Many relief scenarios involve the discharge of a two-phase fluid mixture, and the proper method for sizing the relief valve for these conditions is the subject of considerable discussion. Sizing a valve is based on the flow through an isentropic nozzle, the pressure-density relation for the fluid properties, and a discharge coefficient (Kd) to match the calculated mass flux to that measured for the flow of air or water in the actual valve. For single-phase flow, this is straightforward, since the fluid properties are simple and measured values of Kd are available. For two-phase flow, the density-pressure relation is complex and no values of Kd are available, so a variety of ''models'' have been proposed in the literature to address this problem. Since the various models produce various results, the appropriate value of Kd required to match the model to the actual valve will depend on the model. This paper utilizes a simple, rigorous method for sizing relief valves for two-phase flow that utilizes the fluid properties directly and hence does not require a ''model'' for these properties. It is shown how this method can be applied to two-phase frozen or flashing (equilibrium or non-equilibrium) nozzle flows, and how the available values for Kd for single-phase flow can be used directly with this method, depending on the critical state of flow in the nozzle, to accurately predict two-phase flow in any valve. The calculations are compared with data from the literature for frozen air/water and flashing steam/water flows in actual safety relief valves.
INTRODUCTION
In the 9th Malaysia Plan, the construction sector was the only sector that recorded a positive growth during every quarter of 2009. So that, the construction sector have growth 5% in 2009, and subsequently 8.7% for the first quarter of 2010 as against the overall GDP growth of 10.1% during the first quarter of 2010. (Shaziman, 2010) It was within this scenario that the construction industry act as the momentum to economy, improve the standard of living and create job opportunity to the countries.
The construction industry in particular has been known among the main consumers of resources and energy. Nevertheless, the construction by nature is not a friendly activity to the environment. It creates serious environmental problems with deadly consequences such as air pollution, water pollution, landslides, flooding and many others. Moreover, the construction industry also reported generating unacceptable levels of construction wastage. A report published by the Institution of Civil Engineers (ICE 1996) indicates that over 500 million tonnes of construction waste are generated each year. Landfill space is becoming scarce and the cost of tipping materials is very high and rising. (Cooke & Williams, 2004)
Generally material wastage in the construction industry can be divided into on-site and off-site operational activities. On-site activities which mean the activities related to the construction works. It requires sufficient adjacent to the actual construction area on which to carry out the work. While off-site activities are the activities out of the construction site including manufacturing and transportation of materials and components.
Interrelated to each other, both off-site and on-site activities also produce huge quantity of construction waste and cause serious environmental consequences to our environment. In some country they have adopted some strategies of wastage deposition to manage such a huge quantity of construction waste.
Conventional construction encompasses traditional forms of construction for structural load-bearing elements which fabricated on-site. It typically consists of reinforced concrete, brickwork and or structural steel. The conventional construction has the advantages of easy transportation of wet concrete. It is flexible in any shape of design and on-site adjustment can be arranged easily provided carpenter is available. The disadvantages of the conventional construction is it fabricated in an 'unprotected' environment, additional time is required for the curing process, and it requires more temporary works and space to store the construction materials such as timber, steel, cement and many others.
Cast in-situ system formwork is a system which consists of the table form and tunnel form construction method. These construction methods are technically to all type of building construction and it can increase productivity and quality of work through the use of better construction machinery, equipment, materials and extensive pre-project planning. The objective of cast in-situ system formwork method is to eliminate and reduce the traditional site-based trades like traditional timber formwork, brickwork, plastering and reduce labour content, in order to speedy construction, low maintenance, durable structure and low cost.
In Malaysia, even through cast in-situ system formwork construction is not new and have many published on the subject. Nevertheless, conventional construction seems the main choice of the contractors in the construction industry. At a time of financial difficulty when competition is fierce, any construction method which can get better savings that can be achieved must be the first choice of the clients and contractors.
Rationale of Study
Some degree of waste of material is inevitable in the construction process; all Quantity Surveyors will allow wastage when pricing a bill of quantities. Experience shows, however, unless the management of control material is very strict, material wastage can frequently exceed with a huge amount.
Generally in the conventional construction, the contractors will make sure all the construction activities are carry on fast and smoothly to prevent any delay of construction period and earning more profit in the project. Despite the contractors need to speed up the construction progress, but they cannot lack of attention to the material wastage on site. Whereas the cast in-situ system formwork, it has the advantages over the conventional construction that include speedy construction, low maintenance, durable structure and low cost.
Since the trend of adopt the cast in-situ system formwork in Malaysia has been growth, it is believed that this study will contribute to various project participants in the future. Besides that, this study will help to reduce material wastage in the construction industry and various methods of waste prevention will be discussed. And, it is suitable for them to refer and choose a suitable construction method to manage the material waste and achieve a desirable profit.
Aims and Objectives
The aim of this study is to investigate the construction wastage in construction industry. In order to achieve the aim of the study, there are three objectives established as follows:
To determine the types of material wastage;
To identify the causes of construction waste;
To establish the waste prevention methods in construction for conventional and cast in-situ system formwork.
Scope of Study
Scope of research determined to facilitate the literature research, by focusing on certain field in literature research and data collection process. The research covers:
Research area involved in Kuala Lumpur and Selangor.
Collect data on the materials wastage generated in construction building.
Focus on materials waste between conventional and table formwork and tunnel formwork.
Limitation
In fact, there are some of people not familiar with the table form and tunnel form system so that will consider this is a new technology in construction industry. Moreover, they probably associate table form and tunnel form are only used for limited sector of construction project such as multi-storey building. For this reason, the usage of table form and tunnel form system is uncommon for local construction industry compared to conventional construction.
Therefore, this may affect the respondents to respond the questionnaire because they lacked of knowledge and experiencing in the table form and tunnel form system. In addition, they also lack of opinion about the problems encountered by the conventional building system.
Research Methodology
The research methodology is an essential part for the researcher to know the ideal methodologies in order to meet the aim and objectives of this study. In this study, the researcher will collect information from reference books, and journal articles to introduce some theories regarding to material wastage between conventional and cast in-situ system formwork. Moreover, internet sources also a part of the research methodology for the researcher to get the latest updated information of construction waste issues.
In order for the researcher to get some practical information from the construction industry, the data collection can be collected by using mail questionnaire. To strengthen the finding of the survey and to assist in providing more information about building material wastage, the case study was also conducted in this research. The method and detail on this data collection, location, and analysis will be explained in more detail in chapter 3 and 4.
Chapter Outline
Chapter 1
Introduce the area being investigated for this study. These are the background of the relevant material wastage level in construction industry, rationale of study, aims and objectives, scope of study, limitation and research methodology.
Chapter 2
Define the comparison between conventional and table form and tunnel form system in term of definition of waste, types of waste material, causes of construction waste, waste prevention methods in Malaysia and others country, materials wastage level between conventional and cast in-situ system formwork and conclusion.
Chapter 3
Explains the method of research for this study included the research strategy, method of data collection, the technique to analysis the collected data and conclusion.
Chapter 4
Discuss of the interpretation and analysis of the results obtained from the survey research and findings from the case study.
Chapter 5
States the conclusion and recommendation of the entire study.
LITERATURE REVIEW
Introduction
Building materials are the materials which used for construction purposes. It is an important input into the site production process which will affect the construction projects finish in the time specified with the required specification. Any attempt to quantify the materials in term of costs would come to the realization that they contribute a significant proportion towards the total construction costs. Due to the building materials contribute a significant proportion towards the total construction costs and consist of various types of material in different quantity, thus the building materials must be controlled by applying a strategic and systematic material management.
The construction industry by nature is not an environmental friendly activity. It creates serious environmental problems with deadly consequences and generating unacceptable levels of material wastage. Unacceptable levels of material wastage will increase the construction costs and lower the profit margin. Any projects which do not have a workable and efficient material management will face the material wastage problems.
Definition of Waste
Under the United Kingdom's Environmental Protection Act 1990 (EPA 90) Section 75 stated that waste includes any substance which constitutes a scrap material, an effluent or other unwanted surplus arising from the application of any process or any substance or article which requires to be disposed of which has been broken, worn out, contaminated or otherwise spoiled. It means that the construction waste consists of unwanted material produced directly or incidentally by the construction industry.
The wastage of construction materials can be classified into two types, which are direct and indirect material waste. Direct waste consists of the loss of those materials, which damaged and could not be repaired and subsequently used, or lost during the building process. By contrast, indirect waste normally occurs when the materials were not lost physically and it represented only a monetary loss.
In the other term, the definition of waste in Lean Production paradigm described it as a concepts related to process and operation. Process refers to the flow of activity form one worker to another worker; whereas operation is an activity taken by worker such as the worker transforms the raw material to finished product or walking to another location to get parts (Shingo, 1988).
Womack and Jones (1996) describe waste are related to the human activity which absorbs the time, resources or place but works with no value to the product, such as the process steps that are not needed, production of items that completed but not comply with the instruction, workers waiting for instruction and so on.
Types of Waste Material
Timber
Timber as describes wood which has been cut for use as structural material for construction. The majority used of timber in construction sites are in formworks during casting the structural elements. According to Waste Online (2006), timber waste form construction is produced in large amount all over the world. In the UK, it is estimated that each year up to 750,000 tonnes of timber waste is produced by construction and demolition.
Timber possesses many advantages that make it a popular building material. It is relatively inexpensive, high load capacity and lightweight material that is easy to cut, shape and join by relatively cheap and simple hand or power operated tools in the production of structural elements or formworks. The timber can be cut and shaped to producing any unique and complex forms of concrete structures. However, the timber has the disadvantages of low durability and reusability cause the timber one of the high wastage material.
Steel
Steel are referring to the reinforcement used in reinforced concrete and reinforced masonry structures. It is very important in the construction giving ridges for better frictional adhesion to the concrete. Concrete are strong in compression but weak in tension and contrary the steel are strong in tension and weak in compression. However, the operative's ability to measure the lengths of steel to obtain the most economical cuts is very important and condition of steel while storing must take into account to prevent serious rusting because steel is relatively expensive compared to other materials and the wastage of steel material will cause a significant impact on the project cost.
Concrete
Concrete is a building material composed of cement as well as other cementitious material such as course aggregate, fine aggregate, water and chemical admixtures. Concreting works is a major building process for structural elements and most of the works are made from ready-mixed concrete. However, the concrete also one of the high wastage material caused by loss attributed to excessive material ordering, overtime of concrete, broken formwork and redoing due to poor concrete placement quality.
Brick
Brick is a building material made from clay, calcium silicate, and concrete. The standard size of brick is 215mm x 102.5mm x 65mm and there are so many types of bricks such as common brick, facing brick, and engineering brick. Masonry works is the building process to enclose and protects a building or serves to divide buildings into compartments or rooms. However, the brick also one of the waste material caused by loss attributed to excessive material ordering, carelessness off-loading and handling due to the fragile characteristic of the material and redoing due to poor bricklaying workmanship.
Causes of Construction Waste
In generally, waste will occurs on site for a number of reasons, it resulting from all stages of building process starting from the design stage until the handover of the projects. There are many factors contribute to the generation of material wastage no matter direct or indirect wastage. The factors which cause the material wastage in a project were identified in four major sources as shown in Table 2.1: (1) design, (2) procurement, (3) material handling, and (4) operational. (Ekanayake & Ofori, 2000)
Table 2.1: Sources and causes of construction waste
Design
The most often causes occur during the design stage are the designers pay less attention to the dimensional coordination of products and the standard sizes available in the market. It may resulted the standard sizes available in the market cannot fit with the designed sizes and the workers have to cut the materials to suit the designed sizes. Following causes happened in a construction project is the changes of the design made by the client and the designer while construction. These may caused the previous works done has to be aborted and also resulted huge of material wastage in that project.
The complexity of detailing in the drawings and specification are usually make the project participates confused and improper planning. Due to the complicated of the assembly process stated in the specification and the lack of knowledge and experience by the workers may lead to the material wastage in the construction project.
Procurement
The material wastage of a construction project during procurement is involved to both of materials suppliers and the contractor or subcontractor. During the procurement stage the most often causes are incorrect taking-off and scheduling of materials, material ordering errors, supplier's error and others. According to Illingworth (2000), such situations generally start with incorrect taking-off of materials. If material over measure, where the quantities have been ordering is delivered, it will cause huge of material waste. If under ordering, waste can be created by delay to the contract. This shows that incorrect requisitioning and ordering of materials will lead to the material wastage in construction industry.
Material Handling
During the handling of the materials, the material wastage can be subjected to occur due to the unfriendly attitudes of the project team and labourers. The building material were damage or broken during transportation because of poor packing or insufficient protection during loading. Moreover, inappropriate storage material leads to damage or deterioration. So that, pre-planning to the space required for storage of materials is essential, it may consideration on the various delivered materials is to be placed for safe keeping and avoiding loss, vandalism and thief.
Operational
The material wastage of a construction project during operation is related to the errors made by tradespersons or labourers; accidents due to negligence; damage to work done caused by subsequent trades; use of incorrect material, thus requiring replacement; equipment malfunctioning and so on. The errors made by tradespersons or labourers such as fails to comply with the contract drawings or fails to comply with instruction given will cause the material wastage in the construction project. Damage to work done caused by subsequent trades. Sometimes, the site workers use the incorrect material therefore requiring for the contractor to redo the works.
Waste Prevention Methods
In fact, unacceptable levels of material wastage in construction projects will creates serious environmental problems with deadly consequences and increase the project cost meanwhile lowering the contractor' s profit margin. Due to the building materials contribute a significant proportion towards the total construction costs and consist of various type of material in different quantity, thus the building materials must be controlled and the material wastage must be prevented. In order to reduce the material wastage in construction projects, certain waste prevention methods need to be adopted at all stage of building process starting from the inception stage until the handover of the projects.
Good Attitudes of Project Participants
Hussey and Skoyles (2004) stated that a change in the attitudes of project participants including clients, designers, contractors and construction workers towards the practice of sustainable construction waste management may be more efficient than changes in construction technology. The clients may take the lead to wish the construction waste can be minimized during the construction period. Following by the changes of designer's attitude to reduce the construction waste in a construction project including reduce the changes of design while construction is in progress; reduce the complexity of detailing in the drawings and specification; and pay more attention to the dimensional coordination of new products and the standard sizes available in the market.
The changes of contractors and his workers' attitude in reducing the construction waste are important because they occupy a critical position in the construction waste generation chain and their attitudes have a direct and immediate impact upon the efficiency of construction waste management.
In addition, the necessary training to cope with the waste management procedures throughout the construction process are important to all levels of the consultants, contractors, subcontractors and site workers.
Material Storage Management (MSM)
Nowadays, Material Storage Management (MSM) is in great concern in many countries. It is no longer a new and hot issue in Malaysia construction trend, but still have most of local construction company are not using this kind of management system. Some of the construction company still not fully appreciate that material waste means financial loss and will direct increase the production price.
In fact, effective Material Storage Management (MSM) is essential to suit the current trend. The concept of Material Storage Management includes the planning, inventory control, purchasing, receiving and stores, material handling and physical distribution. It effective for company to reduce wastage, maximise profits, establish needed controls and reduce costs. (Ping et al., 2009)
Material Procurement System
An improvement in material procurement system may help to reduce the construction waste in a construction project. To reduce the ordering error, sufficient information is vital to mitigate the effect of those delays to the entire project progress. In order, communication between the each party for responsible to the material procurement are necessary, such as quality control personnel in charge of the areas of specifications, contracts, scheduling, purchasing and stock control. Often there is no established pattern for issuing information on the progress of delivery of materials. Thus panic situation are often occur at every delay resulting from late arrivals. To reduce these problems, Hira (1984) had suggested that in a large company it is need to provide a purchase functions are carried by a team of material procurement personnel whose duties are as outlined in Figure 2.1.
Figure 2.1: Duties of a team of material procurement personnel
Recycling Material
Recycling involves processing used materials or waste into new products or usable raw material in order to prevent the waste of potentially useful materials, reduce the demand on finite natural resources, save energy in production and transportation, and reduces the risks of pollution. Some materials are often of better quality and purity and have a better potential for recycling. Pichtel (2005) found that the C&D steel recycling rate is about 85% (18.2 out of 21.4 million tons generated). Due to the recycling rates of metal among the materials recovered from C&D sites are highest, so it has the good market in existence especially for ferrous metals such as copper and brass.
A specification can be amended in construction industry to regulate the use of recycled materials as hardcore in foundations, sub-base in road pavement and concrete in less technically demanding works. There are many different materials can be recycled with a different technique. For example, concrete aggregate collected form demolition sites are put through a crushing machine, often along with bricks, dirt and rocks. Smaller pieces of concrete are used as gravel for new construction projects. Crushed recycled concrete can also be used as dry aggregate for brand new concrete if it is free of contaminants.
Design to Minimize Material Wastage
During the design stage of a construction project, detailed in the drawings and specifications, and dimensional coordination of products and the sizes available in the market should be taken into account by the designer to avoid significant amount of waste. Generally, the design of a building is closely oriented to the building process. The more complex of design in a building, the more complicated detailing in the drawings and specifications, thus the more significant in construction waste.
Although changes of design while construction maybe required, the design should be flexible enough to accommodate changes without causing any material wastage. In the US, some of the company have adopted Design for Environment (DFE) to minimize the environment impact such as waste in the construction process, in order without sacrificing function and quality. DEF will identify the concept, scheme and detail design among will cause the waste and adopt a waste reduction approach to solve each causes of the wastage in construction industry. (Keys, Baldwin, & Austin, 2011)
Use of Cast In-situ System Formwork Method
Cast in-situ system formwork construction is technically to all type of building construction and it can increase productivity and quality of work through the use of better construction machinery, equipment, materials and extensive pre-project planning. The objective of the cast in-situ system formwork is to eliminate and reduce materials and labours content in construction process, so it is considered as an effective and efficient method for waste minimization.
Just in Time (JIT) System
According to Griffith and Watson (2006), Just in Time (JIT) philosophy has been used in the manufacturing for a number of years. JIT is an approach to manufacturing which can improve a company's performance. The concept is based on making the process more customers orientated, simple and co-ordinated.
Just in Time (JIT) system is focused on improving the productivity of the industry and eliminate the waste of non-value-adding activities which impacting by materials and plants. It provide the most efficient and effective way for a company by eliminating any waste, in order to ensure the product is produce at a lower cost, faster and at a high quality level, while using a minimum amount of resources.
Comparison Material Wastage Between Conventional and Table Form and Tunnel Form Construction
Robert et al. (2006) stated that usage of cast in-situ system formwork greatly reduces conventional formworks and falseworks in the construction process. Compared to conventional construction, cast in-situ system formwork generally has the benefit in achieving cost savings through considerable savings in erection and dismantling time.
The cast in-situ system formwork as well as table form and tunnel form have the advantage for reuse of formwork in numerous times example for tunnel form, it can usually be reused for 500 to 1,000 times. Additionally, table form and tunnel form using appropriate quality control to achieve a smooth, high quality concrete surface finish and dimensional accuracy eliminates finishing works like plastering. Since these system can reduces the required finishing works, thus providing another cost savings and speeding up the entire construction process.
Conclusion
As a conclusion, construction waste can be classified into two types, which are direct waste and indirect waste. Direct waste is a complete loss of materials which is damage or theft from site. Whereas indirect waste is a monetary loss and the materials were not physically.
The materials waste occurs at all stages of building process starting from the design stage until the handover of the projects. There are many factors contribute to the generation of material wastage no matter direct or indirect wastage. The factors which cause the material wastage in a project were identified in four major sources such as in design, procurement, material handling and operation stage.
Hence, certain waste prevention methods need to be adopted at all stages of building process starting from the design stage until the handover of the projects to reduce the material wastage in construction projects.
RESEARCH METHODOLOGY
Introduction
The research methodology is an essential part for the researcher to know the ideal methodologies in order to meet the aim and objectives of the study. Malaysia Nuclear Agency [MNA] (2007) stated that the term research is often described an entire collection of information about a particular subject, and is usually related to a problem that needs to be solved. An organized and suitable research methodology will ensure the effectiveness and smoothness of the research process.
There are certain research methodologies and procedures are used by the researcher to identify the causes of construction waste and the waste prevention methods, and to differentiate the material wastage levels between conventional and cast in-situ system formwork construction in order to achieve the aim and objectives of the study.
Research Strategy
Research method is defined as the way in which the research objectives can be questioned. It can be classified into two distinct types which is quantitative research and qualitative research. (Richardson et al., 2005)
Quantitative Research
In quantitative research, the information obtained from the respondents is expressed in numerical form, which the quantities of things can be measured such as number of items recalled, reaction times, percentage of items used, etc. Quantitative data can be collected by using a structured questionnaire that contains closed-ended questions. The advantage of quantitative research is less tedious and easy to understand when analyzing quantitative data. Moreover, when the survey involves a convenience sample, the data can be collected and analyzed fairly quickly.
Qualitative Research
In qualitative research, the information obtained from respondents is not expressed in numerical form, which cannot be measured quantitatively. Qualitative data can collect by using the method of interview, case study, and observational study. This research can focuses on lifestyle, culture of respondents or behaviour of respondents to other people and environment and so on. Hence, the qualitative research can explore topics in more depth and detail than quantitative research.
Data Collection
In generally, the data can be classified into primary data and secondary data. Primary data is the data which are collected from the field under the control and supervision of an investigator. This type of data is generally collected for the first time by direct observation. In order for the researchers to get some practical information from the construction industry, there are several methods of data collection such as observation method, personal interview, telephone interview, case study and mail survey can be used by the researchers to collect the primary information.
However, the secondary data is obtained from existing records, publications, etc. This means that the secondary data are collected from sources which have already been created or the purpose of first time use and future use. The secondary data can be obtained from internal sources and external sources. The internal sources of secondary data for marketing applications are sales records, marketing activity, cost information, distributor reports and customer feedback. Where the sources for external sources are from government publications, journals, books, magazines, newspapers, annual reports, etc. (Panneerselvam, 2009)
In this research study, the researcher will use case study and questionnaire to get some practical information from the project manager and the site personnel in the construction site. There are few reasons why the researcher will choose the case study and questionnaire to collect the primary information in this research study.
Case Study
A case study involves in depth, contextual analysis of similar situations in other research, where the nature of the problems and the problem definition happen to be the same. The researcher may intervene in the participant's functioning, such as asking questions to the site personnel. Nevertheless, in some case study it may not only use in interviews, where observation also play an important role in the collection of information. (Coolican, 1999)
The researcher will collect the data from two case studies of construction projects with each using conventional and table form and tunnel form construction method. The material wastage level of these two types of construction method will be evaluated and analyzed as a result in this research study.
Questionnaire
The main source of information obtain for data analysis in this research is use the questionnaires method. A success of survey methods is depends on the strength of the questionnaire used. Normally, the questionnaire consists of a set of well-formulated questions to probe and obtain responses from respondents. There are pros and cons of the questionnaire in the primary information. (R.Panneerselvam, 2009)
Table 3.1: Pros and cons of questionnaire method
Pros
Cons
Less cost of data collection
Less time of data collection
Wider coverage of population
Better accuracy of data
Absence of interviewer's bias
The identity of the respondents is not known to the interviewers.
The questionnaire may be filled in by the assistant.
Source respondents may not return filled in questionnaire.
Delay in returning the filled in questionnaires by respondents.
The survey questionnaire will be set by the researcher in order to achieve the objectives, which stated in Chapter1.3. The questionnaire designed for this research is divided into five parts as following:
Part I: Respondent Profile
Part II: Project Information
Part III: Types of Material Wastage
Part IV: Causes of Construction Wastage
Part V: Waste Prevention Methods
Data Analysis
After data are collected, the descriptive statistics method will be used by researcher to classification and analysis of data. The purpose of using the descriptive statistics method is to have a general overview of the results obtained from construction industry. Therefore, survey questionnaire will be analysis by using percentage and presented by using a bar chart, pie chart or graph according to the data collected.
The survey question 1 in Part IV, respondents was requested to indicate the degree of agrees to the causes of material waste by using the 5-point rating scale (from "strongly agree" to "strongly disagree"). For researcher to analysis this question, the qualitative data can be converted to quantitative data by using the following formula:
5N5+4N4+3N3+2N2+N1
Conversion formula = 5(N5+N4+N3+N2+N1)
N5= Number of respondent strongly agree
N4= Number of respondent agree
N3= Number of neutral respondent
N2= Number of respondent disagree
N1= Number of respondent strongly disagree
Conclusion
As a conclusion, raw data will be collected by using interview survey and the methods of analyzing the raw data will be descriptive statistics method. In addition, the researcher will collect the data from two case studies of construction projects with each using conventional and cast in-situ system formwork construction method. The material wastage level of these two types of construction method will be evaluated and analyzed as a result in this research study.
