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%).

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.

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.

The 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. El creciente interés por el desarrollo de alternativas frente al uso masivo de cementantes tradicionales en aplicaciones geotécnicas, 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 energético y en teoría la baja huella de carbono en su fabricación; además, tienen la posibilidad de utilizar residuos y subproductos industriales como materiales precursores en su fabricación. Este artículo presenta un estado del arte de los diversos materiales empleados convencionalmente en la estabilización química de suelos y realiza una revisión de los artículos publicados en relación con la implementación de cementantes activados alcalinamente, su viabilidad técnica, los impactos ambientales asociados y los retos que se deben superar para lograr posicionarlos como una alternativa sostenible para procesos geotécnicos.

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. Variations of operational speed, average axle width, and mean wheel location showed no significant effects on the same MEPDG outputs. The results of the sensitivity were used to define recommended hierarchical levels for traffic input.

Time and cost overruns in highway construction are usual in Colombia. Contractors regularly fail in cost estimation and construction scheduling. An analysis of important factors on time and cost overruns in highway construction in southwest Colombia is presented in this paper. Forty highway construction projects were reviewed. Data from construction documents were collected to prepare a data base for probabilistic analysis. Data collected include scheduled construction time and cost, actual construction time and cost, and unexpected events which could have affected the construction process. Data were used in a probabilistic cost and schedule risk analysis to identify critical factors in construction time and cost overruns in the region. It was found that the activities that most affect the time and cost overruns are the construction of the granular base and the asphalt layer. The most common causes of construction overruns were found to be poor cost and duration estimates, rain, and materials supply problems.