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espanolEl creciente interes por el desarrollo de alternativas frente al uso masivo de cementantes tradicionales en aplicaciones geotecnicas, tales como cemento y cal, se debe en gran medida a los retos ambientales y costos asociados en este tipo de aplicaciones. Los cementantes activados alcalinamente surgen como una de las alternativas de mayor sostenibilidad, particularmente por su bajo consumo energetico y en teoria la baja huella de carbono en su fabricacion; ademas, tienen la posibilidad de utilizar residuos y subproductos industriales como materiales precursores en su fabricacion. Este articulo presenta un estado del arte de los diversos materiales empleados convencionalmente en la estabilizacion quimica de suelos y realiza una revision de los articulos publicados en relacion con la implementacion de cementantes activados alcalinamente, su viabilidad tecnica, los impactos ambientales asociados y los retos que se deben superar para lograr posicionarlos como una alternativa sostenible para procesos geotecnicos. EnglishThe growing interest in the development of alternatives to the use of traditional binders in geotechnical applications, such as cement and lime, is largely due to the environmental challenges and associated costs in this type of applications. Alkali-activated binders emerge as one of the most sustainable alternatives, particularly because of their low energy consumption and in theory the low carbon footprint in their manufacture. In addition, this type of binders have the possibility of using industrial waste and by-products as precursor materials in their production process. This article presents a state of the art of the various materials conventionally used in the chemical stabilization of soils and performs a review of published articles in relation to the implementation of alkali-activated binders. The technical feasibility, the environmental impacts associated, the challenges that must be overcome in order to position them as a sustainable alternative for geotechnical processes, and the advantages and disadvantages of its application are considered.

The interest of the construction industry in alkali-activated materials has increased to the extent that these materials are recognized as alternatives to ordinary Portland cement-based materials in the quest for sustainable construction. This article presents the design and construction of a prototype of an eco-friendly house built from concrete blocks produced using alkali activation technology or geopolymerization. The prototype meets the requirements of the current Colombian Regulations for Earthquake Resistant Buildings (NSR-10) and includes standards related to the performance of the materials, design, and construction method for earthquake-resistant confined masonry of one- or two-story buildings. The alkali-activated blocks were obtained from different precursors (aluminosilicates), including a natural volcanic pozzolan, ground granulated blast furnace slag, fly ash, construction and demolition waste (concrete, ceramic, brick, and mortar), and red clay brick waste. The physical-mechanical characterization of the alkali-activated blocks allowed their classification according to the structural specifications of the Colombian Technical Standard NTC 4026 (equivalent to ASTM C90). The global warming potential (GWP) or “carbon footprint” attributed to the raw materials of alkali-activated blocks was lower (25.4–54.7%) than that of the reference blocks (ordinary Portland cement concrete blocks). These results demonstrate the potential of alkali-activated materials for application in the construction of eco-friendly houses.

El estado de la infraestructura vial impacta el entorno social, económico y político de una nación. La evaluación de la condición superficial del pavimento es esencial para planificar intervenciones oportunas y eficaces. Las acciones oportunas evitan sobrecostos de operación, impiden el deterioro no controlado y disminuyen los inconvenientes operacionales y de seguridad. El problema expuesto plantea la inquietud de estudiar alternativas para evaluar el estado del pavimento, por lo cual un gran número de investigaciones sobre detección automática de fallas superficiales en pavimentos flexibles a través de técnicas de procesamiento de imágenes han sido desarrolladas. El objetivo de este artículo es revisar y analizar estos aportes. Sobre la base de la revisión, se concluyó que el rendimiento de este tipo de sistemas está determinado por dos factores: la recopilación de los datos y su procesamiento. El análisis presentado se despliega en función de estos factores. Se considera oportuno el desarrollo de sistemas que aprovechen las cualidades de diferentes sensores en la adquisición de datos y que integren la detección y clasificación de variedad de fallas incluyendo datos de severidad.

The search for new alternatives for soil stabilization by means of wasted materials promoted the development of this exploratory research to perform a preliminary evaluation of the geotechnical properties of a fine subgrade soil stabilized with different percentage (4 %, 8 %, 12 % y 16 %) of Used Engine Oil (UEO). In the development of this research, tests of Atterberg limits, permeability coefficient (k), unconfined compression stress (qu), and water-density ratio were performed on a soil classified as MH. The tests were performed both on the unstabilized soil and on UEO stabilized soil. Results show that the liquid and plastic limits tend to lower as the percent of UEO increases, the maximum dry density lightly increase, the optimal water content lower significantly, the unconfined compression stress (qu) stays constant with up to 8 % of UEO and permeability (k) does not show significant variation., La búsqueda de nuevas alternativas para estabilizar suelos con desechos motivó la realización de esta investigación exploratoria para evaluar en forma preliminar las propiedades geotécnicas de un suelo fino de subrasante mezclado con diferentes porcentajes (4 %, 8 %, 12 % y 16 %) de Aceite de Motor Usado (AMU). En el desarrollo de esta investigación se realizaron ensayos de límites de Atterberg, coeficiente de permeabilidad (k), compresión inconfinada (qu), y relación humedad-densidad de un suelo clasificado como MH. Los ensayos se realizaron tanto para el suelo sin estabilizar como para el suelo estabilizado con AMU. Los resultados muestran que los limites líquido y plástico tienden a disminuir con el incremento de AMU, la densidad seca máxima se incrementa ligeramente, el contenido de humedad optima disminuye significativamente, la resistencia a la compresión inconfinada (qu) se mantiene constante para contenidos de AMU hasta el 8 % y la permeabilidad (k) no muestra variación significativa.

In this study, a clayey soil classified as A-7-5 according ASTM D3282, was stabilized using alkali-activated cementitious materials (AAC) added to the soil dry in percentages of 20 and 30%. Fly ash (F1, F2) with high unburned carbon content (up to 38.76%), hydrated lime (L) and granulated blast furnace slag were used. Unconfined compressive strength and flexural strength at 28 days of curing and the durability after 12 wetting-drying cycles were evaluated. The results were compared with a soil-cement reference mixture. The soil treated with AAC-F1L showed a volume expansion of 0.51% and volume contraction of -0.57% compared with the 0.59% expansion and -0.68% contraction of the soil-cement reference mixture. Additionally, the mass loss after the wetting and drying cycles is only 3.74% which is slightly lower than the mass loss of the soil stabilized with ordinary Portland cement (OPC) (3.86%) and well below the value specified in Colombian regulations (7%). En este estudio, un suelo arcilloso clasificado como A-7-5 según ASTM D3282, se estabilizó utilizando materiales activados alcalinamente (AAC) en porcentajes de 20 y 30%. Se utilizaron cenizas volantes (F1, F2) con alto contenido de inquemados (hasta 38,76%), cal hidratada (L) y escoria granulada de alto horno. Se evaluó la resistencia a la compresión confinada y la resistencia a la flexión a 28 días de curado y la durabilidad después de 12 ciclos de humectación-secado. Los resultados se compararon con una mezcla de referencia suelo-cemento. El suelo tratado con AAC-F1L mostró una expansión y contracción volumétrica del 0,51% y -0,57% respectivamente, en comparación con el 0,59% y -0,68% de la mezcla de referencia suelo-cemento. Además, la pérdida de masa después de los ciclos de humectación y secado es sólo 3.74%, valor ligeramente inferior a la del suelo estabilizado con cemento Portland (3.86%) y muy inferior al valor especificado en la normativa colombiana (7%).

espanolLa construccion de pavimentos en placa-huella de concreto reforzado se ha incrementado en Colombia en los ultimos anos. La gran mayoria de los proyectos se basa en la especificacion 500-1P que presenta un diseno general, del cual se desconocen los criterios tenidos en cuenta en su elaboracion, lo que genera muchas dudas para su uso en diferentes proyectos. En el presente articulo se hace un analisis de los pavimentos en placa-huella, y se dan recomendaciones de diseno y construccion de este tipo de pavimentos, considerando las condiciones de uso actual, las cargas esperadas, las caracteristicas de suelo de soporte y las calidades de los materiales. portuguesA construcao de pavimentos em placa de concreto armado tem aumentado na Colombia nos ultimos anos. A grande maioria dos projetos baseia-se na especificacao 500-1P, que apresenta um desenho geral, do qual se desconhecem os criterios considerados em sua elaboracao, o que gera muitas duvidas para seu uso em diferentes projetos. Neste artigo, faz-se uma analise dos trilhos em placa de concreto e dao-se recomendacoes de desenho e construcao desse tipo de pavimentos, levando em conta as condicoes de uso atual, as cargas esperadas, as caracteristicas de solo de suporte e a qualidade dos materiais. EnglishThe construction of reinforced concrete strip road pavements hasincreased in Colombia in recent years. The vast majority of the projects are based on the 500-1P specification, which presents a general design, of which the criteria taken into account in its elaboration are unknown, which generates many doubts for its use in different projects. In the present article, an analysis of strip road pavement is made and recommendations are given for the design and construction of this type of pavement, taking into account current conditions of use, expected loads, characteristics of the supporting soil, and qualities of materials.

The goal of this paper is the use of a fly ash with high unburned carbon which generally has lower demand in the market because, according to ASTM C618, it cannot be used in Portland cement concrete. Alkali-activated cements (AACs) based on this industrial by-product were prepared using granulated blast furnace slag (GBFS) and lime (L) as calcium sources. The AACs were used for A-4 type soil improvement. The unconfined compressive strength, flexure strength, and durability (volume change and mass loss) of the soil treated were evaluated. The results showed that under soaked conditions the compressive strength increased up to 119.4% at 7 days of curing and 78.6% at 28 days of curing. Additionally, the mass loss percentage after twelve (12) wetting and drying cycles was less than that allowed by Colombian specifications for stabilized soil. This demonstrated that it is possible to use this type of fly ash as an environmentally sustainable alternative to replace Portland cement as soil stabilizer in applications for road construction. The proposed solutions are thus considered competitive with current chemical stabilization techniques. However, further studies on the long-term performance of AACs stabilized soils, and the cost of applying AACs in soil stabilization are worth being conducted.

In this study, blocks were manufactured from clay soil and alkali-activated binders. The soils used were classified as A-4 and A7-5 according to ASTM D3282. The binder was produced from fly ash with a high content of unburned material (carbon). Blast furnace slag and lime were used as calcium sources. The physical–mechanical results of the blocks showed that the texture of the soil is a very important parameter for manufacturing this type of compacted soil masonry element, because the soil with the highest sand content (soil A-4) showed a higher dry density, indicating that this property corresponded to a lower percentage of permeable pores, a lower water absorption and an average compressive strength of 17 MPa at an age of 28 days. A life cycle analysis of the blocks was carried out and the results compared to that of the concrete paving blocks and fired clay blocks, which showed that the Global Warming Potential (GWP) can be reduced from 38 to 75%. Of the materials used to prepare the activated blocks, lime and silicate generate the greatest impact. In general, the results show the technical feasibility of manufacturing alternative blocks to traditional pavers with alkaline activation processes by using natural soils as the basic raw material and a low-quality fly ash as precursor.

The mechanistic-empirical pavement design guide (MEPDG) includes a software tool to perform the large number of calculations involved in the design of pavement structures. Large number of input parameters from traffic, materials, and climate are required to use MEPDG. Data collection to accomplish calibration and implementation of MEPDG may be done more efficiently focusing on the most sensitive parameters. This research studies the sensitivity of MEPDG to traffic input parameters on two flexible pavements using the techniques for sensitivity of complex computer codes with Latin hypercube sampling, rank transformation, standardised regression coefficients, and Gaussian stochastic models. The results showed that roughness, rutting, and bottom-up cracking as predicted by MEPDG are sensitive to variations of two-way average annual daily traffic (AADT), traffic growth, dual tyre spacing, percent trucks in the design direction, percent of heavy vehicles, traffic wander, and percent of trucks in design lane. Va...

The Mechanistic–Empirical Pavement Design Guide (MEPDG) is the result of NCHRP Project 1-37A. This pavement design procedure uses mechanistic and empirical models calibrated with national data. Calibration of MEPDG is required to improve the accuracy of the models for local conditions. The data needed for calibration require numerous tests to characterize materials. The fieldwork for collecting the data to verify the models is laborious. This research studied the sensitivity of MEPDG to material input parameters. The main goal of this research was to determine the influence of material parameters on pavement performance as predicted by MEPDG. Results from sensitivity analyses can be used for planning data collection for calibration, implementation, and general understanding of MEPDG. However, MEPDG is so complex that the sensitivity analysis methodology was carefully designed to identify the relative importance of input variables. This research employed space-filling computer experiments with Latin hypercube sampling, standardized regression coefficients, and Gaussian stochastic processes to categorize the relative importance of material inputs in MEPDG for two flexible pavement structures that used Level 3 analysis. The methodology worked well for analyzing the sensitivity of material inputs in MEPDG, with the advantages of varying all parameters at once and requiring a relatively small number of runs for a completed analysis of the entire input space. Effective binder content, as-built air voids, Poisson's ratio, surface shortwave absorption of asphalt layers, and resilient modulus of subgrade had a significant effect on pavement performance.

La construcción de pavimentos en placa-huella se ha incrementado en Colombia en los últimos años, este tipo de pavimento se utiliza para vías rurales con bajo tránsito. El tipo de placa huella utilizado en el país es de concreto reforzado, basado principalmente en un diseño general definido por la especificación particular 500-1P, que genera muchas dudas para su aplicación en diferentes proyectos. En la presente investigación se realizó una modelación con elementos finitos para estudiar el comportamiento de los pavimentos con placa-huella ante diferentes condiciones de carga y soporte. Se analizó la posibilidad de diseñar pavimentos con placa-huella de concreto simple, para las cargas máximas del camión C3 y con periodo de diseño de 20 años. Se encontró que desde el punto de vista del criterio de fatiga esto sería posible, pero el comportamiento por erosión de estos pavimentos es incierto, debido a que en la actualidad no existe suficiente información para calibrar un modelo para realizar la evaluación por este criterio. The construction of strip road pavements has increased in the recent days in Colombia. This type of pavements is being used for rural lowtraffic volume roads, the type of strip road pavement used nationwide is made of reinforced-concrete, the construction in based mainly on the particular construction specification 500-1P that has only one configuration of the pavement, which raises doubts on its application for different projects. In this research, a finite element analysis was performed to study the response of concrete strip road under different load configurations and soil support. The design of plain-concrete strip roads pavements was evaluated for the maximum loads of C3 trucks and 20 years of design period. The results showed that although this type of strip road may meet fatigue criteria, the erosion criteria is uncertain due to lack of data to calibrate an erosion model to perform this evaluation.

En el diseño racional de pavimentos flexibles se utilizan modelos de fatiga para estimar los esfuerzos y deformaciones admisibles, los cuales son comparados con los esfuerzos y deformaciones actuantes calculadas con modelos de respuesta. Los modelos de fatiga desarrollados para diferentes materiales y condiciones de servicio producen resultados diferentes, lo que genera la necesidad de realizar calibración de modelos para condiciones locales de uso. En Colombia no se han realizado esfuerzos de calibración de modelos de fatiga para pavimentos, los diseñadores de pavimentos se ven obligados a recurrir a leyes de fatiga desarrolladas en otros países, para materiales y condiciones diferentes a las nacionales, lo que genera imprecisiones en el dimensionamientos de los pavimentos y su desempeño a largo plazo. El objetivo de esta investigación es evaluar la incidencia de diferentes leyes de fatiga en el dimensionamiento y costos iniciales de construcción de pavimentos flexibles. Para esto se evaluaron dos estructuras diseñadas por el método racional, empleando el modelo de respuesta Bisar y diferentes leyes de fatiga. Se encontró gran variación en dimensiones y costos, revelando que el desarrollo y calibración de modelos de fatiga puede conllevar a ahorros significativos en la construcción de pavimentos en el país. Rational design for flexible pavement uses fatigue models to determine allowed stresses and deformations in pavement structures which are compared with stresses and deformations calculated with response models. Fatigue models developed for different materials and climatic conditions produce different results. Due to this reason, fatigue models need to be calibrated for local conditions. No pavement fatigue models calibrations have been performed in Colombia. Pavement designers need to use fatigue laws developed for materials and conditions different to national ones, thus creating high uncertainty in the calculated pavement dimensions and long-term performance. The main goal of this research was to evaluate the effect of different fatigue laws used over the final dimensions and construction prime costs of flexible pavements. In order to do this, two pavement structures designed by the rational method were evaluated using the Bisar model and different fatigue laws. As a result, a large variation in costs and dimensions was found, thus confirming that the development and fatigue models calibration may result in significant savings when constructing pavements within the country.

Las demoras y sobrecostos en la construcción de carreteras son cotidianos en Colombia. Se presentan imprecisiones en la estima ción de los costos y en la programación de la construcción. Este artícu lo presenta un análisis de los fa ctores determinantes en las de moras y sobrecostos en la construcción de carreteras en el sur occident e colombiano. Se revisaron 40 proyectos viales construidos en l a región, la información revisada incluyó la programación de tiempo y costo, los datos de duraciones y costos reales de cada actividad, y l as bitácoras de obra. Se realizó una simulación para evaluar probabilísticam ente las prácticas de programación e identificar factores deter minantes en las demoras y sobrecostos de la s obras. Se encont ró que las act ividades que más inciden en las demoras y sobrecostos son la ba se granular y la carpeta asfáltica, las causas más comunes son las malas es timaciones de costos y duración, la lluvia y los problemas de s uministro de materiales.