6 Field-Observed Cracking of Paired Lightweight and Normalweight Concrete Bridge Decks

Research has suggested that conventional lightweight concrete can offer durability advantages due to reduced cracking tendency. Although a number of publications exist providing the results of laboratory-based studies on the durability performance of lightweight concrete (with lightweight coarse aggregate) and internally cured concrete (using prewetted lightweight fine aggregate), far fewer field studies of durability performance of conventional lightweight concrete bridge decks in service have been performed. This study was commissioned to provide insight to a highway agency on whether enhanced durability performance, and therefore reduced maintenance and longer lifecycles, could be anticipated from existing lightweight concrete bridge decks that were not intentionally internally cured. To facilitate performance comparison, each lightweight bridge deck selected for inclusion in this study was paired with a companion normalweight bridge deck on a bridge of similar structural type, deck thickness, and geometric configuration, with similar age, traffic, and environmental exposure. The field-observed cracking of the decks was recorded and evaluated, and crack densities for transverse, longitudinal, and pattern cracking of the normalweight and lightweight deck in each pair were compared. Although some trends linking crack prevalence to geographic location, traffic, and age were observed, a distinct difference between the cracking present in the paired lightweight and normalweight bridge decks included in this study was not readily evident. Statistical analysis using analysis of covariance (ANCOVA) to adjust for age and traffic influence did not indicate that the type of concrete deck (lightweight or normalweight) is a statistically significant factor in the observed cracking. Therefore, for these service environments, lightweight decks did not consistently demonstrate reduced cracking

Recycled brick masonry aggregate concrete : use of recycled aggregates from demolished brick masonry construction in structural and pavement grade portland cement concrete

Reuse of construction waste as aggregates is becoming increasingly popular for a number of environmental and economic reasons. In this study, structural- and pavement-grade portland cement concrete (PCC) mixtures were developed using crushed recycled brick masonry from a demolition site as a replacement for conventional coarse aggregate. Prior to developing concrete mixtures, testing was performed to determine properties of whole clay brick and tile, as well as the crushed recycled brick masonry aggregate (RBMA). Concrete mixtures exhibiting acceptable workability and other fresh concrete properties were obtained, and tests were performed to assess mechanical properties and durability performance of the hardened concrete. Results indicated that recycled brick masonry aggregate concrete (RBMAC) mixtures can exhibit mechanical properties and durability performance characteristics comparable to that of structural- and pavementgrade PCC containing conventional coarse aggregates. Based on current North Carolina Department of Transportation (NCDOT) requirements, the suitability of RBMAC for use in pavement applications was evaluated, and the Mechanistic-Empirical Pavement Design Guide procedure was used to compare the potential performance of RBMAC pavement to conventional PCC pavement. Results indicated that RBMAC provides acceptable performance in pavement applications, where its thermal properties produce thinner pavement sections than PCC. This research gives designers a first look at some of the salient material properties that will influence future use of RBMA and RBMAC

UAV Selection Methodology and Performance Evaluation to Support UAV-Enabled Bridge Inspection

This project performed preliminary work to support use of Unmanned Aerial Vehicles (UAV)-based for bridge inspections, providing an economical and safer alternative to conventional inspection practices. The main challenge is that most existing technologies rely on general-purpose UAV platforms and there is no verified methodology for UAV-enabled bridge inspection principles and relevant considerations to reliably obtain inspection data. There have been some efforts to use general-purpose commercially available UAVs for bridge inspection. However, the turbulent environment that often exists around bridges requires customized and enhanced UAV platforms with a higher level of robustness, taking into account the bridge type and structure as well as the weather conditions around the bridge. Additionally, the data-acquisition capabilities of commercially available UAVs need to be compared to those required for bridge inspection. Previously, there has not been a study to quantify the gap between the performance of the commercially available UAVs and ideal desired performances. In this multidisciplinary project, a comprehensive set of experiments were developed for selection, testing, and evaluation techniques of candidate UAVs, the complex nature of flying UAVs in close proximity to bridges was explored, and the limitations of UAV flight due to turbulent flows around bridge components and nearby terrain was assessed. Commercially available platforms for bridge inspection were selected, tested, and evaluated. Deliverables from this project include: (1) measurable metrics to evaluate the performance of UAVs for bridge inspection, (2) experiments to test the suitability of UAVs for bridge inspection, and (3) a comprehensive analysis near-bridge environment flow field. Computational analysis of air flow patterns near bridge elements shows that the bridge geometry creates areas of turbulence and flow variation which impact the control requirements of the UAV. Local weather conditions can amplify these areas. Test flights were performed at selected structures to provide additional insight into the flight and data collection capabilities of the UAVs under consideration. Findings and deliverables from this project will help NCDOT justify capital purchases made to support UAV-assisted inspection, as well as additional research needed to integrate UAVs into their current bridge inspection processes. Ultimately, this work supports a follow-up project to develop workflows and implementation tools for efficient UAV-enabled bridge inspection

Learning from the World Trade Center Collapse – Use of a Failure Case Study in a Structures and Materials Laboratory Course

The use of failure case studies has been shown to benefit technical, professional, and ethical student learning outcomes in undergraduate education. Recently, incorporation of failure case studies into undergraduate civil engineering, civil engineering technology, construction management, and architecture curricula has been facilitated by the development of educational resources as part of a National Science Foundation (NSF) grant. This paper outlines the approach utilized to incorporate the World Trade Center Collapse case study into a junior-level Structures and Materials Laboratory course in an engineering technology and construction management program, identifying the technical and professional component outcomes supported by this case study. Assessment techniques utilized to evaluate technical comprehension of the building performance, as well as to evaluate the impact of this case study on student’s interest in the engineering profession, are presented and discussed

Learning from the World Trade Center Collapse – Use of a Failure Case Study in a Structures and Materials Laboratory Course

The use of failure case studies has been shown to benefit technical, professional, and ethical student learning outcomes in undergraduate education. Recently, incorporation of failure case studies into undergraduate civil engineering, civil engineering technology, construction management, and architecture curricula has been facilitated by the development of educational resources as part of a National Science Foundation (NSF) grant. This paper outlines the approach utilized to incorporate the World Trade Center Collapse case study into a junior-level Structures and Materials Laboratory course in an engineering technology and construction management program, identifying the technical and professional component outcomes supported by this case study. Assessment techniques utilized to evaluate technical comprehension of the building performance, as well as to evaluate the impact of this case study on student’s interest in the engineering profession, are presented and discussed

Influence of Lightweight Aggregate Concrete Materials on Building Energy Performance

Due to their porous nature, lightweight aggregates have been shown to exhibit thermal properties that are advantageous when used in building materials such as lightweight concrete, grout, mortar, and concrete masonry units. Limited data exist on the thermal properties of materials that incorporate lightweight aggregate where the pore system has not been altered, and very few studies have been performed to quantify the building energy performance of structures constructed using lightweight building materials in commonly utilized structural and building envelope components. In this study, several lightweight concrete and masonry building materials were tested to determine the thermal properties of the bulk materials, providing more accurate inputs to building energy simulation than have previously been used. These properties were used in EnergyPlus building energy simulation models for several types of commercial structures for which materials containing lightweight aggregates are an alternative commonly considered for economic and aesthetic reasons. In a simple model, use of sand lightweight concrete resulted in prediction of 15–17% heating energy savings and 10% cooling energy savings, while use of all lightweight concrete resulted in prediction of approximately 35–40% heating energy savings and 30% cooling energy savings. In more complex EnergyPlus reference models, results indicated superior thermal performance of lightweight aggregate building materials in 48 of 50 building energy simulations. Predicted energy savings for the five models ranged from 0.2% to 6.4%

Influence of Lightweight Aggregate Concrete Materials on Building Energy Performance

Due to their porous nature, lightweight aggregates have been shown to exhibit thermal properties that are advantageous when used in building materials such as lightweight concrete, grout, mortar, and concrete masonry units. Limited data exist on the thermal properties of materials that incorporate lightweight aggregate where the pore system has not been altered, and very few studies have been performed to quantify the building energy performance of structures constructed using lightweight building materials in commonly utilized structural and building envelope components. In this study, several lightweight concrete and masonry building materials were tested to determine the thermal properties of the bulk materials, providing more accurate inputs to building energy simulation than have previously been used. These properties were used in EnergyPlus building energy simulation models for several types of commercial structures for which materials containing lightweight aggregates are an alternative commonly considered for economic and aesthetic reasons. In a simple model, use of sand lightweight concrete resulted in prediction of 15–17% heating energy savings and 10% cooling energy savings, while use of all lightweight concrete resulted in prediction of approximately 35–40% heating energy savings and 30% cooling energy savings. In more complex EnergyPlus reference models, results indicated superior thermal performance of lightweight aggregate building materials in 48 of 50 building energy simulations. Predicted energy savings for the five models ranged from 0.2% to 6.4%

Methods of Test for Concrete Permeability: A Critical Review

The transport of liquids, gasses, and aggressive agents into concrete is responsible for a variety of durability issues. To obtain the low-permeability concrete required for long-lasting, sustainable infrastructure, stakeholders desire the ability to specify concrete based upon the permeability rating for specific uses. The mechanisms of moisture ingress into concrete are complex phenomena, and they are highly dependent on materials, mixture characteristics, curing conditions, and other factors. This review article provides an overview of the available permeability test methods and identifies existing gaps in the current field and knowledge. It discusses the mechanisms and key factors influencing moisture movement within concrete (capillary suction, absorption, water, and gas permeability) and outlines the procedures, advantages, and limitations of available permeability test methods. Despite a variety of tests available for water permeability, widespread acceptance for use of a single (or even a few) tests has not been achieved. No clear link exists between these tests and acceptable field performance. Additionally, several tests are viewed as problematic from a time, cost, or variability standpoint. Therefore, improved rapid permeability tests are needed to provide a pathway for agencies to move toward performance specifications with confidence. Recommendations regarding future work to support the development of improved test methods and, potentially, a model that would predict moisture ingress based on electrical resistivity, are also presented.This article is published as Milla, Jose, Tara L. Cavalline, Tyson D. Rupnow, Bharath Melugiri-Shankaramurthy, Gilson Lomboy, and Kejin Wang. "Methods of Test for Concrete Permeability: A Critical Review." Advances in Civil Engineering Materials 10, no. 1 (2021): 172-209. DOI: 10.1520/ACEM20200067. Copyright 2021 ASTM Int'l. Posted with permission

Building Materials Reclamation Program

This report describes work conducted on the Building Materials Reclamation Program for the period of September 2008 to August 2010. The goals of the project included selecting materials from the local construction and demolition (C&D) waste stream and developing economically viable reprocessing, reuse or recycling schemes to divert them from landfill storage. Educational resources as well as conceptual designs and engineering feasibility demonstrations were provided for various aspects of the work. The project was divided into two distinct phases: Research and Engineering Feasibility and Dissemination. In the Research Phase, a literature review was initiated and data collection commenced, an advisory panel was organized, and research was conducted to evaluate high volume C&D materials for nontraditional use; five materials were selected for more detailed investigations. In the Engineering Feasibility and Dissemination Phase, a conceptual study for a regional (Mecklenburg and surrounding counties) collection and sorting facility was performed, an engineering feasibility project to demonstrate the viability of recycling or reuse schemes was created, the literature review was extended and completed, and pedagogical materials were developed. Over the two-year duration of the project, all of the tasks and subtasks outlined in the original project proposal have been completed. The Final Progress Report, which briefly describes actual project accomplishments versus the tasks/subtasks of the original project proposal, is included in Appendix A of this report. This report describes the scientific/technical aspects (hypotheses, research/testing, and findings) of six subprojects that investigated five common C&D materials. Table 1 summarizes the six subprojects, including the C&D material studied and the graduate student and the faculty advisor on each subproject