Comparative study of eco-friendly wire mesh configurations ...

30 Dec.,2024

 

Comparative study of eco-friendly wire mesh configurations ...

The materials used in the research process were cement, fine aggregate and coarse aggregate, three types of gabions (welded wire mesh, hexagonal wire mesh and expanded metal wire mesh) reinforcement bar, super plasticizer admixture and potable water. The physical and chemical composition properties of these materials have been duly investigated.

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The chemical reaction associated with the decarbonation of limestone at high temperature, which produces cement, releases a substantial amount of carbon dioxide38. Ordinary portland cement (OPC) used in this study which satisfies the standard of the building codes of Ethiopia. The specific gravity properties of OPC were 3.15, Standard consistency was 34% and initial setting time was 40 min. The consistency and setting time test was conducted based on the ASTM-C191-. The curing days greatly affect the concrete compressive strength. On 28 days of curing, the concrete gains the highest strength. The current study chose 14 curing days due to the superplasticizer admixture with 0.2% in concrete which enhances earlier concrete strength. An admixture known as superplasticizer with a proportion of 0.2% was used in order to facilitate the strength-gaining period of the concrete. Potable water readily available in the local area was used which satisfies the drinking standard of Ethiopia.

River sand readily available which satisfies the requirement to be used in concrete casting was used. The sieve analysis of fine aggregate is conducted in the laboratory to study the physical properties as depicted in Table 1. Lightweight sand provides the same tensile strength as natural sand but lowers the compressive strength of Ferro-cement specimens40.

Table 1 Sieve analysis of fine aggregate.

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The sand used in the research was tested for its basic properties. The laboratory tests made fine aggregate are sieve analysis, specific gravity, and silt content tests. The majority of the sand used was passed through a 4.75 mm sieve. The sieve analysis test was performed based on ASTM -C136/C136M-. The gradation test result shows that the sand is well-graded sand with a fineness modulus of 2.25 as shown in Fig. 1.

Figure 1

Gradation of sand.

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Since the presence of more silt or organic matter made concrete or mortar decrease the bond between the materials to be bound together and hence the strength of the mixture. The finer particles do not only decrease the strength but also the quality of mixture produced resulting in fast deterioration. Therefor it is necessary that one make a test on the silt content and checking against permissible limits. According to the Ethiopian Building Code Standard, if the silt content of the sand is more than 6% it shall not be used for construction. But the result (2.45%&#;<&#;6%) complies with the standard and we used the sand material as shown in Table 2.

Table 2 Silt content of fine aggregate.

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The main objective of the laboratory test is to determine the specific gravity and the water absorption capacity of fine aggregate. The test has been made according to ASTM-C-128-97 manual. Though the aggregates and sand we used were from a construction site on the main campus it has been found that duly studying the behavior of the materials is an important stage since it affects the final output of the concrete cast by the materials. Table 3 depicted the outcomes of specific gravity and water absorption of fine aggregate.

Table 3 Specific gravity and water absorption of the sand according to ASTM-C-128-97.

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The aggregate that has used in the research had been examined for the fulfilment of ASTM-C-136-01 sieve analysis results and ASTM-C-127-88 standard test results for specific gravity determination42. Since the main intention of this research is to add aggregate for Ferro cement structures examining the gradation of the aggregate to be used is important. As a result, the sieve analysis results of the aggregate are depicted in Table 4. The aggregate has a maximum size of 14mm and most of the aggregate is retained in the 5mm sieve as shown in Fig. 2. Since some codes recommend not using materials that are finer than 5 mm as aggregate a sieving process has been made before casting the concrete.

Table 4 Sieve analysis result of the aggregate ASTM-C-136-01.

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Figure 2

Gradation chart of coarse aggregate.

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It is vital to determine the dry density in order to make the mix design calculations as well as to decide the compressive strength of the final cast concrete and as Ferro cement is a lightweight structure, we wanted to improve the material by lightweight aggregate in order to make it light as much as possible. The dry density of coarse aggregate is shown in Table 5. The specific gravity may be expressed as bulk specific gravity, bulk specific gravity [saturated surface dry (SSD)] or apparent specific gravity as shown in Table 6. Those parameters are used to determine the volume requirements and in determining the mix ratio calculations based on mass.

Table 5 Dry density of the coarse aggregate.

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Table 6 Specific gravity and water absorption coarse aggregate ASTM-C-127&#;88.

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Gabion (steel wire) meshes are thin steel wires has served in many fields of real-life applications though in different orientations and different mechanisms of applications. Most of the applications of gabion include that uses as a fence, uses in soil and water conservation works to prevent excessive erosion, and in some developed societies as building decoration works as well. The materials have very flexible behavior to be used in making different forms of ornamental works like different shapes in places where people used to recreate.

Different types of meshes are available almost in every country in the world. Two important reinforcing parameters are commonly used in characterizing Ferro cement and are defined as the volume fraction of reinforcement; it is the total volume of reinforcement per unit volume of Ferro cement. The specific surface of the reinforcement is the total bonded area of reinforcement per unit volume of the composite. The principal types of wire mesh currently being used in this research are hexagonal (chicken) wire mesh welded square wire mesh and expanded metal mesh among the available steel wire meshes. The addition of wire mesh layers as reinforcement improves flexural strength, cracking behavior, and energy absorption capability greatly.

Hexagonal or chicken wire mesh is readily available in most countries, and it is known to be the cheapest and easiest to handle. The mesh is fabricated from cold drawn wire which is generally woven into hexagonal patterns. Special patterns may include hexagonal mesh with longitudinal wires. The chicken wire mesh used in this research has a thickness of 2.2mm and opening spacing of 35mm as shown in Fig. 3a. The yield strength of the steel wire mesh is considered as 450Mpa as taken from the manufacturer&#;s specifications.

Figure 3

Different types of mesh (a) Hexagonal (chicken) wire mesh, (b) Welded square wire mesh (c) Expanded metal mesh.

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In welded square wire mesh, a grid pattern is formed by welding the perpendicular intersecting wires at their intersection. This mesh may have the advantage of easy molding into the required shape; it has the disadvantage of the possibility of weak spots at the intersection of wires resulting from inadequate welding during the manufacture of the mesh. Welded square wire mesh with a thickness of 0.7mm was used during the research as shown in Fig. 3b.

Expanded metal mesh is formed by cutting a thin sheet of expanded metal to produce diamond shape openings. It is not as strong as woven mesh, but on cost to strength ratio, expanded metal has the advantage. This type of mesh reinforcement provides good impact resistance and crack control, but they are difficult to use in construction involving sharps curves as shown in Fig. 3c.

As recommended by43 that the design strength for the mesh reinforcement shall be based on the yield strength fy of the reinforcement but shall not exceed 690 N/mm2. Design yield strengths of various mesh reinforcements are shown in the Table 7 as per the data from the material manufacturers and recommendations of Sharma studies. These shall be used for design only when test data are not available. In the research, we used this data for qualitative comparisons of the results got from the laboratory tests.

Table 7 Minimum values of yield strength and effective modulus for steel meshes and bars recommended for design.

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Mix design

The chemical composition of the cement, the nature of the fine aggregate, coarse aggregate, and the water-cement ratio are the major parameters governing the properties of the concrete. The concrete matrix is designed for its appropriate strength and maximum denseness and impermeability, with sufficient workability to minimize voids and to avoid map cracking. Cement mortar used in ferro concrete acts as a good insulator and the reinforcing wire mesh can reduce surface upheaval better than plain concrete44. Precautions are necessary to maintain the small cover and in the selection of aggregates, mixing, placing, and curing. Mortar recommended for Ferro cement shall comprise particles or aggregates of limited size. The mortar matrix usually comprises more than 95 percent of the Ferro cement volume and has a great influence on the behavior of the final product. The cement mortar should be mixed with a proper sand-cement ratio (ranging from 1.5 to 2.5 by weight) and water-cement ratio (between 0.35&#;0.45 by weight) in order to achieve sufficient plasticity and facilitate easy casting. Many defects are possible due to a lack of complete infiltration and consolidation.

To avoid caking, the ingredients for mixing concrete, including the water, should be precisely batched by weight before poured into the mixer45. The sand-cement ratio should be calibrated to generate a fluid mix for the first infiltration of the armature, followed by a stiffer, more highly sanded mix at the finish, whereas the w/c should be as low as feasible46. As recommended that the CS should be at least 35 MPa for 28 days of curing with cube dimension of 150&#;×&#;150 mm47. According to the recommendations for ferroconcrete, we have used a water-cement ratio of 0.4 and a material proportion of 1:1.5:2 (cement, sand, and coarse aggregate respectively to cast a concrete of grade more than 35 Mpa. Since the concrete material is expected to possess good strength in a small thickness, the result is considered as ferro cement material improved by the addition of coarse aggregate of maximum size 14 mm taking in to account the opening of the gabion. Normally the slump of fresh concrete we cast was a true slump with 37mm as shown in Fig. 4. Admixtures or additives have been added to improve the performance and workability of the concrete.

Figure 4

Workability test of concrete.

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Due to the lack of readily available standard molds in the laboratory temporary molds were prepared for the flexural specimens and for the energy absorption test specimens. The molds were prepared in such a way that the dimension of the inner mold satisfies the requirement of the standard molds. Two types of molds were prepared with inner dimensions of L:W:D (500:100:100) in mm for flexural mold and the second type slabs for energy absorption test with inner dimensions L:W:D is 400mm:300mm:75mm, by considering the two-way aspect ratio and the deep beam effect which shall be greater than 4 to avoid deep beam effect.

Experimental plans

With a large number of samples, the study would have greater statistical power, meaning it would be better able to detect true differences or relationships between variables. This is important for drawing accurate conclusions and making reliable predictions. While increasing the sample size may require additional resources and time, the benefits in terms of the study's validity and reliability often outweigh these costs. Researchers in concrete research should aim to optimize their sample sizes to ensure that their findings are robust and applicable to real-world scenarios. Therefore, considering the aspect of time and money, the authors chose ninety prisms and thirty-three cubes for their experimental design which is sufficient enough to draw accurate conclusions and make reliable predictions.

Flexural tests

Flexural test gives another way of estimation for the tensile strength of concrete. Many heterogeneous aggregate materials, such as rocks, concretes, and certain ceramics, as well as some metals, have improved fracture resistance due to a toughening mechanism caused by the shielding of the crack tip by a nonlinear zone of dispersed microcracking or void formation48. The application of ferrocement cover raises the ultimate flexural stress and the first fracture load. The percentage of mesh reinforcement and the thickness of the ferrocement layer increased the first fracture load. For specimens with a ferrocement coating, there was a significant reduction in crack width and spacing (64&#;84%). In this research, a total of 45 prisms with a total dimension of (100*100*500mm) was casted in a readily made mold. Casting process of the model specimens was done in a special mold prepared from timber due to the absence of enough molds in the laboratory. The flexural test specimens were made up of three different types of gabion reinforcements used in four different set ups. The sample specimens of different wire mesh reinforced concrete models as shown in Figs. 5, 6, and 7.

Figure 5

Casting of ferro concrete beam model using hexagonal (chicken) wire mesh.

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Figure 6

Casting of ferro concrete beam model using welded square wire mesh.

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Figure 7

Casting of ferro concrete beam model using expanded metal wire mesh.

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The testing was made in a universal compression machine with ultimate loading capacity of  kN. The beam was placed between the two jars and load was applied vertically till the cracks appears. Figure 8a depicts the specimen during the test condition while Fig. 8b after the ultimate load when failure occurred.

Figure 8

Flexural test (a) Specimen during test and (b) after ultimate failure.

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Compressive strength tests

A total of 33 compressive specimens have been prepared for 11 different specimens. A prepared layers of each mesh type according to the number of layers required to the test was prepared and casting of the specimens was made in a standard 150*150*150 cubes readily available in the laboratory. The casting was done by first placing the wire meshes inside the cube by providing the necessary concrete covers as illustrated in the Fig. 9.

Figure 9

Cubes prepared before concrete casting.

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The specimens then were allowed to cure for 14 days to attain the maximum strength hence admixture was used. During the specimen preparation due to the interruptions in the power the compaction was made using tamping rod and hand mixes was also used. Finally, the samples were made ready for the testing using universal testing machine. The load was applied vertical at a constant rate till the sample failure as shown in Fig. 10.

Figure 10

Testing of cube specimen.

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Energy absorption test

The crack-arresting mechanism of such composites is improved by the uniform distribution and high surface area-to-volume ratio of the reinforcement (wire mesh)49. The wire mesh deformation and failure absorbed more than 80% of the impactor's kinetic energy, while frictional energy dissipation only accounted for roughly 10% of impact energy50. A total of 45 specimens have been prepared for energy absorption tests in which the details of the specimen types as shown in Fig. 11. To prepare the different specimens a temporary form work of dimensions 400*300*75 (length, width and thickness) respectively was prepared. Slabs reinforced by different types of mesh and with different number of layers were casted and cured for 14 days. The specimens were prepared as simply supported slab and a 3.028 kg cylindrical steel alloy is allowed to fall freely from a 1.0m height on the top of the slab specimen. The number of blows was recorded at the instant where first crack was observed and at ultimate failure (total collapse of the structure) as shown in Fig. 12.

Figure 11

Slab specimens prepared for casting and during casting.

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Figure 12

Energy absorption test set up and results after failure.

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Advantages and disadvantages of gabion baskets

Advantages and disadvantages of gabion baskets

Gabion baskets are steel wire mesh baskets most commonly used to create retaining walls in order to stabilise slopes and banks and offer protection against erosion. Also known as gabions or gabion cages, gabion baskets can also be used for a variety of other landscaping applications, from unique outdoor seating to natural garden borders. These are often with gabion stone but can also be filled with other materials.

 We stock a variety of sizes to suit different projects. So, whether you are considering purchasing a gabion basket for a DIY project, such as a gabion planter, or you need multiple high-quality gabion baskets to create a gabion retaining wall, browse our range today.

 There are countless advantages to using gabions, from being easy to install to being beneficial to the environment. However, there are also some drawbacks.

 Advantages.

  • Easy to assemble.

 Gabion baskets are commonly sold in flat packs which are lightweight and easy to assemble. All there is required to do when assembling gabions is to prepare the ground, fasten the baskets together and fill the baskets with your desired material. If you want to create a tall retaining wall where you have to pile the baskets on top of each other, you might need an extra pair of hands and even some machinery. However, smaller projects can be easily achieved with less help and no machinery.

  • Create a strong structure.

 When stacked together, gabions will create a strong and robust structure that can support a large amount of weight. This makes gabions ideal for stabilising sloping terrain and controlling water. Due to their strong bases, it makes it incredibly difficult for gabions to be dragged away by heavy downpours or vandals.

  • Allow drainage.

 The space between the stones in gabion baskets allows for water to easily pass through. At the same time, gabions can absorb and decrease the water velocity, protecting areas at risk of erosion. So, not only do gabion baskets allow water to drain but these also work to reduce or prevent erosion.

 Disadvantages.

  • Not attractive to everyone.

 Even though we believe thatgabion baskets are a beautiful addition to any outdoor space due to the varied choice of gabion stones, some people do not find gabions as aesthetically pleasing as we do. However, low-quality gabion baskets can start rusting quickly and become unsightly. 

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