Experimental Investigation of Lightweight Wall Panel Using Cenosphere Incorporated with Ground Granulated Blast Furnace Slag

The secondary form of waste is the major outcome of the various industries. Likewise, Cenosphere and Ground Granulateds Blast Furnace Slag (GGBS) are the waste material obtained from thermal power plants and the steel industry. This waste requires a large land area for disposal. In such cases, these can be used in the construction field. This paper investigated the lightweight wall panel made with cenosphere and GGBS as a replacement for cementitious material. Cenosphere was replaced at 5%, 10%, 15%, 20%, 25% and 30% respectively by weight of cement and GGBS was at 15% constant replacement of cement. The properties of wall panels such as compressive strength, flexural strength, and water absorption have been studied. The flexural behavior was carried out by inhibition of fiber into the matrix. The samples were tested at 7, 14, and 28 days respectively. The SEM analysis of the cenosphere has been carried out. The results infer an increase in the percentage of cenosphere does not impart strength to the mix. Therefore, 15% of constant replacement of GGBS to the mass of cement stabilize the strength which was lost due to the addition of the cenosphere. On an overall view, it was recommended that the strength loss of mixture due to the addition of the cenosphere can be alleviated by GGBS and nevertheless a secure value of strength can be gained.

grade of the cenosphere. The sizes such as 1-100 µm [30], 1-300 µm [31], 1-400 µm [32-34], 1-600 µm [35]. [35] stated that a high percentage of the cenosphere has a size range of 20 to 300µm. As the grade decreases, the fineness of the material increases. The density of the cenosphere is around 300-800 kg/m3. [36] used cenosphere as an aggregate in making lightweight concrete. Cenosphere is used as a filler material in the construction field. Using a cenosphere, a lightweight concrete achieved a strength of 60 MPa [8]. [7] reported that finer particles enhance durability properties. The autogenous shrinkage can also be eliminated, by promoting the durability properties of concrete [37][38][39]. Ground Granulated Blast furnace slag (GGBS) also enhances the properties of cement.
[40] GGBS can be used as an alternative to ordinary Portland cement. The properties of GGBS highly enhancing the corrosion resistance [40][41][42][43] and durability [44][45][46]. The particles of GGBS are finely in nature which inhibits the bond [47-51] and controls the permeability in concrete [52-55] studied the performance of RC beam using GGBS. When GGBS was added up to 40% of replacement to cement, there is slight decrease in compressive strength with time. Alternatively, there is a contrast in the strength development when GGBS added below 30%. Also, it controls the steel reinforcement from corrosion [56][57][58][59] higher the percentage of GGBS, higher the tensile strength. The outcome of this study reduces the consumption of cementitious material thereby contribution of CO2 emission can be reduced. Lightweight structures are made by using secondary waste which meet the strength parameter similar to that of conventional. This study is the first attempt in making a lightweight wall panel using a secondary form of waste such as cenosphere and Ground Granulated Blast furnace slag.

Materials used
The materials used in this study are cement, cenosphere, and GGBS.

Cement
The ordinary Portland cement (OPC) is used conforming to the code IS 1226-1987. It is commonly made of limestone, shells, clay, and silica sand. The properties of OPC are tabulated in table 1.

Cenosphere
Cenosphere is obtained from fly-ash as a by-product. It is a hollow, inert material comprised largely of silica and alumina. It has been used as a filler material in lightweight construction. The SEM images of the cenosphere have been shown in figure 1. The porous structure in a cementitious material when added with the cenosphere can be viewed. The porosity occurs at 43%, whereas 70% of cenosphere in weight fraction with a water-binder ratio of 0.70 [33].  [68] This is due to the fact that spherical particle of the cenosphere leaves more air voids and also possess a lower iso-static strength. The pozzolanic reaction takes place in the cementitious material where the particles consume themselves thereby increasing the calciumsilicate-hydrate gel. The reaction of the cenosphere in a cementitious material composite is the reason for enhancing the greater strength with reduced unit weight. The interfacial property between the cenosphere and the cementitious matrix can be seen with the crack growth in figure 2(b). The shell of the cenosphere is not cracked, alternatively, it passes through the weaker zone of the particle. This infers that the cenosphere has a better bond with the cementitious material. Cenosphere has predominantly silica and alumina content (i.e) 45 to 80% of total ash is silicious and aluminous material [60]. Therefore, the cenosphere is also knowns as alumino-silicate [31, [61][62][63][64][65]. The cenosphere depends on Fe2O3. Therefore, the lesser the Fe2O3 higher will be the cenosphere [61]. [66] discuss the phase minerals in the cenosphere. The minerals such as rutile, quartz, calcite, mullite, alumino-silicate. But quartz and mullite are the high percentages of minerals present in the cenosphere [31,62]. The cenosphere has roughly comparable properties of fly-ash since it is a by-product of fly-ash obtained from coal consumption [12]. The presence of silica results in high strength whereas alumina for quick setting property and also lowers the clinker temperature [67]. The chemical composition of the cenosphere has been tabulated in table 1. Ground Granulated Blast furnace slag Ground Granulated Blast furnace slag (GGBS) is a secondary form of waste obtained from the steel industry. It is a cementitious material and rich in calcium silicate hydrate. It advances the strength, durability, and appearance of concrete. The properties of GGBS are tabulated in table 1.

Mix proportioning
A total of 7 samples were made including the control mix. A mix consist of cement, cenosphere and GGBS with different proportions of cenosphere such as 5%, 10%, 15%, 20%, 25%, 30% respectively with constant 15% of GGBS.  Results and Discussion Compressive Strength of Mortar by Using Cenosphere The cenosphere having a low density with high compressive strength compared to normal concrete. Contradictory, [68] concluded that the addition of the cenosphere may decrease the strength so that it can be stabilized by the addition of silica fume. The property of nano-silica is to improve the interfacial transition zone in concrete, thereby obtaining an earlyage strength and attains a high compressive strength [69][70][71][72] stated that a slight decrease in strength of the mortar even at low density and low thermal conductivity of the cenosphere. 65] stated that strength loss in mortar can be strengthened by improving the interfacial property by using the cenosphere. The compressive strength of mortar cube specimen of size 70.6 × 70.6 × 70.6 mm3 has been taken and tested at 7 days, 14 days, and 28 days respectively as shown in figure 3.

Compressive Strength of Mortar At 15% Constant Replacement of GGBS
The compressive strength of mortar cubes has been tested as shown in figure 3.3 at 7 days, 14 days, and 28 days respectively. The cenosphere has been replaced as cementitious material at 5%, 10%, 15%, 20%, 25%, and 30% respectively by weight of cement in addition to 15% constant replacement of GGBS. The test outcomes are discussed in table 4 and figure 6. The test results at 7days strength show that the strength of mixture M1, M2, M3, M4, M5, M6, and M7 increases by 2.85%, 11.42%, 14.28%, 20%, 28.57%, and 31.42% in contrast with M1.

Flexural Strength of Mortar
Generally, lightweight structures are brittle. Cenosphere has been incorporated into cementitious material with fiber such as polyethylene fiber [73], steel fiber [74], and polypropylene fiber. In this study, fiberglass mesh has been used. The flexural behavior of mortar was tested at 7 days, 14 days, and 28 days respectively. The cenosphere has been replaced at various percentages such as 5%, 10%, 15%, 20%, 25%, and 30% respectively by the weight of cement. The test results are discussed in   The wall panel has been tested against the mechanical properties. The mold of the sample has shown in figure 8. Figure 9 shows the prototype of the wall panel. Conclusion This study has been carried out with the mortar cubes which can be produced with a blend of cenosphere and GGBS as a replacement for cement. The material properties have been analyzed. Cenosphere is a by-product of fly-ash which resembles the properties of fly-ash material. It has a hollow spherical particle. Generally, spherical particles aid strength to the mortar or concrete. In this research, the mechanical properties of the mortar have been tested. From the test results, the following conclusions are made 1. The cenosphere was replaced with cement. The compressive strength infers that an increase in the percentage of cenosphere decreases the strength compared to the conventional mix.
2. To stabilize the strength loss caused by the cenosphere and also to improve the strength, a constant 12% replacement of GGBS has to be made.
3. The cenosphere and GGBS were replaced to cement up to 30% and 12% respectively. According to a strength basis, the cenosphere improves the strength up to 30% of replacement. Beyond 30% of the cenosphere, decreases the strength.
4. Therefore, it is suggested to replace the cenosphere as a cementitious material up to 30% to the mass of cement.

Generally, the concrete is strong in compression however vulnerable in tension.
To improve the tensile property, the fiber is placed in the mix to improve the flexural strength.
6. The water absorption test has been taken and the specimen was categorized under vitrified. Therefore, it possesses high durability and water resistance.
7. The test on mortar cubes discovered that strength loss of cement occurs due to the replacement of the cenosphere. However, the loss of strength can be stabilized by adding GGBS.