Relationship between procurement duration and project performance in design-build water/wastewater projects

The design-build (DB) project delivery system (PDS) has been widely applied and studied in the construction industry. Its advantages include shortened project duration, lowered risk to the owner, improved project performance, and possibly reduced cost. Researchers have also studied the factors related to the improved performance in DB projects, especially in the building and transportation industries. Compared to the building and highway industries, the application of DB in water/wastewater (WW) projects has been rarely studied before. One of the potential factors that may influence project performance is procurement duration (PD). By focusing on DB applied to WW projects, this study explored the relationship between PD (from Request for Proposal issue date to proposal due date) and project success. The project success criteria was defined as cost and schedule growth, which were objective measurements and thus provided more convincing data analysis. Project data was collected through an on-line questionnaire given to owners and design-builders who had experience in DB WW projects. The data was used to analyze how PD impacts project performance in terms of cost and schedule growth. The relationships between PD and performance in DB WW projects were compared to DB transportation projects. Both similarities and differences were found. To explore the reasons of these similarities and differences, content analysis was conducted to compare the DB WW and transportation procurement documents. Variables were defined and analyzed based on their frequency of use within procurement documents. Hypotheses were given based on the similarities and differences found between DB WW and transportation projects procurement items as to which might influence the project success. Related suggestions were provided for owners in the DB WW industry regarding the time given for design-builders to prepare proposals and items that should be required in the DB proposal.\u2

A Survey on Users' Perspectives to Functionalities of Web-Based Construction Collaboration Extranets

Construction collaboration extranets (CCEs) provide various functionalities depending on the vendors' origins, history, experiences, and financial status. Previous research has listed and described the functionalities that extranet systems can be capable of providing. However, no publication was found so far to systematically analyze users' perspectives to the provided functionalities. This article is to bridge this gap through a questionnaire survey to the users. It aims at examining user's attitude to functionalities of CCEs. The result may be useful to information system vendors, end-users and researchers involved in CCEs development and implementation

Survey of the current status of sustainable concrete production in the U.S.

The wide use of concrete in construction has significantly impacted energy use and environmental quality. Fortunately, the emergence of sustainable concrete, often made with alternative or recycled waste materials, offers great opportunities to improve concrete sustainability. This paper studies the current status of sustainable concrete production in the U.S. through a questionnaire survey. It revealed that the surveyed companies varied largely in their recognition and adoption of supplementary cementitious materials (SCMs) and alternative aggregates (AAs). Of the various alternative materials available, the most widely used by survey participants were limited to the three SCMs (fly ash, slag cement, and silica fume) and two types of aggregates (lightweight and recycled concrete aggregates). Multiple benefits and barriers to the adoption of SCMs and AAs, e.g., concrete properties, cost, and local availability, were also disclosed by survey participants. Statistical comparisons identified differences in sustainable concrete production between ready mixed concrete suppliers and concrete prefabricators, as well as in its applications in structural and non-structural concrete components. The findings provide a better understanding of the U.S. sustainable concrete production and offer insights into how researchers can help address industry concerns about the implementation of sustainable concrete

Additive Manufacturing Of SiC-Sialon Refractory With Excellent Properties By Direct Ink Writing

Additive manufacturing of SiC-Sialon refractory with complex geometries was achieved using direct ink writing processes, followed by pressure less sintering under nitrogen. The effects of particle size of SiC powders, solid content of slurries and additives on the rheology, thixotropy and viscoelasticity of ceramic slurries were investigated. The optimal slurry with a high solid content was composed of 81 wt% SiC (3.5 µm+0.65 µm), Al2O3 and SiO2 powders, 0.2 wt% dispersant, and 2.8 wt% binder. Furthermore, the accuracy of the structure of specimens was improved via adjustment of the printing parameters, including nozzle size, extrusion pressure, and layer height. The density and flexural strength of the printed SiC-Sialon refractory sintered at 1600 °C were 2.43 g/cm3 and 85 MPa, respectively. In addition, the printed SiC-Sialon crucible demonstrated excellent corrosion resistance to iron slag. Compared to the printed crucible bottom, the crucible side wall was minimally affected by molten slag