A decision support system for methods of measurement in construction projects

The standard Methods of Measurement is an important topic when it comes to the process of the preparation of the Bill of Quantities of a construction project. This is because the Method of Measurement provides a set of guidance rules to prepare the bill that could have less discrepancies decreasing the risk of having problems during the cost control of the construction project during execution. This paper is for developing a decision support system for choosing the suitable standard Method of Measurement for a construction project based on certain project parameters. Three popular international standard MOMs are researched which are the CESMM for civil projects, NRM for building projects and POMI for different project types and their usage in the Middle East is investigated. The literature review is explored to present main information about the characteristics and usage of the each method. Data about the method of measurements usage is then collected through a questionnaire distributed among a sample of quantity surveying professionals in the Middle East. An expert system in the form of a decision model is created that automates the process of the Method of Measurement selection for different projects in the Middle East based on five project parameters which are the project type, client and contractor’s nationality compared to the country where the project is executed, project value and contract type. This model is then verified to check its logic and validated through case studies of real life projects and comparing the model choice of the suitable Method of Measurement for a certain project with the one actually used in that project and then the results are explained. Finally, a conclusion is reached regarding the use of the three MOMs in the Middle East and that they are recognized with POMI and CESMM as the most recognized ones. Also, the model created may be suitable for choosing the suitable method of measurement for civil projects unlike building projects since NRM is still a new method which is still not used in projects. This conclusion is followed by a list of recommendations to improve the future research such as improving the model by adding more project parameters and also recommendations to serve the topic of standard Methods of Measurement within the professional field like making future researches to develop codes for some Middle Eastern companies as Egypt

Controlling Performance of Crumb Rubber-Modified Binders through Addition of Polymer Modifiers

The use of tire rubber as a modifier to enhance the properties of asphalt mixes through the wet process has proved to be a successful procedure, but full control of the properties of crumb rubber-modified binders has been a challenge. The literature indicates a wide variation on adding rubber to asphalt and that the degree of success of rubber modification in AC mixes depends on several factors, the majority of which relate to the method of mixing, storing, and transporting and to construction technologies. Understanding the nature of the interaction process between asphalt cement and crumb rubber-modifier (CRM) helps explain the development of binder properties. This paper covers the wet process, a relatively different technology in the application of CRM in asphalt with virgin polymers used to control and enhance the performance properties of CRM binders. The paper provides some clear insights into the mechanisms by which the interaction, with and without the existence of polymer modifiers, takes place. Effects of the interaction process variables, time and temperature, are explained. Results of this research are based on monitoring the changes in the rheological parameters of the developed binder

Investigation of the Physical and Molecular Properties of Asphalt Binders Processed with Used Motor Oils

In this work we investigated the performance aspects of addition of used motor oils (UMO) to neat and crumb rubber modified asphalts (CRMA) and related that to the change of molecular size distribution of modified asphalt’s fractions; asphaltenes, saturates, naphthene aromatics, and polar aromatics. Based on the results of temperature sweep viscoelastic tests, addition of crumb rubber modifier (CRM) alone or with UMO results in the formation of internal network within the modified asphalt. Based on the results of short and long term aged asphalts, the utilization of combination of UMO and CRM enhanced the aging behavior of asphalt. Bending beam rheometer was utilized to investigate the low temperature behavior of UMO modified asphalts. Based on those tests, the utilization of the UMO and CRM enhanced the low temperature properties of asphalts. Based on the results of the asphalt separation tests and the Gel Permeation Chromatography (GPC) analysis, it was found that saturates and naphthene aromatics are the two asphalt fractions that have similar molecular size fractions as those of UMO. However, UMO only shifts the molecular sizes of saturates after interaction with asphalt. Results also show that polar aromatics pose higher molecular size structures than UMO

Integration of Mechanistic-Empirical Pavement Design Guide Distresses with Local Performance Indices

The pavement management system (PMS) is the organizational entity within a state highway agency responsible for the condition of the pavement network. Visual distress surveys are typically combined into an index to provide an overall measure of performance. Decision makers use these familiar indices in a number of facets. A recent survey suggests every state highway agency has implemented or plans to implement the Mechanistic-Empirical Pavement Design Guide (MEPDG). As they do so, maintaining the role these local indices play is critical for upholding the system\u27s continuity. However, using the MEPDG output directly in calculating performance indices becomes problematic because local distresses and MEPDG distresses are not always congruent. Therefore, there is a need to develop procedures for calculating local performance indices with locally calibrated MEPDG output. Doing so will allow interchangeable use of both while preserving the role of the local indices. The Nebraska Department of Roads (NDOR) PMS serves as a model case. NDOR employs three indices in network-level PMS analyses for flexible pavements. MEPDG flexible distress models were calibrated by using local agency data and input into the existing index functions. This paper explores how the current measures of network condition used in decision making can coexist with the new design methodology. This connection allows mechanistic-empirical analyses of fund allocation, needs estimations, performance modeling, planning, and remaining service life. In addition, local indices can provide much more meaningful failure criteria in the MEPDG to local designers. Practical methods for index calculations are introduced. Detailed guidance for local calibration is also presented

Improving Prediction Accuracy in Mechanistic-Empirical Pavement Design Guide

Model calibration plays a fundamental role in the implementation of the mechanistic-empirical pavement design guide. The data used in the default calibration effort, which were afforded by the Long Term Pavement Performance (LTPP) database, have a network-level inference space. As implementation proceeds, state highway agencies may be inclined to calibrate at a local network level. However, with a focus on the calibration data set to local project-level conditions, model prediction error can be reduced further. Under this study, Nebraska Department of Roads Pavement Management System data were used to calibrate two design guide smoothness models at the local project level. The focused data set was categorized by annual daily truck traffic and surface layer thickness. Results showed that project-level calibrations reduced default model prediction error by nearly twice that of network-level calibration. This study offers a window into the accuracy that can be achieved with local focus calibrations of design guide prediction models

Influence of Guayule Resin as a Bio-Based Additive on Asphalt-Rubber Binder at Elevated Temperatures

This study seeks to find the influence of replacing a portion of the asphalt–rubber binder with the bio-based material “guayule resin.” This replacement could be beneficial in terms of sustainability, economics, and environmental concerns related to the asphalt industry. Nine asphalt-rubber-guayule binders were investigated to find their rheological properties. Consecutively, the study proceeded with five selected binders being compared to the original asphalt (PG64-22). Investigations underwent whole matrices (crumb rubber modifier (CRM) residue included) and liquid phases (CRM residue extracted). Additionally, these properties were partially sought for their corresponding asphalt–rubber binders to compare and judge the contribution of the guayule resin. Likewise, a thermo-gravimetric analysis was done for the guayule resin to recognize its moisture and composition complexity. Such an analysis was also done for the as-received CRM and some extracted CRMs to determine the release and residue of rubber components. Outcomes showed that the guayule resin has the potential to compensate the performance required against the original asphalt at elevated temperatures while greatly decreasing the asphalt cement proportion. For instance, a blend of 62.5% asphalt, 12.5% CRM, and 25% guayule resin provided better performance than that of the original asphalt

Mechanism of Interaction of Asphalt Cement with Crumb Rubber Modifier

The nature of the interaction process between asphalt cement and crumb rubber modifier (CRM) has not been fully understood. Two main types of mechanisms that affect the produced binder properties are reported: particle swelling and degradation (devulcanization and depolymerization). These mechanisms occur as the binder is subjected to different combinations of interaction time and temperature. Insight into the mechanisms by which the interaction between the two materials takes place through monitoring the changes in the rheological parameters of the binder is provided. The effects of the interaction process variables, time and temperature, are explained. The effect of CRM properties, including particle size and material source, is also discussed

Variability in Resilient Modulus of Reclaimed Asphalt Pavement as Base Layer and its Impact on Flexible Pavement Performance

The use of reclaimed asphalt pavement (RAP) as a base layer is gaining popularity, but there are gaps in the literature about its material performance. One problem not well investigated is the variability in the resilient modulus (MR) of RAP as a base layer, as compared with typical granular material, and the impact of this variability on pavement performance. Selection of one MR value has its own variability, beyond the expected variability in the base layer R that results from the use of aggregates with different qualities. This paper investigates the effect of three sources of variability to determine the base layer resilient modulus in the laboratory for RAP as compared with granular material. The three sources considered were (a) the variability in the material and sample preparation for the MR testing, (b) the constitutive model used to predict the resilient modulus, and (c) the state of stress used to predict the base layer modulus. The study compared the variability of the MR of RAP with the MR of unbound granular materials on the basis of actual test results. The impact of MR variability on the flexible pavement distresses for RAP as compared with granular material was investigated using the Mechanistic-Empirical Pavement Design Guide

Effect of Crumb Rubber Dissolution on Low-Temperature Performance and Aging of Asphalt-Rubber Binder

Asphalt binder plays a critical role in defining the low-temperature performance of asphalt pavement, and, therefore, enhancing its mechanical behavior at low service temperatures through modification always has been of great interest. Crumb rubber modification of asphalt is one of the common practices in the industry. However, the effect of a crumb rubber modifier (CRM) on low-temperature performance of the binder is not well understood. A CRM swells by absorbing the aromat-ics and light molecular components of asphalt at low interaction temperatures (i.e., 160°C) and dissolves at higher interaction temperatures (i.e., 190°C, 220°C). Each of those activities affects the performance of the CRM asphalt differently. In this research, the activities of CRMs in asphalt controlled accurately through regulating the interaction conditions and the effect of each of those activities on low-servicc-temperature properties of asphalt were studied by using the bending beam rheometer (BBR) and modulated differential scanning calorimetry. The BBR was used to measure the mechanical behavior of CRM asphalt and its liquid phase at low temperatures as a function of CRM dissolution, and modulated differential scanning calorimctry was used to investigate possible changes in glass transition of the liquid phase of the modified binder. Results indicate that the stiffness and m-value of the modified binder are developed in two different manners, and the factors that affect these two parameters are different. Also, results show that through certain interaction conditions, optimization of the low-temperature performance of the CRM asphalt is possible