Constr. Mater., Volume 4, Issue 1 (March 2024) – 16 articles

This research investigates the fatigue behaviour and fracture mechanics of high-performance concrete (HPC), including various compositions such as HPC with basalt aggregates (HPC-B), HPC with gravel (HPC-G), and high-strength coarse mortar (CM) under static and cyclic tensile loading within the special priority program SPP 2020. The study aims to integrate fracture mechanics into structural analysis to enhance design guidelines for slender cross-sections and safety-related high-performance structural components. The experimental investigations reveal HPC-B’s remarkable superiority, displaying its higher compressive strength, modulus of elasticity, and tensile strength compared to HPC-G and CM. A modified disk-shaped compact tension (MDCT) based on ASTM standards, aided by digital image correlation (DIC) unveils fracture behaviour, emphasizing fracture energy as a crucial parameter. HPC-B exhibits improved crack resistance and notch sensitivity reduction attributed to crushed basalt aggregates and an enhanced interfacial transition zone (ITZ). The research scrutinizes factors like material characterization, aggregate morphology, stress levels, and the displacement rate on crack formation. High-cycle fatigue tests show HPC-B’s superior performance, and the post-fatigue analysis reveals enhanced residual fracture toughness attributed to nano-level structural changes, stress redistribution and aggregate-matrix interaction. A 3D image analysis via Computed Tomography (CT) scans captures mesostructural crack propagation and provide quantitative insights. This research marks a significant shift from conventional aggregate-focused approaches and introduces a novel approach by integrating excess paste theory and mesoscale analysis, highlighting the critical role of aggregate choice in material characterization and mesoscale design in enhancing the structural efficiency of HPC. Furthermore, the study advances the understanding of HPC fatigue behaviour, emphasizing the interplay of aggregate types and morphologies and their dynamic response to cyclic loading, offering valuable insights for optimizing design guidelines and fostering innovation in structural engineering. Full article

The work presented in this paper includes the construction methods and lessons learned from the placement of a non-proprietary ultra-high performance concrete (UHPC) overlay through the rehabilitation of a concrete bridge deck located in Socorro, New Mexico, USA. The selected bridge is a multi-cell, box girder bridge with four spans and a total length of 91.4 m and a width of 16.5 m with two traffic lanes. Rehabilitation of the bridge involved removing the top surface of the existing deck (deteriorated concrete), installing a high-performance deck (HPD) leveling course, and placing a 25 mm UHPC overlay. Sensors were installed in the bridge superstructure (multi-cell box girders, HPD, and overlay) for long-term monitoring. Overlay assessment included physical testing to evaluate the condition of the overlay–substrate bond by chain dragging and direct tension pull-off testing. Conclusions and lessons learned from this investigation serve as a fundamental list of best practices and recommendations for field construction of a non-proprietary UHPC overlay. Recommendations for preparatory tasks including material selection, substrate surface preparation, placement preparation, handling of materials, and UHPC mixing are provided. The recommendations also list best practices concerning the placement of the overlay, curing procedures, and quality assurance testing. Lastly, suggestions are presented for contracts pertaining to UHPC overlay projects. Full article

The mechanistic-empirical pavement design guide (MEPDG) is a commonly accepted design principles guide that aids in jointed plain concrete pavement (JPCP) design and performance analysis. The MEPDG uses three different design parameter input levels, referred to as level one, level two, and level three, providing increasing confidence in the analysis at the lower numbered levels, which use more locally relevant (level two) or project-specific (level one) data. The state-of-the-art pavement ME software (version 2.6.2) uses MEPDG design principles to predict pavement performance. The three performance indicators for JPCP systems (international roughness index (IRI), joint faulting, and transverse cracking) experience significant changes when simulating under a different input level. The IRI and faulting indicator changed by 78 percent when using inputs varying from level one to level three, with the cracking indicator change being more severe at 87 percent. To accommodate the change in performance indicator values between input level one and input level three, increasing the concrete slab thickness is necessary to achieve comparable pavement performance. An increase in the Portland cement concrete (PCC) layer from one inch to two inches is required when input level three simulations are performed, demonstrating the economic and sustainability benefits of using project-specific level one inputs. Understanding the impact of simulation input levels will help to meet design and sustainability goals and improve the lifecycle performance of JPCP systems. Full article

Recovery and re-utilization of materials are regarded as key strategies for reducing greenhouse gas emissions in the built environment. Within those end-of-use scenarios, recycling is one of the widely used tactics, demonstrated by established infrastructure and developed supply chain networks in many geographic locations. While recycling is an increasingly common practice in the built environment, accurately defining recycling quality in order to compare technologies and material types remains methodologically contested. This is mainly due to the vast spectrum of scenarios that typically fall under the term ‘recycling’. Remanufacturing, downcycling, upcycling, and even direct reuse are all referred to as types of recycling in non-scientific circles, depending on the sector they occur in. The main challenge in assessing the material recovery quality of those solutions is that they exist on a continuum without clear divisions. Within that context, this article presents and compares four methods for assessing recyclability. The featured methods measure recycling potential from different perspectives: economic dimensions of the recycling industry; patterns of resource depletion; the energy cost of recycling; and the carbon intensity of recovery processes. The scientific foundations of the four methods are presented and a range of widely used construction materials are tested. The performance of materials is then compared across the four assessment methods to note observations and gain insights. Some of the materials are found to consistently outperform others, whereas some materials perform well on one method while performing poorly on others. This comparative study is followed by a discussion that looks at the limitations of each approach and reasons, or lack thereof, for the adoption of one method over the others in industry and academia. Lastly, the article looks at future research trajectories and examines the path ahead for recycling in the construction industry. Full article

This study investigated the potential of lightweight deflectometer (LWD) data in predicting layer moduli and response measurements within the Mechanistic–Empirical Pavement Design Guide. To achieve this goal, field repeated LWD tests and laboratory repeated load triaxial tests were carried out on granular base material compacted at 3% and 6% water content, sandy subgrade soil compacted at 3%, 4% and 9% water content and silty sand subgrade soil compacted at 8% and 10% water content. The results revealed that substituting traditional repeated load triaxial (RLT) data with LWD data for predicting these parameters was notably effective for cohesionless materials, especially for unbound granular materials (UGMs) compacted at optimum water content. The accuracy and reliability of predictions were remarkably high, showcasing the potential of LWD to enhance efficiency and precision in pavement design within this context. Conversely, for cohesive road materials, the study emphasized the importance of considering specific material properties and water content when integrating LWD into the Mechanistic–Empirical Pavement Design Guide. The distinctive characteristics and behaviors of cohesive materials necessitate a nuanced approach. This understanding is critical to ensuring the accuracy and reliability of pavement design and assessment across diverse conditions. In summary, the study presents a promising avenue for utilizing LWD data in cohesionless road materials, offering potential cost and time-saving advantages. Additionally, it underscores the necessity of tailored approaches when considering material properties and moisture content for cohesive materials, thereby advancing the field of pavement engineering by providing insights for improved practices and adaptable frameworks. Full article

The present work analyzes the behavior in terms of corrosion resistance of three reinforced concrete formulations over a period of 1 year. The samples were subject to a monitoring methodology using the Electrochemical Impedance Spectroscopy (EIE) technique, working only with the real component over time. Three mixtures were used, one conventional without pozzolanic addition (REF) and two others with pozzolanic additions, rice husk ash (RHA) and metakaolin (MK). Prototypes were created and exposed to the action of a 165 g/L NaCl sodium chloride solution. The characterization of the materials was carried out by determining the chloride diffusion profile (ASTM 1556), analyzing images using tomography and with the support of analytical techniques such as X-ray fluorescence and X-ray diffraction. The monitoring methodology using EIE demonstrated the positive effect of the insertion of pozzolans, rice husk ash (RHA) and metakaolin (MK) in delaying the process of chloride diffusion in the concrete, resulting in greater resistance to corrosion. The EIE also showed that the active mineral addition in concrete, resulting in aluminum-silicic composition (MK), had a predominant protective effect on the steel/concrete interface against the attack of chloride ions. Full article

This paper aims to investigate the interface efficiency of Carbon Fiber Reinforced Polymers (CFRP) adhesively bonded on concrete, a commonly used retrofitting measure applied for enhancing the deformability and strength of decaying structures or existing ones with low capacity. The efficiency quantification is expressed with the Interface Capacity Index (IC). The index correlates the thickness and strength of each layer of the strengthening system and accounts for the transferred loads (IC_L) and the strain distribution that causes the failure propagation on the concrete substrate (IC_fp). The investigation focuses on different CFRP strengthening schemes (laminated fabrics, prefabricated plates, Near Surface Mounted bars-NSM) applied to concrete substrates using different adhesive layers. Two cases were studied for different levels of concrete’s integrity: (a) healthy and (b) containing corrosion products. The experimental results were used to calibrate the numerical models and to evaluate the effects of different strengthening strategies. The results show the tendency of the strengthening systems to shift the interface performance from fully elastic to non-linear. Further, the quantification of the efficiency of retrofitting can be addressed by accounting for the mechanical and geometrical properties at the interface level, representing different failure modes and integration levels. Full article

This study investigated the influence of carbon fibre addition on the thermal performances of gypsum compositions doped with 20 wt % of phase-change material (PCM) microspheres. The influences of the length (150 µm/3 mm) and additive amount (0.5/2/4 wt %) of the carbon fibres were investigated. Characterizations were performed throughout the various preparation steps to check that the materials aligned with the construction standards. The consistency of compositions with 3 mm carbon fibres did not seem to be suitable for construction implementation. On the contrary, thanks to an adequate amount of thinning additive, the compositions with 150 µm carbon fibres showed acceptable implementation properties. The materials were tested in a climatic chamber under temperature cycles that were either favourable (15 °C/40 °C) or unfavourable (20 °C/40 °C) for the regeneration process of the PCM. Tests with a plateau at 40 °C/15 °C were also performed to obtain a better understanding of the thermal behaviours. The tests were performed using walls with thicknesses of either 15 mm or 30 mm. The results show that, in all cases, the addition of carbon fibres was not beneficial to the thermal performance of the PCM. These observations were in opposition to those of other studies in the literature. We hypothesized that the performances of these composite materials would be different under convective or conductive fluxes. It was also shown that, in unfavourable conditions (20 °C/40 °C), the large thickness of 30 mm could not be fully regenerated, even in the compositions with carbon fibres. However, the PCM of boxes with 15 mm thick walls was deactivated faster (after ~400 min) than that of those with 30 mm thick walls (after ~700 min). Finally, the laboratory results were compared with the results of a previous large-scale study. It was estimated that, despite a surface-to-volume ratio that was 25 times higher, the energy storage efficiency was only increased by a factor of 2.6 between our laboratory study and the large-scale study. Hence, the PCM storage process seems to be mainly involved in maintaining the temperature of the gypsum walls rather than the temperature of the air. Full article

Measuring the flow properties of fiber-laden fresh concrete poses a substantial challenge because not only the fraction of fibers but also their orientation process during the measurement influence the measured quantities. Numerical simulations of the flow in a ball probe rheometer are used to determine the fiber orientation process during the measurement of the flow properties and its influence on the measured variables. Through analytical considerations and comparison with measurement results, it can be shown that the constitutive law applied can reproduce the real flow behavior very well, taking the fiber orientation into account. At the same time, it is investigated why no orientation influence on the torque is recognizable in the experimental measurement curves, although the orientation process demonstrably exceeds the duration of the measurement process. The results show that fluid inertia is overcome before the recognizable onset of fiber orientation, and the spatially inhomogeneous flow minimises the impact of the orientation process on torque. The simulation model aligns well with experimental outcomes, indicating a linear increase in effective viscosity with increasing fiber volume fraction. The findings can be used to accurately measure the objective material parameters of the orientation-considering constitutive law using ball probe rheometers, so that an accurate prediction of the flow process of fresh concrete with fibers is made possible, for example for the simulation of formwork fillings. Full article

Nowadays, roadway infrastructures are designed in order to satisfy technical and economical requirements, as well as to guarantee advanced environmental performance. Focusing on that, this paper deals with an innovative procedure for the characterization of pavement materials, both asphalt and cement-bound mixtures. The methodology takes its cue from a previous study in which the so-called Environmental Asphalt Rating (EAR) was firstly introduced as a reference parameter for asphalt pavements to evaluate technical offers and for the assignment of scores, in terms of environmental impacts, during the tender phase. In this work, the EAR methodology is revised with a focus on the main variations and improvements related to the new version of the ISO standard. By applying the same approach to rigid or concrete pavements, a preliminary version of the Environmental Concrete Rating (ECR) is presented. For ECR, a correction is provided regarding functionality through a fatigue-related parameter and the surface characteristics related to the IRI value. Despite its strong applicability to the pavement sector, the strength of the proposed method is its ability to be fine-tuned to different fields by varying the associated performance coefficients. Full article

The valorisation of lignocellulosic resources, such as oat husks, as components in cementitious composites presents challenges regarding their compatibility with the matrix due to the solubilisation of their surface components and products from alterations induced by the alkaline environment of lime-based matrices. These negatively affect the matrix. This study aims to fill the knowledge gap regarding the compatibility and effects of the extractives found in oat husks with the cement matrix. It intends to characterise oat husks’ structural composition, evaluate the extractive removal efficiency, assess their influence on cement matrix hydration using thermogravimetric techniques, and analyse mechanical strength development between 3 and 28 days. The study concludes that hot water is more efficient for extractive removal, and the immersion duration is more relevant than the number of washing cycles. Furthermore, it confirms that husks’ extractives inhibit cement matrix hydration products and mechanical strength development, especially in the presence of degradation products. These findings are essential for determining more efficient approaches to enhance compatibility between oat husks and cementitious matrices. Full article

Concrete stands as the most widely used construction material globally due to its versatility, encompassing applications ranging from pavement, multifloor structures, and bridges to dams. However, these concrete structures endure structural stress and require close monitoring to prevent accidents and ensure sustainability throughout their complete life cycle. In recent years, artificial intelligence (AI) and computer vision (CV) have demonstrated considerable potential in diverse applications within construction engineering, including structural health monitoring (SHM) and inspection processes such as crack and damage detection, as well as rebar exposure. While it is undeniable that CV and deep learning models are transforming the construction industry by offering robust solutions for complex scenarios, there remain numerous challenges pertinent to their applications that require attention. This paper aims to systematically and critically review the literature of the past decade on the application of deep learning models in the construction industry for SHM purposes in concrete structures. The review delves into proposed methodologies and technologies while identifying opportunities and challenges associated with these applications in practice. Additionally, the paper provides insights to bridge the gap between theory and application. Full article

Fire is a significant threat to human lives and the integrity of buildings. To better understand the complex behavior of masonry exposed to high temperatures, thermal analyses were carried out to evaluate the temperature distribution in concrete blocks and stack-bond prisms exposed to high temperature levels. The effects of distinct specimen boundary conditions (restrict or easy access to air circulation inside the voids of the block and prisms) on the thermal response of the masonry materials were investigated. Thersys 2.0 software was used to implement three-dimensional thermal analysis of distinct finite element models. Four-node tetrahedral elements and full integration were used in all models. The modeling approach was validated by experimental data obtained from thermocouples embedded into masonry components. The results indicated that the boundary conditions significantly affected the time required for homogenization of temperature in blocks and prisms. Easy access to air circulation inside the voids of the prisms provided a faster temperature homogenization. In this scenario, the prism reached temperature ranges of (300 ± 0.5% × 300) °C and (600 ± 0.5% × 600) °C after exposure times of 2 h and 2 h 10 min, respectively. When access to air circulation within the voids of the prisms was limited, the same temperature ranges were achieved after exposure times of 5 h 20 min and 6 h, respectively. Full article

Increasing the amount of crushed natural and recycled fine aggregates in mortar and concrete can help to reduce depletion of resources and increase the recycling rate of construction and demolition waste. Differences in particle morphology influence fresh and hardened mortar and concrete properties. The quantitative assignment of this impact to specific characteristics, such as shape or angularity in differentiation to other mix design parameters, is currently scarcely known. Therefore, a multiple linear regression analysis was performed to investigate the impact of crushed natural and recycled fine particles on rheological and strength properties of mortar. The emphasis lies on the impact of differences in shape and angularity, which were quantified by the three-dimensional particle representation obtained from micro-computed tomography. A total of 160 mortar mixtures containing 5 sands of different origins and varying water-to-cement ratios, binder-to-aggregate ratios, and shapes of grading curves were produced. The results indicate that the particle shape and angularity of the crushed natural and recycled fine aggregates had a complex impact on fresh and hardened mortar properties and interacted with other mix design parameters. Careful composition of the aggregate fraction with respect to shape and angularity and their interaction with mix design parameters is necessary to maintain sufficient mortar properties. Full article

The ordinary Portland cement (OPC) component of concrete is the highest contributor to concrete’s cost and carbon footprint. Historically, code-writing organizations have required a high volume of paste in concrete mixtures by imposing minimum limits on the OPC content for a given application. However, high paste contents can result in dimensional instability, higher costs, higher carbon footprints, and lower durability. Minimizing the OPC content in concrete can provide economic, durability, and sustainability benefits. This study hypothesizes that the amount of OPC required to achieve some required fresh and hardened characteristics is highly dependent on the aggregate characteristics, supplementary cementing material (SCM) characteristics, and proportions of these. Given this, this research proposes using the amount of voids in the aggregate system (AV), or more specifically the paste volume-to-aggregate void ratio (PV/AV); SCM reactivity; and the SCM replacement level as key parameters to proportion concrete mixtures with minimum OPC contents to meet sustainability, economic, and resilience (SER) requirements. A new mixture proportioning procedure, referred to here as the SER proportioning method, is developed in this study based on assessing AV and identifying an optimal PV/AV that satisfies the required concrete characteristics. The results show that implementing the SER mixture proportioning method and including SCMs, or more specifically off-spec fly ashes (OFAs), can lead to significant reductions in the paste content and associated reductions in the cost and embodied carbon footprint of concrete. Full article

The world is currently grappling with the two critical issues of global warming and climate change, which are primarily caused by the emission of greenhouse gases. The construction industry and buildings significantly contribute to these emissions, accounting for roughly 40% of the total greenhouse gas emissions. In response to this pressing issue, environmental organizations and governments have pushed the construction industry to adopt environmentally friendly practices to reduce their carbon footprint. This has led to a greater emphasis on designing and planning sustainable buildings that are in line with the principles of sustainable development. Hence, it is imperative to evaluate buildings in terms of their greenhouse gas emissions and explore ways to reduce them. This research examines the impact of material selection on the carbon footprint of reinforced concrete buildings, aiming to reduce embodied carbon. For this purpose, two reinforced concrete buildings are designed for their embodied carbon to quantify their environmental impact. The first building employs commonly used materials such as ceramics, clay bricks, stone, and plaster. In contrast, the second building incorporates sustainable materials such as cork, plywood, and rockwool. According to the findings, using sustainable materials in the second building leads to a 41.0% reduction in the carbon footprint of the construction process. Additionally, using sustainable materials can mitigate pollution levels in the three categories of endangerment to human health, ecosystem pollution, and resource consumption by 31.4%, 23.7%, and 33.3%, respectively. Full article