@article{abbasian-hosseini_leming_liu_2016, title={Effects of Idle Time Restrictions on Excess Pollution from Construction Equipment}, volume={32}, ISSN={0742-597X 1943-5479}, url={http://dx.doi.org/10.1061/(ASCE)ME.1943-5479.0000408}, DOI={10.1061/(asce)me.1943-5479.0000408}, abstractNote={AbstractConstruction vehicles and equipment contribute to air pollution. To reduce pollution, numerous state and local jurisdictions limit the amount of time diesel engine vehicles or equipment can run at idle without shutting down. These restrictions vary widely indicating a need for improved understanding of the relationships between pollutant emissions and regulations establishing a maximum idle time in a construction setting. Previous studies have found that a reduction in operational efficiency will increase the amount of excess pollution, that is, the amount of pollution created in excess of that emitted by a construction operation under ideal conditions. Shutting down an engine can create a delay in re-entering the work stream and, therefore, reduce operational efficiency. In another study, the authors found that excess pollution would be minimal with a reasonably well-balanced, minimum or near minimum cost, construction equipment fleet composed of a single wheel loader (WL) working with different ...}, number={2}, journal={Journal of Management in Engineering}, publisher={American Society of Civil Engineers (ASCE)}, author={Abbasian-Hosseini, S. Alireza and Leming, Michael L. and Liu, Min}, year={2016}, month={Mar}, pages={04015046} }
 @article{abbasian-hosseini_liu_leming_2015, title={Comparison of Least-Cost and Least-Pollution Equipment Fleet Configurations Using Computer Simulation}, volume={31}, ISSN={0742-597X 1943-5479}, url={http://dx.doi.org/10.1061/(ASCE)ME.1943-5479.0000360}, DOI={10.1061/(asce)me.1943-5479.0000360}, abstractNote={AbstractConstruction vehicles and equipment, like all other fuel-powered vehicles, contribute to air pollutant emissions, such as nitrogen oxides (NOX) and particulate matter (PM). The U.S. Environmental Protection Agency has established standards for pollutant emissions for different tiers of equipment to attain a “least-pollution” equipment spread or fleet. Although using higher-tier vehicles and equipment can reduce pollutant emissions under otherwise identical conditions, policies and contractor operations can also significantly affect the total pollutant emitted for a given amount of work, such as cubic yards of earth moved or tons of surface course placed. Previous studies demonstrated the direct relationship between pollutant emissions and operational productivity and the quantitative effects of that relationship using real-world emissions data. This paper describes the results of a study conducted using computer-based simulation techniques to compare costs and pollutant emissions for a typical ear...}, number={6}, journal={Journal of Management in Engineering}, publisher={American Society of Civil Engineers (ASCE)}, author={Abbasian-Hosseini, S. Alireza and Liu, Min and Leming, Michael}, year={2015}, month={Nov}, pages={04015003} }
 @article{mccoy_seracino_leming_2015, title={Modified Layered-Sectional Analysis for Forensic Investigation}, volume={29}, ISSN={["1943-5509"]}, DOI={10.1061/(asce)cf.1943-5509.0000583}, abstractNote={AbstractThis paper describes a modification to the layered-sectional analysis approach, which provides the engineer with a tool to assess structural behavior of concrete beams with localized damage, a problem not well suited to classical, closed-form solutions. The modified layered-sectional analysis (MLSA) framework is applied to a forensic investigation case study in which two prestressed double-tee beams are exposed to a short duration, intense fire in a parking structure. The results of the MLSA are within 1% of the case study load test, which indicates that the MLSA could be a useful, computationally efficient tool for the investigating engineer to predict the postfire serviceability and strength of damaged beams, and potentially eliminate the need for expensive load testing. A short parametric study is included for the research engineer interested in the MLSA for predicting the postdamage behavior of non-standard materials such as enhanced sustainability concrete (ESC).}, number={4}, journal={JOURNAL OF PERFORMANCE OF CONSTRUCTED FACILITIES}, author={McCoy, Brad C. and Seracino, Rudolf and Leming, Michael L.}, year={2015}, month={Aug} }
 @article{mccoy_leming_seracino_2014, title={Crack Density and Elastic Properties of Sustainable Concretes}, volume={111}, DOI={10.14359/51686443}, abstractNote={This paper examines relationships between changes in the microstructure and selected elastic properties of various concrete mixtures exposed to moderately elevated temperatures. The crack density parameters before and after exposure were estimated from the shear modulus measured wet and dry of 1 in. thick by 4 in. diameter (25 x 100 mm) disks. Mixtures examined included both granitic and lightweight coarse aggregates in combination with cementitious systems containing either 20% fly ash, 60% fly ash, termed enhanced sustainability, or 60% slag cement. This study found that the changes in crack density parameter resulting from exposure to elevated temperatures appear to be more sensitive to differences between cementitious materials than to differences between aggregate type or cementitious material proportions. A critical finding was that the relationship between initial crack density parameter and changes in crack density parameter were similar regardless of fly ash content.}, number={1}, journal={ACI Materials Journal}, author={Mccoy, B. C. and Leming, M. L. and Seracino, R.}, year={2014}, pages={13–21} }
 @article{abbasian-hosseini_hsiang_leming_liu_2014, title={From Social Network to Data Envelopment Analysis: Identifying Benchmarks at the Site Management Level}, volume={140}, ISSN={0733-9364 1943-7862}, url={http://dx.doi.org/10.1061/(ASCE)CO.1943-7862.0000875}, DOI={10.1061/(asce)co.1943-7862.0000875}, abstractNote={AbstractIt is widely accepted in the construction industry that contract documents, specifying the responsibility and risk of each participant, are the basis for project managers’ and superintendents’ decision making (DM). However, in practice strict adherence to the formal procedures and chains of command would not always be possible without an unacceptable expenditure of time and money. Although much attention is given to the decisions at the project manager and superintendent level, the underlying rules and mechanisms for the moment-to-moment DM at the site management level has not been documented. In this paper, a social network (SN)–based data envelopment analysis (DEA) benchmarking procedure (SDBP), which combines DEA (assessing the relative efficiency of DM units) and SN (concentrating on the relationships amongst DM units) to identify the benchmarks for the inefficient specialty trades (STs). This paper also uses a case study to illustrate how to implement the SDBP. This research contributes to th...}, number={8}, journal={Journal of Construction Engineering and Management}, publisher={American Society of Civil Engineers (ASCE)}, author={Abbasian-Hosseini, S. Alireza and Hsiang, Simon M. and Leming, Michael L. and Liu, Min}, year={2014}, month={Aug}, pages={04014028} }
 @article{vaughan_leming_liu_jaselskis_2013, title={Cost-Benefit Analysis of Construction Information Management System Implementation: Case Study}, volume={139}, ISSN={0733-9364 1943-7862}, url={http://dx.doi.org/10.1061/(asce)co.1943-7862.0000611}, DOI={10.1061/(asce)co.1943-7862.0000611}, abstractNote={AbstractIn construction projects, construction managers spend a significant portion of their time gathering project data, assessing production rates, communicating with project participants, and tracking project quality. Executing those tasks manually reduces efficiency and can result in less effective project management operations. In order to improve efficiency of information process flow, various types of construction information management systems (CIMSs) have been introduced to construction projects. However, due to the difficulty of tracking fragmental and illusive data, measuring the cost and benefit of the implementation and evaluating the trade-off remain a challenge for construction practitioners. This paper’s contributions to the body of knowledge include (1) proposing a framework to assess tangible and semitangible or intangible costs and benefits of innovative construction technology application, (2) determining costs and benefits of the use of CIMSs by conducting a product-specific case stud...}, number={4}, journal={Journal of Construction Engineering and Management}, publisher={American Society of Civil Engineers (ASCE)}, author={Vaughan, Joshua L. and Leming, Michael L. and Liu, Min and Jaselskis, Edward}, year={2013}, month={Apr}, pages={445–455} }
 @article{he_reyes_leming_dean_lappi_ducoste_2013, title={Mechanisms of Fat, Oil and Grease (FOG) deposit formation in sewer lines}, volume={47}, ISSN={["0043-1354"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84879016648&partnerID=MN8TOARS}, DOI={10.1016/j.watres.2013.05.002}, abstractNote={FOG deposits in sewer systems have recently been shown to be metallic salts of fatty acids. However, the fate and transport of FOG deposit reactant constituents and the complex interactions during the FOG deposit formation process are still largely unknown. In this study, batch tests were performed to elucidate the mechanisms of FOG deposit formation that lead to sanitary sewer overflows (SSOs). We report the first formation of FOG deposits on a concrete surface under laboratory conditions that mimic the formation of deposits in sewer systems. Results showed that calcium, the dominant metal in FOG deposits, can be released from concrete surfaces under low pH conditions and contribute to the formation process. Small amounts of additional oil to grease interceptor effluent substantially facilitated the air/water or pipe surface/water interfacial reaction between free fatty acids and calcium to produce surface FOG deposits. Tests of different fatty acids revealed that more viscous FOG deposit solids were formed on concrete surfaces, and concrete corrosion was accelerated, in the presence of unsaturated FFAs versus saturated FFAs. Based on all the data, a comprehensive model was proposed for the mechanisms of FOG deposit formation in sewer systems.}, number={13}, journal={WATER RESEARCH}, publisher={Elsevier BV}, author={He, Xia and Reyes, Francis L., III and Leming, Michael L. and Dean, Lisa O. and Lappi, Simon E. and Ducoste, Joel J.}, year={2013}, month={Sep}, pages={4451–4459} }
 @article{wang_liu_hsiang_leming_2012, title={Causes and Penalties of Variation: Case Study of a Precast Concrete Slab Production Facility}, volume={138}, ISSN={0733-9364 1943-7862}, url={http://dx.doi.org/10.1061/(asce)co.1943-7862.0000475}, DOI={10.1061/(asce)co.1943-7862.0000475}, abstractNote={Concrete precast plants require strict control over and adherence to the timing and sequence of operations. Variation for this research is divided into the variation in task starting time (the difference between the planned and the actual starting time) and the variation in task duration (the difference between the planned and the actual task duration). This study determined causes of variation in task starting time and duration of precast concrete slab production tasks. It also identified penalties associated with not reducing variation, which include an increase in project duration, Work in-Progress (WIP) and cost and a decrease in labor productivity. Additionally, two execution policies (keeping laborers waiting before preconditions are ready and keeping laborers busy) in the face of variation were compared by using STROBOSCOPE simulation techniques. It was found that simply keeping workers busy is insufficient for managing variation. Management effort should be devoted to eliminate causes of variation in the planning stage to make a reliable work plan. The results will help prefabricators to understand causes and penalties of variation, which is the starting point of attacking and reducing it. Although this study is based on a concrete slab production facility, this research can have a broader effect on the construction industry because the research method and simulation models developed in this study are applicable to other fabrication processes as well.}, number={6}, journal={Journal of Construction Engineering and Management}, publisher={American Society of Civil Engineers (ASCE)}, author={Wang, Chao and Liu, Min and Hsiang, Simon M. and Leming, Michael L.}, year={2012}, month={Jun}, pages={775–785} }
 @article{lewis_leming_rasdorf_2012, title={Impact of Engine Idling on Fuel Use and CO2 Emissions of Nonroad Diesel Construction Equipment}, volume={28}, ISSN={["0742-597X"]}, DOI={10.1061/(asce)me.1943-5479.0000068}, abstractNote={It is difficult to quantitatively assess the impact of engine idling on fuel use and emissions of construction equipment because of a lack of sufficient data. This paper presents a methodology for evaluating the impact of idling on fuel use and carbon dioxide ( CO2 ) emissions of diesel construction equipment. The results are based on field data collected from 34 items of equipment. Engine idle time may be quantified in terms of equipment operational efficiency ( η ), which is defined as the ratio of nonidle time to total equipment use time (nonidle time plus idle time). Using η and the ratio of idle to nonidle fuel use and CO2 emission rates ( r ), the percentage increase in the total quantities of fuel used and CO2 emitted ( NE ) were calculated for each item of equipment for values of η less than the maximum theoretical operational efficiency of 100%. Results showed that as η decreased (or idle time increased), NE increased. A mathematical model that uses η as a predictor variable was developed to esti...}, number={1}, journal={JOURNAL OF MANAGEMENT IN ENGINEERING}, author={Lewis, Phil and Leming, Michael and Rasdorf, William}, year={2012}, month={Jan}, pages={31–38} }
 @article{mata_leming_2012, title={Vertical distribution of sediments in pervious concrete pavement systems}, volume={109}, DOI={10.14359/51683701}, abstractNote={Pervious concrete pavement systems (PCPSs) are a unique and effective means to address important environmental issues and support green, sustainable growth by capturing storm water and allowing it to infiltrate into the underlying soil. Sedimentation leading to clogging, however, is a potential problem in the serviceability of PCPS. This article examined the sedimentation rates of pervious concrete with 20% porosity with three different soil types: sand, clayey silt, and clayey silty sand. Pervious concrete cylinder specimens were exposed to sediments mixed in water to simulate runoff with a typical load of soil sediments. The sedimentation tests confirmed that most sand sediments will be trapped on top of the concrete. However, part of the finer sand will be deposited within the concrete or travel through the concrete. This can affect the permeability of the PCPS.}, number={2}, journal={ACI Materials Journal}, author={Mata, L. A. and Leming, M. L.}, year={2012}, pages={149–155} }
 @article{lewis_leming_frey_rasdorf_2011, title={Assessing Effects of Operational Efficiency on Pollutant Emissions of Nonroad Diesel Construction Equipment}, ISSN={["0361-1981"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-83655197006&partnerID=MN8TOARS}, DOI={10.3141/2233-02}, abstractNote={ Operational efficiency is a simple way of addressing nonproductive time of diesel-powered construction equipment that performs a construction activity and is defined as the ratio of nonidle activity time to total activity time including idle time. The effects of diesel equipment operational efficiency on total emissions for construction activities have not been fully established; thus a fundamental understanding of operational efficiency is needed to evaluate the effects on total pollutant emissions of diesel-powered construction equipment. This paper presents a methodology to assess the effects of equipment operational efficiency on the total pollutant emissions of construction equipment performing construction activities. This methodology estimates the percentage of additional pollutants emitted due to a reduced operational efficiency, based on the ratio of idle to nonidle emissions. Results for a case study of six bulldozers indicate that pollutant emissions, in addition to the minimum amount required to complete a specific quantity of work, increase as operational efficiency decreases. This conclusion allows the savings resulting from increased efficiency to be determined. Furthermore, additional pollutant emissions for a specified operational efficiency increase as the ratio of idle to nonidle emissions increases. The ratio of idle to nonidle emissions varies according to pollutant and is approximately 1:2 for hydrocarbons and carbon monoxide, 1:5 for nitrogen oxides, and 1:7 for particulate matter. }, number={2233}, journal={TRANSPORTATION RESEARCH RECORD}, author={Lewis, Phil and Leming, Michael and Frey, H. Christopher and Rasdorf, William}, year={2011}, pages={11–18} }
 @article{dilek_leming_2008, title={Elastic dynamic young's modulus and permeability of concrete in fire damaged structural members}, volume={20}, DOI={10.1061/(ASCE)0899-1561(2008)20:2(102)}, abstractNote={This article reviews the results of two studies examining the effects of exposure to elevated temperatures on the dynamic elastic (Young’s) modulus ( Ed ) and air permeability index (API) of concrete. The relationship between Ed and API in fire damaged concrete, and the use of Ed and API to determine both the extent of damage due to exposure to fire and the presence and extent of damage gradients are reviewed. Cores were removed from a precast, prestressed concrete beam containing lightweight aggregate and from a reinforced concrete structural wall containing conventional mineral aggregates. Both of these structures were exposed to intense fires and the laboratory investigation of cores was part of a forensic engineering evaluation to determine the extent of damage to the structure and the necessary repairs prior to returning to service. The Ed and API were determined using 25 mm thick disks sawn from the cores. The findings of the study suggest that Ed and API are linearly related for a given set of raw ...}, number={2}, journal={Journal of Materials in Civil Engineering}, author={Dilek, U. and Leming, M. L.}, year={2008}, pages={102–110} }
 @article{dilek_leming_2007, title={Comparison of pulse velocity and impact-echo findings to properties of thin disks from a fire damaged slab}, volume={21}, DOI={10.1061/(ASCE)0887-3828(2007)21:1(13)}, abstractNote={The engineering assessment of fire damage to a concrete slab provided the opportunity to compare the results of in situ, nondestructive evaluation (NDE) techniques and laboratory testing of specimens taken from cores extracted from the fire damaged slab. This paper discusses and compares results of in situ pulse velocity and impact-echo testing with dynamic elastic modulus and air permeability index test results of 25 mm (1 in.) thick disks sawed from concrete cores removed from selected areas of the damaged slab. Both the NDE techniques and the laboratory testing of thin disks identified the presence of damage as a result of the fire. Analysis of the relatively thin concrete specimens permitted assessment of the presence and degree of damage in thin layers, and provided important and useful data on concrete properties for engineering assessment which was not available from NDE alone. Compressive strength results were consistent with the results of other tests but largely inconclusive by themselves. Impact-echo testing was able to identify the presence of a severely deteriorated concrete layer but could not identify the extent or depth of damage or clearly identify less damaged areas. A distressed layer of concrete was found by subsequent laboratory testing to be limited to a near-surface zone in some areas as suggested by the pulse velocity evaluation, but pulse velocity based analysis resulted in an overestimate of the depth of the damage. The findings highlighted a shortcoming of using conventional strength testing alone on investigations involving relatively thin layers of damage and pointed out several key limitations in the use and interpretation of nondestructive evaluation and associated analysis in a field assessment project.}, number={1}, journal={Journal of Performance of Constructed Facilities}, author={Dilek, U. and Leming, M. L.}, year={2007}, pages={13–21} }
 @article{dilek_leming_2007, title={Deicer salt scaling resistance of concrete containing manufactured sands}, volume={35}, ISSN={["1945-7553"]}, DOI={10.1520/JTE100475}, abstractNote={Abstract}, number={2}, journal={JOURNAL OF TESTING AND EVALUATION}, author={Dilek, Ufuk and Leming, Michael L.}, year={2007}, month={Mar}, pages={134–142} }
 @inbook{dilek_leming_guth_2004, title={Relationship between elastic modulus and permeability of damaged concrete}, ISBN={0309094909}, DOI={10.3141/1893-07}, abstractNote={ The study examined the effects of selected damage mechanisms on the dynamic elastic (Young's) modulus (Ed) and air permeability index (API) of concrete. The relationship between Ed and API in damaged concrete and the use of Ed and API to determine both the extent of damage due to various exposures and the presence and extent of damage gradients are reviewed. The Ed and API were determined by using 25-mm-thick disks sawed from high-strength and conventional- strength concrete cylinders, before and after static fatigue damage; from cores removed from a lightweight, precast, prestressed concrete beam after exposure to intense fire; and from cores removed from an elevated concrete slab after exposure to thermal shock and subsequent cryogenic temperatures. The findings of the study suggested that Ed and API were linearly related for a given set of raw materials until damage was significant, that analyzing concrete disks at 25-mm (1-in.) depths provided insight into damage gradients, and that the durability of high-strength concrete in service may have been better than conventional-strength concrete under similar stress conditions. Ed and API were found to be effective tools in the assessment of damaged concrete and gradients of damage. API was found to be particularly sensitive to fire damage and associated severe drying. }, number={1893}, booktitle={Concrete, 2004}, publisher={Washington, DC: Transportation Research Board}, author={Dilek, U. and Leming, M. L. and Guth, D.}, year={2004}, pages={53–60} }
 @article{dilek_leming_2004, title={Relationship between particle shape and void content of fine aggregate}, volume={26}, DOI={10.1520/cca11916}, abstractNote={Abstract}, number={1}, journal={Cement, Concrete and Aggregates}, author={Dilek, U. and Leming, M. L.}, year={2004}, pages={14–20} }
 @article{leming_nguyen_2000, title={Limits on alkali content in cement - Results from a field study}, volume={22}, DOI={10.1520/cca10462j}, abstractNote={Abstract}, number={1}, journal={Cement, Concrete and Aggregates}, author={Leming, M. L. and Nguyen, B. Q.}, year={2000}, pages={41–47} }
 @article{cutshall_leming_johnston_1999, title={Comparison of strength and construction tolerances in concrete}, volume={96}, DOI={10.14359/685}, abstractNote={Two approaches to the tolerance limit for compressive strength of concrete in reinforced members are compared. One tolerance limit for strength, in use since 1971, is f' sub c - 500 psi (3.4 MPa). Another tolerance, based on 0.90 f' sub c provides a more direct link between design and quality control criteria, consistent with the use of strength reduction factors. The utility of each tolerance was evaluated by comparing the effect of the tolerance on selected structural capacities with the effects of other typical construction tolerances. On this basis, the investigation found that a strength tolerance of 0.90 f' sub c is a more consistent representation of allowable concrete strength variation than f' sub c - 500 psi (3.4 MPa). While this approach is not sufficient by itself, it does indicate that the 0.90 f' sub c criteria is a more rational approach to compressive strength tolerance.}, number={4}, journal={ACI Structural Journal}, author={Cutshall, B. E. and Leming, M. L. and Johnston, David}, year={1999}, pages={491–494} }
 @article{leming_1999, title={Probabilities of low-strength events in concrete}, volume={96}, DOI={10.14359/670}, abstractNote={Concrete that does not meet specified tolerances incurs costs. The likelihood of nonconforming concrete tests and associated costs are considered in developing bids and are therefore of concern to the owner, the engineer, the contractor, and the concrete supplier. Knowing the probability of various events is necessary for an informed assessment of risk. American Concrete Institute (ACI) 318-95 requires the minimum average strength of concrete to be high enough that both the probability of the average of any three consecutive tests falling below f' sub c, and the probability of a single individual test falling below f' sub c - 500 psi (3.4 MPa), will not be greater than 1%. Under these conditions, the probability of at least one low-strength event (LSE) for a 4,000 cu yd (3,058 cu m) project could lie between 35% and 70%. Since any LSE will result in a shift in the average strength level, the probabilities for subsequent tests are changed, and accurate estimates of the probability of an LSE cannot be obtained directly. Computer-based simulation was used to estimate the probability of LSEs, explicitly including the effects of process interference with two mutually dependent quality control criteria, with only random variation of strength.}, number={3}, journal={ACI Structural Journal}, author={Leming, M. L.}, year={1999}, pages={369–376} }
 @article{leming_nau_fukuda_1998, title={Non-destructive determination of the dynamic modulus of concrete disks}, volume={95}, DOI={10.14359/353}, abstractNote={The nondestructive determination of the dynamic modulus of concrete using circular disks has many potential applications. Circular disks, sawn from cores or cylinders, are widely used in measuring the chloride ion permeability of concrete. The dynamic modulus of disks taken from cores used in assessing structured adequacy is useful. Similarly, the dynamic modulus of "cover-crete," the concrete over the reinforcing steel, determined from cores too short to be used for conventional testing, is valuable. Existing methods of determining the dynamic modulus of concrete based on fundamental frequency measurements do not include methods for concrete disks. An investigation was conducted to determine the feasibility of nondestructively measuring the elastic modulus of relatively thin, circular concrete disks cut from a standard 100 mm-by-200 mm (4 in-by-8 in) test cylinder, using fundamental frequency techniques. This study indicated that the dynamic modulus of the concrete specimens can be quickly, easily, and accurately determined using readily available, off-the-shelf technology.}, number={1}, journal={ACI Materials Journal}, author={Leming, M. L. and Nau, J. M. and Fukuda, J.}, year={1998}, pages={50–57} }
 @article{mitchell_leming_1998, title={Quantity of alkali silica gel and its effect on concrete properties}, volume={10}, DOI={10.1061/(ASCE)0899-1561(1998)10:2(106)}, abstractNote={A quantitative gel fluorescence technique was used to investigate relationships between the extent of alkali silica reactivity (ASR) and properties of concrete cores of varying ages taken from over 20 bridges or pavements in North Carolina. The cores had varying degrees of ASR and were composed of a wide variety of aggregates and cementitious materials. The technique, combining image processing and analysis with a Strategic Highway Research Program qualitative gel fluorescence method, is described and results are discussed. The effects of lamp intensity, thresholding, video averaging, and color based discrimination to differentiate fluorescing areas are reviewed. Preliminary statistical analysis of the technique is presented. While no useful correlation was found between the mechanical properties of cores and the apparent gel content, a strong correlation was found between the percent area of fluorescing material and the log (base 10) expansion of cores after immersion in an alkaline solution for 90 days.}, number={2}, journal={Journal of Materials in Civil Engineering}, author={Mitchell, J. F. and Leming, M. L.}, year={1998}, pages={106–111} }