Study on the Mechanical and Leaching Characteristics of Permeable Reactive Barrier Waste Solidified by Cement-Based Materials

The durability against wet-dry (w-d) cycles is an important parameter for the service life design of solidified permeable reactive barrier (PRB) waste. This study introduces the potential use of cement, fly ash, and carbide slag (CFC) for the stabilization/solidification (S/S) of PRB waste. In this study, solidified PRB waste was subjected to different w-d cycles ranging in times from 0 to 10. By analyzing the mass loss, the unconfined compressive strength (UCS), initial resistivity (IR), and the leaching concentration under different durability conditions, the results demonstrate that these variables increased and then tended to decrease with the number of w-d cycles. The UCS of contaminated soil is significantly correlated with IR. Moreover, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD) analyses indicate that the hydration products calcium silicate hydrate (C-S-H) and ettringite (AFt) are the main reasons for the enhancement of the UCS. However, the increase in concentration leads to a decrease in hydration products and the compactness of solidified soil, which has negative effects for the UCS and the leaching ion concentration. In general, the durability exhibited by the PRB waste treated with S/S in this paper was satisfactory. This study can provide theoretical guidance for practical engineering applications.

Evaluation of Moisture and Decay Models for a New Design Framework for Decay Prediction of Wood

Performance-based, service-life design of wood has been the focus of much research in recent decades. Previous works have been synthesized in various factorized design frameworks presented in the form of technical reports. Factorization does not consider the non-linear dependency between decay-influencing effects, such as between detail design and climate variables. The CLICKdesign project is a joint European effort targeting digital, performance-based specification for service-life design (SLD) of wood. This study evaluates the feasibility of using a semi-empirical moisture model (SMM) as a basis for a digital SLD framework. The performance of the SMM is assessed by comparison against a finite element model (FEM). In addition, two different wood decay models (a logistic, LM, and simplified logistic model (SLM)) are compared. While discrepancies between the SMM and FEM were detected particularly at high wood moisture content, the overall performance of the SMM was deemed sufficient for the application. The main source of uncertainty instead stems from the choice of wood decay model. Based on the results, a new method based on pre-calculated time series, empirical equations, and interpolation is proposed for predicting the service life of wood. The method is fast and simple yet able to deal with non-linear effects between weather variables and the design of details. As such, it can easily be implemented as part of a digital design guideline to provide decision support for architects and engineers, with less uncertainty than existing factorized guidelines.

Service Life of Concrete Pedestal without Air Entrainment

Service life of nine wind power unit pedestals, which concrete grades between C45 and C55, were studied with four different service life models. The exact service life could be calculated only with two of them with the initial data. The service life models that were used in calculations: • Factor method • Deterioration and service life prediction of concrete subjected to freeze-thaw cycles in Na2SO4 Solution-method Service life models that were considered only at theoretical level: • FIB Bulletin 34 – Model Code for Service Life Design, and • An equation for determining freeze-thaw fatigue damage in concrete and a model for predicting the service life. The latter two methods are more theoretical, and they require laboratory tests to obtain more information before the calculations can be properly executed. This article concludes that damage to concrete due to freeze-thaw cracking is still poorly known and a sufficiently accurate service life model has not yet been developed for its computational modeling. Therefore, there is a need to develop a service life model suitable for Finnish climate and concrete grades, which could be used for estimating the damage rate of an existing concrete structure.

Call for papers on special issue “Performance-based Service Life Design of reinforced recycled aggregate concrete”

Aim & Scope: Sustainability requires a judicious use of natural resources. Reducing the consumption of natural aggregates and ensuring adequate durability of reinforced concrete infrastructures are major steps towards sustainability. Performance-based Service Life Design and recycled aggregate concrete are intense research fields. Considering the research maturity of each subject on its own, it is time to couple them and deliver knowledge on performance-based Service Life Design for reinforced concrete structures incorporating recycled aggregates. This Special Issue of Materials International constitutes a way to disseminate results and findings from original studies, experimental programs, empirical, analytical and numerical modelling of initiation period (carbonation- and chloride ion-related), propagation period or both (service life). Probabilistic, semi-probabilistic and deterministic approaches are welcome.