Evaluating causes of construction waste in East Java Province of Indonesia using RII method

Indonesia’s construction industry is still expanding. The construction sector is a major contributor to global waste production. Over 30% of construction waste is disposed of in landfills, leading to a detrimental impact on the environment. This study aims to identify the causes of construction waste in East Java’s Construction industry. The causes of construction waste were divided into two categories: causes of natural material waste and causes of fabricated material waste. Data for this study were collected using the questionnaire. The sample consisted of 32 respondents from medium-to large-scale construction enterprises involved in 4 building construction projects. The method used to identify the dominant waste is mean analysis, meanwhile the causes of construction waste is analyzed using Relative Importance Index (RII) method. The results show that the main cause of natural material waste is inaccurate field measurements resulting in excess volume, and the main cause of fabricated material waste is the cutting of leftover materials that cannot be used anymore. Through the findings the prevention or minimization of construction waste can be carried out according to the causes.


Introduction
The construction industry in Indonesia has developed over the past few years.Based on the 2023 State Budget (RAPBN), the infrastructure budget has grown by 7.75% compared to 2022 [1].The growth rate of the construction sector in Indonesia has reached 6-7% annually, and it is expected to continue growing by 10-15% by 2050 in line with the Masterplan for the Acceleration and Expansion of Indonesia's Economic Development (MP3EI).This indicates that the construction industry's growth in Indonesia will continue to increase.
Alongside intensive construction activities, there is an inherent issue of construction waste [2].The amount of Construction and Demolition (C&D) waste generated on -site depends greatly on the perspectives and knowledge of key stakeholders involved in construction projects [2].The building life cycle broadly includes planning, construction, utilization, and demolition [3].A significant amount of waste is generated from industrial construction activities, particularly in construction and demolition.Globally, the construction industry responsible for over 30% of the waste that ends up to landfill [4].By 2050, it is estimated that the world's construction waste will increase by 70%, and produce 3.40 billion tons of waste annually, which is a significant increase from 2.01 billion tons in 2016 [5].In 2020, 27 European Union member countries produced 2.135 billion tons of waste, with 37.5% of it being construction and demolition waste [6].In Indonesia, the annual amount of construction waste reaches 29 million tons.The increasing quantity of waste each year proves that the development of construction activities leads to a rise in waste production.
In building projects, 50-60% of the project budget is allocated to materials [7].The cost of material include purchasing, storage, transportation, and disposal to landfill sites, as well as the time and resources used in the waste disposal process [2].However, the costs incurred in minimizing environmental damage should also be considered.Therefore, the material losses due to construction waste are significant.Besides causing financial losses, construction waste also has an environmental impact.The increasing quantity of construction waste leads to a corresponding rise in municipal waste at landfill sites, adding to the environmental burden.Many contractors in Indonesia assume that waste management will lead to increased costs and project delays.Consequently, they do not make sufficient preventive efforts in managing the construction waste generated.This paper aims to identify the dominant construction waste produced in construction projects and determine the significant factor causing construction waste.It also reviews previous research on construction waste to provide a comprehensive understanding of the current waste situation.In the previous research, the cause of construction waste was not differentiated according to the type of material, and it was not linked between the dominant waste produced and the potential cause of the waste.To fill this gap, this research has focused on the causes of building waste with differentiating the type of material, namely natural material and fabricated material, and linked the dominant of waste with the potential waste sources.Therefore, this paper is expected to increase insight among construction stakeholders regarding the sources and causes of construction waste by considering the type of materials.As the result, the appropriate preventive measures can be taken which leads to the minimization of construction waste.

Literature Review
This section presents a review definition of construction waste, the classification of construction waste, and followed by causes of construction waste generation.

Definition of Construction Waste
Construction waste is defined as residual material that cannot be used physically or functionally and has a negative impact on the environment.Construction waste can originate from a construction or demolition.There are several authors who have defined construction waste as follows: Construction waste is generated from damage materials, packaging, on-site operations, replacement, or demolition, then will be disposed of in the landfills.Oyeshola Femi Kofoworola, Shabbir H. Gheewala [8] Construction waste is waste that produce from several construction activities, such as new construction, renovation or demolition, and its can be classified as part of municipal solid waste (MSW) Ida Ayu R.W, I Nyoman Yudha A. and Ni Luh A.I. [9] Construction waste can be defined as an amount of materials that are unused in the construction process, such as over-ordering materials, damaged items, and materials that are no longer usable.Chakkrit Luangcharoenrat, Singh Intrachooto, Vachara Peansupap and Wandee Sutthinarakorn [10] Construction waste is defined as building materials that cannot be reused, leftover construction materials, materials damaged during construction process.

Shitaw Tafesse and Tamene
Adugna [11] Construction waste is one of the main causes of environmental and health problems of the society.Ahsan Nawaz, Jian Chen, and Xing Su [12] Waste is a loss that occurs during the construction process, adding no value to the project but incurring cost losses.
Based on the definitions of construction waste from several authors as listed in Table 1, it is found that construction waste is waste that originates from construction or demolition activities, which add no value to a project, and has a negative impact on the environment.

Classification of Construction Waste
There are several authors who have classified construction waste as show in Table 2  Ajay Sharma, Neha Shrivastava, Jagdish Lohar [15] Construction waste is divided into three categories: 1. Difficult to recycle such as: asbestos, paints, 2. Direct recycling is not possible but may be recycled, such as glass, oil, timber, plastic, paper 3. Easy to reuse or recycle, such as tiles, concrete, brick, soil Liang Wang and Chenggang Xi [16] Divided into two categories based on physical and chemical properties which are inert construction waste and non-inert construction waste.1. Inert construction waste : waste concrete, waste stone, waste asphalt, waste bricks 2. Non-inert construction waste : divided into two which are general solid waste (such as: waste wood, waste paper) and toxic and hazardous solid waste (such as: asbestos waste, waste organic solvents).
In this study, only focus on physical waste.There are two categories of physical waste on the construction sites as follows : a) Natural material waste is a type of physical waste that originates from natural resources without undergoing the fabrication process, such as sand, wood.b) Fabricated material waste is a type of physical waste that originates with the fabrication/manufacturing process, such as steel bar, steel profile, concrete, brick, ceramic, gypsum board, glass.

Sources and Causes of Construction Waste Generation
Construction waste generation has been influenced by many causes.The majority of waste in the sector is produced during the design and construction phases due to the higher propensity to produce trash [19].There are several sources of construction waste, according to the findings of earlier studies are presented in Table 3.  J. H. Brouwers research, based on design sources, some causes of building waste are error in the contract documents, incomplete contract documents at the start of construction, design modifications, choices regarding product parameters, selecting inferior goods, lack of consideration for the sizes of used things, designer is unfamiliar with the possibilities of various items, lack of understanding of construction and absence of contractor influence [17].

Procurement.
Procurement errors can be due to ordering items that do not meet specifications, supplier mistakes, and transportation damage [2].According to B. A. G. Bossink & H. J. H. Brouwers [17], the procurement process could result in ordering errors, overordering, underordering, etc., the inability to acquire small quantities, and the use of products that do not suit the specifications.In order to prevent construction waste, a construction project must have a sufficient procurement system for the proper materials in the right quantities.

Material Handling.
The improper handling and storage of construction materials causes deterioration and damage [11].Previous research in Malaysia found that the local construction industry's biggest causes of waste generation are improper material handling and storage [7].According to B. A. G. Bossink & H. J. H. Brouwers [17], the material handling procedure could lead to damaged during transit to site/onsite, incorrect storage leading to damage or deteriorization, unpacked supply, and throwaway packing.

Operation.
Dependent on the collaboration, attitudes, and actions of those participating in the construction process, waste from construction can be effectively managed and reduced [10].A lack of trained laborers is a constant problem at many building sites due to the ongoing workforce issue.Workers who lack instruction and training, are unqualified to perform the jobs they have been given, and are uncooperative will affect the quality of the work, which will lead to additional work and repairs [10].The issue is not only with the workers' skills, but also with the inadequate quality of equipment, which can also lead to construction waste.Therefore, operational errors can result from mistakes made by tradespeople or laborers, malfunctioning equipment, inclement weather, accidents, damage caused by subsequent trades, use of incorrect materials necessitating replacement, method of laying the foundation, required quantity of products unknown due to inadequate planning, and information about the types and sizes of products that will be used arriving at the contractor too late [17].
2.3.5.Residual.One of the sources of waste is residue, which is generated from leftover materials after use.According to B. A. G. Bossink and H. J. H. Brouwers, the causes of construction waste based on residual include conversion waste from cutting uneconomical shapes, offcuts from cutting materials to length, overmixing of materials for wet trades because of ignorance of requirements, waste from the application process, and packaging [17].

Others.
Construction waste can also be influenced by various other factors beyond the immediate construction site.In addition to construction-related activities, external issues like theft and vandalism can also cause waste to develop at any stage of the construction process [17].

Research Methodology
This research is a quantitative with a survey approach using a questionnaire.The research was conducted in the following stages:

Data Collection
The questionnaire was distributed to 32 respondents.The research respondents consisted of contractors and consultants in 4 building construction projects.The sample building projects and their companies responsible for the project as shows in Table 4.The questionnaire was divided into three sections.The first section discusses the respondents' general background.The second section discusses the dominant waste in building construction projects.In this study, construction waste was classified into two categories: natural material waste and fabricated material waste.Natural material waste includes sand and wood.Meanwhile, fabricated material waste includes reinforced bar, profile steel, concrete, brick, ceramic, gypsum board, and glass.
The third section of the questionnaire discusses the causes of natural and fabricated construction waste in four different building construction projects.These causes were classified into six categories based on their origins, such as design, procurement, material handling, operation, residual, and others.The questionnaire was distributed to a sample of thirty-two construction personnel.This research is conducted out using IBM SPSS Statistic 27 to establish validity values and reliability coefficients.Then it is determined that each indicator in the questionnaire is valid and usable.The reliability coefficient for the construction waste is 0.832, while the reliability coefficient for the causes of natural and fabricated construction waste are 0.946 and 0.937.The standard acceptable value for reliability coefficients is 0.8 and above [20].Based on that standard, the questionnaire is reliable.The Likert scale was used to create the questionnaire.Respondents are asked to rate the statements on the questionnaire form using a Likert scale of 1 to 5: (1) strongly disagree; (2) disagree; (3) neither agree nor disagree; (4) agree; (5) strongly agree [10].The causes of waste from both natural and fabricated materials are listed In Table 5 below.

Analysis Techniques
Once the data has been collected, statistical analysis is performed using the SPSS (Statistical Package for Social Science) program to verify the validity and reliability of a measurement.After ensuring that the data is accurate and trustworthy, the results of dominant waste construction in projects were analyzed using the descriptive statistics method (mean-standard deviation analysis) and the results of main cause of waste were analyzed and represented using the Relative Importance Index (RII).Microsoft Excel is utilized for both analyses.
The mean value can be calculated using Equation (1).
Meanwhile the standard deviation value can be calculated using Equation (2).
where x is the mean value; S is the standard deviation value;   is weight that gives by the respondents; and n is the total number of respondents (in this case, 32).The relative relevance index (RII) is a statistical approach that ranks several factors [21].Several authors adopted the RII analysis, such as Luangcharoenrat [10] used RII to rank construction wasterelated factor influencing in construction projects.Ya'Cob [22] used RII to identify factors that affect sustainable construction waste management.Consequently, this research likewise used the same methodology to analyzed the main causes of construction waste in four building projects.The index can be computed using Equation (3).
where W is the weight that gives to each factor by the respondents, which can range from 1 to 5 ('1' is strongly disagree and '5' is strongly agree); N is the total number of respondents; and A is the highest weight (in this case, 5).The relative Importance Index (RII) value ranges from 0 to 1 (0 < RII < 1).

Result and Discussion
The survey results are described in the following subsections: (a) the respondents' profile; (b) the descriptive statistics method (the mean and standard deviation value) of dominant waste in the project building; and (c) relative importance index (RII) of natural and fabricated causes of waste construction.

Respondents' Profile
This study involved 32 valid respondents from 4 building construction projects.The respondents of this study include contractors (50 %) and consultants (50%).Of those, 50% of respondents (see Figure 1) have worked on construction projects for more than ten years.The decision of which responders to choose was based on factors connected to the comprehension of the trash produced in the relevant construction project.

Dominant Waste Construction
Data of waste construction collected from questionnaires were then analyzed using descriptive statistics method based on mean and standard deviation value.Table 6 show the rank of mean and standard deviation value.Based on the results in Table 6, it is known that wood materials are in the first rank for the type of natural material waste that occurs in the construction project with a mean value of 2.25 and a standard deviation of 1.As for fabricated material waste, the first rank is ceramic with a mean value of 2,1875 and a standard deviation of 0,91059.Therefore, from the results, it can be known that the dominant of waste construction in four projects building according to the type of material, namely wood and ceramics.

Causes of Natural and Fabricated Waste
In this research, the causes of waste are grouped according to the type of material, i.e., natural material waste and fabricated material waste.The RII analysis is used to establish the main cause of construction waste that happens during the project.After calculating the RII index for each factor, the ranking is done from the highest to the lowest index.Table 7 shows the rank of causes of natural waste, and Table 8 shows the rank of causes of fabricated waste.8 shows that the main cause of fabricated material waste is leftovers from material cutting that cannot be reused with a RII index of 0.73125.This main cause as most contributing cause of fabricated waste production, in this research is ceramic.The main cause can arise when cutting ceramic material creates too small remnants that cannot be used for another location.The research by Boosink and Brouwers [17] discovered that cutting factors were mostly responsible for the generation of waste stone tablets, sand-lime bricks, and elements, and that the remainder of such cutting could not be used.The residual amounts of these cuts can be caused by imperfections in the product, the inability to adjust between different product sizes [17].At the time of cutting the material, it is possible for parts to be damaged due to worker error, so that they do not satisfy the specifications and cannot be reused.

Conclusion
This study determined the ranking among eighteen (18) causes of natural material waste and twenty (20) causes of fabricated material waste.The relative importance index method was adopted in this study to quantify and rank the causes of waste.The findings of this study show that the main cause of natural material waste is inaccurate field measurements resulting in excess volume, and the main cause of fabricated material waste is the cutting of leftover materials that cannot be used anymore.The main cause of waste can be increased the amount of dominant waste on the project site.This findings can be used as a recommendation for the project, therefore project can be carried out more efficiently.The findings also indicate that it is advisable for all parties involved in construction to tackle these issues throughout every phase of their project and establish a waste management strategy.Periodic monitoring is necessary when designing a waste management plan to reduce material misuse that results in additional waste.Coordination among stakeholders is also required to unite thoughts and reduce construction waste.Furthermore, similar studies concentrating on different types of building projects might be conducted to get greater insight into the causes that lead to the creation of construction waste on other objects.

5 2. 3 . 1 .
Design.The design is crucial to the entire construction process.Before beginning the construction process, design is the first phase in the development of construction projects.In B. A. G.Bossink & H.

Table 1 .
Definitions of construction waste

Table 2 .
bellow: Classifications of construction waste 2. Non-inert waste is material waste cannot be reused or recycled, and commonly disposed in landfills.Examples of non-inert waste include plastics, glass.

Table 3 .
Sources of construction wasteIn this study, sources of construction waste were adopted from the research findings of B. A. G. Bossink & H. J. H. Brouwers, as indicated in Table3.There are 6 sources of waste and various causes associated with each of them.

Table 4 .
Overview of the building projects investigated

Table 5 .
Sources of waste, code, and causes of natural and fabricated material waste

Table 6 .
The mean and standard deviation value of waste construction

Table 7 .
Causes of natural material waste