Diverse alternative materials obtained in construction and demolition processes in civil construction worked have been studies as possible replacements for NA, with the purpose of reducing these environmental impacts. The foregoing study presents a state of knowledge review referring to the use of recycled concrete aggregates (RCA) when these are used in the manufacturing of asphalt mixtures (mainly hot-mix asphalt HMA type). Environmental aspects are presented, as well as possible benefits and limitations of using RCA as replacements for NA in asphalt mixtures. However, it is not possible to establish a behavior pattern, since the characteristics of the RCA are very heterogeneous and vary from the original source of the concrete. It is highlighted from the literature that RCA has a wide potential for use in the manufacture of asphalt mixtures, since in most studies, the mixtures with these materials comply the quality requirements contemplated by the construction specifications, mainly in low-volume roads. Additionally, based on the literature review, some recommendations and suggestions are presented for future research.

The objective of this paper is to use autoregressive, integrated, and moving average (ARIMA) and transfer function ARIMA (TFARIMA) models to analyze the behavior of the main water quality parameters in the initial components of a drinking water supply system (DWSS) of a megacity (Bogota, Colombia). The DWSS considered in this study consisted of the following components: a river, a reservoir, and a drinking water treatment plant (WTP). Water quality information was collected daily and over a period of 8 years. A comparative analysis was made between the components of the DWSS based on the structure of the ARIMA and TFARIMA models developed. The results show that the best water quality indicators are the following: turbidity > color > total iron. Increasing the time window of the ARIMA analysis (daily/weekly/monthly) suggests an increase in the magnitude of the AR term for each DWSS component (WTP > river > reservoir). This trend suggests that the turbidity behavior in the WTP is more influenced by past observations compared to the turbidity behavior in the river and reservoir, respectively. Smoothing of the data series (moving average) as the time window of the ARIMA analysis increases leads to a greater sensitivity of the model for outlier detection. TFARIMA models suggest that there is no significant influence of past river turbidity events on turbidity in the reservoir, and of reservoir turbidity on turbidity at the WTP outlet. Turbidity outlier events between the river and reservoir occur mainly in a single observation (additive outliers), and between the reservoir and WTP also have a permanent effect over time (level shift outliers). The AR term of the models is useful for studying the transfer of effects between DWSS components, and the MA term is useful for studying the influence of external factors on water quality in each DWSS component.

The regions with the best economy have a greater capacity to develop low-income or social-impact housing, thus contributing to the reduction of poverty and, therefore, to the fulfillment of Sustainable Development Goals. This is observed in fewer people living in extreme poverty and with fewer unmet basic needs. This present article analyzes the correlation between the development in the main economic sectors in different regions (departments) of Colombia and the supply of low-income housing. Nevertheless, the most remarkable relation that was found was between the economic development of the regions (GDP) and the supply of non-social housing (more expensive commercial value) (Spearman’s Rho: 0.9). This means that there is an imbalance between regional economic capacity and the low-income housing supply because the regions with higher economic potential should have a less demanding population, that is, people living in poverty. These correlations are better when they go hand in hand with activities that are mostly developed in an urban environment, such as manufacturing, construction, real estate, and finance and insurance. On the contrary, these correlations are worse with industries such as mining and agriculture that mostly operate in rural areas. The analysis between low-income housing and economic sectors’ GDP yields low correlations, but these are worse for rural industries. Also, the investigation shows a positive change in the correlations’ trend for the year 2021, the beginning of the post-pandemic economic recovery.

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).

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.

It is generally assumed that there is a statistically valid correlation between the length of a roadway network, in addition to other factors such as its classification and/or average travel speed, and economic indicators such as Gross Domestic Product (GDP) and the Municipal Relative Weight (MRW), considering that the roadway network and transport development generate economic development in a region. This study reports the results of correlating several variables which are economic indicators of roadway networks, both at a municipal and a departmental level, in Colombia; it was concluded that at the level of municipalities, there is no valid correlation between MRW, as a dependent variable, and the average travel speed and the sum of the length (in kilometers) of the roadways that connect villages, as independent variables. There was a correlation with neither the MRW as an independent variable nor the traveling distance and time for each municipality concerning the capital city of each respective department. Finally, it was found that the department agribusiness GDP was associated with the length of the tertiary roadway network and with the primary network, with an R2 of 0.7. This study concludes that activities in rural zones are the ones that generate the greatest impact on roadway investment within a region.

Urban trees provide different ecosystem benefits, such as improving air quality due to the retention of atmospheric particulate matter (PM) on their leaves. The main objective of this paper was to study, through a systematic literature review, the leaf macro-morphological traits (LMTs) most used for the selection of urban trees as air pollution biomonitors. A citation frequency index was used in scientific databases, where the importance associated with each variable was organized by quartiles (Q). The results suggest that the most biomonitored air pollutants by the LMTs of urban trees were PM between 1–100 µm (Q1 = 0.760), followed by O3 (Q2 = 0.586), PM2.5 (Q2 = 0.504), and PM10 (Q3 = 0.423). PM was probably the most effective air pollutant for studying and evaluating urban air quality in the context of tree LMTs. PM2.5 was the fraction most used in these studies. The LMTs most used for PM monitoring were leaf area (Q1) and specific leaf area (Q4). These LMTs were frequently used for their easy measurement and quantification. In urban areas, it was suggested that leaf area was directly related to the amount of PM retained on tree leaves. The PM retained on tree leaves was also used to study other f associated urban air pollutants associated (e.g., heavy metals and hydrocarbons).

Introducción: El artículo muestra un análisis de la evolución hasta la fecha (4 de mayo de 2021), de las estadísticas oficiales de casos de coronavirus (CC) y el número total de muertes (TND) por SARS-CoV-2 en Colombia. Dicha información se muestra en correlación con otras variables como son la tasa de casos fatales (CFR), el rango de edad de las personas, sus comorbilidades típicas reportadas y las ciudades donde ha habido mayor concentración de casos. Materiales y Métodos: En una base de datos fue registrada diariamente, desde el 16 de marzo de 2020 a la fecha, información concerniente al número diario de nuevos casos confirmados (DNC) y los fallecimientos diarios confirmados (DD). También se registró la edad de las personas fallecidas, así como su género, sus comorbilidades previas y ciudad de deceso. La evolución del TND con el tiempo de diferentes países fueron modelados matemáticamente y comparados con el de Colombia. Resultados: En Colombia, la edad promedio de las personas que mueren por COVID-19 es de 69.5±14.7 años (mediana y moda de 71 y 80 años, respectivamente) y el virus es menos letal en la población menor de 40 años. La mayor parte de las muertes se han producido en personas con comorbilidades previas y del género masculino. Conclusión: La mayoría de las personas fallecidas son personas de edad avanzada, principalmente con comorbilidades previas, y predominantemente de sexo masculino. Los picos epidemiológicos de COVID-19 son consistentes con las temporadas de lluvias e invierno, y con los picos epidemiológicos tradicionales de gripe o influenza. Como citar este artículo: Rondón-Quintana Hugo Alexander, Zafra-Mejía Carlos Alfonso. Covid 19 death analysis in Colombia. Revista Cuidarte. 2021;12(3):e.1528 http://dx.doi.org/10.15649/cuidarte.1528

La generación y gestión de residuos sólidos industriales se considera una problemática ambiental a nivel mundial. Razón por la cual, diversos estudios se han enfocado en la implementación de Residuos de obras de Construcción y Demolición (RCD) para capas de pavimentos, centrándose en el uso de Agregados Reciclados de Concreto (RCA por sus siglas en inglés). El objetivo de este artículo fue establecer el impacto de la implementación del RCA en una mezcla asfáltica sobre algunas de sus propiedades físico-mecánicas, bajo tres escenarios: i) sustitución de la fracción gruesa, ii) fina y iii) 100% de la granulometría del agregado convencional (AC). Se evaluó la resistencia bajo carga monotónica de las mezclas (ensayos Marshall y Tracción Indirecta – RTI) y la resistencia al desgaste Cántabro. La sustitución de la fracción fina del AC por RCA, disminuye notablemente la resistencia bajo carga monotónica de la mezcla de referencia. Al sustituir la fracción gruesa, se cumplen los criterios de diseño de la mezcla asfáltica de referencia y se aumenta el RTI, pero se hace necesario incrementar ligeramente el contenido de asfalto. Al sustituir la totalidad de los agregados por RCA, se obtuvo un comportamiento satisfactorio ante la acción de cargas monotónicas, pero también se hace necesario incrementar ostensiblemente el contenido de asfalto. Un aumento del RCA en la mezcla incrementa la pérdida por desgaste Cántabro.

The objective of this paper is to show a study on the influence of vegetation on the outdoor thermal comfort (OTC) of a high-altitude tropical megacity. The OTC is evaluated by the PET (Physiological Equivalent Temperature) index and by establishing three simulation scenarios: (i) Current OTC, (ii) OTC under RCPs 4.5 and 8.5 (Representative Concentration Pathway), and (iii) OTC under RCPs and ENSO (El Niño–Southern Oscillation). The results show that the hourly variation range of the current OTC in urban areas with vegetation is greater (+3.15 °C) compared to impermeable areas. Outdoor thermal stress due to cold in vegetated areas is 1.29 °C lower compared to impervious areas. The effect of vegetated coverage on the improvement of urban OTC increases as the phenomenon of global warming intensifies. On average, in the current, RCP4.5, and RCP8.5 scenarios for each 10% increase in urban vegetation coverage, an increase of 0.22, 0.24, and 0.28 °C in OTC is obtained, respectively. The hourly variation range of the PET index increases during the ENSO scenario (vegetated areas: +16.7%; impervious areas: +22.7%). In the context of climate change and variability, this study provides a reference point for decision-makers to assess possible planning options for improving OTC in megacities.

When a hot-mix asphalt (HMA) ages, its mechanical properties, resistance, and durability change. Several studies have been conducted throughout the world to evaluate the effects of aging in HMAs. However, few studies have analyzed the influence of gradation. The main objective of this study was to evaluate the influence of gradation on the mechanical properties of aged HMA mixes. For such purposes, three HMA mixes with different gradations were manufactured (named HMA-10, HMA-19, and HMA-25), which were conditioned in STOA (short-term oven aging) and LTOA (long-term oven aging) by following the guidelines established by the AASHTO R30 specification. Marshall, Indirect Tensile Strength (ITS), resilient modulus, permanent deformation, fatigue (under controlled-stress condition), and Cantabro tests were performed. These tests were carried out to evaluate resistance under monotonic and cyclic load as well as the resistance to moisture damage and abrasion. The best performing mix in the test was HMA-19. There is no clear trend about the influence of gradation over the susceptibility of mixes for aging. This susceptibility changes depending on the test performed and the property measured. Furthermore, in resilient modulus tests, it is observed that the influence of gradation on aging susceptibility changes depending on the test temperature.

Leachate has been reported as the most significant source of landfill pollution. Predicting the characteristics of untreated and treated leachate may be useful during optimal scheduling of leachate treatment systems. The objective of this paper is to show an analysis of the operation of a landfill leachate treatment system in a Latin American megacity (Bogota, Colombia) by means of auto-regressive integrated moving average (ARIMA) models. A comparative analysis of the leachate treated with respect to reference legislation is carried out. The influence of climate variables during the operation of the treatment system is also considered. The results suggest that the concentrations of heavy metals (HMs), BOD5, and COD in untreated leachate do not follow the same annual cycles observed for the quantity of solid waste disposed within the landfill. This difference is possibly associated with the hydraulic retention time (HRT) of the leachate inside the conduction and pre-treatment system (storage/homogenization ponds). The ARIMA analysis suggests an HRT of up to one month (AR = 1) for the HMs identified as indicators of untreated leachate (Cu, Pb, and Zn). It is noted that the removal efficiency of HM indicators of the operation of the leachate treatment plant (Fe and Ni) is probably conditioned by operations carried out over a period of one month (AR = 1). The high input concentration of these HM indicators may prevent changing their ARIMA temporal structure during leachate treatment. This is reflected in the low removal efficiencies for all HMs under study (average = 26.1%).

Hot-mix asphalts exposed to hot weather and high traffic volumes can display rutting distress. A material that can be used to increase the stiffness of asphalt binders is gilsonite. On the other hand, from an environmental point of view, the virgin natural aggregates of asphalt mixtures can be replaced with recycled concrete aggregates. For these reasons, this study modified the asphalt binder with gilsonite by wet-process to improve rutting resistance, and replaced (by mass and volume) part of the coarse fraction of the aggregate with recycled concrete aggregate in two hot-mix asphalts with different gradations. Unlike other studies, a larger experimental phase was used here. Marshall, indirect tensile strength, resilient modulus, permanent deformation, fatigue resistance, and Cantabro tests were performed. An ANOVA test was carried out. If the replacement of the virgin aggregate by recycled concrete aggregates was made by volume, both materials (gilsonite and recycled concrete aggregate) could be used in hot-mix asphalts for thick-asphalt layers in high temperature climates and any level of traffic. The use of both materials in hot-mix asphalts is not recommended for thin-asphalt layers in low temperatures climates. It is not advisable to replace the aggregates by mass.

El envejecimiento produce cambios en las propiedades de las mezclas asfálticas como debilitar la adhesión asfalto - agregado y el incremento de la rigidez y la viscosidad del asfalto. Adicionalmente, esos cambios afectan la durabilidad del pavimento asfáltico. El objetivo de este estudio es evaluar el comportamiento de las mezclas asfálticas bajo diferentes condiciones de envejecimiento comparando muestras sometidas a envejecimiento en cámara de radiación UV y otras extraídas de vías en terreno. Las mezclas de laboratorio se fabricaron con material granular de una fuente y un cemento asfaltico. Cuatro grupos de mezclas se analizaron: No envejecidas, envejecidas en laboratorio mediante UV y Vaso de envejecimiento presión y envejecidas en campo. Para el tratamiento de envejecimiento por radiación ultravioleta, se diseñó una cámara y las muestras se trataron en periodos de 100, 200 y 500 horas. Se extrajeron muestras de pavimentos en servicio de edades entre 1,5 y 11 años después de la construcción. El comportamiento mecánico se evaluó mediante ensayos de modulo dinámico, deformación permanente y fatiga trapezoidal. Lo resultados mostraron que el envejecimiento incrementa la rigidez del material hasta dos veces con respecto al material sin envejecer. La deformación permanente muestra un mejor desempeño en las muestras envejecidas que en aquella sin exposición al envejecimiento. Por otro lado, el envejecimiento afecta de manera negativa la vida de fatiga dado que se presentan