Sustainable Alternative Ceiling Boards Using Palm Kernel Shell (PKS) and Balanite Shell (BS)

This paper presents an experimental study to investigate sustainable alternative ceiling boards using PKS and BS. The ceiling boards were prepared by mixing BS/binder, PKS/binder, and PKS/BS/binder at different ratios of 20/80, 40/60, 60/40, and 80/20 and represented as samples (A1, A2, A3 and A4), (B1, B2, B3 and B4), and (C1, C2, C3 and C4) respectively. The samples were cast by flat press process in rectangular sheet shape mould of 187 mm × 125 mm × 3 mm, cut into specimen sizes of 30 mm × 40 mm then tested for dry shrinkage, water absorption, apparent porosity, bulk density, flaking, and hardness properties. The morphology of the samples was examined using SEM. Results of the analysis show that irrespective of the filler loadings the properties of PKS / binder particularly at 20/80 ratio ‘‘B1” displayed better dry shrinkage of 3.7%; water absorption of 12.4%; apparent porosity of 15%; bulk density of 2.3 g/cm3; flaking of 0.05 g and hardness of 57.6 Hv which approximates those of the conventional specimen with better physical properties compared to BS/binder at 20/80 ratio ‘‘A1” and PKS/BS/binder at 20/80 ratio ‘‘C1”. These results, therefore, suggest that PKS at 20/80 ratio with improved strength could be used as a sustainable alternative in the production of ceiling boards.


Introduction
A ceiling board is a building material required for ceiling systems in commercial structures, residential, and institutional buildings. When joints and faster heads are covered with a joint treatment system, its design provides a monolithic surface [1]. Generally, it is not considered a structural element but a finished surface concealing the underside of the roof structure of a building which reduces heat and solid transmission and sound in the house [2]. Of recent, there has been an increase in the growth of the world's population. The need for shelter and structural accessories such as ceiling sheets is in high demand. Studies have shown that Nigeria and other developing countries make use of asbestos and Plaster of Paris (P.O.P) in buildings for covering the upper layer of the internal sections [3].
In the past, asbestos known as a fibre present in rocks were used for the production of ceiling boards due to its poor heat conductivity and high fire resistance. Ceilings with a good quality upper surface and excellent heat insulation are good for hot climates. These fibres such as amosite, crocidolite, and chrysotile, however, results in asbestosis 1 3 which causes cancerous as well as malignant mesothelioma in humans and tumours in other animals [4,5]. Homeownership for the financially challenged in the society is also becoming more difficult because the cost of building materials and other inputs into housing development is escalating beyond the reach of the vulnerable strata in society. This is particularly imperative because trillions of people around the world, most of whom live in rural areas are either homeless or are incapable of securing sustainable habitation. Thus, if this group of people must have a roof over their head, then, there is an urgent need to develop suitable and affordable alternative building materials which would afford easy access to housing. This has therefore forced researchers to increase the drive for locally sourced eco-friendly building materials with the possibility of utilizing agricultural waste for ceiling board production in the nearest future [5].
Natural fibres and agricultural waste utilisation as fillers in polymeric composites have gained tremendous application in polymeric composite materials. This is largely due to their lightweight, low cost, good physical and mechanical properties, biodegradability and are eco-friendly [6,7]. Natural fibres impact negatively on water absorption [8], thermal stability and wear resistance when used as fillers. However, these drawbacks can be mitigated by the use of chemical treatments to modify interface interactions between the filler and the matrix [8,9].
Palm kernel shell (PKS) as an agricultural by-product is generally regarded as waste from palm oil processing. They are obtained after extraction of the palm oil, the nuts are broken and the kernels are removed with the shells mostly left as waste (Edmund, Christopher, and Pascal) [10]. The hard stony endocarp (PKS) surrounding the kernel and shell consists of pyroligneous liquor (45%), charcoal (33%) and combustible gas (21%) [11,12]. Some areas where PKS are considered are: on roads to improve vehicular traction was there are no tarred roads, combustion processes for electricity and heat generation, etc. [13,14].
Balanite aegyptiaca also known in English as "desert date" can be sourced in different kinds of habitat, and tolerates a wide variety of soil types, from sand to heavy clay and climate moisture levels, from acid to sub-humid. This species of tree which is up to 12 m high is classified either as a member of the Zygophyllaceae or the Balanitaceae [15]. The fruit is an ellipsoid drupe, about 2.5-4 cm long and 1.2 cm in diameter which turns yellow and glabrous when mature and are edible. Though the treatment of liver and spleen diseases and the elimination of schistosomiasis and bilharzia flukes carrying snail can be achieved with the fruit. However, the industrial engrossment of natural fibre composites will keep increasing due to their architectural usage, flexibility, environmental durability etc. [16,17]. A common feature of natural fibres in cement composite is the reduction in density, good stiffness, reduced pollution level during production, affordable, good structural performance and improved physical and mechanical characteristics. Therefore, the best way of checkmating natural waste nuisance is to channel it into important purposes. The significance of this study is to explore the potential of using PKS and Balanite shell as a sustainable alternative filler for the production of ceiling boards which is very affordable and contributes to reducing CO 2 in the atmosphere.
Studies on the incorporation of natural fibres as fillers in the hybridization of polymeric composites and their influence on mechanical properties and morphology of polymeric composites have been studied [18,19]. Results obtained showed enhancement in tensile modulus, hardness. tensile and flexural strengths [20].

Materials
The materials used for this investigation are thus presented.

Materials Preparation
Three hundred gram of PKS was stirred in 3 L of water and left for 72 h to remove extraneous organic matters. The clarified water was decanted leaving a cleaner PKS. The shell (PKS) (Fig. 1a) was sun-dried for 3 days, ground and sieved through a BSS 36 sieve to obtain fine particles (Fig. 1c). The process was repeated for the BS (Fig. 1b) to also obtain fine particles (Fig. 1d). The filler obtained PKS or BS were mixed with OPC in a ratio of 20/80, 40/60, 60/40 and 80/20 represented as samples (A 1 , A 2 , A 3 and A 4 ), (B 1 , B 2 , B 3 and B 4 ) and (C 1 , C 2 , C 3 and C 4 ) respectively (Fig. 2). The mix was moulded to the desired shape using a corresponding mould and was sun-dried for 14 days preparatory to the test to be carried out (Fig. 3a, b and c).

Test Procedures
The atomic absorption spectrometry (AAS) was determined by taken some sample of the portland cement for compositional analyses at FETCH GATE LABORATORY (FGL), Gbagada, Lagos, Nigeria. The analyses were ascertained using dispersive X-ray Fluorescence Spectrometer model 9900 intel. A certain quantity of the cement was pressed in a hydraulic laboratory press which was immediately loaded into the sample chamber of the spectrometer. With a system current of 1 mA, at a voltage of 23 kV and for 43 s, the loaded sample was excited. Thereafter, the system software was used for the analysis of the results. The 100% OPC board was used as control sample (Fig. 2).
The dry shrinkage (DS) was determined by weighing 30 mm × 40 mm of each dried specimen as (L d ) and later as (L o ) after over-drying at 150 °C for 90 min. The DS was calculated using Eq. (1): The water absorption (WA) was determined by immersing a dried 30 mm × 40 mm weighed specimen (W d ) in a 250 mL beaker of water for 45 min. After which they were taken out, wiped with a clean cloth, weighed (W w ) and recorded according to BS EN1097-6:2000. The WA was calculated using Eq. (2).
where W d = Initial dried weight.W w = Final weight.
Apparent porosity (AP) and Bulk density (BD) was determined using BS EN1097-6:2000 by weighing a 30 mm × 40 mm dried specimen (W d ) of each filler ratio. The specimens were soaked in water for 45 min and the wet weight of the specimens taken as (W w ). Finally, the specimens were weighed as (W s ) when suspended in water. The AP was calculated using Eq. (3) while the BD was determined with Eq. (4) where ρw is the density of water. A dried specimen board 30 mm × 40 mm was weighed (W 1 ). A hard shoe brush was used to make 20 strokes of forward and backward movements each against the two surfaces of the board. Thereafter, the board was weighed (W 2 ). The F t was calculated using Eq. (5) [13].
where F t = Flake test.W 1 = Initial dried weight.W 2 = Final weight.
The microhardness (MH) was determined by placing a specimen in a Leitz Hardness (OS-2H) tester. This tester had a diamond indenter, in the form of a right pyramid with a square base and an angle 136° between opposite faces under a load of 3°N following ASTM E384-17. The scanning electron microscope (SEM) was determined by placing a small piece of the dried compacted specimens in a PHENOM G2 Pro SEM machine to access the morphology of the specimen on the monitor screen using 15.0 kV.

Results and Discussion
The results in Table 1 revealed that the Portland cement had Fe 2 O 3 , SiO 2 , CaO, Al 2 O 3 and MgO percentage contents of 3.85%, 23%, 65.88%, 3.22% and 2% respectively. These percentage contents are within the acceptable standard for These are influential circumstances for predicting cement samples effectiveness. Other mineral oxides such as Na 2 O, K 2 O and SO 2 with a percentage value of 0.21%, 0.31% and 1.50% respectively are regarded harmless and may help in improving the cement properties since their values are below 1.75%. If not, essential elements of the cement may be displaced. Akanni et al. [21], Yahaya [22], Faleye et al. [23], and Sam et al. [24] also had related results to compare with for Nigeria cement.

Dry Shrinkage
Across the various filler ratios in Fig. 4, the control specimen (Fig. 2) had the least percentage rate of 0.5% followed by a 3.7% of 20/80 ratio of PKS (B 1 ). This could be as a result of the interactions in the network as well as the low strain of expansion and contraction on account of constitutes in the board within the particles and binder in the board compared to other ratios.

Water Absorption
The control specimen in Fig. 5 shows the least absorption rate of 4.3% followed by a 12.4% of 20/80 ratio of PKS (B 1 ). This is probably due to the increased closure of internal pores which ensures that there is reduced space for water to percolate through the specimen. Also, it gives a positive correlation to the interfacial adhesion between the cement matrix and the reinforcement. The water rate can be taken as a measure of the resistance of the board to liquid penetration. Very poor resistance to liquid penetration is an indication of a very high-water absorption rate. The same trend was obtained by Opuada Ameh, Tijani Isa, and Sanusi [25] on palm seed particulate composites.

Apparent Porosity
The apparent porosity of the ceiling board had a unique property relative to that of water absorption. However, the control specimen displayed the least apparent porosity percentage rate of 1.5% due to a better closing up of voids within its particles. Amongst other ratios, the 20/80 ratio also shows the least apparent porosity rate of 15% for PKS (B 1 ). This is most likely due to better interlocking of the particles and binder as shown in Fig. 6 which ensures the presence of free water content during hydration. The mechanism

Bulk Density
The bulk density is a measure of the change in weight of the ceiling board with respect to the total volume of the ceiling board; where the total volume is the sum of both closed and open pores. From the graph shown in Fig. 7, there was a gradual decrease in bulk density across the filler ratios. The bulk density in the (PKS) ranges between 0.93 and 2.3 g/ cm 3 ; in the (BS), it is between 0.85 and 1.2 g/cm 3 ; and in the (PKS / BS) it is between 0.88 and 1.4 g/cm 3 . This closing up of internal pores reduces the effective volume resulting in increased bulk density for a given weight of the board. This also means that the specimen from PKS has better bulk density property compare to others. Amongst the various specimens for PKS, the 20/80 ratio (B 1 ) exhibits a maximum bulk density of 2.3 g/cm 3 indicating better closing-up of internal pores thereby reducing the penetration of water particulate which may slow the hydration process. Similar results were also reported by Osei and Jackson [27] on palm kernel shells as coarse aggregates in concrete.

Flaking
The flaking of the boards at various ratios shown in Fig. 8 revealed that 20/80 of the BS specimen (A 1 ), as well as 80/20 of PKS specimen (B4), exhibited higher flaking values of 0.36 g and 0.37 g respectively. This may be as a result of poor fusion as well as cohesive bond within the individual particles in the board. However, the least flake occurred at 20/80 of PKS (B 1 ) with a value of 0.05 g; at 80/20 of BS (A 4 ) with a value of 0.09 g and 20/80 of PKS / BS (C 1 ) with a value of 1.0 g. This may be due to a better network structure and stronger bond within the individual particles. However, the curing duration also leads to improved hydration and compaction of the composites. Though amongst the various specimen the control stands out with a negligible flake rate. This further indicates that the lesser the inner pores, the denser the specimen. The stronger the fusion within the individual particles in the board, the lesser the flake rate. Obam [13] reported similar results on composite ceiling board properties.

Microhardness
The microhardness of the various ratios of the ceiling board is shown in Fig. 9. Across the ratios, the control and 20/80 ratio of PKS (B 1 ) exhibits the highest hardness value of 88.7 Hv and 57.6 Hv respectively. This could be attributed to an increase in solid-state fusion compared to others with lower/weak cohesive bond within the individual particles. Or the actual stress transfer acquired along with better interfacial adhesion. In other words, it could be described as the denser the specimen, the stronger the bond within the particles in the board. A similar result was reported by Opuada Ameh, Tijani Isa, and Sanusi [25].

Morphology Characteristics
With the magnification of 320×, Fig. 10a which is the SEM micrograph of the asbestos (Control) sample exhibits tight edge-to-face (EF) and edge-to-edge (EE) flocculation which present an increased closed network of structures.
Although the surface appears rather rough but the attraction between masses indicates stronger force bonding them resulting in the decrease in flakes and porosity and also an increase in hardness and bulk density. Figure 10b shows the morphology of A 1 (BS) of the ratio (20/80)% sample. This sample reveals some amount of porosity and de-bonding in many areas which indicates less connection of the particles, very weak bonds and poorly aggregated particles that may readily disaggregate when they come in contact with water. The morphology of B 1 (PKS) of ratio (20/80)% sample in Fig. 10c, show well-aggregated particles with high bonding area and coarse surface. With such tight bonds, dispersion is inhibited due to strong force bonding the particles and the tightness also promotes an increase in hardness and bulk density as well as a decrease in porosity and flakes; which combats dispersive behaviour. Figure 10d reveals the flocs with tight masses for C 1 (PKS/BS) of ratio (20/80)% sample indicating fairly strong bonding with macro-cracks, small discontinuities and reasonably uniform distribution of particles in some areas with also a moderate non-dispersive appearance.

Conclusion
From the study, the phase identification, as well as the microstructural analysis of the PKS (B1 20/80), exhibits almost the same physical and morphological appearance as that of the conventional (asbestos) ceiling board. Also, the ceiling board produced with PKS aggregates are denser and stronger than that of the BS and PKS/BS ceiling board with acceptable physical and mechanical properties. However, for more optimum results, the reinforced particles should be treated to improve the cement hydration process. Further research work should be carried out on cement/ PKS with other particulates or fibres, with more reduced size, for possible modified properties of the ceiling board composites. Finally, ductility, as well as strength, revealed better improvement at the optimum filler ratio of 20/80% for the PKS/cement mixture. This could be beneficial to the environment by contributing to the reduction of CO 2 in the atmosphere and as well as discourage importation thereby saving Nigeria's economy.