Construction Waste Control

01 Apr 2020 Long Read

MANASA N and DR NIRMALA DB write on the cost-optimisation technique for the waste management of construction materials.

The amount of waste generated by construction and demolition is tremendous. Materials used by the construction industry pass through a number of processes before they are eventually incorporated in construction. In other words, waste is any inefficiency that results in the use of equipment, materials, labour, or capital in larger quantities than those considered as necessary in the production of a building. Further, according to some researchers, waste in construction and manufacturing includes delay times, quality costs, lack of safety rework, unnecessary transportation trips, long distances, improper choice of management, methods or equipment, and poor constructability.

In this article, we delve into how a single building information modelling (BIM) model helps integrate cost optimisation for both, the design and construction phases, in the construction of a three-storied building.

BIM benefits

Various techniques were proposed to quantify and control construction wastes successfully.

BIM can manage construction and demolition waste by avoiding design problems and reworks. It facilitates the project contributors to enhance the strategies and technologies in the planning, construction and demolition process, thereby managing and minimising construction and demolition waste efficiently.

BIM is one of the spatial technologies as well as data communication technologies commonly used in the architecture, engineering and construction industry, and can be systematically and efficiently integrated with identification and data-acquisition technologies. It provides improved planning and scheduling, and helps to ensure just-in-time arrival of labour, equipment and materials. Better construction planning and management using BIM can also significantly reduce construction and demolition waste generation by avoiding rework and unnecessary material handling, and by efficiently using raw materials based on accurate measurement for material ordering, layout and cutting.

To create a BIM model, a BIM tool is needed. There are currently several companies providing software for BIM, such as Autodesk, Bentley Systems, Nemetschek and Graphisoft. For this study, Autodesk Revit Architecture is used to demonstrate the creation of a 3D BIM model.

Project planning and scheduling Objectives of planning:

Minimise time consumption
Remove the uncertainty or minimise risk
Reduce resource usage
To improve the efficiency of operation
Give early warnings in case of a potential problem.

Objectives of the work:

To identify the potential opportunities of BIM for efficient construction and demolition waste management and minimisation in the planning, design, construction, and demolition phases
To understand the key design measures for driving waste minimisation in construction projects
To propose a model for an estimate of construction waste during the execution process of buildings through design and production features
To examine the construction demolition waste generation flow progression during the construction of buildings
To explore a model and establish sets of design strategies for waste-efficient construction projects.

Methodology

An apartment building with three storeys (G+3) is used for development of the waste quantification process. The material specification used includes concrete of M10 and M25 mix and coarse aggregate of 20 mm and 40 mm nominal size.

The method adopted consists of three stages. First, a prototypical framework of a computational 3D BIM model for construction waste quantification is developed in Revit software. Second, the

waste-generation level is introduced in Revit software in which the model is developed. Third, quantified waste from the tool is compared with the waste generated of an ongoing construction project.

Cost owing to time delay is calculated using Primavera P6 software. Further, the results are verified with the original site data.

Unlike traditional methods that use lines, points and arcs to draw the building components, a designer directly uses 3D digital objects to create the model in commercial BIM software, Revit 2017. This is often referred to as the ‘Construction Model’.

The waste quantification method was incorporated to the project using a 3D BIM model.

The system quantifies the onsite waste-generation level by monitoring the quantity of variation of structural elements of the project. Developing a BIM model helps to know the original variation of the material quantities. The waste-generation property is not a default family of the 3D BIM Revit model. This is an additional parameter incorporated by the user to the Revit model. The

waste-generation level is the key data required for the waste-generation property. Thus, it can create a new parameter from the Cloud and modify the necessary parameters in the property window.

Analysis

Activities are the basic and functional key elements of a project. They should have durations, costs, and resource and role requirements. Each activity is interrelated with relationship.

After the list of activities, duration and the relationship assigned to each and every activity, the next step is to schedule the project. Primavera project management starts the schedule from the start of the project and continues till the close of the project, giving an early start and early finish to each activity.

Resources are the quality and quantity of items required for the complete project. The resource analysis will ensure that the organisation undertakes the project with effective resource management.

Results

Mainly, waste generation is considered on construction materials such as concrete, blocks, plywood and steels. Miscellaneous materials, such as nails, binding wires, shutter oil and cover blocks, are also considered. As per the site data collection, the amount of wastage of materials is shown in the table. It is an ongoing project and, until now, the total wastage of cost for concrete, blocks, steels, plywood and other miscellaneous materials is Rs.512,304.

Cost overrun owing to time delay:

As per the scheduling done in Primavera, the cost overrun of the project can be calculated. This apartment building (G+3) project is concluded as per planning.
As planned: Project duration – 536 days | Planned budget – Rs.31,550,252
After updating with day-to-day progress report: Original duration – 619 days | Actual cost – Rs.32,019,004
According to the results obtained, the project is still progressing and delayed by about two months as per the plan; the cost overrun owing to time delay is added to the overall budget
As per scheduling: Total labour cost – Rs.15,294,305 | Total material cost – `16,724,699 | Total cost – Rs.32,019,004 |

Total amount of work done –

85 per cent work completed | Estimated cost – Rs.31,550,252
Cost overrun owing to time delay: Total cost ( Rs.32,019,004) minus estimated cost (`31,550,252) = Rs.468,752, which is largely because of time delay
Total cost owing to wastage and time delay: Rs.468,752 plus 512,304 = Rs.981,056.

Conclusion

It is concluded that the wastage of material in the construction industry is mainly because of site management, procurement stage, material handling and operational attributes. This report proposes a computational BIM for construction waste management by first developing a 3D BIM model that gives a BIM-based quantification of components. The computational BIM model developed in the study will automatically calculate

the waste generation quantities and estimate the potential amount of waste generated through BIM take-off. The site collected data is incorporated into the developed model to estimate the waste amount.

Thus, a 3D BIM waste-generation model was formulated for an ongoing construction project.

From this, it is concluded that:

BIM can be used effectively for waste quantification.

8 per cent of concrete waste reduction can be achieved by using BIM 3D waste quantification.

3.5 per cent of steel waste reduction can be achieved by using BIM 3D waste quantification.

6 per cent of blocks waste reduction can be achieved by using BIM 3D waste quantification.

35 per cent of miscellaneous materials like plywood, nails, binding wire and shutter oil can be achieved by using BIM 3D waste quantification.

The extra cost from wastes generated at site works to be 2 per cent of the estimated cost.
The extra cost owing to time delay on site works out to be 1.5 per cent of the estimated cost.
Extra cost owing to waste generation is worked out to be Rs.512,304 and cost overrun because of time delay is `468,752. Hence, 3.5 per cent extra cost is added to the budgeted amount.
Thus, BIM can help minimise the waste generated at site by continuous monitoring and keeping updates on waste optimisation separately.

About the authors:

Manasa N, BE in Civil Engineering and MTech in Infrastructure Engineering and Management, is Assistant Professor at the Mysuru Royal Institute of Technology.

Dr DB Nirmala, BE in Civil Engineering and MTech in Industrial Structures, is Assistant Professor at the JSS Science and Technology University, Mysuru.

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