Journal of Materials in Civil Engineering

The use of blended cements incorporating supplementary cementing materials and cements with low ${\mathrm{C}}_3\mathrm{A}$ content is becoming common to prevent the deterioration of concrete structures subjected to aggressive environments. This paper presents the results of an investigation on the performance of finely ground volcanic scoria (VS)-based ASTM Type I and Type V (low ${\mathrm{C}}_3\mathrm{A}$ ) blended cement concrete mixtures with varying immersion periods of up to $48\text{months}$ in environments characterized by the presence of mixed magnesium–sodium sulfates. The concrete mixtures comprise a combination of two Portland cements (Types I and V) and two VS-based blended cements with two water-to-binder ratio of 0.35 and 0.45. Background experiments (in addition to strength and fresh properties) including X-ray diffraction (XRD), differential scanning calorimetry (DSC), mercury intrusion porosimetry (MIP), and rapid chloride permeability (RCP) were conducted on all concrete mixtures to determine phase composition, pozzolanic activity, porosity, and chloride ion resistance. Deterioration of concrete due to mixed sulfate attack and corrosion of reinforcing steel were evaluated by assessing concrete weight loss and measuring corrosion potentials and polarization resistance at periodic intervals throughout the immersion period of $48\text{months}$ . Plain (Type I/V) cement concretes, irrespective of their ${\mathrm{C}}_3\mathrm{A}$ content, performed better in terms of deterioration and corrosion resistance compared to Type I/V VS-based blended cement concrete mixtures in mixed sulfate environment.

Stay-in-place formwork is an attractive alternative to traditional formwork (steel or wood) and is known to improve constructability and produce a more durable final product. In the work presented, the effect of a patented polyvinyl chloride (PVC) stay-in-place forming system on the mechanical performance of concrete that it encases is examined. The compressive and flexural performance of the system are investigated. The results indicate that the PVC encasement enhances both compressive and flexural performance. Compressive strength is increased by the confining action of the PVC and flexural performance is improved due to the increased tensile capacity of the sections under flexural loading.

With increasing concerns of global warming and increasing emissions, the asphalt industry is making a constant effort to lower its emissions by reducing the mixing and compaction temperatures of the asphalt mixture without affecting the properties of the mix. Several proprietary chemicals are available in the industry that can help reduce the mixing and compaction temperatures. A significant reduction of required heat can be achieved in most cases. Several studies have been conducted evaluating the properties of the warm mix asphalt; however, properties of the binders containing these chemicals have not been studied in great detail. Warm asphalts were produced using two of the available processes utilizing five different asphalt binder sources, and some rheological tests were conducted (dynamic shear rheometer and viscosity). The results indicated that binders containing the inorganic additive Aspha-Min (Eurovia, France) underwent minor or no changes compared to the base binders in terms of flow properties, stiffness, and response to creep. However, the flow of binders with the additive Sasobit (Sasol Wax, Germany), which consists of aliphatic hydrocarbons, changed from Newtonian to shear thinning at $60°\mathrm{C}$ , and the viscosity of the binder at $60°\mathrm{C}$ increased. Sasobit also improved the stiffness and penetration resistance of the base binders, and binders with Sasobit had significantly lower permanent deformations after repeated creep-recovery tests compared to the base binders.

When employing linear elastic layer analysis, which is widely used for the structural analysis of flexible pavements, it is commonly observed that most critical tensile strains occur at the bottom of an asphalt layer. It is well known that an asphalt mixture is a viscoelastic material, so its response is time and rate dependent; therefore, the results from the elastic assumption may not be borne out in the response of the asphalt layer. This study utilized viscoelastic analysis to identify critical tensile strains and their time-dependent responses. It was found that tensile strains occurred at the bottom and at the top of an asphalt layer and grew because of the rheological behavior of an asphalt mixture. As load repetitions continued, the strain at the top showed a higher strain value than the strain value at the bottom. A sensitivity analysis performed on various design parameters indicated that the development of strains at the top and at the bottom is a function of the structural characteristics of pavement structures. Expected trends were observed and findings compared favorably to results of field-calibrated top-down cracking model predictions.

Carbonation is one of the main concerns for concrete service life in tropical countries. The mechanism and materials that produce it have been widely studied as well as natural and accelerated methods to report and analyze it. In spite of reported investigations, there is a need for information that could allow an adequate interpretation of the results of the standardization process. This lack of information can produce variations not only in the interpretation but also in the predictions of service life. The purpose of this paper is to analyze and discuss variables that could be sources of error, especially when performing accelerated tests. As a result, a methodologies to minimize variations when interpreting and comparing results is proposed, such as specimen geometry and preconditioning, spacing, relative humidity, and $\mathrm{C}{\mathrm{O}}_2$ concentration.

A field study was undertaken to evaluate the performance of model geotextile-reinforced mechanically stabilized earth walls constructed using locally available marginal backfill soils without and with cement modification. Cyclic plate load tests were carried out on the constructed walls both at optimum moisture content and in fully wet conditions in the case of plain backfills and in fully wet condition for cement-modified backfills. The performance and utility of the proposed built-in soil cement facing with folded-back geotextile layers were also examined. The reduction in load-carrying capacity of walls upon wetting could be compensated by cement modification of marginal backfills while maintaining the pullout resistance of reinforcing layers with nominal variation in the flexibility of walls. The performance of model walls constructed using cement-modified marginal backfills is found to be even superior to the wall constructed using free draining sand backfill in terms of higher load-carrying capacity with reduced lateral facing deformations. It was observed that the geotextile-reinforcing layers in marginal backfills also facilitate the internal drainage.