There is a limited number of research scholarships offered by the university per year. The competition for these is very intense and scholarship is awarded on the basis of academic merit. Further information can be obtained from the Division of Research & Graduate Studies.

We invite potential PhD and Master's by research scholars to consider pursuing the research topics listed below. Please contact Professor Michael Chew for the details:
Homepage: http://courses.nus.edu.sg/course/bdgchewm/homepage/default.htm
Tel: (65) 6516 4412
Fax: (65) 6777 3953
Email: bdgchewm@nus.edu.sg

For other research areas, please visit our academic staff's web pages.

 

Research Topic (1)

Study of Internal Factors Affecting Practical Performance of Construction Sealant – A Brief Proposal

INTRODUCTION

I.	The said internal factors comprise factors in sealant selection, application methods, curing conditions, and sealant formulation. These factors depend on actions from users and producers other than the external elements like temperature, sunshine and so on. Take curing conditions as an example. One factor in this respect is, curing in the presence of rain and a series of conditions can be tested, say, totally without rain, with application half an hour before rain, with application one day before rain and so on, to investigate whether rain during curing has any effect on practical performance for specific uses, what this effect depends on, and how significant this effect is, so as to provide the users with a comprehensive guideline on consideration of the application time in relation to rain.
II.	The said practical performance comprises practical performance in general conditions and practical performance in particular conditions.
III.	The tests to evaluate practical performance should be performance tests like cyclic movement, QUV, hot water immersion and simulated performance test instead of property tests like standard mechanic tests. A package for assessment of practical performance should be designed.
IV.	The objectives of this work are detailed below.
	i.	To provide systematic guidelines to customers, applicators, examiners and suppliers on how to achieve high performance in the use of construction sealants under different conditions.
	ii.	To explore "importance" weights of various internal factors in the use of construction sealants that affect practical performance under different conditions, such as general purpose, tropical use, and so on. Models can be established for this investigation.
	iii.	To give theoretical and solid explanations for failures and limits of current construction sealant application.

THEORETICAL CONTRIBUTIONS

I.	Basic Work
	i.	Definition and Establishment of Internal Factors Internal factors of sealant performance refer to the elements that are relevant to and controlled by users, applicators and/or producers. They are related to actions taken in sealant selection, sealant application, curing conditioning and sealant formulation. The objective of this project is to study and optimize the impact of internal factors on specific use-conditions. Although many internal factors are well realized by those people involved, such as treatment of substrate surface, there are still factors that have yet to be found or established. Thus, gathering of existing internal factors and establishment of new internal factors are an important part of this study.
	ii.	Classification of Use-Conditions Impact of internal factors on sealant performance also depends on external use-condition. The impact study has to be performed under specific use-conditions, like general conditions or the tropical conditions. Thus set-up of major classes of use-conditions for study and investigation constitutes the first step of this study.
II.	Exploration of Ways to Do Research on Internal Factors Efficient and inventive ways to research need to be developed in this study, including the following contents.
	i.	Method to investigate the impact of a specific factor.
	ii.	Method to determine the "importance" weight of a specific factor.
	iii.	Method to extract generalized findings by data handling and modeling.
	Either theoretically or practically, the above methods are of novelty because for many internal factors to be studied, there still have not been any standard test methods for measurement or investigation.
III.	Findings with Internal Factors These findings cover the following aspects.
	i.	The way and extent that a specific internal factor affects the total sealant performance under a specific class of use-conditions.
	ii.	New internal factors.
	iii.	"Importance" weights of various internal factors under a specific class of use-conditions.
	iv.	Theoretical and instrumental explanations to new findings.
	v.	Integration of various findings into generalized conclusion or theory.

DELIVERABLES

I.	Consultation Software A software can be developed based on the results from this study to provide consultation to sealant users, applicators and producers on how to make correct actions to achieve the best sealant performance under a required use-condition set.
II.	Sealant Formulation Sealants with excellent performance under unusual use-conditions can be formulated based on the results of the study.
III.	Application Technology New application machines, application procedures and application solutions can be established based on the results of the study to enhance sealant performance.

METHODOLOGY

I.	Investigation of Specific Internal Factors Detailed procedures of investigation are to be established for different internal factors.
II.	Application of Advanced Instruments Advanced instruments like SEM, FTIR and others are to be used in the investigation to give solid conclusion and explanation.
III.	Data Handling Efficient data handling methods or software are to be used to facilitate the integration of the study results.

 

Research Topic (2)

Mould Growth in Buildings

PURPOSE

From the recent study on building maintainability in the tropics, building dampness due to, for example, water seepage and condensation was found to be the most significant contributor to building defects. Among the defects that had attracted the most attention is biological growth such as moulds. Recent events in the US and Europe have sent a very strong and clear signal that other than their effect on building durability, some moulds are particularly toxic and could result in serious health consequences. Few studies have attempted to measure, identify and address the effects and prevention of mould growth in buildings under tropical conditions.

This study attempts to identify and categorize mould species found in both indoor and outdoor environments of buildings in the tropics and correlate the concentration to building usage, material and environmental exposure. The results will form the basis of a comprehensive study for the evaluation of the permissible level of mould on various materials to their nature of use; the development of guidelines on building design, construction and maintenance in the prevention of mould growth; the development of efficient technology/product for the prevention and remediation of mould growth.

The objectives of the project are:

•	To study the type and extent of mould growth in buildings of different uses under tropical conditions.
•	To correlate the mould concentration to (i) building materials, e.g. exposed and hidden surfaces of wall paper; carpet; ceiling boards, (ii) environments, e.g. high moisture due to seepage; condensation; water and air-tightness ; RH.
•	To identify the remediation and prevention strategies against major mould growth.
The project aims to deliver the following:
•	Compilation of common building related moulds under tropical conditions.
•	The results will form the basis of a follow-up comprehensive study for the evaluation of the permissible level of mould on various materials to their nature of use; the development of guidelines on building design, construction and maintenance in the prevention of mould growth; the development of efficient technology/product for the prevention and remediation of mould growth.

BACKGROUND

Human health is directly affected by air quality. The level and type of microbial contamination in an indoor environment depends significantly on external environmental conditions and on the nature of the building’s use. Fungi species such as Cladosporium and Aspergillus usually occur naturally in the external environment and enter as spores attached to dust particles due to ineffective filtration systems. From past researches, it was found that such outdoor airborne fungi concentrations in tropical countries were higher than those in temperate zones. This may be attributed to the high relative humidity and rainfall levels in tropical countries. The large difference in the types of flora found in both climates also affects the types of microbes found in buildings under such climates.

In addition, the permissible level of microbial contamination varies across building uses. Buildings such as hospitals and schools by nature of its use require a much lower permissible level of microbial contamination. This study thus attempts to identify and categorize mould species found in both indoor and outdoor environments of buildings in the tropics and correlate the concentration to building usage, material and environmental exposure. The results will form the basis of a comprehensive study for the evaluation of the permissible level of mould on various materials to their nature of use; the development of guidelines on building design, construction and maintenance in the prevention of mould growth; the development of efficient technology/product for the prevention and remediation of mould growth.

PROGRAMME

1.	Field survey 10 buildings will be selected for each building use type. In this study, building use type will be categorized into residential, commercial, schools and hospitals. A total of 40 buildings will be surveyed. As-built drawings, M&E drawings, etc of the buildings will be studied. At each location of sampling, surface temperature moisture content, relative humidity and ambient temperature will be measured.
2.	Air and surface sampling Anderson samplers will be used to collect particles directly onto a culture dish for incubation and subsequent examination and identification of the growth product. Air sampling will be carried out at ceiling, breathing and floor levels. Surface vacuuming will be conducted to collect samples from exposed and hidden surfaces such as carpets. The contents of the cassette will be examined by light microscope.

 

Research Topic (3)

CFD Simulation of Wind-driven Rain (WDR) on Building Façades

INTRODUCTION

Wind driven rain (WDR) is defined as rain carried along by wind and moving at certain angle to the vertical. Its inclination is a function of the wind speed and the size of the raindrop (droplet size).

From past weather data, the WDR trajectory to vertical increases with wind speed, but the extreme wind speed decreases with increase in rainfall intensity. WDR trajectory is a function of the wind speed and the size of the raindrop.

This study will look into the development of CFD models to simulate WDR and the water runoff on building surfaces.

THEORETICAL CONTRIBUTIONS

Review the limitations of K- model and explore new ways of modeling the said phenomenon.

PROGRAMME

Study using wind tunnel, full scale measurements and simulations of WDR and water runoff will be carried out on selected buildings taking into consideration the various environmental variables and boundary conditions.

DELIVERABLES

A simulation model to be developed to simulate WDR and water runoff on surfaces of buildings.

 

Research Topic (4)

Ignition and Spread of Flame of Building Materials in Fire

ABSTRACT

Ignition of solids and the rate of flame propagation along the surface of solids determine the likely size and severity of fire involving a large area of combustible materials. The physical behaviour of ignition and flame spread is studied to examine and quantify critical parameters of ignitability, ease of ignition and flame spread for improved parametric modelling of fire processes. The ignition and burning behaviour of wood is considered for the different surface orientation, direction of propagation, fuel thickness, thermal capacity and geometry of samples as exposed to continuous heat flux. This research aims to expound and gain a better understanding of the physical processes governing initiation and propagation of combustion for wood-based building materials.

INTRODUCTION

Ignition is a process by which a rapid, exothermic reaction is initiated, which then propagates and causes the materials involved to undergo change, producing temperature greatly in excess of ambient. Ignition is hitherto important as it represents the initiation to flaming combustion. Most published studies have dealt with the ignition of wood and found that wood may ignite by flaming directly, or it may ignite in a glowing mode, which then may or may not be followed by flaming, as when exposed to radiant, or radiant with convective heating [1]. However, there is scanty information pertaining to ignition by direct flame impingement [2]. Most reported tests, whether practical or experimental, have been much too brief to produce useful data on this point.

Flame spread can be considered as an advancing ignition front in which the leading edge of the flame acts as both the source of heat and as the source of pilot ignition. It involves non-steady state heat transfer problem similar to that encountered in the pilot ignition of solids. Several studies[3-7] have indicated that the rate of flame spread can depend as much on the physical properties of a material as on its chemical composition. Using wood as the substrate, the characteristics of flame spread over combustible materials can be examined as a basic component of fire growth.

RESEARCH PROBLEM

When exposed to heat, polymers pyrolyse to initiate the combustion cycle. The burning characteristics and char formation of polymers can be examined from the structural and morphological changes. Laboratory-simulated results of the condensed phase and gas phase processes are to be correlated with the parametric combustion to establish the quantitative parameters for ignition and flame spread processes.

RESEARCH OBJECTIVES

To determine critical value of

•	The amount of heat to be reduced to below that required to sustain combustion;
•	The amount of flammable volatiles to be reduced through chemical intervention to modify the pyrolysis process;
•	The heat flow back to the polymer to prevent further analysis

RESEARCH DELIVERABLES

•	Critical ignition parameters based on different heat fluxes correlated to full-scale fire;
•	Flame spread properties of burning wood solids correlated to full-scale compartment fire;
•	Parametric data for further fire modelling and hazard assessment of compartment fire;
•	Physical data for chemical intervention strategies of wood-based materials.

RESEARCH METHODOLOGY

1.	Morphological Changes [8]
	•	Spectroscopy to detect the graphitic material in chars from both pyrolysis and burn experiments;
	•	Infra-red spectroscopy to recognise residual hydrogen and polar groups;
	•	X-ray photoelectron spectroscopy (XPS) and solid phase NMR to study the incorporation of hetero-elements, such as phosphorus elements in chars.
2.	Controlled Pyrolysis
	•	Dynamic Thermogravimetry (TG) to evaluate the kinetics of pyrolysis under controlled atmosphere and heating rate;
	•	Dynamic Differential Scanning Calorimetry (DSC) to study the kinetics of the condensed phase reactions.
3.	Burn Experiments
	•	Polymer combustion in Cone Calorimeter and the related parameters of combustion;
	•	Dynamic smoke measurement, soot formation and smoke release rates using Cone Calorimeter;
	•	Static smoke measurement using the NBS Smoke Density Chamber.

 

Research Topic (5)

Building Maintainability

Building Maintainability – specialized focus areas to be derived from the recently completed research project on the building maintainability. The purpose of the research was to improve the standard and quality of design, construction and maintenance of buildings to produce efficient buildings that require minimal maintenance. The main deliverables including a defect library, material manual and a proposed maintainability scoring system are discussed (http://www.hpbc.bdg.nus.edu.sg/).

The study focused on two main tasks,

1.	improving the knowledge on maintainability
2.	setting the maintainability benchmarks.

Improving the knowledge of maintainability has to be enhanced mainly due to,

a.	Facing difficulties in maintenance with increasing number of occurrence of defects, maintenance managers are becoming painfully aware of the lack of knowledge and tools in their organizations.
b.	Designers are not well focused to achieve maintainable designs, owing to poor awareness of the maintainability problems during the service life.

Setting maintainability benchmarks:

It is of compelling logic to improve the level of maintainability right from the design stage. The rational of the benchmark is to enable the decision maker to choose a more maintainable design option. Yardsticks like scoring systems would assist in the selection of highly maintainable building designs.

An example of a focus area can be:

AN INTEGRATED APPROACH TO MAINTAINABILITY OF BUILDINGS

Purpose

Maintainability of buildings is a key initiative of the Construction 21 – the blueprint for developing Singapore's construction industry up to year 2010. This proposal is designed to study the maintainability issues of various categories of buildings under various conditions. It aims to improve the standard and quality of the practices in design, construction and maintenance of buildings so as to produce efficient buildings that require minimal maintenance.

The objectives of the study are:

•	to evaluate the implications of design, construction and maintenance on the performance and maintainability of building,
•	to define 'acceptable' standards and benchmark 'maintainability',
•	to derive a maintainability scoring system.

PROGRAMME

Scope problem areas

Existing data on maintainability relating to various elements of tall buildings will be collected. New series of data will be generated for the latest buildings where no previous information is available. The major problem areas according to different building types will be identified and their impact on the various performances will be quantified using the approach of total building performance.

Evaluation of causes

The probable causes for each problem will be analyzed. The implications of design, application, workmanship, materials and maintenance will be evaluated and quantified. The current standards and practices for design, construction, material selection and maintenance will be reviewed. Solutions will be proposed and their effectiveness tested by running on-site and laboratory simulations.

Consolidation of findings

Consolidate findings through dialogues sessions and workshops with relevant parties including suppliers, designers, contractors, practitioners, maintenance specialists etc. Good design and detailing practices, specifications, application and maintenance practices will be drafted. Comments from the relevant parties will be sought.

Development of Maintainability Scoring System

'Acceptable' standards for different types of buildings will be evaluated and the maintainability issues benchmarked. Various mathematical/quantitative models will be experimented for the development of a prototype maintainability scoring system based on data collected from earlier parts of the project. The effectiveness of the system will be quantified by measuring the performances on-site and off-site before and after the application of the system

 

References

1. Dougal Drysdale (1999). An Introduction to Fire Dynamics. 2nd Edition, John Wiley & Sons Ltd, England.
2. Vytenis Babrauskas (2002). Ignition of Wood: A Review of the State of the Art. Journal of Fire Protection Engineering, Vol 12 (Aug), 163-189.
3. Friedman, R. (1977). Ignition and Burning of Solids. In: Fire Standards and Safety, ASTM 614, (Ed., A.F. Robertson), p91-111. American Society for Testing and Materials, PA.
4. Fernandez-Pello, A.C and Hirano, T (1983). Controlling Mechanisms of Flame Spread. Combustion Science and Technology, 32, 1-31.
5. Fernandez-Pello, A.C (1984). Flame Spread Modelling. Combustion Science and Technology, 39, 119-134.
6. Fernandez-Pello, A.C. (1995). The Solid Phase. In: Combustion Fundamentals of Fire (Ed., G. Cox). P31-100, Academic Press, London.
7. Lim Siew Mei (2002). The Study of High Temperature Decomposition of Wood and Its Kinetics In Response to Fire. Master Thesis, National University of Singapore, Singapore.
8. Levchik, S.V. and Wilkie C.A. (2000). Fire Retardancy of Polymeric Materials. (Eds.,) A.F. Grand and Wilkie C.A., Marcel Dekker Inc., New York.