Strength of paving block by replacing up to 40% of fine aggregate by weight with plastic waste

. Plastic waste in Indonesia in 2020-2021 occupies the second largest position in terms of the amount of accumulated waste, namely 17.15% and 15.54% after the type of food waste. Plastic is difficult to degrade or is difficult to decompose in the soil. Plastic dumped into the sea is dangerous. In 2020, Physeter Macrocephalus (protected whale) was found to have died from ingesting plastic and not digesting it properly. Replacing/modifying materials is an alternative to help overcome waste environmental problems in the construction sector. Most of the research using waste is the manufacture of concrete with certain compressive strength criteria. As a form of support for green building, research utilizes plastic waste to replace some of the fine aggregate in the manufacture of paving blocks. This study reviewed the strength class of paving block Grade B or Min. 17 MPa, where fine aggregate is replaced by plastic waste up to 40%. Plastic waste is cleaned and cut into small pieces. The results showed that the replacement of fine aggregate with plastic waste up to 30% still produced Grade B or Min. 17 MPa.


Introduction
The waste problem has long been a case that should not be underestimated, this problem has become a global problem.In the Law of the Republic of Indonesia No. 18 of 2008 concerning waste management, waste is defined as the remains of daily human activities and/or natural processes in solid form [1]. Based on data obtained from the National Waste Management Information System, plastic waste in Indonesia in 2020-2021 occupies the second largest position in terms of the amount of accumulated waste, namely 17.15% and 15.54% after the type of food waste [2].
Plastic waste is harmful to health and the environment.Plastic takes hundreds of years to degrade or completely decompose in the soil.Plastic waste dumped into the sea is also dangerous because it cannot be decomposed.In 2020, Physeter Macrocephalus (protected whale) was found to have died from ingesting plastic and not digesting it properly in the marine area of Kapota Island, Wakatobi Regency, Southeast Sulawesi.Then three turtles died from eating plastic in the sea area of Pari Island, Thousand Islands, North Jakarta [3].
Waste not only has a negative impact on the environment, but also has social and economic implications.To overcome the waste problem requires management, disposal, and recycling.Even though several efforts have been made, other supporting efforts are still needed that contribute greatly to the achievement of a circular economy.The construction industry is one of the big impactors on the environment because it takes natural resources.Taking excessive *Corresponding author: arifs@ft.untar.ac.id natural resources will damage the environment.Replacing natural resources is an alternative in reducing environmental problems [4].
There are many studies on the use of waste products in various construction materials, and most of them are in the manufacture of concrete with certain compressive strength criteria.
One of the studies utilizing waste from the food industry, is utilizing Anadara Granosa shells.Anadara Granosa shell has a high calcium carbonate mineral composition like limestone, the raw material for cement.Anadara Granosa shells are crushed into powder and filtered using No. 325 filter without being burned so as not to produce carbon dioxide (CO 2 ), with the aim of partially replacing cement.Anadara Granosa powder without being burned reacts very weakly with water.The results showed that the compressive strength decreased but increased the initial compressive strength of the mortar (7 days).Anadara Granosa powder were able to partially replace cement and be efficient at a composition of 20%.[5].
Research using recycled plastic waste which is heated to liquid as an alternative binder for paving block production, shows that it can increase compressive strengths and reduce water absorption [6].Research using low-density polyethene (LDPE) waste plastic as a binding material in the production of LDPE bonded sand paver blocks showed that the best results were observed at LDPE to sand ratio of 3:7 [7].Research using plastic waste in varying proportions of 40%, 50%, 60% and 70% were used to replace cement showed that compressive strength increased with an increase in the proportion of plastic content.But it has the disadvantage that its strength will decrease when the temperature is very high, such as LDPE which will soften when the temperature reaches 70°C [8] This research will take an approach to making brick pavers by replacing some of the fine aggregate with plastic waste without melting to reduce contribution the global warming process.The manufacturing method from Rebricks Indonesia to find brick pavers suitable for use after mixing plastic waste.Because plastic waste cannot be bound properly by cement paste such as fine aggregate, it is possible that the strength of paving blocks will decrease.
Paving block is a composition of building materials made from a mixture of portland cement or similar hydraulic adhesives, water and aggregate with or without other additives which do not reduce the quality of the concrete bricks [9].
To maintain product quality, we continue to use the applicable standard references.Paving block must have a flat surface, no cracks and defects, the corners and ribs are not easily crushed by the force of your fingers.Paving block must have a minimum nominal thickness of 60 mm with a tolerance of + 8% [9].
The classification of paving blocks/bricks based on ASTM C-902 [10]: • Class SX -brick intended for use where the brick may be frozen while saturated with water, Min.48.3 MPa.• Class MX -exterior use where resistance to freezing is not a factor, Min. 17 where  is compressive load (N) and  is pressure area (mm 2 ).
Because Indonesia does not have winter, the target of this research is Grade B or Min. 17 MPa.With the aim of getting used for parking lots, can be used by the wider community, and supports environmentally friendly.

Research methods
The mix design used by Rebricks Indonesia to achieve 25 MPa: -Water cement ratio (w/c) is 0.6.
-The ratio of cement to fine aggregate is 1:6.
Rebricks Indonesia makes paving blocks using the two-layer method.The top layer uses a standard mix while the bottom layer is a mixture where the fine aggregate is partially replaced with plastic waste.This method aims to maintain the appearance of paving blocks as usual when used.This method limits the replacement of fine aggregate to 40%, if it is 50% then there will be no fine aggregate on the bottom layer.
Most of the plastic waste obtained is from food packages or sachet drinks.Then cleaned and cut into small pieces using a shredding machine as shown in Fig. 1.The results of plastic waste after being cut into small pieces are shown in Fig. 2. Plastic waste has a lower specific gravity than fine aggregate, so a volume ratio is used to get the weight of plastic waste to be used.The plastic waste obtained consists of many types, so it needs re-measurement.The measurement method uses a 500 ml measuring cup and 700 g of fine aggregate is obtained while 35 g of plastic waste.Then the weight of the replaced fine aggregate will be divided by 20 to become the weight of the plastic to be used.The fine aggregate replaced with plastic waste is a multiple of 5%, ranging from 5% to 40%.The process of mixing the ingredients for each layer is carried out using two machines simultaneously as shown in Fig. 3 and the look after it leaves the mold as shown in Fig. 4. The size of the paving block made is (105 x 210 x 60) mm.
Paving block is treated with curing for 28 days.Paving Block is weighed and tested in the Construction and Concrete Technology Laboratory of Universitas Tarumanagara.Weighing machines used is shown in Fig. 5.The compressive test machine used is shown in Fig. 6.

Results
The resulting compressive strength using Equation 1 is shown in Table 1.Can be seen replacing fine aggregates with plastic waste up to 30% still meets Grade B or Min. 17 MPa and has an average weight of about 2.95-3.05kg.While replacing above 30% does not meet Min. 17 MPa and has an average weight of 2.85 kg and below.The collapse pattern of all paving blocks is only 1 as shown in Fig. 7. Paving block crushed only on all sides of the edge, while the middle becomes fragile.As a result of using the two-layer method and the middle part that has been fragile, paving blocks are easily separated between the top and bottom layers.Keep in mind this collapse occurs due to uniform load on the upper surface.The comparison of the weight of each percentage of the test objects can be seen in Fig. 8.The normal weight of paving blocks without plastic is usually around 3 kg.Based on the regression line (Linear) on the graph, the more fine aggregate is replaced with plastic waste, the lighter the paving block will be.
The comparison of the compressive strength of each percentage of the test objects can be seen in Fig. 9. Based on the regression line (Linear) on the graph, the more fine aggregate is replaced with plastic waste, the lower the strength of the paving block.

Conclusion
Replacing fine aggregates with plastic waste can be an alternative to making paving blocks.This might help reduce the problem of plastic waste.
From the experimental results, replacing fine aggregates with plastic waste will reduce the strength of the initial plan with a unique pattern.In the replacement of 5-15%, the strength drops by 10% more than the percentage of replacement.In the replacement of 20-30%, the strength dropped by 20%.And in the replacement of 35-40%, the strength drops again by 10% more than the percentage of replacement.
Replacing fine aggregates with plastic waste is recommended between 20-30%.
.2 MPa.• Class NX -Not for exterior use, Min.17.2 MPa.The classification of paving blocks based on SNI 03-0691-1996 [9]: • Grade A or Min.35 MPa is used for roads.•Grade B or Min. 17 MPa is used for parking lots.•Grade C or Min.12.5 MPa is used for pedestrians.•Grade D or Min.8.5 MPa is used for parks and others.The compressive strength test is represented by 10 specimens.Compressive strength is calculated by the following Equation 1[9]:Compressive strength =

Fig. 8 .
Fig. 8. Graph of the weight of each percentage of the test object.

Fig. 9 .
Fig. 9. Graph of the compressive strength of each percentage of the test object.

Table 1 .
Compressive strength test results.