Experimental study on the performance of polymer pervious concrete using recycled concrete aggregate

The phenomenon of population growth exerts a significant influence on alterations in land utilization, hence causing a reduction in the catchment area and subsequently giving rise to issues related to surface runoff. Stormwater control can be effectively achieved with the use of pervious concrete, which is a porous material that allows surface water to seep into the underlying soil. Because of its ability to transfer surface water into the ground through its pores, pervious concrete was developed as a stormwater management tool to address these issues. Unfortunately, previous concrete has lower quality than normal concrete due to its voids. Several investigations have been carried out to enhance the quality of earlier concrete, one of which involves the use of polymers to strengthen the binding between particles. The primary objective of conducting experimental investigations on polymer pervious concrete incorporating recycled concrete aggregate is to evaluate the performance of polymer pervious concrete using recycled aggregate concrete to support sustainable construction. The study revealed that incorporating recycled concrete aggregate into pervious concrete results in a decrease in its compressive strength. On the other hand, it has been demonstrated that using polymer as an adhesive effectively increases the compressive strength of pervious concrete that contains recycled concrete aggregate.


Introduction
Pervious concrete is a type of concrete with high porosity that allows water to flow through it and infiltrate into the soil underneath.It offers several environmental benefits such as stormwater management, groundwater recharge, and mitigation of urban heat island effects.However, despite its benefit, pervious concrete has lower strength compared to conventional concrete due to its higher porosity [1].Therefore, the application of pervious concrete is limited to paths, parking lots, garden areas, and low-traffic roadways [2].To meet the specifications for pavement concrete, pervious concrete must balance its permeability and compressive strength.The permeability and compressive strength of pervious concrete are significantly influenced by the kind, size, and composition of the aggregates [3].Pervious concrete consists of voids and pores, ranging in size from 2 to 8 mm, that provide efficient drainage.Furthermore, the porosity and void ratio of permeable concrete exhibit a range of 15% to 35%, although its compressive strength falls within the range of 2.8 to 28 MPa.To achieve maximum 1311 (2024) 012022 IOP Publishing doi:10.1088/1755-1315/1311/1/012022 2 efficiency in production, it is advisable to maintain a water-to-cement ratio within the range of 0.26 to 0.45.One way to maintain an acceptable void content in concrete is to use coarse aggregate that is to use uniformly graded aggregate between 19 and 9.5 mm.It has also been shown that a lower void ratio results in a higher compressive strength [2].Numerous studies have been undertaken utilizing diverse methodologies in order to enhance the performance of pervious concrete.The addition of mineral admixtures to improve the strength property and hydraulic properties were evaluated [4], [5], [6].
Being introduced in 1971, polymer concrete has received a great deal of attention as a result of its strong performance.The utilization of polymer as a binder in pervious concrete should be further expanded in order to address the numerous drawbacks associated with this material, such as the lack of sand and inadequate bonding resulting from the use of cement paste as a binder to support sustainable construction.The performance of several types of polymer has been evaluated the compressive strength and flexural strength of polymer-modified pervious concrete by incorporating to utilize a cement combination inside its composition.The findings indicated a prolonged curing process of polymermodified mixes, along with enhanced mechanical strength and resistance to raveling and freeze-thaw cycles.The utilization of polyvinyl acetate polymer proved to be a highly favorable choice [7].Borhan and Karawi in 2020 conducted experimental investigations on polymer-modified pervious concrete and found that the higher polymer content resulted in higher hydration products and hence higher compressive strengths.Further, increasing the polymer content increases the modulus of rupture and splitting tensile strength, indicating that polymer improves ductility of pervious concrete, while comparing polymer-modified pervious concrete to ordinary concrete produces lower water discharge [8].
In the forthcoming decades, the escalation of worldwide population growth and urbanization is anticipated to generate a substantial need for building development.Concrete, as the second most widely utilized substance globally, is a significant contributor to the substantial release of carbon dioxide, making it a leading cause of environmental concern.The production process of concrete constituents has two significant environmental impacts.Firstly, the cement manufacturing process generates a substantial amount of carbon dioxide (CO2), which is destructive to the environment.Secondly, the extraction of coarse aggregate and fine aggregate for concrete involves extensive exploitation of natural resources [9].One strategy employed to mitigate the extensive exploitation of natural resources is the utilization of construction waste through the process of reuse.However, the practice of reusing construction debris has not been widely adopted due to the inferior quality of recycled coarse aggregate concrete in comparison to natural coarse aggregate concrete.The quality of recycled coarse aggregate is comparatively poorer when compared to that of natural coarse aggregate.The presence of mortar derived from concrete waste adhered to recycled coarse aggregate results in the formation of many pores inside the recycled aggregate, hence resulting in porous and absorptive properties [10].While polymer concrete is known for its excellent qualities, the use of polymers in recycled aggregate concrete is expected to improve the quality of recycled aggregate concrete.So that the use of recycled aggregates can increase [11].The incorporation of fly ash in polymer concrete serves as a micro filler, effectively occupying minuscule pores.Additionally, this practice offers economic advantages by repurposing coal waste and contributes to ecological considerations by mitigating environmental contamination through waste reduction.The utilization of polymers as adhesives in replace of cement has the potential to enhance the compressive strength of pervious concrete with recycled concrete aggregates [12].Considering all the information provided, the experimental study of the performance of polymer pervious concrete using recycled aggregate needs to be examined to promote sustainable construction.

2.1.Material Used A. Cement and fly ash
The cement-based pervious concrete was made using Portland composite cement (PCC) in this experimental study to evaluate the performance of the polymer pervious concrete.Unsaturated Polyester 3 (UP) resin was used as an adhesive material in polymer pervious concrete.Furthermore, the addition of fly ash type C to the mix with polymer as filler in the pervious concrete were also examined.

B. Aggregate
To evaluate the effect of the utilization of recycled coarse aggregate, the natural coarse aggregate was used as a control specimen.The recycled coarse aggregate was produced from construction waste with a minimum quality of the parent concrete was 300 kg/cm 2 .The aggregate size used was 5 mm -20 mm.Furthermore, the NCA was maintained to have the same size distribution as the RCA to minimize the effect of aggregate size distribution.Figure 1 shows the natural coarse aggregate and recycled aggregate used in this study, while their particle size distribution is illustrated in Figure 2. The physical properties of natural coarse aggregate and recycled coarse aggregate are listed in Table 1.Oven dry density and water absorption are two parameters that indicate the quality of aggregate.It is clear that the natural coarse aggregate had better quality compared to recycled coarse aggregate as it produced higher oven dry density and lower water absorption.

2.1.Methods A. Preparation of specimens
Five types of mix design were used in the experiment to evaluate the performance of polymer pervious concrete.Cement-based pervious concrete using 100% NCA and RCA was made as the control specimens to polymer pervious concrete.Polymer pervious concrete with the fully used RCA mixed with 20% and 30% of polymer to replace cement as a binder by volume was also used in polymer pervious concrete mixes, while the effectiveness of fly ash as micro filler in pervious concrete was also examined using the addition of 5% of fly ash by volume of the aggregate in 30% polymer pervious concrete.The water-to-cement ratio of cement-based pervious concrete was set to 0.27, while the cement to aggregate was set to 1:4.To maintain the workability of pervious concrete, 1.5% of superplasticizer was added.The mix design of cement-based and polymer pervious concrete are listed in Table 2 and Table 3, respectively.Cylinder specimens with a diameter of 10 cm and height of 20 cm were prepared for casting the cement-based polymer pervious concrete.After molding, the cement-based pervious concrete specimens were cured according to ACI 552R-10.

B. Density of pervious concrete
The method to determine the density and percentage of pores to the volume of concrete was according to ASTM C1688.This test was carried out on fresh concrete, and illustrated the characteristics of pervious concrete further to evaluate the void ratio of pervious concrete.Void Ratio is the ratio between the volume of the pores and the volume of the solid.

C. Permeability
The permeability of pervious concrete is a crucial characteristic that enables the drainage of water through its pore structure.The flow rate of water through concrete is affected by the porosity of the material.In its practical implementation, this technology serves the purpose of facilitating the diversion of rainwater into the soil, thus contributing to solving surface runoff problems.Falling head permeability tests of pervious concrete were conducted according to ACI 522R-10 to determine the ability of concrete to absorb water.

D. Compressive strength test
As the main characteristic of concrete is its compressive strength, the compressive strength test was conducted to evaluate the strength performance of polymer pervious concrete using recycled coarse aggregate.The compressive strength of cement-based pervious concrete was conducted at 28 days after casting according to ASTM C39, while the polymer pervious concrete compressive strength was tested at age 7 days.

3.1.Density of Pervious Concrete
Density and void ratio are carried out in fresh concrete.The test results are listed in Figure 3.As many pores exist in the recycled coarse aggregate due to attached mortar from the parent concrete, they produce a lighter weight compared to a dense natural coarse aggregate.Furthermore, based on the data obtained, the density of polymer pervious concrete produced lighter material compared to cement-based pervious concrete as a polymer material is lighter compared to cement paste as a binder in pervious concrete.The density of fresh pervious concrete then was calculated to measure the void ratio of pervious concrete.The void ratio indicates the volume of the pores in the pervious concrete.From the data collected, as shown in Figure 4, the void ratio ranges from 2.80% to 28.36%.The cement-based pervious concrete using recycled coarse aggregate produced the highest void ratio compared to natural coarse aggregate pervious concrete.This is because the recycled coarse aggregate contains many pores that exist in the mortar attached.However, a higher proportion of polymer in the pervious concrete noticeably reduced the void ratio since the voids were filled by the polymer.Furthermore, the addition of fly ash as micro filler in polymer pervious concrete also indicates to reduce void ratio for the reason.Therefore, the P30FA produced the least void ratio only 2.8% of pervious concrete compared to other specimens.

3.2.Permeability of pervious concrete
The permeability test of pervious concrete was conducted to evaluate the ability of pervious concrete to drain water.This permeability test is carried out in accordance with ACI 522R-10.This test uses the flow test method and uses a falling head tool for concrete.This test is carried out at age 18 days for cement-based pervious concrete and 7 days for polymer pervious concrete.This test was carried out by calculating the time needed to drain water.The dimensions of the sample are with a diameter 10 cm and with a height of 20 cm using the falling head permeability test.Figure 5 illustrates the permeability of pervious concrete.It indicates that polymer use in pervious concrete reduces the permeability of pervious concrete.The same trends were obtained as the void ratio of pervious concrete.Compared to natural coarse aggregate, cement-based pervious concrete with recycled coarse aggregate generates higher permeability due to the existence of pores in the recycled aggregate.It leads to contribute higher speed in draining the water.Furthermore, the utilization of polymer as a binding agent for aggregates has demonstrated a notable decrease in the permeability coefficient, with reductions of up to 30% observed in the case of pervious concrete incorporating recycled aggregates.While the addition of fly ash as micro filler into the polymer pervious concrete mix resulted the lowest permeability of pervious concrete due to the fact that fly ash also seals the void in pervious concrete.

3.3.Compressive Strength
Compressive strength tests were carried out at 28 days for cement-based pervious concrete and 7 days for pervious concrete using polymer.The results of the tests are listed in Figure 6.It shows that the utilization of recycled coarse aggregate reduced up to 12.3 % of the compressive strength of cementbased pervious concrete compared to natural coarse aggregate.This is consistent with aggregate quality, which indicates that natural coarse aggregate is superior to recycled coarse aggregate in terms of quality, having higher oven dry density and less water absorption contrasted to recycled coarse aggregate.When polymer was used as a binder in pervious concrete utilizing recycled coarse aggregate, the compressive strength increased by up to 23%, surpassing the compressive strength of cement-based pervious concrete prepared with natural coarse aggregate.The incorporation of a 30% polymer binder in pervious concrete, along with the utilization of recycled material, results in a notable enhancement in the compressive strength of pervious concrete, with an increase of up to 66.3%.The utilization of fly ash as a micro filler in pervious concrete, with a polymer content of 30%, yields the maximum compressive strength, increasing the compressive strength of pervious concrete using recycled aggregate up to 69%.The observed phenomenon can be attributed to the enhanced cohesion among aggregates resulting from the utilization of polymers as binders in pervious concrete.

Conclusions
The incorporation of recycled aggregate in pervious concrete has the potential to diminish its compressive strength as a result of the presence of mortar adhered to the aggregate originating from the parent concrete.The presence of numerous pores in this mortar leads to a decrease in the quality of recycled aggregate.This is evident by the observation of lower oven dry density and higher water absorption rates in comparison to natural coarse aggregate.In contrast to the compressive strength of concrete, the inclusion of pores in recycled aggregate has been shown to result in an increase in both void ratio and permeability.These hydraulic qualities are significant in the context of utilizing pervious concrete.This finding suggests that an increase in void ratio and permeability can lead to a reduction in the compressive strength of pervious concrete.
The incorporation of polymer as a binding agent in pervious concrete has been empirically demonstrated to enhance the compressive strength of the pervious concrete due to improved bonding between aggregates.However, the observed enhancement in compressive strength also influences the reduction of void ratio and permeability in concrete, since polymers fill the voids within pervious concrete.Moreover, the incorporation of fly ash as a fine particulate additive in polymer pervious concrete has proved to enhance its compressive strength.However, this enhancement comes at the expense of reduced void ratio and permeability in the resulting polymer pervious concrete mixture.

Table 1 .
Aggregate Physical Properties

Table 2 .
Mix design of cement-based pervious concrete