Construction waste constitutes a major source of solid waste. Proper management is very much needed to reduce its negative impacts towards the environment. Common causes of construction waste generation are off cuts from cutting materials to desired length, improper handling, stacking and storage, end of life cycles, spillage and leftover materials. Material waste has been recognized as a major problem in the construction industry that has important implications both for the efficiency industry and for the environmental impact of construction projects. As pointed out by previous research, residual waste such as material off-cuts was identified as the highest contributor to construction waste.
In the present study, data on material wastage level, waste index, as well as the construction waste conversion factors (density) and its standard measurement method was collected and compiled. The collected/compiled data functions as an input to the Standard Code of Practice for Construction Solid Waste Management, which is under developed by the Construction Industry Development Board (CIDB) and other related industry players, with the aim to provide appropriate guidance to relevant stakeholders, including waste generators of small to large scale, collectors, transporters, recycling and disposal facilities, as well as those who are involved in construction works.
To realize the objectives of the study, various mythologies were applied: (i) structured questionnaire survey, (ii) literature search, and (iii) case study. The quantitative research method in the form of questionnaire survey was employed to obtain the wastage level. With a sample size of 75, responses on the material wastage from the professional quantity surveyors (QS), project managers (PM), and site engineer (SE) were surveyed, by asking their perception on the percentage of wastage from a list of building materials. Besides, the respondents were also asked to rate nine identified factors that contribute to material wastage on site. Info with regard to waste index and conversion factor was collected through the conduction of detailed desk top assessment on past literature. In order to derive a list of volume-to-weight conversion factors for individual waste products, a case study was conducted. The study site took place at Pantai Bintang, Bangsar, where the demolition works was undertaken. Pieces of waste product such as bricks, steel, plastics, tiles etc. were transported back to the Construction Research Institute of Malaysia (CREAM) for determining the weight and volume.
The study successfully determined the wastage level for different materials commonly used in the construction site. Furthermore, the study revealed that off-cuts from cutting materials to length and packaging is the major contributor of waste generation, followed by the damage due to weather, and mishandling of materials, lack of site materials control. By conducting Kruskal-Wallis and the respective post-hoc test, opinion given by PM and SE on the level of material wastage are very much similar as compared to QS. This is the result of the extent to which one person involves in the project. While the QS does make allowances for waste when assessing the price of a material, most of the time, he/she is just based on his/her own estimation from the desktop assessment or experiences from the past project. Since the activities on a construction site change as the project progresses, the quantity of the associated waste may also change. PM and SE, on the other hand, share the high similarity because they are fully involved during the construction stage and to keep record of the waste disposal. This is especially true for the SE as he/she is the person that makes visual assessment of the main materials in each waste stream, as well as confirming that waste associated with all the main materials being used on-site is represented in the waste stream identified.
Through literature search, the study found that that the availability of data on waste index with regard to the Malaysian building industry was relatively scarce. A list of waste index compiled from the local studies for both commercial and residential building was presented in this study. However, these figures cannot be considered representative of the sector, not only because of the relatively small samples, but also because the relative importance of each material waste is likely to vary according to the building type (for example, residential, commercial, industrial, and so on) and technologies involved. Such list of waste index is better to be viewed as a reference to guide readers in making estimation on waste generated. Finally, a list of volume-to-weight conversion factors for individual waste products was produced by using sample wastes from a demolition site. The list covers a range of common material wastes found in the construction site: concrete, concrete with rebar, brick, electrical conduit, coaxial cable, wooden door frame, wooden joist, wall/floor tile, road pavement tile, high tensile bar (25mm), round bar (8mm), aluminum, and plastic. For reference purpose, the volume-to-weight conversion factors for C&D waste published by other organizations were also presented in this study, with the aim to provide useful information to the readers. It is hoped that the findings of the present study will function as an input to the Standard Code of Practice for Construction Solid Waste Management, which is under developed by the Construction Industry Development Board (CIDB), thereby contributing to the improvement of C&D waste estimation, as well as enhancing knowledge-based decision-making in developing appropriate strategy for construction waste management.