Zhili Gao

Use of steel slag as a granular material: Volume expansion prediction and usability criteria

The theoretical equation for predicting volume expansion of steel slag is deduced based on both chemical reaction and physical changes of free lime in steel slag during the hydration process. Laboratory volume expansion testing is conducted to compare the results with the theoretical volume expansion. It is proved that they correlated well. It is furthermore experimentally proved that certain volume expansion of steel slag can be absorbed internally by the void volume in bulk steel slag under external surcharge weight making the apparent volume expansion equal zero. The minimum (lowest) absorbable void volume is approximately 7.5%, which is unrelated to the free lime content. A usability criterion is then developed based on the volume expansion of steel slag (%) and the minimum percentage of the volume that can take the volume expansion of steel slag (%). Eventually the criterion (relationship) is established based on the free lime content, the specific gravity and bulk relative gravity of a specific steel slag sample. The criteria can be used as guidance and specification for the use of steel slag and other expansion-prone nonferrous slags, copper, nickel for instance as a granular material in highway construction.

Evaluating Sustainability of Architectural Designs Using Building Information Modeling

BIM (Building Information Modeling) has been recently implemented by many Architecture, Engineering, and Construction firms due to its productivity gains and long term benefits. This paper presents the development and imple- mentation of a sustainability assessment framework for an architectural design using BIM technology in extracting data from the digital building model needed for determining the level of sustainability. The sustainability assessment is based on the LEED (Leadership in Energy and Environmental Design) Green Building Rating System, a widely accepted national standards for sustainable building design in the United States. The architectural design of a hotel project is used as a case study to verify the applicability of the framework.

Selecting an architecture‐engineering team by using fuzzy set theory

Purpose – Selecting the most appropriate architecture‐engineering (AE) team, one of the most significant decisions leading to the successful completion of a construction project, is usually conducted in a multi‐criteria environment, which is mostly dependent on the subjective judgment of decision makers and is influenced by the uncertainty and vagueness of each individual construction project. This paper aims to present an assessment method to evaluate the capability of an AE team with respect to the criteria defined by decision makers.Design/methodology/approach – In addition to a proposed tender price, the evaluation of potential AE teams should be also based on other criteria such as its financial soundness, experience, expertise, availability, and compatibility of personality. A selection model is developed, in which different decision criteria and its subcriteria, and their combinations are simultaneously taken into account by using the concept of fuzzy set theory. An illustrative example is also pro...

A Multi-objective Generic Algorithm Approach for Optimization of Building Energy Performance

This paper presents the results of a pilot study conducted to optimize building energy performance using a Multi-objective Generic Algorithm (MOGA), an evolutionary adoptive approach. In this study, a Building Information Modeling (BIM) model was built to provide design data, such as building form and space layout, and site and building orientation to IES , a building energy simulation software. Energy performance of design options was evaluated. The optimal settings of the design parameters were then obtained using a MOGA approach. This study indicates that the MOGA approach (1) enables continuous investigation of design parameters over their entire spectrum, (2) accounts for that fact that design parameters dynamically, not statically, impact energy performance, and (3) optimizes multiple design criteria simultaneous. This study concluded that MOGA is an appropriate approach that can better ensure a global optimal solution for design of energy efficient buildings.

Mechanical Properties of Mortar with Recycled Clay-Brick-Powder

Replacing cement with recycled clay-brick-powder could reduce carbon dioxide (CO2) emission, enhance conservation of natural resources, and decrease the cost of waste disposal sites. This paper studied the effect of recycled brick-powder on mortar mechanical properties, including flow, compressive strength, and flexural strength. Three level of cement replacement ratio (10%, 20%, and 30%) and four different average particle size of clay-brick-powder (0.3mm, 0.1mm, 0.06mm, and 0.04mm) were considered. Total 13 mixes, including one normal cement mortar as reference, were tested. The water/cement ratio (W/C) and sand ratio were kept constant for all mixes. Testing results showed that recycled clay-brick-powder could be used as partial replacement of cement in mortar without reducing its properties. Compared with normal cement mortar, samples with 10% of 0.1mm and 0.06mm clay-brick-powder had similar or even higher mechanical properties. The effect of clay-brick-powder on the flow and compressive strength depended on its replacement level and average particle size. Generally, compressive strength decreased as the replacement level and average particle size increased. However, mortar with and without clay-brick-powder had similar flexural strength.

Prediction of Pavement Concrete Strength Development, Joint Sawing and Opening Time Using FEMLAB

This paper describes a new Finite Element Modeling Laboratory (FEMLAB) model that can be used to predict pavement strength development and consequently the pavement joint-sawing and opening times. The strength prediction was based on the temperature history of the concrete pavement, which was determined by the rate of heat generation and the heat exchange between the pavement and the environment. Pavement joint-sawing and opening times were defined as the times when concrete strength reached 4.3 and 24.1 MPa, respectively. Using this model, the effects of weather conditions, fly ash and slag replacement, concrete placement time and temperature, and pavement thickness on concrete strength, joint-sawing time, and pavement opening time were evaluated. Results showed that weather conditions and the use of fly ash and slag had a significant impact on strength development, joint-sawing time, and pavement opening time.

Properties and Early-Age Cracking Potential of Blended Cement Concrete

Stress due to the temperature and moisture gradients in concrete slab often causes pavement curling and warping that may further cause concrete crack if the slab is under restraint conditions. The adding of supplementary cementitious materials (SCMs) can reduce the risk of cracking by reducing the temperature stress. However, under cold weather condition, the slower strength development due to SCMs could increase the risk. This paper reported a study result of using blended cement to reduce such a risk. In this study, the properties of ternary cement concrete, such as setting time, heat of hydration, and datum temperature, were investigated. The risk of early-age cracking for different concrete mixes under different weather conditions was evaluated by the HIPERPAV. The test results indicated that fly ash replacement generally increases the setting time; while the slag replacement reduced the setting time. Both fly ash and slag replacement reduced the generated heat. When the amount of slag increased, the datum temperature and activation energy increased. HIPERPAV analysis indicated that there was little risk of early-age cracking for binary or ternary cement concrete under average summer weather conditions due to proper strength development of the concrete. However, the risk of early-age cracking for the concrete pavement increased under spring or fall weather conditions.

Travel Demand Based Optimization Model for Urban Mixed Traffic Systems

The large population and urban mixed traffic flow have caused many urban traffic problems in China. This paper considers the basic factors that influence the choice behaviors of individual travelers, and presents a system optimization model for urban mixed traffic networks using bi-level programming. The model uses the variational inequality method and increases optimization for an urban mixed traffic system and provides a powerful tool to improve city traffic situations. A case study to illustrate the applications of the model and its algorithm is also included in the paper.

A Usability Study of an Object-Oriented Design and Specification System for Transportation Projects

Currently, individuals learn about the project requirements by studying a combination of paper and electronic copies of various construction documents. This can be a tedious process since one needs to go back and forth between documents to obtain information about the entire project. This study utilizes the object-oriented computer-aided design (OO-CAD) technology to turn paper-based design standards and construction specifications into an object-oriented design and specification (OODAS) system. Individuals can use the system through a handheld wireless book-size laptop that includes all of the necessary software for operating in a 3D environment. All parties involved in transportation projects can access all of the standards and requirements simultaneously using a 3D graphical interface. An OODAS prototype model was created and demonstrated to potential users representing counties, cities, and the state. Findings suggest that a system like this could improve productivity to find information by as much as 75% and provide a greater sense of confidence that all relevant information had been identified. It was also apparent that this system would be used by more people in construction than in design. There was also concern related to the cost to develop and maintain the complete system. The future direction should focus on a project-based system that can help the contractors and DOT inspectors find information more rapidly as it pertains to a specific project.