Journal of Materials in Civil Engineering

This study evaluates the effects of aggregate angularity in bituminous mixtures. Previous studies have predominantly focused on the effects of aggregate angularity on the resistance to permanent deformation, while little work has investigated the role of aggregate angularity related to mixture volumetrics and fatigue fracture performance. To investigate the effect of aggregate angularity on mixture performance and characteristics, five mixes with different combinations of coarse and fine aggregate angularity are evaluated by performing the uniaxial static creep test and the indirect tensile fracture energy test. The asphalt pavement analyzer test is also performed with five-year field project mixtures. Fracture energy test results are then incorporated with finite-element simulations of virtual specimens produced to explore the detailed mechanisms of cracking related to the aggregate angularity. Rutting performance test results indicate that higher angularity in the mixture improves rut resistance due to better aggregate interlocking. The overall effect of angularity on the mixtures’ resistance to fracture damage is positive because aggregate blends with higher angularity require more binder to meet mix design criteria, which mitigates cracking due to increased viscoelastic energy dissipation from the binder, while angular particles produce a higher stress concentration that results in potential cracks. Finite-element simulations of mixture microstructure support findings from experimental tests.

Using a design-oriented model recently developed for prediction of the moment-curvature relationship of a cross section of beams made by strain-softening or strain-hardening fiber reinforced concrete (FRC) and that can also include a certain percentage of longitudinal steel bars, a parametric study is carried out to evidence the effect of relevant characteristics of the post-cracking behavior of these materials in the moment-curvature and force-deflection responses of this type of structural elements. The study also analyzes the influence of the reinforcement ratio of longitudinal steel bars, $\rho$, in order to show that for a certain content of fibers the benefits of fiber reinforcement, mainly at serviceability limit state conditions, decrease with the increase of $\rho$. Adopting the formulation of the CEB-FIB final draft Model Code, the moment-crack width relationship of FRC beams reinforced with steel bars are obtained and the predictive performance of this approach is assessed by comparing analytical and experimental results.

This research examined the perspectives held by members of the Japanese concrete industry on sustainable practice and materials through a two-part investigation consisting of interviews with industry experts and a broader survey of industry members. The investigation sought to evaluate the level of sustainable knowledge, develop a conceptual model for sustainable practice, establish evaluation criteria for sustainable concrete materials, and identify barriers for implementing said practices and materials while considering the differences in perspectives among different industry groups. The results show that the Japanese industry is focused on reducing environmental impact through extending infrastructure service life by enhancing durability and considering life-cycle cost and ${\mathrm{CO}}_2$; this can be related to the Japanese socioeconomic conditions of an aging population with a decreasing workforce and a decreasing investment in construction. When examining the variation among industry stakeholder groups, little difference could be seen in their general concept for sustainable concrete practice and materials, but a larger difference could be identified in the barriers to each group for achieving those goals.

The dry-wet cycle is one of the aggressive environmental conditions suffered by concrete. This paper focuses on the experimental study and theoretical simulation of water distribution in normal- and high-strength concrete through dry-wet cycles. The experimental results show that under dry-wet cycles, the variation in the interior humidity of concrete occurs mainly within a certain depth from the drying/wetting face. This depth is called the influencing depth under dry-wet cycles. The interior relative humidity of concrete within the influencing region periodically changes under dry-wet cycles. As concrete undergoes wetting, a fast rise in interior humidity occurs in a short time, and finally the relative humidity reaches approximately 100%. By contrast, as concrete undergoes drying, the interior relative humidity does not drop immediately, but in a more gradual manner. In the modeling, a model taking both cement hydration and moisture diffusion into account synchronously is used to simulate the moisture distribution in concrete under dry-wet cycles. A comparison between model and experimental results concludes that the model can predict the moisture distribution in concrete, as well as its variations, through dry-wet cycles.

Fluid ingress is a primary factor that influences freeze-thaw damage in concrete. This paper discusses the influence of fluid ingress on freeze-thaw damage development. Specifically, this paper examines the influence of entrained air content on the rate of water absorption, the degree of saturation, and the relationship between the saturation level and freeze-thaw damage. The results indicate that whereas air content delays the time it takes for concrete to reach a critical degree of saturation it will not prevent the freeze-thaw damage from occurring. The results of the experiments show that when the degree of saturation exceeds 86–88%, freeze-thaw damage is inevitable with or without entrained air even with very few freeze-thaw cycles.

To study the effect of crushed clay bricks as coarse aggregate on creep behavior of concrete, a comprehensive testing program was conducted. Concrete cylinder specimens having characteristic or specified compressive strength of 17.2, 24.0, and 27.5 MPa were prepared from both natural stone and crushed clay brick aggregate. Mix design ratios were evaluated in a way so that volumetric content of coarse aggregate, both brick and stone, remained same for all concrete samples. Specimens were subjected to creep testing at the 7th and 28th day after casting and creep strain data were recorded up to 300 days. Results show that although strength and other environmental parameters remain the same, concrete made from crushed clay brick as coarse aggregate have a higher creep strain than that of concrete made from natural stone aggregate. This increase in creep strain ranges from 30% to as high as 45% for the 300-day loading history considered. Additionally, to select an appropriate model to predict creep in brick aggregate concrete, the effectiveness of five widely used prediction models were examined. Predicted creep strain from ACI 209R, CEB-FIP, B3, GL2000, and Eurocode 2 models were compared with experimental results. By using statistical analysis, the authors established that prediction of creep by GL2000 model is closest to the experimental results. Finally, a modification factor has been proposed that may be incorporated so that prediction of creep strain by the GL2000 model in brick aggregate concrete becomes more realistic.

Mode I (tensile) fracture is the most commonly observed failure in geostructures resulting from cracks in soil. Direct or indirect tensile tests have been used to evaluate the tensile strength of geomaterials. In this paper, the unconfined penetration device and experimental procedure were modified to reduce measurement errors. It was then used to determine the tensile strength of compacted soil. Factors influencing the tensile strength of the compacted soil, including the plasticity index, rate of loading, and size of specimen were discussed in detail, as well as its reliability. Experimental results indicated that the modified, unconfined penetration technique is sufficiently reliable and operator-friendly for determining the tensile strength of compacted soil.