1 Introduction

The pressing need to reduce carbon emissions and minimize the consumption of resources is prompting a transformational movement within the construction sector toward environmentally sustainable methods. When it comes to low-cost house settings, the engineers have to consider construction and material costs too. One of the solutions is to use a traditional housing material using engineering techniques that are compressed stabilized earth blocks (CSEB). Compressed Stabilized Earth Blocks (CSEBs) offer cost-effective, eco-friendly construction. Utilizing local resources reduces costs and environmental impact. Excellent thermal qualities of CSEB increase comfort and energy economy [1]. As no burning is required like burnt bricks, it minimizes carbon emissions too [2]. However, the problem is that CSEBs are fragile to tensile strength, have less compressive strength, and have a low capability of water resistance. To minimize the problem, many researchers have incorporated natural fibers into earthblocks. In a study, it was found that 0.8% coconut fiber increases the compressive and tensile strength of CSEB significantly [3]. The tensile strength of the CSEBs having 0.5 to 2% jute fiber increased from 0.69 to 0.74 MPa [4]. Improvement in the ductility of CSEB may be obtained by using banana fibers [5]. The length of fiber plays a vital role in the strength property of CSEB. The compressive strength of longer (12 mm) PP fibers at 28 days is superior to that of shorter (6 mm) fibers [5].

The areca nut is the fruit of the areca palm (Areca catechu), which is found in large portions of the tropical Pacific, South Asia, Southeast Asia, and East Africa. It is often referred to as areca nut. Total global areca nut production was 1,429,000 tons in 2018 [6]. India emerged as the leading producer, contributing to 43.01% of the total production area, followed by Bangladesh (33.00%), Indonesia (11.27%), Myanmar (5.71%), and Sri Lanka (a few percent) [7]. Specifically, in Bangladesh, the areca nut production is 346 kilotons per year [8, 9]. The husk, which constitutes between 50 and 75 percent of the weight and volume of an areca fruit, serves as the source of fiber. Based on this, the estimated husk production in Bangladesh is around 150,000 tons (assuming 43% husk content). Meanwhile, in India, the largest areca nut producer, husk production stands at approximately 1,300,000 metric tons per year [10]. Additionally, Myanmar produces around 226 kilotons of areca nut annually, generating around 100 kilotons of husk as a by-product [11]. Although areca nuts are exported to countries with high consumption rates, such as Pacific countries, the husk of the areca nut remains unexported.

Areca nut is produced in all the regional areas of Bangladesh. But the districts of the southern part of Bangladesh like, Jashore, Khulna, Noakhali, Pirojpur, Bagerhat, and Lakshmipur are the leading producers of areca nuts. The produced areca nuts are sold all over Bangladesh, especially in large cities like Dhaka, Chattogram, Khulna, Sylhet etc. The local vendors remove the husk and sell only the nuts. But the husk they remove is often thrown away in wastage. Alarmingly these thrown-away husks decompose slowly due to their lignocellulosic composition, leading to environmental issues when large biomass heaps are not properly disposed of [12, 13]. Unfortunately, in the cities of Bangladesh, it is often thrown away in the drains. So, thrown-away areca fibers become solid wastes of drainage systems that block the drain passage while boggling themselves together with a slow decomposition rate. Moreover, the areca nut fibers attract other solid waste like plastic waste, polyethylene bags, etc., and wrap them together that create a larger object which is one of the primary causes of drain blockage. Almost 90% of areca nuts in Bangladesh remain unutilized and are eventually disposed of in drains. Similarly, in India, a significant amount of husks are disposed of in drains due to lack of utilization. This trend is reportedly observed in other countries as well, where the husk of the areca nut remains unused and is likely disposed of in drains. Consequently, the accumulation of areca nut husks is causing hazardous environmental issues in countries such as Bangladesh, India, Indonesia, Myanmar, and Sri Lanka. Addressing this issue through effective utilization is crucial for mitigating environmental risks and promoting sustainable practices in areca nut cultivation regions.

A study investigated areca nut fiber-reinforced Stabilized Mud Blocks (SMB) and found that 3% fiber shows better strength properties [14]. However, the study was limited only to 3% areca nut fiber content and varying water content of SMBs. The incorporation of natural fibers like jute, and coconut coir in CSEBs has already been studied. But jute and coconut coir are costly fibers and they are used in other industries too. On the other hand, areca nut fiber is cheaper and has the potential for use as reinforcing material. However, no such study has been found on incorporating areca nut fiber specifically in CSEBs that examines the strength properties of areca nut fiber-reinforced CSEBs. This study aims to fulfill the study gap by examining the suitability of using areca nut fiber as reinforcing material for CSEBs through a specific objective of determining the optimum areca nut fiber content based on compressive and tensile strength performance, density, and water absorption test.

Stabilization of Compressed Stabilized Earth Blocks (CSEBs) is crucial for improving the properties and assuring long-term durability [15]. Cement and lime are two popular stabilizers in this procedure. Choosing the appropriate stabilizer, either Ordinary Portland Cement (OPC) or lime, depends on the soil composition. OPC effectively stabilizes soils with low clay content (PI < 15%, LL < 40%) and finer particles (< 0.425 mm) [3, 16]. Conversely, lime is better suited for soils with high clay content (PI > 15%) [17, 18]. Importantly, stabilizer content, particularly OPC, significantly impacts block strength. Optimal cement content lies between 5–10%, with higher amounts hindering cost-effectiveness [19, 20]. For instance, a study found that 10% OPC is sufficient to develop non-structural CSEBs [21]. Additionally, several studies found a significantly higher strength by adding 10% cement to CSEB [22,23,24]. Selecting the right stabilizer and content enhances CSEB’s strength and durability, solidifying its position as a sustainable construction option.

It is essential to maintain OMC while preparing samples. The soil below OMC is too dry to compact effectively, resulting in insufficient density and reduced strength. On the other hand, above OMC, too much moisture prevents appropriate compaction and results in inadequate load-bearing capacity. Compaction efforts and moisture content should be balanced to ensure the best soil properties for long-lasting, sustainable CSEB. It is observed that reinforced soil compressed on the wet side of an OMC provides greater strength [3, 25].

When a building’s load-bearing masonry walls are subjected to an earthquake, they may encounter in-plane and out-of-plane forces that cause them to suddenly collapse. Split tension tests are carried out on masonry panels to determine the tensile strength of masonry because a state of pure shear results in diagonal tension and compression. Splitting tensile strength is used to assess the tensile strength of these materials since a direct tensile test cannot be carried out on brittle materials like brickwork [26].CSEB’s capacity to absorb water is a major worry since it will affect the material's use under the influence of the weather. The water absorption rate of mud blocks refers to how much water they can hold when exposed to moisture. It is a critical characteristic that determines how resilient and resistant the blocks are to damage caused by water and the elements. Some of the factors that influence how quickly mud blocks absorb water include the porosity of the blocks, the curing conditions, and the makeup of the mud mixture. Mud blocks frequently absorb more water than other building materials like concrete or bricks because of their porous texture. And more water absorption refers to more voids. The way the earth block specimen breaks or cracks when subjected to compression force is known as the earth cube failure pattern. It could indicate the strength and the quality of the mixture. Satisfactory and unsatisfactory failures are the two categories of failure that are taken into consideration. The cube's diagonal must show a consistent fracture pattern for a failure to be considered satisfactory, indicating that the cement paste and aggregate were firmly bonded together. Unsatisfactory failures are those that have an irregular fracture pattern, such as explosive, shear, or tension cracks, which point to a weak aggregate or a bad bond. In addition, voids in blocks could also increase the probability of an unsatisfactory failure pattern sometimes damaged completely for the weaker void plane. In splitting tensile loading, the natural fiber is found to, bridge the failure plane and resist the planes from being completely separated from each other causing a catastrophic failure whereas blocks without fibers found the complete separation of the failure plane as reported in several studies [3, 5]. This sign is good for structure. Figure 1 shows which patterns are satisfactory and which are unsatisfactory for earth blocks [27, 28].

Fig. 1
figure 1

Types of failure pattern for blocks (satisfactory or unsatisfactory) (Sources: [27, 28])

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2 Materials

2.1 Soil

The soil was collected from the Chittagong University of Engineering and Technology campus, Chattogram, Bangladesh at 1 m depth (Latitude: 22.4572 and Longitude: 91.9704). The soil in the Chattogram region is mostly sandy loam with low clay and Redish. The soil used in this study was also redish. The other parameters like mechanical properties and index properties of the soil sample were tested in the laboratory and listed in Table 1.

Table 1 Properties of soil
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2.2 Cement

Ordinary Portland cement (OPC) was used in the study. OPC was chosen cement as a stabilizer because the soil contains a very low amount of clay with a plasticity index of less than 15%. The use of 10% or less cement in CSEBs is economical and shows better strength than other types of stabilizers like lime or fly ash, as per existing literature. The physical and chemical properties of OPC are listed in Table 2.

Table 2 Properties of cement
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2.3 Areca nut Fiber

The fibers were collected from a local vendor. These fibers were produced by washing, drying, and removing the fibers from the husk. No cutting was required because the fiber’s length, 20 to 38 mm, was its natural length. The fibers were treated with water, 3% sodium hydroxide, and 0.1% potassium permanganate. The properties of fibers are given in Table 3.

Table 3 Properties of areca nut fibers
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3 Experimental study

3.1 Determination of optimum moisture content

A key factor for soil and soil composites is the optimum moisture content (OMC). It refers to the soil’s maximum stability and compactibility at a certain moisture content. Proctor compaction testing is a typical process used to determine OMC. In this study, the proctor test was conducted following the ASTM D698 code to find out the OMC of the soil used for the study [29]. Figure 2 depicts the compaction curve for the Proctor test performed on locally available soil for this investigation. The curve indicates an OMC of 12.08% with a maximum dry density of 1.74 kg/m3.

Fig. 2
figure 2

Moisture content vs. dry density graph

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3.2 Test Sample preparation and finding the optimum mix

Steel moulds with dimensions of 100 mm × 100 mm × 100 mm (4″ × 4″ × 4″) were used to produce test samples. For ease of testing procedure, 4″ × 4″ × 4″ cubic blocks have been made in this study. However, the blocks can be made as per the standard commercial bricks and block sizes for practical uses. The compaction energy used in the manufacturing of Cement stabilized earth blocks was kept constant in comparison to the conventional Proctor test. All of the test samples were made with almost 3% more water than the ideal moisture content (OMC) as reinforced soil compressed on the wet side of an OMC provides greater strength.

Cubic samples were prepared for 5 separate areca nut fiber content and were stabilized with 10% cement and investigated. No fiber content and 0.85%, 2%, 5%, and 8% fiber contents were the varying parameters in the investigation. The raw fibers were treated initially with water then with 3% Sodium Hydroxide for 30 min and air dried for 30 min. After that, it was treated with 0.1% potassium permanganate for 30 min and then air died. Further, it was oven-dried at 110 °C and then the fibers were mixed in earth blocks. The soil was thoroughly mixed with 10% cement (by weight of dry soil) and fiber contents, subsequently, water content exceeding the optimum moisture content (OMC) was added at 15% of the dry soil weight (as suggested by previous literature), to produce three samples of each category. The areca nut fiber was randomly mixed with dry soil cement (Ref Fig. 3.). Lubrication with grease was provided on the inner surface of the mould to ensure the prevention of damage while demoulding. The moistened soil was compacted in three separate layers, each covering about one-third of the height of the mould after being compacted. A standard Proctor rammer of weight 2 kg and a flat wooden plate of dimensions 80 × 90 × 6 mm were adopted throughout the production to achieve the required uniform compaction. The samples were wrapped with wet gunny bags for 7, 28, and 90 days and subsequently tested at the end of each curing period. The standard 28-day curing period is typical for cement composites, while the additional 7 and 90 days of curing were conducted to evaluate early strength gain and assess long-term effects, respectively. Compressive strength, tensile strength, bulk density, and water absorption rate of the samples were investigated to evaluate the performance of the CSEBs. Splitting tensile strength was used to assess the tensile strength of these materials since a direct tensile test cannot be carried out on brittle materials. The compressive strength of CSEBs was calculated using the equation,

$${\text{Stress}},\sigma = F/A$$
(1)

where F is the Applied Force in KN and A is the Surface area of the block that the force was applied to in mm2.

Fig. 3
figure 3

Fiber dispersion in the mix

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The splitting tensile strength of CSEBs was calculated using the equation,

$${\text{Stress}},\sigma = {\text{ 2F}}/\pi {\text{bd}}$$
(2)

where F is the Applied Force in KN, b is the Width of the specimen in mm, and d is the Depth of the specimen in mm.

The bulk density of the block is calculated using the formula below:

$$\rho = M/V$$
(3)

where M is the Mass of blocks in Kg and, V is the Volume of the blocks in m3.

The water absorption rate of CSEBs is calculated using the following formulae,

$${\text{Water absorption}}\left( \% \right) = \left[ {\left( {{\text{M1}}{-}{\text{M2}}} \right)/{\text{M2}}} \right] \times {1}00]$$
(4)

where M1 represents the wet weight of the material. M2 represents the dry weight of the material.

4 Results and discussion

4.1 Compressive strength

Figure 4 shows the compressive strength of CSEBs with varying Areca Nut fiber content for different curing periods.

Fig. 4
figure 4

Compressive strength of CSEB with varying content of areca nut fiber at different curing ages

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The study observed that the highest compressive strength was 5.796 MPa for 0.85% areca nut fiber content when cured for 90 days. And of all fiber contents, 0.85% areca nut fiber showed the highest value for the other curing periods which was 2.82 Mpa for 7 days and 4.01 Mpa for 28 days of curing. Earth blocks must have an average compressive strength of at least 20 kgf/cm2 (1.96 MPa) for Class 20 and 30 kgf/cm2 (2.94 MPa) for Class 30 according to Indian Standards [30]. Also, according to the international compressed earth block codes, a CSEB should have a minimum dry compressive strength of 2 MPa [31, 32].

Figure 4 shows that as the percentage of areca nut fiber content increases from 0 to 0.85%, the compressive strength increases by 62.85% for 7 days, 75.06% for 28 days, and 83.76% for the 90-day curing period. The increase is clearly seen for the addition of fiber content. This result may have been caused due to the hydration interaction between the areca nut fiber and CSH, as evidenced by the mix's enormous amount of silica [33]. The solidified structure of cement helps to maintain a high compressive strength.

But, after that, the strength started to decrease for % of areca nut fiber above 0.85%. It is observed that the decreasing curve is steeper for additional fiber content from 0.85 to 2%. After that, a slightly linear decrease can be seen. This is because the areca nut fiber was scattered throughout at the end of the block face and allowed water to escape during the drying process, leaving gaps in the soil. The compressive strength of soil depends on density, which was reduced by the presence of fiber. The density of the soil went down as a result of the existence of voids.

For fiber content up to 0.85%, the fibers were not seen from outside which might be a cause of increased strength too as the extra water was not passed out through the fibers and did not increase the volume of fiber too much. However, the optimum amount of water entered and completed the hydration process of cement and filled up weaker voids.

In studies on CSEB, a decrease in compressive strength is seen by adding jute fiber [4]. A study found by adding 0.8% coconut fiber to CSEB the compressive strength increases significantly [3]. A significant increase in compressive strength is also found by adding 3% coir fiber in CSEB [34]. This study also found an increase in compressive strength by adding 0.85% areca nut fiber.

Therefore, a decision can be made that 0.85% of areca nut fiber addition to CSEBs is optimum and gives the highest strength. The study recommends that the compressive strength of CSEB increases significantly in the range of 0.5% to 1.5% areca nut fiber content.

4.2 Tensile strength

The split tensile strength of CSEBs with different Areca Nut Fiber Content at different curing ages are shown in Fig. 5.

Fig. 5
figure 5

Split tensile strength of CSEB with varying areca nut fiber at different ages

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From Fig. 5, it is observed that the investigation has encountered the highest tensile strength is 0.971 MPa at 0.85% areca nut fiber content for 90 days. The corresponding strengths are 0.535 MPa for 7 days and 0.885 MPa for 28 days of curing period. The tensile strength of blocks is found very low. None of the samples tested crossed 1 MPa strength in the test period. However, the mix of 0.85% areca nut fiber increased the tensile strength prominently (near about 1 MPa). However, the modulus of rupture strength of CSEB of 0.34 MPa is acceptable [31].

Figure 5 describes that there is an increase in tensile strength for adding areca nut fiber content up to a certain percentage of 0.85% of areca nut fiber content. Then split tensile strength decreases for further addition of areca nut fiber content above 0.85% up to 2%. Then, again the tensile strength increases up to 5% fiber content and then again decreases. However, the tensile strength at 5% fiber content is still less than the tensile strength of 0.85%.

The percentage increase in split tensile strength for 0.85% is 7.99%, 3.91%, and 8.89% than that for curing periods of 7 days, 28 days, and 90 days respectively. The increase is due to good bonding between areca nut fibers and soil cement material. Areca nut fiber acts as a reinforcement that resists tensile stress. Due to the large quantity of fiber in the blocks, there was a balling up that created gaps in the block causing reduced tensile strength of the blocks for higher percentages.

It was observed that the treated areca nut fiber had significantly improved the tensile strength. When compared to reinforcements made with untreated fibers, it was found that the tensile strength of the treated fibers had greatly increased. This is because the sodium hydroxide and potassium permanganate treatment enhanced the roughness of the fiber surface, which in turn caused the blocks' tensile strength to rise [26].

In studies on CSEB, the highest 0.17 MPa tensile strength was found using coconut fiber [3]. Also,0.95 MPa tensile strength using banana fibers, 0.3 MPa using pineapple leaf fiber and 5% cement, and,0.74 MPa using jute fiber were found in existing research outcomes [4, 5, 26].

Split tensile strength of 0.971 MPa using 0.85% areca nut fiber content which was the highest tensile strength found in the study. That is much more than other fiber studies. However, 0.85% areca nut fiber content is found as the optimum percentage for improving the split tensile strength of earth blocks.

4.3 Bulk density

Figure 6 represents a decrease in bulk density with the increase of areca nut fiber. The graph of different fiber contents follows an exponential downward trendline indicating decreasing bulk density with the increase of areca nut fiber addition. The areca nut fibers inside the earth block replace the soil, by volume that is lighter in weight than the soil. However, the block remains in the same shape resulting in a decreased bulk density. Similar weight reduction effects have been observed in studies incorporating other natural fibers like coconut coir (adding 10% cement and 0.2% coconut coir reduced bulk density) [3] and pine gum or sugarcane bagasse [24].

Fig. 6
figure 6

Bulk density of CSEB with varying areca nut fiber at different curing ages

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This reduction in bulk density can translate to several construction advantages. Lighter-weight blocks are easier to handle and transport, potentially leading to faster construction times and reduced labor costs. Additionally, the lower weight of the blocks can contribute to a decrease in the overall dead load of the structure, potentially offering benefits for foundation design.

While reduced bulk density offers construction advantages, it’s crucial to consider minimum density requirements for stabilized earth blocks to ensure adequate strength. SLS 1382 specifies a minimum density of 1750 kg/m3 for gaining adequate strength [35]. Figure 6 shows a range of 1975 to 2101 kg/m3 for a fiber content of 0.85% that complies with SLS 1382 specification. Incorporating fibers like areca nut can offer weight reduction benefits for CSEBs, but optimizing fiber content is essential to achieve the desired balance between weight reduction and meeting minimum density requirements for structural performance.

4.4 Water absorption rate

Figure 7 shows the variation of water absorption % of CSEBs with varying areca nut fiber contents for different curing ages.

Fig. 7
figure 7

Water absorption rate of CSEB with the varying content of areca nut fiber at different curing ages

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The minimum water absorption % is found to be 9.08% for 0.85% fiber content of CSEBs cured for 90 days. However, the values for the 28-day curing period are crucial for the water absorption test. After 28 days the cement gains 90% of maximum compressive strength. So, the correlation between water absorption and compressive strength can be established for earth blocks. For 28 days curing period, the water absorption is found as 11.16%, 9.45%, 13.52%, 16.32%, and 22.66% respectively for 0%,0.85%, 2%, 5%, and 8% of areca nut fiber content in the mixture. Here again, it is observed that the water absorption for 0.85% areca nut fiber content is the lowest.

As per Indian standards, the earthblock should not absorb more than 15% of its weight [36]. It is seen that only for the CSEB of 8% areca nut fiber content, water absorption is more than the specified value. The maximum water absorption capacity of 240 kg/m3 is advised by the ASTM code for blocks [37].

With varying % of areca nut fibers, there is an initial decrease in the water absorption % in the graph (Fig. 7) up to 0.85% of areca nut fiber content. An increase in fiber content increases water absorption as the fibers create pores in the block. However, in this study, it is seen that there is a significantly lower value for water absorption up to 0.85% fiber. Then the water absorption rate started to increase. But above 2% fiber content addition, the water absorption % increases alarmingly crossing the value of the control block. Standards for water absorption % of earth block is below 15% [36].

The reduction in pore spaces caused by the finer lime, cement, clay, and wood ash particles due to filling the voids that drastically reduce the flow of water within the soil blocks is the cause of the decreased permeability [38]. Alternatively, the pH value of the moulding water may have increased due to the partial dissociation of calcium hydroxide, which is another possible explanation. These calcium ions (Ca+) mix with the soil’s reactive silica or alumina, or both, to create insoluble calcium silicates or aluminates, which prevent water from passing through soil blocks [37].

No fiber content was observed outside the block for 0.85% fiber mix. So, another explanation can be given that as no fibers were outside and the insoluble calcium silicate or aluminates blocked the pores, the waters were not allowed to pass inside excessively.

The water absorption rate of fiber depends on the amount of cellulose material in the fiber. Increased cellulose material increases the water absorption tendency of the fiber. The cellulose material in areca nut fiber is high. However, it was treated with sodium hydroxide and potassium permanganate which removes the cellulose material from the fiber [39]. This could be a reason too for decreased water absorption tendency.

The observed low water absorption in the CSEBs indicates a promising outlook for durability and weathering resistance. Lower water absorption is associated with denser blocks, which are less susceptible to moisture-related damage and erosion, potentially extending their field life beyond several years, as reported in studies on properly constructed CSEBs [40]. This aligns with research highlighting a negative correlation between water absorption and wet compressive strength, suggesting a more durable material when wet [41]. Therefore, the specimen with 0.85% fiber is durable enough to withstand weathering and last for several years.

However, it is also evident that when the fiber content rose above 0.85%, the water absorption also increased. As the fiber content further rises, the matrix’s ability to pack the fibers effectively decreases, leading to an increase in the void volume, a reduction in density, and an increase in water absorption [42]. In other words, the density hypothesis, which states that samples with greater densities are less prone to absorb water, and vice versa, is consistent with this conclusion. The outcome follows a similar pattern to an earlier study, which showed that soil fibers stretch as they absorb water during mixing and drying [43]. At least on a micro level, the fibers’ expansion pushes the earth aside. When a fiber dries, it loses moisture, virtually shrinks back to its original size, and leaves incredibly tiny holes all around it [44]. This also decreases the strength of the block. But these pores reduce thermal conductivity too as air is a good insulator.

4.5 Failure pattern

The way the earth block specimen breaks or cracks when subjected to compression force is known as the earth cube failure pattern. The failure pattern was compared with typical satisfactory patterns and unsatisfactory patterns (Fig. 1). And satisfactory or non-satisfactory patterns were evaluated. (Ref. Fig. 1 and Figs. 8, 9, 10, 11).

Fig. 8
figure 8

Diagonal failure due to compressive load of areca nut fiber reinforced block (Satisfactory)

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Fig. 9
figure 9

Completely crushed pattern of un-reinforced stabilized earth block subjected to compressive loading (unsatisfactory)

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Fig. 10
figure 10

Failure pattern of un-reinforced block subjected to tensile load (unsatisfactory)

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Fig. 11
figure 11

Failure pattern of areca nut fiber reinforced block subjected to tensile load (satisfactory)

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The areca nut fibers bridge the failure plane in the case of tensile loading seen in Figs. 8, 9, 10, 11 for the fiber-reinforced block. Un-reinforced blocks’ failure pattern was found unsatisfactory whereas reinforced blocks show satisfactory failure pattern.

4.6 Cost-effective usage and sustainability

In the context of low-cost housing, the reduction of construction costs using eco-friendly materials has been a great challenge for interested researchers to think about alternative materials. The utilization of areca nut fiber as a reinforcement material for earth blocks holds significant potential in the low-cost house construction industry. The block is built from a waste material (areca nut fiber) that is often thrown away outside in drains and rivers, causing a blockage in the usual flow system. Re-using the fiber will cut down the pricing of blocks in contrast to the use of other costly natural fibers like jute and coconut fiber in the block, which are used on a large scale in other industries. In this study, 4″ × 4″ × 4″-dimension CSEBs have been manufactured at a cost of only 3 Taka per block. In comparison, CSEBs reinforced with other costly fibers would cost approximately 4.5 Taka per block, while a fired clay brick would typically cost between 10 to 15 Taka per brick, depending on the class. The CSEB gives comparatively good physical and mechanical properties as found in this study, as well as it will also lower the ill environmental effects. Compared to burnt bricks, the areca nut fiber-reinforced stabilized earth blocks consume less energy during production and cause almost zero pollution to the environment. Additionally, the areca nut-reinforced CSEBs are easy to make compared to traditional bricks due to less complication in the manufacturing process and locally available material and facilities. Moreover, the areca nut fibers were observed to bridge between the failure planes of the blocks, which made the CSEB ductile. For these characteristics, these blocks can be used in seismic areas to provide advance warning prior to complete collapse. However, the use of these blocks has vast scope beyond just low-cost housing construction. Their versatility makes them ideal for non-structural applications and partition walls in both affordable and higher-cost housing settings. Furthermore, given that CSEBs are composed of earthen materials, they offer commendable thermal and sound insulation, thereby augmenting the comfort of residents. Overall, the incorporation of areca nut fiber in earth blocks provides a sustainable alternative to traditional building materials.

5 Conclusion

The study found the potential significance of using areca nut fiber in CSEB which can be summarized below:

  • The highest compressive strength of CSEB was found as 5.79 MPa for 0.85% areca nut fiber content at 90 days. Strength of 4.012 MPa and 2.823 MPa are observed at an age of 28 days and 7 days for 0.85% fiber content that meets the minimum requirement for class 20 and 30 blocks according to IS specifications.

  • The highest tensile strength was found as 0.971 MPa for 0.85% areca nut fiber content at the curing age of 90 days. Also, strength of 0.885 MPa and 0.535 MPa were observed respectively for 28 days and 7 days curing period.

  • The bulk density of CSEBs ranged from 1810 kg/m3 to 2101 kg/m3 for 0.85% areca nut fiber content.

  • The lowest water absorption percentage was observed as 9.079% for 0.85% areca nut fiber content at 90 days of curing age. However, during the 28-day curing period, the water absorption is found to be 9.455% closely matching the lowest water absorption value meeting the requirement specified by IS and ASTM for masonry block.

  • 0.85% areca nut fiber mix is recommended as the optimum mix for areca nut fiber reinforced CSEB.