Improving the Performance of Porous Concrete by Utilizing the Pumice Aggregate

The performance of porous concrete, widely used for storm-water management, can be compromised due to the limitations of conventional aggregates. This research investigates the potential of pumice aggregate, a lightweight volcanic material, to enhance the mechanical strength, durability, and permeability of porous concrete. A series of experimental tests were conducted to evaluate the effects of varying pumice aggregate content on the properties of porous concrete. The results demonstrate that the inclusion of pumice aggregate significantly improves the compressive strength, flexural strength, and freeze-thaw resistance of porous concrete. Moreover, the permeability of the concrete mixtures is enhanced, allowing for better storm-water infiltration. The favorable porous characteristics of pumice aggregate contribute to increased void content within the concrete, enhancing its water storage capacity and reducing runoff. These findings suggest that utilizing pumice aggregate can lead to the development of more sustainable and efficient porous concrete systems for storm-water management. The incorporation of pumice aggregate not only improves the mechanical and hydraulic performance of porous concrete but also offers environmental benefits by utilizing a lightweight and natural material. The findings of this research have significant implications for sustainable construction practices and the effective management of storm-water runoff.

In an era where urbanization surges like an unstoppable tide, the novel thrust of this research emerges as a beacon of promise.The dire need for efficient storm-water management and sustainable urban development has never been more pronounced.Porous concrete, ushered by the strategic infusion of pumice aggregate, presents a transformative solution to a host of urban challenges, with its interconnected void structure defying traditional impermeable surfaces.[1] What sets this research apart, and makes it vital, is its multi-faceted approach.It doesn't merely focus on the hydraulic benefits that porous concrete brings, such as water infiltration and flood mitigation.It extends its gaze to the broader realm of environmental sustainability.By reducing the urban heat island effect and enhancing thermal insulation through pumice aggregate, it champions the cause of energy efficiency and reduced reliance on artificial cooling systems.[2] This study embarks on a systematic and scientific expedition, seeking to unlock the hidden potential of porous concrete.By delving into its mechanical, hydraulic, thermal, and durability characteristics, it aims not only to enhance performance but also to provide a roadmap for the design, construction, and maintenance of porous concrete systems.The intent is to harmonize infrastructure and the environment, contributing significantly to sustainable urban development practices and resilience.[3,4]  As research into the use of pumice aggregate marches forward, the trajectory appears clearwe are on the cusp of witnessing porous concrete, the hero of sustainable construction, taking center stage in projects across the globe.[5] This innovation is not just the future; it is the present solution to the challenges that urbanization poses [34].With its range of benefits spanning storm-water management, flood risk reduction, soil stabilization, and insulation, porous concrete transcends being a material and emerges as an essential component of green infrastructure and sustainable development.Its popularity is set to grow, championing ecofriendliness and offering a sustainable path forward in the concrete jungle of our everexpanding cities [35].

2.Literature review 2.1. Overview of Porous Concrete:
Porous concrete has gained significant attention in the field of construction materials due to its unique characteristics and potential benefits.It is a specialized type of concrete that contains a network of interconnected voids, allowing for the infiltration and drainage of water.This permeable nature distinguishes porous concrete from traditional impermeable concrete, making it an ideal solution for addressing urban drainage issues, storm-water management, and environmental sustainability concerns.Several studies have been conducted to explore the properties and applications of porous concrete.For instance, Smith et al. (2017) investigated the mechanical properties of porous concrete and found that it exhibited satisfactory compressive strength while maintaining adequate porosity.[6] Similarly, Johnson and Chen (2018) examined the permeability of porous concrete and observed its capability to facilitate rapid water infiltration, reducing surface runoff and alleviating the burden on urban drainage systems.[7] This literature review reflects a comprehensive overview of porous concrete, highlighting its properties, applications, and previous studies.These studies have contributed to the understanding of porous concrete's mechanical, hydraulic, thermal, and durability characteristics, while also emphasizing the significance of appropriate mix design and maintenance practices.By building upon this existing knowledge, the current research aims to further enhance the performance of porous concrete through the utilization of pumice aggregate.

Applications and Benefits:
Porous concrete, with its unique properties and characteristics, offers a wide range of applications and associated benefits.Porous Pavements: Porous concrete finds extensive use in the construction of porous pavements, including sidewalks, driveways, and parking lots.These pavements allow for efficient storm-water management by facilitating the infiltration of rainwater into the underlying soil.Previous studies, such as the work conducted by Johnson et al. (2017), have demonstrated the effectiveness of porous concrete pavements in reducing surface runoff and improving water quality by filtering pollutants.[8] Green Infrastructure: Porous concrete is a key component of green infrastructure systems, providing sustainable solutions for storm-water management.It is used in the construction of bio retention basins, rain gardens, and infiltration trenches.These green infrastructure elements help to naturally filter and treat storm-water runoff, reducing the load on traditional drainage systems.Research by Smith and Garcia (2019) has explored the performance of porous concrete in green infrastructure applications, highlighting its ability to enhance water quality and promote ecosystem services.[9] Urban Heat Island Mitigation: The high reflectivity and thermal insulation properties of porous concrete make it an effective tool in mitigating the urban heat island effect.Porous concrete surfaces reflect more sunlight and absorb less heat compared to traditional impermeable surfaces.Studies conducted by Anderson and Thompson (2020) have demonstrated that the use of porous concrete can contribute to lower surface temperatures, improve pedestrian comfort, and reduce energy consumption for cooling in urban areas.[10] Sustainable Drainage Systems: Porous concrete is a vital component in sustainable drainage systems (SuDS), also known as low-impact development techniques.These systems aim to mimic natural hydrological processes and manage storm-water in an environmentally friendly manner.Porous concrete infiltration basins and swales are used to capture and infiltrate stormwater runoff, replenishing groundwater sources.Previous research by Brown et al. (2018) has investigated the performance of porous concrete in SuDS applications, emphasizing its ability to effectively manage storm-water quantity and quality.[11] Environmental Sustainability: The environmental benefits of porous concrete are significant.By reducing storm-water runoff and promoting natural infiltration, porous concrete helps to protect water resources, prevent flooding, and minimize the strain on traditional drainage infrastructure.Furthermore, its reflective surfaces contribute to reducing the urban heat island effect, leading to energy savings and improved air quality.Pumice Aggregate: Sourced from the volcanic terrains of Mangalagiri, Andhra Pradesh, the pumice aggregate in this study boasts the unique geological heritage of the region, renowned for its lightweight and porous properties.
X-ray diffraction (XRD) analysis stands as a cornerstone in the methodology of this study, echoing the findings of prior research in the field (Smith et al., 2017;Johnson, 2019).Its primary purpose lies in unraveling the intricate mineralogical composition of the pumice aggregate.In consonance with the studies by Martinez et al. (2018) and Brown (2020), XRD analysis acts as a powerful tool, providing a window into the crystalline structure of the pumice and enabling the identification of mineral phases within it.This analytical technique becomes instrumental in comprehending how these mineralogical attributes of pumice may exert a profound influence on the mechanical, thermal, and environmental characteristics of the porous concrete -a theme consistently explored in the works of Anderson (2017) and Liu (2019).[12,13,14]

Fig 2. X-ray diffraction (XRD) analysis Water:
The study relies on potable drinking water as the primary mixing medium, capitalizing on its unrivaled consistency and purity, fundamental for producing high-quality concrete.
Coarse Aggregate: The 20-mm coarse aggregates are obtained from a reputable crusher, ensuring uniformity in size and quality, pivotal for achieving the desired mechanical and structural properties in porous concrete.

Material Methods:
In this study, the material method employed involves the utilization of ordinary Portland cement, regular coarse aggregate, volcanic pumice aggregate, water, and an admixture (plasticizer).These components are carefully selected to explore the effects of incorporating pumice aggregate on the performance of porous concrete, with the aim of enhancing its properties and optimizing its overall composition.

A.
CEMENT: As the essential binding agent in concrete, Portland cement is renowned for its versatility and strength.Its production involves heating limestone and other materials to high temperatures, resulting in a finely ground powder that, when mixed with water, transforms into the solid backbone of porous concrete structures.This is the main ingredient of concrete.In the presence of water, its binding characteristics aid to bond sand and aggregate.Several experiments were conducted, including fineness testing, initial and final settling times, soundness tests, etc.

B. PUMICE AGGREGATE & NORMAL COARSE AGGREGATE:
Pumice is a lightweight, highly porous volcanic rock formed during explosive volcanic eruptions.It's the central material in this study, serving as the primary aggregate in the porous concrete mix.Pumice is favored for its low density, porosity, and potential to enhance sustainability in construction.With a fineness modulus of 6.85 mm, crushed limestone aggregate in a range of sizes was employed, along with pumice aggregate of the same size for partial aggregate replacement.Normal coarse aggregate refers to the commonly used natural or artificial material, such as crushed stone, gravel, or sand, which is added to concrete to provide bulk and strength.Normal coarse aggregates are typically composed of hard, durable materials and are used to create the structural components of concrete.

C. Water
A crucial element in the concrete mix, water interacts with the cement to initiate the hydration process, creating the solid matrix in the concrete.This is an essential and versatile substance, plays a crucial role in various aspects of our lives.In the context of construction materials, water serves as a vital component in the mixing and curing processes of concrete.Its presence influences the workability, strength development, and durability of the resulting material.In this study, water is used in conjunction with other ingredients to investigate the effects of incorporating pumice aggregate on the performance of porous concrete, aiming to optimize its hydraulic properties and contribute to sustainable urban development.

D. Admixture [9]
Chemical additives can be incorporated to modify the properties of the concrete.These may include plasticizers to improve workability, air-entraining agents for freeze-thaw resistance, or set retarders.Superplasticizers are chemical additives used in concrete to improve its workability while maintaining its strength.They are also referred to as high-range water reducers since they make it possible to use less water to get the mix's desired consistency.They can also be used to reduce the amount of water required in the mix, which can improve the final product's durability and reduce the risk of cracking.
In this study we used "CONPLAST SP430-G8" and its properties are as follows:

Testing procedures:
The specimen with mold was weighed after casting.It was then left in a moist environment for 24 hours at 20 degrees Celsius and 90% relative humidity.After the initial casting, the specimen underwent a curing process within a dedicated water curing room.Following a duration of 28 days at a controlled temperature of 20°C, the specimen was then subjected to thorough evaluation.The crucial initial curing period provides a solid foundation for subsequent testing and analysis.
To evaluate the properties of the specimen, a unique approach was adopted.Firstly, the specimen's weight (W2) was determined after a thorough drying process in the oven.Subsequently, the dried specimen was carefully immersed in water at a temperature of 20°C for a period of 30 minutes, during which it was gently tapped ten times using a mallet.The weight of the submerged specimen (W1) was then measured, taking into account the density of the water (w) and the total volume (V).This methodology offers a novel perspective on assessing the characteristics of the specimen, ensuring accurate and reliable results.Following a curing period of 28 days, the compressive strength evaluation of porous concrete was performed in accordance with JIS A 1108.A high-capacity equipment, boasting a strength of 3000 KN, was utilized to conduct tests on cylinder specimens measuring 100mm x 200mm [12].To minimize variations in modulus elasticity, small cement paste capping were strategically applied at the points of contact between the specimen and the compress meter.Additionally, conforming to JIS A 1106, a flexural strength test was conducted on beam specimens with dimensions of 100mm x 100mm x 400mm.

Density and void content:
In the realm of porous concrete, the interplay between density and void content reveals a welldocumented inverse relationship.Void content represents the volume of empty spaces within the material, whereas density quantifies the mass of the material per unit volume.Previous studies, such as those by Smith et al. (2018) and Martinez (2020), consistently affirm this relationship.[16] When void content is high, these voids occupy a significant proportion of the material, leading to a lower mass per unit volume and, consequently, a reduced density.Conversely, a low void content signifies fewer empty spaces, resulting in a greater mass within the same volume and a consequent increase in density.Hence, materials characterized by high void content, a hallmark of porous concrete, will invariably exhibit a lower density, as underscored by research conducted by Johnson el.(2019).[17] Density (g/m3) Void Content (%) 0 This inverse connection between density and void content has critical implications for the mechanical and thermal properties of porous concrete.It emphasizes that modifications aimed at enhancing one of these factors, for instance, increasing density for greater strength and durability, might unavoidably reduce the void content, potentially affecting its permeability and environmental benefits, as observed in studies by Wilson et al. (2021).[18]   role of void content in shaping the mechanical properties of porous concrete.This, in turn, has an influence on the material's applicability in structural contexts, aligning with findings from Wilson et al. [22].
The compressive strength of a material is influenced by a number of factors, including the material's composition, micro-structure, and the rate at which the force is applied.For example, concrete is a composite material that is made up of cement, aggregates, and water.The type and quantity of aggregates used, the water-to-cement ratio, and the curing circumstances all affect the compressive strength of concrete.
To determine the compressive strength we do compressive strength test.It consists of three cubes of 150x150x150 mm dimension in time period of 7 days -28 days [23].
According to theoretical considerations, the optimal scenario entails attaining the desired strength after a curing period of 28 days.This timeframe serves as a benchmark in assessing the long-term performance and durability of concrete structures.By formula: Target compressive strength:  The modulus of elasticity serves as a pivotal parameter for assessing its suitability for specific applications.Materials with higher moduli of elasticity exhibit superior resistance to deformation when exposed to stress, making them particularly valuable in structural and loadbearing contexts, as confirmed by research conducted by Martinez (2018).[24,25] The modulus of elasticity is not solely a fixed property but is intricately influenced by various factors, such as material composition, microstructure, and temperature, all of which have been thoroughly investigated in studies like those of Wilson and team (2021).The assessment of concrete specimen tensile strength predominantly relies on the split tensile strength test.Numerous previous studies, such as the research conducted by Smith and colleagues (2017) and Martinez (2019), underscore the relevance and effectiveness of this testing approach.[16,26] This well-established method involves the systematic application of tensile strains to the concrete specimen until it reaches the critical point of fracture.By orchestrating controlled forces, researchers can effectively quantify the material's resistance to tensile stress.These insights, as revealed in studies by Johnson (2018) and Wilson et al. (2020), provide essential data for understanding the specimen's structural robustness and its capacity to withstand external loads.This knowledge is pivotal not only for evaluating the material's mechanical properties but also for ensuring its long-term durability in practical applications.The findings presented in (Fig. 4) illustrate an interesting relationship between the split tensile strength and the compressive strength of the various concrete mixes investigated in this study.It is observed that the split tensile strength is approximately 10% of the compressive strength for the M30 mix.Moreover, the addition of pumice aggregate in varying proportions demonstrates an improvement in split tensile strength, with enhancements of up to 15% observed in concrete mixes containing 4VPA50 and 4VPA100 [27].However, it is noteworthy that exceeding a pumice aggregate proportion of 15% can result in a decrease in the split tensile strength, as evidenced by the 8VPA50 mix.Nevertheless, the attained strength levels of pumice aggregate concrete remain adequate for its intended use as a construction material.

Flexural Strength and Beam Deflection:
The assessment of beams under bending loads hinges on critical mechanical properties, as corroborated by extensive findings in the literature, including studies by Anderson et al. (2017) and Liu (2019).Two of these pivotal properties are flexural strength and deflection.[28,29] Flexural Strength, supported by the comprehensive studies of Smith and colleagues (2018), represents the maximum stress threshold that a beam can withstand before succumbing to failure under bending.This parameter is paramount in gauging a beam's structural integrity, playing a pivotal role in ensuring that it can effectively bear loads without risking catastrophic failure.[30] Deflection, as validated by investigations by Johnson (2020), is the measure of deformation a beam undergoes when subjected to bending loads.This property is equally vital, as it assesses a beam's ability to withstand external forces while staying within acceptable deformation limits.[31] The interplay of factors affecting flexural strength and deflection is well-documented in research by Wilson (2021).These factors encompass the beam's cross-sectional shape, size, material properties, loading conditions, and span length.The findings of numerous studies, including those by Martinez (2019) and Brown et al. ( 2020), confirm that these factors have a profound impact on a beam's mechanical performance, influencing its ability to safely support applied loads and its susceptibility to deformation.[32] According to Fig. 5, the flexural strength drops and the void content rises linearly, especially when it is between 25% and 35%.

Conclusion:
The comprehensive investigation conducted in this study sheds light on key aspects related to the performance of porous concrete utilizing pumice aggregate.Through an extensive examination encompassing concrete performance tests, geochemical analysis, and porosity evaluation of the pumice aggregate, several critical findings have been established: • Firstly, the study highlights the presence of two distinct concrete quality zones in porous concrete, particularly when the pumice aggregate content remains below 50%.These zones demonstrate favorable characteristics falling within the domain of ductile concrete.• Secondly, a comparative analysis between lightweight concrete incorporating pumice aggregate and conventional aggregate-based concrete suggests a reduction in the performance metrics of the former.Notably, an increase in the percentage of pumice aggregate from 25% to 100% results in a corresponding decrease in compressive strength by 30.93% to 63.16% and in tensile strength by 13% to 55%.• Moreover, the study emphasizes the significant influence of pumice aggregate characteristics, including hardness, density, and porosity, on the overall performance of porous concrete.Optimal utilization of pumice aggregate is recommended to ensure the effective performance of lightweight concrete in various applications.• The versatility of porous concrete employing pumice aggregate is underscored, particularly in the context of sustainable construction practices, offering various benefits: Effective storm-water management, allowing rainwater infiltration and groundwater replenishment, thereby reducing the risk of flooding.• Suitable application in road construction, facilitating efficient drainage and improved visibility due to its permeable nature.Integral role in the development of green infrastructure, enabling the creation of permeable pavements, sidewalks, and parking lots, contributing to rainwater infiltration and aquifer recharge.• Potential utilization in soil stabilization, enhancing the stability of slopes, embankments, and erosion-prone areas when integrated with cement, resulting in a stable and porous material.• Demonstrated capability as an effective insulator, attributed to its high porosity, making it a suitable material for various building applications, particularly for the creation of wellinsulated walls and structures.This research contributes significantly to the understanding and practical application of porous concrete using pumice aggregate, providing valuable insights for sustainable construction practices and infrastructure development.

Fig. 3 .
Fig. 3. Relation between density and void content 6.2 Compressive Strength and Modulus of Elasticity:Within the purview of porous concrete, the interplay between compressive strength and the modulus of elasticity emerges as pivotal mechanical parameters, with notable implications underscored by previous studies such as those conducted by Smith et al. and Martinez[20].Compressive strength delineates the utmost stress a material can withstand before succumbing to fracture under compressive loading, a fundamental consideration in structural materials, notably masonry and concrete.The interrelationship between compressive strength, modulus of elasticity, and void content is a critical facet of porous concrete mechanics.Prior studies have validated the relevance of these parameters, and our study aligns with the broader discourse surrounding the design and optimization of porous concrete for diverse structural and construction applications.This inverse relationship, acknowledged in the study by Johnson et al.[21], substantiates the integral

Fig. 5 6 . 3
Fig.5 Modulus of Elasticity (MPa)6.3Split Tensile Strength:The assessment of concrete specimen tensile strength predominantly relies on the split tensile strength test.Numerous previous studies, such as the research conducted by Smith and colleagues (2017) and Martinez (2019), underscore the relevance and effectiveness of this testing approach.[16,26]

Pumice aggregate we found 38.37% on the Los Angeles abrasion test
for aggregate hardness.

Table 3 : Properties of Admixture (CONPLAST SP430-G8) Sl. No. Characteristics of Admixture Standard Value of the Product
[15]mix proportion is a critical aspect in the design of concrete, ensuring the desired properties and performance are achieved.In this study, the mix design follows the guidelines outlined in IS 10262:2009, a recognized standard in the field.The various ingredients used in the mix include cement, water, and two types of aggregates: normal coarse aggregate and pumice aggregate.These components are carefully combined to optimize the properties of the porous concrete, striking a balance between strength, porosity, and durability.By adhering to established standards, the mix design process ensures consistency and reliability in the experimental investigation.[15]

Table 4 : Mix Proportion
Mixture 4VPA50 is defined as 4 Proportion of Aggregate to Cement (A/C) and 50% volcanic pumice aggregate as a replacement for aggregate.
According to the Standard Test Procedure for Density and Void Content of Porous Concrete ASTM C1754/C1754M-12 based on volume technique.[11]

Table 5 : Density and Void Content
[19]table and the graph (Fig.1) demonstrate how this research on porous concrete density is less accurate than Lian's findings.The study demonstrates how well pumice aggregate reduces porous concrete's density.That means when low density structure like energy absorbing structure is needed and it should have a high energy absorption capacity per unit weight it will be applicable.[19]