Cost Analysis and Method Comparison on High-Rise Building Column Formworks by Three Formwork Methods

The purpose of this study was to determine how much cost would be incurred and to analyse the difference in price by using three formworks’ methods, they are: the conventional method (According to Ministry Guide Num 1 Year 2022 and PT. Hutama Karya), the System Method with Multiplex and with phenolic film materials (According to Ministry Guide Num 1 Year 2022 and PT. Hutama Karya). This paper also included the analysis of using aluminium formwork method, but it was not the focus of this research. This analysis will also express the advantages and disadvantages of each of these methods. Data used for this research was obtained from shop drawing and calculations provided by PT. Hutama Karya (shortened as PT HK), with the prices for materials and wages for the West Java Region gathered from the Unit Price Journal. For cost estimation (calculation), the Ministry Guide Number 1 Year 2022 was used as guidance. The results of this analysis showed that the formwork with “system” Method using Phenolic film is the most economical formwork method in this study, this is because the type of formwork can be used not only multiple times, but also in buildings with varied column types.


Introduction
Sustainability construction and infrastructure has been a focus in many construction projects, especially since the Sustainable Development Goals (SDG) was introduced.This paper aims to provide results for SDG goal 9: Build resilient infrastructure, promote inclusive and sustainable industrialization and foster innovation and for SDG goal 11: Make cities and human settlements inclusive, safe, resilient, and sustainable.The use of formwork can leave many material wastes, especially in conventional formworks.In this paper we use Conventional Method, System Method, and Aluminium Method to analyse the methods that could be cost effective and can be a sustainable method and formwork material in the projects to come .High-rise buildings come with high investment costs, which increase day by day if delay occurs.The correct use of formwork can be attributed in a successful building project in terms of cost, speed, quality, and worker safety.Choosing a poor equality formwork system with the aim of minimizing project costs directly affects the speed and quality of construction [1].The use of formwork dates to the Roman Empire.At the time, wooden formwork was used by Roman engineers as formwork for building reinforced concrete vaults and arches [2].At present, the development of formwork construction technology is becoming more and more rapid, thus providing construction personnel with choices in the use of formwork methods.Formwork in this research is a reference for concrete formwork or temporary structural components in 1324 (2024) 012007 IOP Publishing doi:10.1088/1755-1315/1324/1/012007 2 the construction industry.The choice of formwork the use of formwork methods plays a key role in the success of structures plays an important role, especially in terms of cost.Conventional formwork is a formwork in which formwork components are removed one by one, while the semi-systematic method is a combination of system formwork and conventional formwork [3].

Formwork
Formwork can be defined as a temporary structure used to support ready-mixed concrete until it gains its own strength [1].There are generally three types of formworks, they are: conventional formwork, semi-system formwork and system formwork.The difference between the three types can be seen in the materials used.Generally, conventional formwork uses wooden planks supported by wooden beams.Semi-system formwork is a reusable formwork construction method that imitates the shape of a building.the material itself uses steel plates, supported by wooden beams [4].Formwork is an important building feature, accounting for 20% to 25% of the total construction cost.Using the most modern formwork methods means that larger elements can be casted faster than normal.The quality of the formwork also determines the yield and quality of the concrete form.Broadly speaking formwork is divided into 3 types, namely [5]: • Conventional formwork is one in which the formwork is removed and disassembled into individual parts that can be formed into the original shape or other shapes.• Semi-system templates are templates dedicated to specific objects or shapes.In principle, this templating approach can be reused irreversibly.The dimensions are usually adapted to the shape of the corresponding concrete.• A system formwork is a formwork which is manufactured at a factory and most of the components are made of steel.The formwork can be used multiple times, besides direct purchase, it can also be rented from formwork equipment suppliers.

Conventional Formwork
Traditional wooden formwork systems or also known as Conventional Formwork, are the oldest type of formwork in construction.It consists of a slab that is part of the concrete formwork and a support system.The support system is the structural part that stabilizes the position of the plate and supports the load on top.Wood, bamboo, masonry, and carpentry are commonly used as the main building materials.It has the advantage of low cost and saves a lot of manpower for transportation and lifting [6].

"Full System" Formwork Method
Fabricated formwork is a formwork system made of steel or other materials, only the parts need to be assembled at the factory and then the formwork parts will be mass-produced and then sent to the project site [7].Full System (or system) formwork is a further development of general formwork that can be used with all options for the most diverse constructions.System formwork implementation is faster than conventional and semi-system formwork because the components have standard size [8].System formwork is formwork that has been developed into a universal formwork, with all the possibilities that can be used in various types of work and the use of formwork [9].

Aluminium Formwork
According to a journal publication in 2017, formwork aluminium panels are made of high-strength aluminium.This aluminium panel has a panel surface consisting of plates with a thickness of 4 mm which are welded and specially designed to form a panel component.These components are strengthened by a simple system of pins which pass through the holes of each panel at a planned distance [10].The aluminium formwork system is a formwork method or system that can be used as a concrete forming medium and can be used directly at the project site (cast in place).In addition, the system can be used to control and plan other construction works, so it can be used to form walls, slabs, columns, beams, stairs, etc.The advantage of this system is its ease of use on many works with a wide variety of shapes, ease of adjustment, and fast to process [11].

Methodology Figure 1. Research Flowchart
Based on the flow chart on Figure 1., there are two data used in this study, namely Primary Data and Secondary Data.The Primary Data in this study are data from field observations and interviews with workers who are directly related to the project location.The Secondary Data in this study are in the form of project Shop drawing data, data on price lists of materials and supplies for the West Java region in 2022, data on price lists of materials and wages (according to PT. Hutama Karya) and Unit Price Analysis for the manufacture and dismantling of formwork per method in accordance with the Ministerial Regulation [12].

Results and Discussion
The First step to look for is the Area and the Number of Columns in each building as shown in the Table 1 to table 3 Shows the Area Recapitulation table and the Number of Column for 3 buildings, the Economy and Business Faculty (from now will be referred as EBF), Art and Design Faculty (from now will be referred as ADF), and Post Graduate (from now will be referred as PG) Buildings)

Area and Column Calculations
Table 1, Table 2, and Table 3 shows the recapitulation for column dimensions, height, counts, and its area.The tables can be seen on the next page.

Start
Determine

Calculation Recapitulation of the Total Cost of Formwork
After the Unit Price Analysis for each method, the Third Step is to make a recapitulation of the total costs of each Formwork method.The following Table 7, Table 8, Table 9, and Table 10 is the price recapitulation for each type of formworks:

Price Recapitulation Graph
After knowing the area and number of columns, then analyse the unit price of each formwork and the total cost that must be incurred in each method.the Forth Step is to make a price recapitulation graph for each method, Figure 2 shows the graph comparison (excluding the aluminium formworks as the graph is to represent the three compared methods) with Table 11 shows a detailed cost.Based on the Figure 2., the cost for the aluminium formwork is higher than other methods due to differences in prices for materials, wages for workers, work coefficients and the material/aggregates used of the 2 column forms (Regular shape and Irregular Shape).Regarding the aluminium formwork, the price used is not based on-site price, but from the unit price journal or from other price sources.Resulting it to be higher than needed.A further analysis is needed regarding the price and method/formula used.But because the aluminium formwork is not the focus of this research and it has no direct comparison of use on-site, this paper used the research only as a reference for future research.
From the graph on Figure 2., the System method (Phenolic Film) is a suitable method (Not too cheap and not too expensive and the amount of formwork that is made is not too much).

Sustainability of Formworks
In Subsections 4.3 and 4.4, it becomes evident that the utilization of the formwork system approach results in lower expenses compared to the traditional formwork method for both formworks.But the highest cost is the Aluminium formwork method, unfortunately this method does not have a direct comparison on the field (PT HK data) nor its results.
Regarding the sustainability of formworks, research by Al-Ashwal [13] says that in socially and environmentally, conventional formworks does not perform well but it can perform well economically in some conditions such as in the 2017 research.It also said that sustainability is not considered in the use of traditional/conventional formworks which required enhancements and considers the impact on environment as well as socially.A conclusion of a research also says that using formwork with a system method (and aluminium materials) could support green construction [14].
A conference proceeding in Bandung says that there are three benchmarks for sustainability of, they area Environmental, Economic, and Social Benchmark [15].These benchmarks propped up the need of sustainable formworks in the form of system method formworks and support the results of the analysis on Subsection 4.3 and 4.4.Such as for the Environmental Benchmarks there are several aspects that support the need for a system method formworks such as: using renewable material, waste generation, structural operation, formwork reusable, waste and material efficiency, and impact on local environment; For the Economic Benchmarks several aspects are: labour cost, material & equipment cost installation cost, cost in-use, life-cycle cost, formwork serviceability, simplicity of technology use, duration of phases, and overlap of phases.For the Social Benchmarks there are: safety assessment & safety design of formwork system, direct employment, safety measures, fire safety, fire resistance.The proceeding also stated that "a sustainable formwork system could be benchmarks in the balance of three main categories." The importance of sustainability of formworks is also supported by research published in a journal.The research uses quantitative method of research, using questionnaire regarding the importance of sustainable concrete formworks.It resulted in 50% of respondents agree that a type of formworks can affect the sustainability of a project, with 39.5% of respondents is moderate.Additionally, the sustainability objectives that consider responsive to formworks systems are Economic, Environmental, and Social Rp0,00 Rp100.000.000,00Rp200.000.000,00Rp300.000.000,00Rp400.000.000,00Rp500.000.000,00Rp600.000.000,00Rp700.000.000,00Objectives; with economics ranking first among the respondents [16].As we can see these three sustainability objectives are like the three benchmarks of the previous research published in a conference proceeding [15].A journal published in 2017 concluded that the aluminium formwork is proven to be more sustainable.On of its points is that aluminium formwork can decrease carbon emission by using recyclable aluminium panels, and producing an easy to assemble system that doesn't need high skills [17].Another journal published in 2021 compare the use of conventional formworks with Alluformworks method where it shows that Alluformworks method, in a sustainability sense: can be used repeatedly, has a more moderate safety precaution, and higher scrap value [11], with another journal published in 2022 which compare conventional formworks against semi system formworks resulted in the semi system is not only faster in time, but also lower in cost [18].

Conclusion and Suggestions
The conclusions based on the analysis taken are: • The total number and area of columns in the three buildings are: 949.36 m² and 1092 Columns (Include Regular and Irregular Shape).• The three methods that are the most suitable in terms of price (not too expensive and not too cheap, but not too much formwork) is the System Method, with the main material using Phenolic Films.Based on this research , several suggestions can be made as follow: • Further research on the Aluminium formworks, the price used is not based on-site price, but either from the unit price journal or from other price sources.Meaning it may be higher than needed.Further research also needed in the aluminium formworks' method regarding the reusability calculations.

Figure 2 .
Figure 2. Comparison of Total Formworks Cost for Each Methods

Table 2 .
Area Recapitulation table and Number of Column for ADF Building

Table 3 .
Area Recapitulation table and Number of Column for PG Building After Knowing the Column Area and the Number of Columns, the second step is to make Unit Price Analysis per Method (Conventional Method, System Method, and Aluminium Formworks) as seen on Table 4, Table 5, and Table 6: 4.2.Calculating Unit Price Analysis for each MethodThe methods used in this paper are: Conventional Method, System Method, and using Aluminium Formworks.

Table 4 .
Analysis of The Unit Price for Conventional Method Formwork on First Use In the Conventional Method, there are 3x uses, each usage differs only in the total price of the Plywood (20% of Reduction).

Table 5 .
Analysis of The Unit Price for System Method Formwork on First Use In the System Method, there are 3x uses (For Multiplex) and 6x uses (For Phenolic Film), each usage differs only in the total price of the Multiplex (15% of Reduction), and Phenolic Film (7% of Reduction).

Table 6 .
Analysis of The Unit Price for Aluminum Method Formwork on First Use The amount of use in this Aluminum Method depends on the division of zones in each building, so the Total Price for first use is in according with table above, then for subsequent use only considers Labor Costs (No Material Costs Required).

Table 9 .
Price Recapitulation of System (Phenolic Film) Formwork Total Formwork Area required (m 2 ), = Area per 1 column x on any floor) x Number of formwork made.*(2) = Total Formwork Price each building (Rp) = (1) x Formwork Unit Price Analysis Conventional method

Table 10 .
Price Recapitulation of Aluminum Formwork Total Formwork Area required (m 2 ), = Area per 1 column x on any floor) x Number of formwork made.*(2) = Total Formwork Price each building (Rp) = (1) x Formwork Unit Price Analysis Conventional method

Table 11 .
Cost Comparison for Each Methods • The total cost of manufacture and demolition of Column formwork using the Conventional Method in three buildings are: Rp 1,543,901,056.84 (For Ministry Guide Num 1 Year 2022), and Rp 1,021,259,538.25 (Project Data), There is a difference of Rp 522,641,518.59;The System (Multiplex) Method in three buildings are: Rp 1,003,648,553.07 (For Ministry Guide Num 1 Year 2022), and Rp 591,092,497.18(Project Data), There is a difference of Rp 412.556.055.089;The System (Phenolic Film) Method in three buildings are: Rp 724,302,445.44(For Ministry Guide Num 1 Year 2022), and Rp 551,447,122.65,There is a difference of Rp 172,855,322.79;The Aluminium Formwork in three buildings are: Rp 2,624,422,889.05;