https://hdl.handle.net/1721.1/102447 2026-04-03T20:55:57Z https://hdl.handle.net/1721.1/153636 Transforming the Role of the Concrete Delivery Professional: A Study on Innovative Solutions for the Ready Mixed Concrete Industry Kirchain, Randolph; Field, Frank; Unger, Elizabeth; Moore, Elizabeth Currently, there is a severe shortage of concrete delivery professionals (CDPs) – the individuals who transport concrete from the plant to the construction site. In fact, according to a recent study by the National Ready Mixed Concrete Association (NRMCA), 70% of concrete producers had to turn away business because their CDP workforce was insufficient to satisfy demand. This report presents the findings of a research project conducted by the MIT Concrete Sustainability Hub (CSHub), with funding by the Concrete Advancement Foundation, that explores both immediate and long-term innovative strategies to address the national CDP shortage and transform the role of the CDP. These solutions are organized into three categories to reflect the primary way in which each impacts the CDP shortage challenge: productivity, recruitment, and retention. The CSHub research team used a multi-disciplinary approach to arrive at these solutions. The approach included an analysis of over 36,000 concrete deliveries to identify efficiency opportunities, interviews with various industry stakeholders; the construction of a representative ready mix operational simulation model to estimate the value of improving productivity, recruitment, and retention; a survey of over 500 CDPs across the U.S.; and an industry workshop to recognize key barriers to the adoption of proposed recommendations. 2024-03-04T00:00:00Z https://hdl.handle.net/1721.1/130043 Research Brief: Creating Customized Fragility Curves for Resilient Building Mulla, Talal; Pellenq, Roland; Ulm, Franz-Josef Fragility curves, which are a statistical tool that represent the probability of exceeding a certain level of structural damage due to various forces applied to a building, are used to assess anticipated building performance. For new construction and retrofitting alike, designers and builders need to understand the risks their buildings face from environmental loads such as hurricanes, floods, or earthquakes. The role of the fragility curve is important when building for resilience, but it is often overlooked due the challenge of applying it early in the design and process. The anticipated damage estimation from fragility curves has far reaching effects downstream in construction and maintenance over the building lifetime, but fragility curves are not readily generated for each building and each loading scenario. Instead, databases like those used by the Federal Emergency Management Agency’s (FEMA) Hazus software rely on a set number of building types and loading classes. The ability to construct on-demand customizable fragility curves for a particular building with a particular load or maintenance level across the building’s lifetime is still an open problem.  2018-11-01T00:00:00Z https://hdl.handle.net/1721.1/130042 Research Brief: The Influence of Incorporating Uncertainties and Treatment Path Dependence in Performance-based Planning Analyses Guo, Fengdi; Gregory, Jeregmy; Kirchain, Randolph According to the American Society of Civil Engineers (ASCE) 2017 Infrastructure Report Card, the backlog for repair of existing highways across the U.S. totals approximately $420 million. With funding at all-time lows, it is important that agencies select maintenance, rehabilitation & reconstruction (MRR) activities through use of efficient budget allocation models. One key consideration during the allocation process is the evaluation of each available treatment. At present, most budget allocation models use a benefit-cost ratio to evaluate treatments. This approach, while convenient, is limited in current implementations because they only consider the benefits of a current treatment and assume a known, fixed future. For example, when evaluating an asphalt overlay such an approach assumes this is always followed with another asphalt overlay. The CSHub has developed a new approach called the probabilistic treatment path dependence (PTPD) model in which MRR treatment decisions consider benefits of each possible current action, the likelihood of future conditions (e.g., road deterioration, prices, etc), and the optimal future actions to take given an uncertain future. With this approach, when evaluating an asphalt overlay, we assume that it may be followed by an asphalt overlay or a concrete overlay depending on future prices and the rate of deterioration. This research brief focuses on the benefits of incorporating uncertainties and treatment path dependence by comparison between the conventional benefit cost ratio (B/C) model and the new PTPD model. 2018-11-01T00:00:00Z https://hdl.handle.net/1721.1/130041 Research Brief: Climate Change Mitigation Potential of Pavement Albedo Xu, Xin; Gregory, Jeregmy; Kirchain, Randolph Albedo is the measure of how much solar energy is reflected by the Earth’s surface. Lighter color, or high-albedo, surfaces absorb less sunlight energy and reflect more shortwave radiation. Increasing pavement albedo has been considered as a technological strategy to mitigate impacts of climate change through a mechanism known as radiative forcing. Studies have applied simple analytical models to quantify the impact of changes in land cover on global climate. However, gaps exist in regards to quantifying the transmittance of radiation through the atmosphere and due to uncertainties with variations in time and space. In fact, the radiative forcing impact due to pavement albedo enhancement for a specific location depends largely on local radiation intensity and atmospheric conditions, which are affected by context-specific factors such as solar angle, water content, and the presence of small atmospheric particles called aerosols. 2018-01-01T00:00:00Z https://hdl.handle.net/1721.1/130040 Research Brief: The Role of Pavements in Meeting GHG Reduction Targets AzariJafari, Hessam To meet the targets for reducing greenhouse gas (GHG) emissions set by cities and states, several solu­tions have been proposed including renewable energy production, subsidies for electric vehicles, and carbon taxes. However, transportation authorities have not considered the role of pavements as a means of reach­ing GHG targets. In fact, apart from impacts associated with materials production and construction equipment, pavements exert a substantial environmental impact by influencing vehicle fuel consumption. To better under­stand the overall effect of the road network on climate change, a high-level analysis is required that inves­tigates how pavement policymaking can help reach GHG reduction targets. Different choices in the budget assigned to road preservation and repair should be considered to find the optimal contribution of the road network to GHG mitigation and meet targets. 2019-08-01T00:00:00Z https://hdl.handle.net/1721.1/130039 Research Brief: Generating Building-specific Fragility Curves Mulla, Talal; Pellenq, Roland; Ulm, Franz-Josef Fragility curves represent a structure’s likelihood of damage under a range of load levels—like those from natural hazards. They, therefore, help to set building code safety factors, resiliency ratings, and even insurance premiums. Unfortunately, there is no real standard for generating these fragility curves for wind loading. FEMA’s HAZUS hurricane model is the closest to a current standard for wind-load fragility curves. However, even this rigorous database generates curves for only specific building types by aggregating the curves of their components (e.g., windows, siding, roof) (see Figure 1). Though useful, this aggregation approach limits the generation of customizable curves for unique buildings that deviate from the standard HAZUS types. 2019-05-01T00:00:00Z https://hdl.handle.net/1721.1/130038 Research Brief: Capillary Stress During Cement Drying Shrinkage Zhou, Tingtao (Edmond); Pellenq, Roland; Bazant, Martin; Gregory, Jeremy; Kirchain, Randolph Imagine a household sponge lying next to a kitchen sink. The sponge looks and feels different when it is wet versus when it is dry. When a sponge dries, it shrinks, curls and hardens due to suction forces (called “capillary stress”) which change its mechanical properties. Although the material compositions are different, the same mechanism occurs in cement paste. The process takes considerably longer for cement paste but, like a sponge, the material is quite porous and when there are changes to outside relative humidity, due to rain or a series of dry days, the pores inside cement can be filled with water or become empty. The water can generate high stresses as the pores expand (when very wet) and shrink (when dry), which in turn affects the properties of the material. This research proposes a general and accurate framework to calculate the consequences of these stresses and explain the cement drying shrinkage curve (drying above 40% relative humidity) based on a model of the pore structure. 2018-06-01T00:00:00Z https://hdl.handle.net/1721.1/130037 Research Brief: Prioritizing Resilient Retrofits Roxon, Jake; Pellenq, Roland; Ulm, Franz-Josef 2017 was one of the most devastating U.S. hurricane seasons ever recorded. State Departments of Public Safety across the country list tens of thousands of destroyed homes and hundreds of thousands more damaged. Although the total economic impact is still being measured, estimates from NOAA’s National Centers for Environmental Information place damage costs for weather and climate related disaster events at over $300B, with hurricane-related costs accounting for more than $200B of that total. While it’s true that rebuilding infrastructure to be more resilient will reduce the risk of future damage, it is not feasible to rebuild entire cities. It is possible, however, to identify the specific buildings in cities that are most vulnerable to failure as a result of intensified wind loads and to make those buildings much more resistant to hurricane damage through already well-known hurricane-proof retrofitting techniques. In this brief we examine how additional long-range city texture parameters can be used to create urban models that enhance our previously established computational fluid dynamics (CFD) methods. 2018-02-01T00:00:00Z https://hdl.handle.net/1721.1/130035 Research Brief: Modeling the Freeze-Thaw Damage Mechanism in Cement Zhou, Tingtao (Edmond); Mirzadeh, Mohammad; Pellenq, Roland; Bazant, Martin Freeze-thaw (FT) damage is a significant threat to roads and pavement, yet the underlying mechanism is still unclear. Conventional thinking attributes the damage to pressure generated by expansion of water upon freezing. However, this idea fails to explain three phenomena: 1) only above a critical degree of water saturation will FT damage occur; 2) the use of de-icing salt aggravates FT damage; 3) cement mortars loaded with benzene, a fluid that shrinks upon freezing, also experience FT damage. While salt crystallization, which occurs during freezing, is correlated with damage in some instances, its role still remains unclear. 2019-01-01T00:00:00Z https://hdl.handle.net/1721.1/130034 Research Brief: Concrete building design optimization for reduced life cycle costs and environmental impacts Hester, Josh; Gregory, Jeremy; Kirchain, Randolph Decisions made at early stages of the building design process can have a large influence on the environmental performance and financial costs of a building. One of the best ways to discover preferable designs is to analyze and compare many different alternatives. However, due to time and data requirements, assessments of a building’s environmental impacts and costs can be time-­consuming and difficult to perform early on. Even with streamlined tools, such as the CSHub-­developed Building Attribute to Impact Algorithm (BAIA), it can still be difficult to minimize lifetime impacts and costs through manual comparisons of alternatives. Combining tools like BAIA with optimization methods can help identify the best ranges for key design parameters. 2018-04-01T00:00:00Z https://hdl.handle.net/1721.1/130033 Research Brief: Validation of Molecular Dynamics-Based Structural Damage Keremidis, Kostas; Pellenq, Roland Windstorms currently generate $28 billion in average annual damage and this figure is projected to potentially rise to $38 billion by 2075. Traditional engineering approaches that analyze the resilience of structures fail to account for non-structural damage because of the difficulties in modeling such damage. Additionally, even detailed frameworks, like FEMA’s HAZUS-MH, provide results only for categories of building types. While it is possible to model the sudden impact of loads from hazards like windstorms using such existing frameworks, a methodology does not exist by which to readily and quantitatively model such damage to unique building designs. 2019-03-01T00:00:00Z https://hdl.handle.net/1721.1/130032 Research Brief: Optimizing Building Life Cycle Environmental Impact and Cost Liu, Jingyi Existing building life cycle assessment tools rely on detailed building models that make it difficult to explore the environmental implications of design strategies in the earliest design phases. Most of these tools are separate from architectural design software tools, which hinders the exploration of a wide range of design solutions and therefore limits opportunities to optimize designs for environmental impacts. We seek to address this gap by developing a plug-in for the design software Rhino that optimizes life cycle environmental impact and cost for early design stage conceptual geometries when only the building shape is specified.  2020-02-01T00:00:00Z https://hdl.handle.net/1721.1/130030 Research Brief: Meeting Greenhouse Gas Reduction Targets in the Building Sector Vahidi, Ehsan; Gregory, Jeregmy; Kirchain, Randolph As the threat of climate change grows, lowering the greenhouse gas (GHG) emissions of high emitting sectors of the economy has become critical. The buildings sector is particularly significant, consuming up to 40% of total global energy demand. To lower the associated emissions and meet GHG reduction targets, stakeholders must consider both the energy consumption over a building’s operational life, or use phase, and the embodied emissions generated during its construction. Since concrete is a ubiquitous building material and significantly influences both embodied and use phase emissions, its environmental footprint is worthy of investigation. 2019-07-01T00:00:00Z https://hdl.handle.net/1721.1/130029 Research Brief: Simulating the Formation of ASR Gels Dupuis, Romain; Pellenq, Roland Alkali-silica-reaction (ASR) is a significant cause of premature concrete deterioration. Although it has received much research attention, an essential question still remains—how does a soft gel, as is formed by this reaction, induce the critical level of stress to exceed the strength of, and crack the concrete matrix? One possibility is that the ASR gel increases in viscosity as it imbibes calcium with age and a concomitant expansion causes the concrete failure. Another is that the gel’s rate of flow into the porous microstructure is slower than the rate at which it forms, which builds up stresses that cannot be relieved. To better understand ASR mechanisms and to eventually test these hypotheses, we sought a basic understanding at the atomic scale. 2019-04-01T00:00:00Z https://hdl.handle.net/1721.1/130028 Research Brief: A Reaction-­Diffusion Model to Determine Mesoscale Patterns in Cement Paste Petersen, Thomas; Bazant, Martin; Pellenq, Roland; Ulm, Franz-Josef Strength and toughness, two important aspects of the durability of concrete structures, are dramatically influenced by the material’s nanotexture, but the question of how the building blocks of cement paste organize themselves to create this nanotexture is still being answered. Recent modelling efforts by CSHub researchers demonstrated a convincing pathway. Upon mixing water with cement clinker, ions dissolve into the pore solution and precipitate out nanometer-sized grains of calcium-silicate-hydrates (C-S-H). These building blocks are the glue that binds sand and gravel together and the primary ingredient for concrete. The organization of these C-ˇS-ˇH grains drastically influences concrete’s mechanical performance. By better understanding which parameters influence this organization, we hope to create longer-lasting, more durable materials. 2018-08-01T00:00:00Z https://hdl.handle.net/1721.1/130027 Research Brief: A Resilience Assessment of Structures Using Molecular Dynamics Keremidis, Kostas; Abdolhosseini Qomi, Mohammad Javad; Pellenq, Roland; Ulm, Franz-Josef Between 1993-ˇ2012, more than 75% of catastrophic losses in the United States were caused by windstorms (1). The Congressional Budget Office estimated an average annual damage amounting to $28 billion (0.16 percent of GDP), with a potential rise to $38 billion by 2075 – 55% of which is attributed to coastal development (2). This economic impact of wind related events calls for reevaluation of engineering approaches. Traditional structural mechanics approaches evaluate wind damage of structural elements (i.e. beams, plates, walls) in relation to a design code, while not accounting for the contribution of non-ˇstructural elements (i.e. sheathings, windows) which clearly reflect on building integrity (3). While more detailed frameworks accounting for all elements do exist, such as the Federal Emergency Management Agency’s HAZUS-ˇMH (FEMA 2016), they are only limited to specific building types and qualitative damage description (i.e. slight, moderate, extensive damage, and so on) (4). This motivates the development of an approach that can quantitatively address the complexity of buildings in element scale (i.e. structural/non-ˇstructural elements), and system scale (accounting for any building use and geometry). 2018-06-01T00:00:00Z https://hdl.handle.net/1721.1/130026 Research Brief: Implications of energy code evolution on energy performance of multi-­family residential buildings in the US Noori, Mehdi; Gregory, Jeremy The International Energy Conservation Code (IECC), which is created by the International Code Council (ICC), standardizes expectations for the design and construction of buildings with regards to energy use and conservation over the structure’s lifetime. With every new release these codes get more stringent. The goal of this analysis was to quantify how the evolution of these building codes has impacted the energy performance of buildings. 2018-03-01T00:00:00Z https://hdl.handle.net/1721.1/130025 Research Brief: Generating Component-level Building-specific Fragility Curves Mulla, Talal One of the most essential tools for representing the vulnerability of a structure is the fragility curve. By captur­ing the probability of damage at a given load level, fragility curves provide a way to express how a structure may respond to wind, fire, or seismic hazards. CSHub researchers have developed a method to integrate the structural and non-structural members into a single materials-specific fragility curve for any given building type. 2020-11-01T00:00:00Z https://hdl.handle.net/1721.1/130024 Research Brief: Improving Pavement Network Conditions Through Competition Guo, Fengdi Past CSHub research has shown that increased competition among paving material substitutes is correlated with lower unit prices for both asphalt and concrete. Thus, there is potential for increased competi­tion to increase the amount of paving that can be done in a network for the same amount of investment. In this brief, researchers present results of an analysis showing how increased paving competition and a sophis­ticated budget allocation model can improve pavement network condition and reduce GHG emissions. 2020-10-01T00:00:00Z https://hdl.handle.net/1721.1/130023 Research Brief: Mitigation Solutions for GHG Emissions in New Construction Vahidi, Ehsan By 2050, the United States is projected to add 121 billion ft2 of buildings—equivalent to constructing New York City every year for the next 20 years. However, to meet climate change goals the U.S. building sector must also significantly reduce its greenhouse gas (GHG) emissions. In this brief, we investigate which GHG mitigation solutions could help meet these GHG targets even as the nation experiences such unprecedented construction.  2020-09-01T00:00:00Z https://hdl.handle.net/1721.1/130022 Research Brief: Assessing Road Quality Using Crowdsourced Smartphone Measurements Botshekan, Meshkat As the demands on the nation’s roads increase, so too have road maintenance costs. To meet these challenges, agencies must vigilantly monitor road surface quality to properly apportion resources. Traditional methods of assessing road quality, however, remain costly and time-consuming. As an alternative, CSHub has developed a crowd­sourcing tool in collaboration with the University of Massachusetts Dartmouth. This tool, called the Carbin app, can offer agencies high-quality data at a lower price and in real-time. Carbin is available on the App Store and Google Play and has collected over 250,000 miles of data since 2019. 2020-07-01T00:00:00Z https://hdl.handle.net/1721.1/130021 Research Brief: Influence of Treatment Types on Performance-based Planning Guo, Fengdi U.S. departments of transportation (DOTs) currently face significant budget shortages: According to the ASCE 2017 Infrastructure Report Card, the backlog of repairs for existing highways is $420 billion. To optimize DOT spending and improve pavement network performance, the Moving Ahead for Progress in the 21st Century (MAP-21) Act requires transportation agencies to use performance-based planning to develop a strategy for meeting performance targets within a budget constraint using pavement treatments, which mainly include preservation, overlay, and reconstruction (POR). For many DOTs, preservation has had a higher priority due to its low price. However, when compared to overlay and reconstruction, preservation is less durable and offers shorter-term performance. In this study, we explore the influence of different treatment types on pavement network performance and provide insights into performance-based planning.  2019-08-01T00:00:00Z https://hdl.handle.net/1721.1/130020 Research Brief: Molecular Dynamics-based Resilience Assessment of Structures Keremidis, Kostas According to the National Fire Protection Association (NFPA), losses due to fire in structures in America amount to around $13 billion annually. Despite these severe economic consequences, building codes often don’t adequately predict the failure of an entire structure. Instead, they tend to model fire damage in individual elements without considering the greater building ensemble (all the elements together with their connections). Therefore, CSHub has developed a model that quantifies the complexity of fire at the element-scale (such as the spalling of concrete elements) as well as at the system-scale (accounting for any building use, geometry, etc.).  2020-07-01T00:00:00Z https://hdl.handle.net/1721.1/130019 Research Brief: Investigating the Mechanisms of ASR Using Atomistic Methods Dupuis, Romain With 20% of highway pavements in the U.S. in poor condition, mitigating pavement failure has become increasingly important. However, the mechanisms of the alkali-silica-reaction (ASR), a leading cause of damage in concrete pavements, remain unclear. Although it is well known that ASR can lead to cracking over many decades, a need still exists to under­stand the reaction at the atomic scale—in particular, the dissociation and formation of silicates in water. For this, it is necessary to have an atomistic approach. 2020-05-01T00:00:00Z https://hdl.handle.net/1721.1/130018 Research Brief: Can Passive House and Zero-energy Building Standards Promise a Low-carbon Future? Burek, Jasmina Passive house (PH) and zero-energy building (ZEB) standards aim to reduce the energy consumption and carbon footprints of buildings. The PH concept implies a low energy consumption achieved through passive technology such as insulation and energy-efficient HVAC systems. A ZEB is an energy-efficient building that gen­erates enough renewable energy to offset or even exceed the energy it consumes from the grid. Previous research has shown higher embodied energy and costs for PH and ZEB compared to conventional buildings. To date, very few projects have shown that a PH could be done within a budget comparable to similar standard homes, which calls into question the economic viability of PH. However, most analyses were done using comparisons of individual designs for specific scenarios, making it difficult to draw broad conclusions. We conducted an analysis comparing a wide range of conventional, PH, and ZEB designs in order to have a better understanding of the economic and environmental trade-offs of these strategies. 2020-05-01T00:00:00Z https://hdl.handle.net/1721.1/130017 Research Brief: Community-Informed Building-Scale Resilience Assessment Manav, Ipek Bensu It is widely known that natural hazards, like hur­ricanes, cause tremendous levels of damage and that hazard mitigation can significantly curb natural haz­ard-induced losses. However, necessary investments are still needed for the widespread implementation of hazard mitigation practices. We believe that this lack of invest­ment stems from the underestimation of potential losses by present tools, which discount the effect of community characteristics on losses accrued by individual house­holds. This brief presents a framework that incorporates community characteristics like urban texture to enable a community-informed building scale resilience assess­ment. With this framework, stakeholders will be able to capture the true value of hazard mitigation practices. 2020-02-01T00:00:00Z https://hdl.handle.net/1721.1/129352 A Scientific Investigation into Concrete Pavement Durability Pellenq, Roland; Bazant, Martin; Dufresne, Alice; Dupuis, Romain; Gregory, Jeremy; Ioannidou, Katerina; Yip, Sidney; Zhou, Tingtao; Weiss, Jason; Ghantous, Rita; Ideker, Jason; Qiao, Chunyu; Suraneni, Prannoy; Thomas, Michael; Moffatt, Ted; Jack, Areyro; Haist, Michael; Rajabipour, Farshad; Béland, Laurent; Barcelo, Laurent; Ben Haha, Mohsen; Lobo, Colin; Popoff, Nick; Tennis, Paul; Tritsch, Steven Although concrete pavements offer many long-term performance benefits, there are still instances where premature degradation of pavements leads to unexpected and costly repairs. In addition to being a burden to transportation agencies and the driving public, these situations have the potential to unduly tarnish the reputation of concrete pavements. We assembled a multidisciplinary team across multiple universities whose objective was to improve the durability of concrete pavements by improving the scientific understanding of pavement distresses. In particular, we sought to develop a quantitative understanding of the chemical reactions to the physical manifestation of concrete pavement damage from alkali–silica reaction (ASR) and freeze-thaw (FT). This will lay the foundation for connecting pavement material properties and fracture and durability prediction, while also helping to establish the potential for ASR and/or FT damage in a concrete pavement and the rate at which it would happen. In essence, it will identify the conditions that lead to ASR or FT damage. The research approach involved a range of experiments including nano-scale chemomechanical characterization of ASR gels, mechanical and thermal characterization of cement paste after meso-scale FT cycling, and likelihood of ASR damage for concrete mixtures. The modeling approach included analytical and simulation models of ASR, FT, and fracture at the nano-, meso-, and micro scales. The key outcome of this project is a unified theoretical framework for explaining both ASR and FT damage. Detailed explanations for both mechanisms are as follows. FT: by combining mechanical and characterization experiments together with atomistic and mesoscale simulations, we found that there is NO direct impact of an ice phase in damage to the paste and concrete. FT damage in concrete/cement paste appears to result from a disjoining ionic pressure at the C-S-H/ice interface in the capillary pore network which is that fractures the C-S-H matrix. Computer-simulated effects with the type and concentration of ions in the pore solution agree well with experiments. ASR: by combining mechanical and characterization experiments together with atomistic and mesoscale simulations, we found that the swelling of ASR gel is NOT the reason for damage to concrete. ASR damage is likely the consequence of a Na+ Ca2+ exchange mechanism between an initially formed alkali gel that is deficient in Ca (Ca-poor) and C-S-H. Over time this exchange creates a disjoining ionic pressure at the interface between C-S-H and calcified ASR gel (Ca-rich) in the capillary pore network that causes expansion and cracking within the C-S-H matrix. 2021-01-01T00:00:00Z https://hdl.handle.net/1721.1/111671 Research Brief: Evolving the C-S-H Packing Density at the Microscale Petersen, Thomas; Ulm, Franz-Josef Cement paste is a complex multiphase material, roughly 50 percent of which, by volume, is composed of calcium-silicate-hydrates (C-S-H). The C-S-H phase, which lends the material its rigidity, appears to be a dispersion of nanometer-sized particles that densify during the course of the hydration reaction (Ioannidou et al., PNAS 2016). Because the mechanical properties, early-age internal stresses, and microstructure are critically dependent on the distribution of the high density (HD) and low density (LD) C-S-H product, research efforts are underway to better understand nanoparticle packing density at the scale of hundreds of micrometers, where a binary mixture of clinker grains and saturated pore space evolve into a porous hydrated gel. This research brief displays simulated snapshots of cement paste at varying hydration degrees and predicts the evolution of the HD and LD peaks for the distribution of the indentation modulus also observed in nanoindentation experiments. One page research brief 2017-10-02T00:00:00Z https://hdl.handle.net/1721.1/110895 Accounting for Rehabilitation Activity Uncertainty in a Pavement Life Cycle Assessment using Probability and Decision Tree Analysis Mack, James W.; Xu, Xin; Gregory, Jeremy; Kirchain, Randolph In any life cycle assessment (LCA) for pavements, the designer must decide on which rehabilitation activities will be used to maintain the pavement over the analysis period. While this sounds simple, the fact is that there are many different rehabilitation scenarios that could be performed when the pavement requires rehabilitation, and which one is used will impact the LCA results. This creates inherent uncertainty and variability in the LCA results solely due to the selection of the rehabilitation scenario used in the analysis. Currently, most LCA’s apply a single standard rehabilitation scenario to all pavements. The problem with this approach is that because each project is unique, the activities may or may not be representative of the actual set of activities done on that particular pavement. The only way to get meaningful indication of a project’s pavement environmental impact is to look at the impact of all (or at least most) of the potential rehabilitation activities that could be used to maintain the pavement over the analysis period. This paper shows how State Highway Agencies (SHAs) can use probability and decision tree analysis to evaluate many rehabilitation scenarios in order to determine a range of LCA results, as well as a probability adjusted, expected value LCA result. This process quantifies the underlying uncertainty that different the rehabilitation selection can have on the LCA results so that a more informed decision can be made when comparing the alternate pavement designs. A case study based on alternative designs and rehabilitation scenarios used by a SHA demonstrates the decision tree analysis process and shows how the risk profiles for the two alternatives considered are not equivalent. For this case, this results in the probability-adjusted LCA results being different than the single standard rehabilitation scenario results. 2015-08-12T00:00:00Z https://hdl.handle.net/1721.1/110894  Evaluation of the Albedo-induced Radiative Forcing and CO2 Equivalence Savings: A Case Study on Reflective Pavements in Four Selected U.S. Urban Areas Xu, Xin; Gregory, Jeremy; Kirchain, Randolph There is a growing interest in developing cool pavement strategies to mitigate pavement’s impact on the global warming in recent years. One of the mitigation strategies is by increasing the solar reflectance (or albedo) of the pavement surface, which directly contributes to global cooling by adjusting radiative forcing and potentially reduces the energy demand in the urban areas. In this paper, the radiative energy budgets in four urban areas are investigated based on the data derived from NASA satellite measurements. The radiative forcing (RF) due to the change of urban surface albedo as a result of reflective pavements is estimated using a simplified engineering model. The carbon dioxide (CO2) equivalence savings are also calculated with reference to the 100-year global warming potential of CO2. Results show that the implementation of reflective pavement has a great potential to reduce global warming. The CO2 reduction is significant in the urban areas but also affects the surrounding regions to some extent. In the end, we recommend using a climate model incorporating site-specific information that enables the visualization of the outputs through spatial maps. The results from this work would be useful for guiding the implementation of the cool pavement strategies. 2017-08-01T00:00:00Z https://hdl.handle.net/1721.1/110254 How to Improve Pavement Life Cycle Cost Analysis: A Case Study of Minnesota Akbarian, Mehdi; Swei, Omar; Gregory, Jeremy; Kirchain, Randy Life cycle cost analysis (LCCA) frameworks are used by some transportation agencies for economic assessment, but there have been challenges implementing the approach, particularly in the characterization of initial and future costs of materials, as well as their associated uncertainties. This research brief presents a case study which focused on characterizing initial and future pay item costs as a function of project size for a probabilistic LCCA of the entire life cycle including user cost impacts. 2017-06-26T00:00:00Z https://hdl.handle.net/1721.1/108583 Air leakage has strong influence on building life cycle impacts Hester, Joshua; Gregory, Jeremy; Kirchain, Randolph Making informed decisions at the earliest stages of the design process can lead to improved building performance. There are many aspects of a building’s design that can influence overall energy consumption. This research identifies air leakage as influential in determining the life cycle impacts of a residential building. This brief presents results from an analysis using the CSHub’s streamlined building life cycle assessment (LCA) tool, the Building Attribute to Impact Algorithm (BAIA). 2017-05-02T00:00:00Z https://hdl.handle.net/1721.1/107404 Research Brief: Quantifying the impact of pavement reflectivity on radiative forcing and building energy demand in neighborhoods Xu, Xin; Gregory, Jeremy; Kirchain, Randolph Albedo is the measure of the fraction of solar energy reflected by the Earth’s surface. High-albedo surfaces, which are lighter in color, absorb less sunlight energy and reflect more shortwave radiation. The change in radiative energy balance, which is called radiative forcing (RF), reduces nearby air temperatures and impacts the surrounding building energy demand (BED) including heating and cooling energy loads. The impact of reflective surfaces on RF and BED has been investigated by researchers through modeling and observational studies, however previous studies have not assessed RF and BED impacts under the same context and therefore cannot be directly compared. Here, we take a more comprehensive approach in assessing the net impacts of pavement albedo modification strategies in urban areas. 2017-03-13T00:00:00Z https://hdl.handle.net/1721.1/106459 Research Brief: A break-even hazard mitigation metric Miller, T. Reed; Gregory, Jeremy; Kirchain, Randy CSHub researchers developed the Break Even Mitigation Percent (BEMP) to answer the question: “How much should be invested in mitigation for a particular building?” 2017-01-12T00:00:00Z https://hdl.handle.net/1721.1/106458 Research Brief: Minimizing Thermal Cracks in Concrete Pavements Louhghalam, Arghavan; Ulm, Franz-Josef; Petersen, Thomas This brief examines the risk of fracture of concrete pavements due to thermal cycles. CSHub researchers model the risk of fracture due to temperature changes and propose a method for estimating the risk of thermal cracking in transient-state conditions (when pavement is still undergoing a change in temperature) and steady-state conditions. 2017-01-12T00:00:00Z https://hdl.handle.net/1721.1/106456 Research Brief: Examining Freeze-Thaw Damage at the Microscopic Scale Zhou, Edmond; Bazant, Martin Z.; Pellenq, Roland Jm Researchers conducted both theoretical and numerical studies on the microscopic phenomena in cement paste pores to reveal the important roles that ions and electrolytes play in freeze-thaw damage. 2017-01-12T00:00:00Z https://hdl.handle.net/1721.1/106191 Towards Understanding Cement Paste Creep: Implications from Glass Studies Cao, Penghui; Yip, Sidney This research brief presents foundational work toward understanding the mechanics of the complex process of creep by evaluating the phenomena occurring at the nano-scale in metallic glass, a model material, to better understand what causes creep in C-S-H. Research brief 2017-01-04T00:00:00Z https://hdl.handle.net/1721.1/105822 The impact of surface albedo on climate and building energy consumption: review and comparative analysis Xu, Xin; Gregory, Jeremy; Kirchain, Randy This paper presents a state-of-the-art review of the existing research on the climate impacts of albedo. Different analytical approaches and modeling works are synthesized and discussed. 2015-08-01T00:00:00Z https://hdl.handle.net/1721.1/105322 The decision-making process in the design of residential structures Ghattas, Randa; Gregory, Jeremy; Miller, T. Reed; Kirchain, Randolph Building codes and standards have been key drivers in shifting industry towards more energy efficiency, but it is important to take a more holistic approach toward GHG mitigation and evaluate the impact of design decisions from construction, through operation, maintenance, repair and replacement, and end of life. MIT CSHub researchers surveyed architectural firms, homebuilders and developers to understand what decisions are made at different points in the design process so that tools can be targeted accordingly. 2015-03-01T00:00:00Z https://hdl.handle.net/1721.1/105111 The Effects of Inflation and Its Volatility on the Choice of Construction Alternatives Lindsey, Lawrence; Schmalensee, Richard; Sacher, Andrew Life Cycle Cost Analysis (LCCA) is the standard method for costing long-lived construction projects. The LCCA process determines the full costs of mutually exclusive construction options, finding the project design with the lowest total lifetime cost. LCCAs have traditionally ignored the possibility of future changes in relative prices by assuming that the real prices of all construction inputs remain fixed. This study examines historical data on real prices and finds that the assumption of constant real costs is seriously inconsistent with historical experience. 2011-08-01T00:00:00Z https://hdl.handle.net/1721.1/105110 Supplementary Information for Comparative Pavement Life Cycle Assessment and Life Cycle Cost Analysis Swei, Omar; Xu, Xin; Noshadravan, Arash; Wildnauer, Margaret; Gregory, Jeremy; Kirchain, Randolph The MIT Concrete Sustainability Hub (CSHub) is conducting life cycle environmental and cost analyses of pavements under a wide range of contexts. The analyses involve the comparison of new asphalt concrete (AC) and portland cement concrete (PCC) pavement designs for a series of defined scenarios. 2014-07-01T00:00:00Z https://hdl.handle.net/1721.1/105109 Methods, Impacts, and Opportunities in the Concrete Pavement Life Cycle Santero, Nicholas; Loijos, Alexander; Akbarian, Mehdi; Ochsendorf, John A Life cycle assessment (LCA) offers a comprehensive approach to evaluate and improve the environmental impacts of pavements. This research explores and advances three key areas relevant to the pavement LCA field: methodology, quantification, and the supporting science. 2011-08-01T00:00:00Z https://hdl.handle.net/1721.1/105108 Methods, Impacts, and Opportunities in the Concrete Building Life Cycle Ochsendorf, John A; Keith Norford, Leslie; Brown, Dorothy; Durschlag, Hannah; Hsu, Sophia Lisbeth; Love, Andrea; Santero, Nicholas; Swei, Omar; Webb, Amanda; Wildnauer, Margaret Life cycle assessment (LCA) offers a comprehensive approach to evaluating and improving the environmental impacts of buildings. This research explores and advances three key areas relevant to the field of buildings LCA: methodology, benchmarking, and impact reduction opportunities. 2011-08-01T00:00:00Z https://hdl.handle.net/1721.1/104838 Critical Issues When Comparing Whole Building & Building Product Environmental Performance Miller, T. Reed; Gregory, Jeremy; Kirchain, Randolph Guides, standards, product category rules, and environmental product declarations have emerged to evaluate environmental impacts within the buildings sector. These efforts have certainly moved the field forward, but as of yet still do not ensure comparability among building products or whole buildings. In this paper, we aim to address critical issues and make recommendations to practitioners and those developing guidance to enable more robust comparisons of building products and whole buildings. 2016-10-17T00:00:00Z https://hdl.handle.net/1721.1/104794 Life Cycle Assessment for Residential Buildings: A Literature Review and Gap Analysis (Revised) Ghattas, Randa; Gregory, Jeremy; Noori, Mehdi; Miller, T. Reed; Olivetti, Elsa; Greene, Suzanne What is the environmental impact of a house throughout its lifetime? This report summarizes recent research on life cycle assessment of residential buildings in order to identify gaps in understanding as well as best practices for LCA methodology. 2016-10-12T00:00:00Z