Compressive Strength of Structural Lightweight Concrete Using Styrofoam as an Aggregate Substitution

Concrete is one of the important components making up the construction structure. In its development, innovations in the manufacture of concrete both in mixed materials and concrete working methods continue to develop. Lightweight concrete with a mixture of Styrofoam as an aggregate substitution is one of the innovations made as an alternative to natural aggregate which cannot be renewed and can be used up at any time. This study aims to determine the effect of the addition of styrofoam as an aggregate substitution on workability, density, absorption and compressive strength of concrete. The method used in this study is an experimental method of structural lightweight concrete using styrofoam as a substitution of coarse and fine aggregates. Data obtained from testing directly in the laboratory. The variations in the use of Styrofoam as a gross aggregate substitution of 0%, 50%, 100% then continued with 25% and 50% fine aggregate substitution, for the results of density, absorption and compressive strength, respectively decreased as the volume of aggregate substitution increased.


Introduction
Infrastructure development and office areas in Indonesian now increasing which is nothing but to fulfill of facilities and infrastructure needs for supporting public activities, the construction in general cannot be separated from the use of concrete, use of aggregates as a concrete mixture has a greater presentation compared to other materials that is 60% -75% concrete filler material (Portland Cemen Assosiation). In accordance SNI, raw materials is the natural resources that can not be renewed, in use of excess and uncontrolled Is as one of the worlds largest damage. Therefore, it needs an effort to minimize the impact of damage inflicted and need to consider the use of concrete building materials that are made with the concept of friendly environment or other alternative as an environmentally friendly substitute.
One of the innovations in making concrete is use a styrofoam as a concrete mixture for aggregates substitution and can be categorized as environmentally friendly concrete because according to The Institution of Structural Engineers / ISE, 1999 in Ahmad Basuki 2012, making environmentally friendly concrete can be done by realizing 4 (four) environmental sustainability and conservation efforts, that is: (1) Reduction of greenhouse gas emissions ( tha largest co2 ), (2) energy efficiency and basic materials, (3) use of waste material, and (4) reduction of health / safety disrupt effects on construction users, both arising during the construction process or arising during building operations, by using the 4R concept (Reduce, Refurbish, Reuse and Recycle). VOLUME 2 │ NUMBER 3 │ MAY 2020 Available online at http://proceedings.worldconference.id.
ISSN: 2656-1174 (online) Aside from being an alternative to aggregate substitution, the use of Styrofoam can reduce the residual waste of household needs because styrofoam is plastic number 6 in the plastic classification, namely polystyrene. Styrofoam is one of the preparations of polystyrene which is a formation of styrene compounds that use benzene in its processing. Styrofoam waste is classified as inorganic waste which difficult to decompose so that it is bad for health and has the potential to damage the environment, if allowed to pile up just like that and improper use styrofoam can be very dangerous [Michelli,2017] . This research is expected to be able to add information about the effect of aggregate substitution with styrofoam in structural lightweight concrete on compressive strength of concrete and can reduce environmental damage by reducing the use of aggregates and the use of styrofoam waste as a substitute.

Problem Formulation
Based on the background stated earlier, the main issues in the study are: a. What is the effect of using styrofoam as an aggregate substitution on concrete workability? b. What is the effect of using styrofoam as an aggregate substitution on concrete density? c. What is the effect of using styrofoam as an aggregate substitution on the absorption of concrete water? d. What is the effect of using styrofoam as an aggregate substitution on the compressive strength value of concrete? VOLUME 2 │ NUMBER 3 │ MAY 2020 Available online at http://proceedings.worldconference.id.

Research Purposes
The purpose of this research is: a. Determine the effect of using styrofoam as an aggregate substitution on the workability of the concrete mixture. b. Knowing the effect of using styrofoam as an aggregate substitution on the density of concrete. c. Knowing the effect of using styrofoam as an aggregate substitution on concrete absorption. d. Knowing the effect of using styrofoam as an aggregate substitution on the compressive strength value of concrete.

Methodology
The method used in this study is an experimental method of structural lightweight concrete using styrofoam as a substitution of coarse and fine aggregates. Data obtained from testing directly in the laboratory, The test conducted is testing the concrete workability, concrete density, concrete water absorption and concrete compressive strength. All testing processes and procedures refer to the SNI (Indonesian National Standard) and ASTM (American Society for Testing and Material) methods. Data from the test results on lightweight concrete mechanics are then calculated to get an average value. The value of the compressive strength of experimental concrete with a volume of 0%, 50%, 100% of coarse aggregate substitution and then followed by 25% and 50% of fine aggregate substitution then compared with the value of structural concrete compressive strength as a control. The research method used was an experimental laboratory method in the Concrete Laboratory of PT. Wika Beton is located in the District of Cileungsi by making normal quality concrete and adding styrofoam levels of 0%, 50%, 100% of the volume of coarse aggregate then followed by 25% and 50% substitution of fine aggregate. In the initial planning, the quality of concrete used was K-600. Concrete cylindrical specimens with a diameter of 10 cm A A 16 VOLUME 2 │ NUMBER 3 │ MAY 2020 Available online at http://proceedings.worldconference.id. ISSN: 2656ISSN: -1174 and height of 20 cm. Concrete compressive strength test is done after the test specimen is 7, 14 and 28 days with repeated compressive loading.

Result a. Agregates
The specification of aggregates are based on the test results in the following

b. Concrete Mix Design
The specification of mix design are based on the test results in the following table:

e. Concrete Absorption
The results of the absorption of water in concrete in the following graphic and table: VOLUME 2 │ NUMBER 3 │ MAY 2020 Available online at http://proceedings.worldconference.id. ISSN: 2656ISSN: -1174   Following are the results of the 28-day-old concrete compressive strength test:\ 20 VOLUME 2 │ NUMBER 3 │ MAY 2020 Available online at http://proceedings.worldconference.id. ISSN: 2656ISSN: -1174 Source: Data in research, 2019 Figure 7. Concrete Compressive Strength day 28