LIFE CYCLE ASSESSMENT (LCA) ANALYSIS OF CONCRETE SLAB CONSTRUCTION FOR ESTIMATING THE ENVIRONMENTAL IMPACT

Global warming and air pollution become one of the environmental issues facing the world. the construction sector consumes about 40% of total global energy. Many strategies have been adopted to improve the efficiency of building construction to reduce material consumption and carbon emissions. One way to find out the environmental impact and carbon emissions produced is with a Life Cycle Assessment (LCA). This study aims to predict the environmental impact of concrete slab construction in two-story dwellings using the Life Cycle Assessment (LCA) approach of the material used with the help of software, namely Simapro 9.0. The scope of the study is the cradle to the grave. The results of the SimaPro 9.0 concrete plate construction analysis, especially in global warming are 1.02, E kg CO2 eq. The biggest contribution to the manufacture of concrete slabs is the casting process with a value of 1.00, E kg CO2 eq.


INTRODUCTION
Global warming and air pollution become one of the environmental issues facing the world. According to the World Business Council for Sustainable Development (WBCSD) [1] it has been reported that the construction sector consumes about 40% of total global energy. Another impact of the concrete industry on the environment is related to waste production. Each year the European construction sector produces 850 million tons of waste, representing 31% of the total landfill 40% -67% of construction waste and demolition of concrete [2].
According to Lopez-Mesa [1] the environmental impact of a building with precast concrete slabs is about 12.2% lower than cast plates in place. It can be concluded that concrete slabs have a greater influence on environmental pollution.
One way to find out the environmental impact and carbon emissions generated is the Life Cycle Assessment (LCA). The initial stages of LCA are compiling and inventorying inputs and outputs related to the product to be produced. Then proceed to evaluate the potential environmental impacts associated with the input and output of the product [3]. Based on the results of preliminary research in which construction materials are one of the sources of environmental pollution, this study studies environmental predictions from concrete slab construction in one of the two-story dwellings using Life Cycle Assessment (LCA) of materials used with the help of software such as Simapro. 9.0. SimaPro 9.0 is software that is used to analyze the LCA of a product that affects the environment in the process. GaBi is an LCA software which in this study is used as a validation of the results of the Assessment from SimaPro 9.0.

Life Cycle Assessment (LCA)
Life Cycle Assessment (LCA) is a mechanism for analyzing and calculating the total environmental impact of a product in each stage of its life cycle. Starting from the preparation of raw materials, production processes, sales and transportation, and product disposal [4].

LCA in The International Standard Organization (ISO)
There are four main choices to determine the system boundaries used based on the ISO 14044 standard in an LCA study namely [5], 1. Cradle to grave: including materials and energy production chains all processes from the extraction of raw materials through the stages of production, transportation and use to the final product in its life cycle. 2. Cradle to gate: includes all processes from the extraction of raw materials through the production stage (processes in the factory), until before operation. 3. Cradle to cradle: covers the process from the raw material to the end-cycle phase, namely recycling. 4. Gate to gate: includes processes from the production stage only, used to determine the environmental impact of the production steps or processes.

Concrete Plates
Floor plates are thin structures made of reinforced concrete with horizontal directions and loads that work perpendicular to the structural plane so that in this building Plates function as diaphragms or horizontal stiffeners [7].

SimaPro
SimaPro is the world's leading LCA software among industry, research institutions, and consultants in more than 80 countries [7].

GaBi
GaBi is a full service-LCA based software program, meaning that the software assists in performing an LCA in addition to providing data. Data is accessed via Thinkstep, an international company focused on sustainability on multiple levels. GaBi software is available in multiple forms, each geared for a slightly different purpose [3]. The GaBi software system is a leading tool for life cycle engineering, creating life cycle modeling and balances. Life cycle engineering is a method for the assessment of the technical, economic and environmental impacts of products, services, and systems. GaBi additionally can evaluate socio-economic aspects [8].

METHOD
The initial step in this research is to determine the goals and scope that aim to provide references and limits on the research. This study aimed to analyze the LCA in concrete slab construction. The scope of the LCA in this study is the cradle to grave where research is carried out from the initial preparation of the material to the process of casting concrete slabs. The second step is inventory analysis. This stage is the stage of input and output analysis of existing data and based on predetermined limitations. The third step in an LCA is an impact assessment or an assessment of the environmental impact of the results of an inventory analysis that has been made. The final step in LCA is interpretation.
The data used in this study are the data volume of each material in the manufacture of concrete slabs, the list of material suppliers under construction, and the transportation used to carry the material.
Data that has been entered into the SimaPro 9.0 software is then analyzed. Data from SimaPro 9.0 analysis can show materials or processes from concrete slabs that have a large contribution to the environment. From the conclusions and alternatives, this data can be applied to reduce the impact on global warming.

Data Collection
The location of this research is located in Plaosan Garden Estate owned by PT Adong Property in Malang City. The object of research is 2 story house type 326 with an area of 13.5 m x 16 m. The following Table 1 shows the material needs of concrete plates and Table 2 is information on transportation and distance traveled.

Characterization
The ReCiPe 2016 Midpoint method has various categories of assessment of environmental impacts, namely in terms of global warming, fine particles, fossil depletion, acidification (eutrophication), toxicity, radiation, land use, and the ozone layer.  The total analysis results mainly on global warming are 1.02, E + 07 kg CO2 eq, where the biggest contribution is the process of casting concrete slabs with a value of 1.00, E + 07 kg CO2 eq, then the reinforced bar process of 8800 kg of CO2 eq, formwork 1.52, E + 05 kg CO2 eq, and scaffolding 236 kg CO2 eq according to Figure 2.

Normalization
Normalization is the uniting of units into the same unit, namely units per year for each environmental impact [9]. Normalization results from SimaPro 9 are shown in Figure 3 and

Conclusions
Based on the results of concrete LCA research, it can be concluded that the process that has a major contribution to the environmental impact, especially global warming, is the process of casting concrete plates. The process of casting concrete plates has the biggest contribution due to several factors such as the material in ready-mix, namely cement has the biggest carbon emissions in construction. Also, other factors include air pollution generated from trucks when traveling to the project site as well as pump trucks used when implementing concrete slabs.

Recommendations
Suggestions that are expected to be useful for future researchers include the following: 1. Further research needs to be done with a broader scope so that it can apply the waste scenario. 2. It is necessary to deepen the database or inventory in LCA software in the construction sector so that it is expected to provide a detailed analysis. 3. Before determining the object of research, you must first ensure that material or inventory is available in the software. 4. The validation process needs to be improved. Not only by comparing other software, but can be done using manual calculations that are expected to produce the same value by the results of the software output.