Accurate cost estimates are vital to the effective realisation of construction projects. Extended knowledge, wide-ranging information, substantial expertise, and continuous improvement are required to attain accurate cost estimation. Cost estimation at the preliminary phase of the project is always a challenge as only limited information is available. Hence, rational selection of input variables for preliminary cost estimation could be imperative. A systematic input variable selection approach for preliminary estimating using an integrated methodology of factor analysis and fuzzy AHP is presented in this paper. First, the factor analysis is used to classify and reduce the input variables and their variable coefficients are determined. Second, fuzzy AHP based on the geometric mean method is employed to determine the weights of input variables in a fuzzy environment where the subjectivity and vagueness are handled with natural language expressions parameterized by triangular fuzzy numbers. Then, the input variables are suggested to be selected starting with those having high coefficient and high importance weight. A set of three variables, one from each group, can be added to the estimating model at a time so that the problem of collinearity can vanish and good accuracy of the estimate can be ensured. The proposed approach enables cost estimators to better understand the complete input variable selection process at the early stage of project development and provide a more accurate, rational, and systematic decision support tool.
Emulsion asphalts are cost-effective, environmentally friendly, and sustainable alternatives to hot-mix asphalts. Laboratory curing protocols currently used to simulate field curing of emulsion asphalts have been observed to offer conflicting predictions. This study employed the maturity method to account for the combined effects of temperature and time on fatigue-strength development in emulsion asphalts. An emulsion asphalt, composed of 55% reclaimed asphalt pavement, 45% virgin aggregates, 6.2% bitumen emulsion, and 4% pre-mix water was designed following the Asphalt Institute procedure. A total of 168 specimens from the mix were variously cured at 5 °C, 25 °C, 40 °C, and 50 °C for time intervals of 1, 3, 5, 7, 14, 21, and 28 days, before being tested for fatigue-strengths on the four-point bending test jig. It was observed that fatigue-strengths increased with an increase in cure temperature but decreased with an increase in cure duration. A parabolic hyperbolic fatigue-maturity model was developed from results of specimens cured at 5 °C, 25 °C, and 40 °C and validated with results from specimens cured at 50 °C. A strong correlation was observed between predicted fatigue-maturity and laboratory-determined fatigue-strengths at test strain levels between 125 µm/m and 200 µm/m. The study concluded that the laboratory characterization of emulsion asphalts should consider the curing history of the mix.
Waste generation from agricultural and construction industries is growing at an upsetting rate that causes a heavy burden on landfill facilities. On the other hand, the construction industry is exhausting natural resources thereby posing environmental problems. This study investigates the potential use of agro-industrial waste such as rice husk ash (RHA) and construction waste like reclaimed asphalt pavement (RAP) as promising construction materials. The durability and physical and mechanical properties of concrete were assessed by partially replacing cement and virgin aggregates with RHA and RAP, up to 20% and 50%, respectively. A total of 22 mixes were studied, twelve of which were devoted to studying the collective effects of RHA and RAP on the engineering properties of concrete. Based on experimental results, RHA and RAP decreased slump, compacting factor, density, water absorption and sorptivity. RHA increased compressive and tensile splitting strength, whereas RAP decreased compressive and tensile splitting strength. Comparable strength and favorable sorptivity values were obtained when 15% RHA was combined with up to 20% RAP in the concrete mix. Thus, utilizing RHA and RAP as concrete ingredients can contribute to solid waste management, engineering and economic benefits.
Bitumen emulsion asphalts, especially those incorporating marginal and secondary aggregates, are energy efficient, environment friendly, and sustainable alternatives to hot-mix asphalts. This study set out to compare engineering properties of a bitumen emulsion asphalt composed entirely of virgin aggregates with another composed of 55% reclaimed asphalt and 45% virgin aggregates. The aggregates were bound with a slow setting cationic bitumen emulsion composed of 65% base bitumen and 35% water. Marshall specimens molded at varying pre-mix water and bitumen emulsion contents were cured in molds for 24 h before being de-molded and cured for a further 72 h at 40 • C. Dry densities, porosities, and indirect tensile strengths for the cured specimens were determined in dry and soaked states. Virgin aggregate mix, at an optimum binder content of 6.1%, had a tensile strength ratio of 1.3 with corresponding air voids and moisture absorption values of 10.1% and 0.92%, respectively. Similarly, reclaimed asphalt mix at an optimum binder content of 6.2% had a tensile strength ratio of 1.03, with corresponding air voids and moisture absorption values of 7.9% and 0.38%, respectively. Compared to virgin mix, reclaimed asphalt mix had lower air voids and lower moisture absorption values with the overall benefit of enhanced resistance to moisture damage. ultimate engineering properties upon completion of batching, strength gain in cold asphalts proceed at rates dependent on breaking of the emulsion and evaporation of the resultant water. They behave like improved granular materials in the early stages of their lives but eventually attain properties similar to those of hot-mix asphalts once all the moisture is lost through curing [2][3][4].Compared to hot-mix asphalts, cold asphalts are energy efficient, cheaper, and environmentally friendly, but have the downsides of requiring longer curing times, having high air-void contents, and low early-life strengths [5]. Further, environmental and monetary savings accrue when marginal and secondary aggregates, like recycled asphalts, are used in cold-asphalt mixtures. In their study, Kandhal and Mallick [6] estimated cost savings of between 14% and 34% when recycled asphalt aggregates varying between 20% and 50% by mass of total mix were used in conjunction with virgin aggregates. In another study by Thanaya [7], energy savings of up to 40% were realized when bitumen emulsions were used in place of penetration grade bitumen in asphalt production. A study by Oke et al. [8] estimated savings of between 40% and 60% when cold reclaimed asphalt pavement mixtures were used in place of hot-mix asphalt.Currently, there is no universally accepted laboratory asphalt mix design procedure for cold asphalt mixtures, rather a myriad of procedures have been developed by countries and agencies to suit their local conditions and needs [9][10][11][12][13]. In the United States, Asphalt Institute, Chevron Inc., U.S. Navy, and the states of Oregon, Pennsylvania, Indiana, California, Texas, and New Mexico [14...
Background: At the early phase of project development, highway engineering estimators seek to determine the duration of highway construction projects for the purpose of construction planning and administration. Thus, it is vital to study and analyze the estimation accuracy factors of highway construction project duration. In this regard, several studies have been conducted to identify and analyze the estimation accuracy factors of project duration in various ways to improve the estimation and management performance of all the contracting parties. However, very less effort has been devoted to evaluating the duration estimation accuracy factors in the case of the highway construction industry under fuzzy environment. Objective: This paper aims to analyze and prioritize the critical factors that potentially affect the duration estimation accuracy of the highway construction projects in Ethiopia under fuzzy environment. Methods: An extensive review and discussions with highway engineering experts were carried out to explore and identify the duration estimation accuracy factors. The study data collection process consists of two stages. The first stage is to conduct a questionnaire survey. Whereas, the second stage is to carry out the pair-wise comparison matrix to capture the imprecision and vagueness in subjective responses. Then, a λ-cut set method to reduce the initial list of factors and exploratory factor analysis was used to classify the reduced set of factors into smaller groups. Finally, a fuzzy hierarchy process algorithm with the use of triangular fuzzy numbers was presented for prioritizing critical factors. Results: A cut -off value, λ = 0.95, was verified which resulted in the identification of critical accuracy factors. Accordingly, 12 critical factors were opted and categorized as a cluster of similar items into 5 groups. Finally, the analytical results obtained from fuzzy AHP algorithm revealed that project complexity, project size, bridge type and complexity were found to be the four top-ranked factors based on the global priority weight. Conclusion: These factors must be a serious concern in estimating and administering the contract and the duration of highway construction projects at the early phases of project development so that the time deviation upon the completion of the project can be minimized.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.