Data showing the effects of geotechnical properties of lateritic soil mixed with coconut shell powder in Ado-Ekiti, south western Nigeria

In this data, the effect of locally available additive Coconut shell powder (CSP) substitute in determining the geotechnical properties of Ado Ekiti soil was assessed. The samples were collected from two borrow pits, Ado-Ijan road and Ado-Ilawe road, at two points each, and were treated using substitute of coconut shell powder, considering several percentages of its content at 0%, 2%, 4%, 6%, 8% and 10%. Laboratory tests such as specific gravity, consistency limit test, grain size distribution test, compaction test, CBR test, triaxial compression test, permeability test was conducted on the soil samples collected, and untreated soil was determined. The summary shows that the liquid limit, plastic limit, Plasticity Index, Maximum Dry Density and Optimum Moisture Content increases with increase in percentage of the additive and later decrease at higher percentage of additive, mostly at 8% and 10% respectively. The value of California Bearing ratio in percentage increases as the percentage of additive increases, although at 0% additive, the soil does not meet specification of road construction and the value of permeability ‘k’ also increases. The summary of triaxial test also shows increase in the strength properties of the soil at certain percentage likewise, the summary of unconfined compressive strength shows same. This indicates that the additives improves the geotechnical properties of the soil samples to a certain percentage and conversely, have a negative effect on it at a higher percentage 8% and 10% respectively.


a b s t r a c t
In this data, the effect of locally available additive Coconut shell powder (CSP) substitute in determining the geotechnical properties of Ado Ekiti soil was assessed. The samples were collected from two borrow pits, Ado-Ijan road and Ado-Ilawe road, at two points each, and were treated using substitute of coconut shell powder, considering several percentages of its content at 0%, 2%, 4%, 6%, 8% and 10%. Laboratory tests such as specific gravity, consistency limit test, grain size distribution test, compaction test, CBR test, triaxial compression test, permeability test was conducted on the soil samples collected, and untreated soil was determined. The summary shows that the liquid limit, plastic limit, Plasticity Index, Maximum Dry Density and Optimum Moisture Content increases with increase in percentage of the additive and later decrease at higher percentage of additive, mostly at 8% and 10% respectively. The value of California Bearing ratio in percentage increases as the percentage of additive increases, although at 0% additive, the soil does not meet specification of road construction and the value of permeability 'k' also increases. The summary of triaxial test also shows increase in the strength properties of the soil at certain percentage likewise, the summary of unconfined compressive strength shows same. This indicates that the additives improves the geotechnical properties of the soil samples to a certain percentage and conversely, have a negative effect on it at a higher percentage 8% and 10% respectively. © 2019 The Author(s). Published by Elsevier Inc. This is an open access article under the CC BY license (http://creativecommons. org/licenses/by/4.0/).

Data
The data presented was obtained from four soil samples taken from two borrow pits, i.e. two from Ado-Ijan Road (pit A & pit B) and the other two from Ado-Ilawe Road (pit A & pit B), Ado-Ekiti, Ekiti State, Southwestern part of Nigeria (Fig 1). and analysed in the geotechnics laboratory of Federal Polytechnic Ado Ekiti, Ekiti State, Nigeria. Fig. 1aed shows the procedure of obtaining the coconut shell powder using digital disc milling machine   Value of the data Data can be used to examine the properties and performance of coconut shell powder as alternative material for soil stabilization. Data can be useful for researchers in comparing strength properties of coconut shell powder with other additive useful waste materials (rice hush ash) [2e4] strength properties for soil stabilization.
The test data shows that Coconut shell powder can be used as a biological material for metal removal and recovery technologies.
The test data allows for investigation on the use of coconut shell as another possible material for stabilization material for the reinforcement in concrete. The data allows for further investigation on the use of Coconut shell powder as additive for stabilizing of Lateritic soil in road construction. The test data presented can be useful for construction engineers in appropriating the accurate percentage of Coconut shell powder as an addictive for soil stabilization.

Experimental design, materials, and methods
Soil samples portions were taken using basic tools namely shovel, digger, and Polythene bags for soil storage. Soil samples collected were taken to the laboratory where sample portions were tested to determine the moisture contents, and the rest were sun dry for two weeks. The coconut shells collected were sun dried for over two weeks to achieve sufficient dehydration. They were broken into pieces by pounding in mortar, and were later taken to a pulverization machine, to break them into smaller pieces. After it has been pulverized, it was milled and turn into powdery form using a disk milling machine. Coconut shell powder was added to each of the soil samples in 2, 4, 6, 8 and 10% by weight of the samples before subjecting it to the following preliminary tests: Specific gravity, Consistency limit tests, Grain size distribution tests, Compaction test, CBR test, Triaxial compression tests, Unconfined  compressive strength test, and Permeability test. All tests and geological properties of the soil were determined in accordance with B.S.1337 [5]. Table 1 shows that the specific gravity for both Ado-Ijan pit A and pit B varies from 2.56 to 2.65, and that of Ado-Ilawe. Pit A and pit B varies from 2.01 to 2.05 respectively. With the addition of coconut shell powder 'CSP' as the additive, the samples from Ado-Ilawe varies from 2% to 10%, and Ado-Ijan road samples varies from 2.09 to 2.51. This implies that the addition of the additive shows various   Table 2 shows that the soil sample from Ado-Ijan pit A at 0% of additive has higher percentage of sand i.e. 71.49 to 20.93% of gravel and 7.58% of fine, which can be classified as clayey soil in accordance with unified soil classification system USCS (i.e. C ¼Clayey;>12% fines, PI > 7). While with the addition  of additives, the percentage of sand varies from 66.41% to 76.98%, the same trend was observed in pit B. For Ado-Ilawe pit A at 0% it shows that the percentage of sand is also higher than gravel and fines having 83.13% sand. According to (ASTM D422-63 (2007) Standard Test Method for Particle-Size Analysis of Soils) determined by mechanical method, percentage retained on sieve 2.36mm is  classified as percentage of gravel, percentage passing sieve 75 mic is classified as a percentage of fines (clay or silt) and summation of both subtracted from 100% is termed as percentage of sand. Figs. 1f, 2e4 shows the plots of the graph below. Table 2 shows the summary of grain size distribution tests. Table 3 shows that Ado-Ijan Road with the addition of the additive (CSP) increases the Plasticity Index PI from 22.3 to 38.8, whereas the Plasticity Index for 0% additive is 24.0, the same trend is observed in Pit B. Also, for Ado-Ilawe Pit A show that the Plasticity Index for 0% additive is 22.5 and when mixed with additives it varies from 12.5 to 22.5; furthermore, it is also observed that increment in percentage of additive increases the linear shrinkage of the soil (Shrinkage Limit). Figs. 5e12 shows the graph of consistency limits.   Table 4 shows the details of compaction tests data with maximum dry density (MDD) as well as conforming optimum moisture content OMC of sun-dried soil compacted using west Africa method. In pit A for Ado-Ijan road, MDD increases from 2005Kg/m3 to 2191Kg/m3 with the addition of the additive coconut shell powder CSP, while it is 1786Kg/m3 for an ordinary soil sample. The same trend is also observed in pit B of the same location. Also, in pit A for Ado-Ilawe the MDD increases 1993(Kg/m3) to 2164(Kg/m3) with the addition of CSP, the same trend is also observed in pit B of the location.

Compaction test
The plots of dry density against moisture content of the soils are shown in Figs. 13e16.   Table 5 shows the summary of California Bearing Ratio test (CBR), Figs. 17e20 the graphical illustration of California bearing ratio test is presented. From the table, it can be deduced that in sample location one; Ado-Ijan Pit A has its value of CBR (%) at 2.5mm and 5.0mm for 0% to be 4.91 and 10.05 respectively, but when mixed with additive it increases from 7.17 to 10.45 to 10.42 and 11.06, the same trend is observed in Pit B. In sample location two, Ado-Ilawe which has its CBR (%) at 2.5mm and 5.0mm increases from 10.57 to 9.45 to 14.73 and 13.57 when mixed with additive (CSP) while the ordinary soil is 7.4 and 7.19. It is also noted that with an increase in the percentage of the additive, the Optimum Moisture Content (OMC) increases.

Unconfined compressive strength test
From the summary of unconfined compressive strength (UCS) obtained from the laboratory as shown in Table 6, it was observed that there is increment in the strength of the soil sample with additional CSP at 2%, 4% and 6%, and reduction at 8% and 10% for Ado-Ijan pit A and pit B. For Ado-Ilawe, pit A and pit B shows increment at 2% and 4% then decreases at 6%, 8% and 10% of the additive.

Permeability test
The summary of permeability test for Ado-ijan and Ado-ilawe location is shown in Table 7. However, the values of 'k' for Ado-ijan location reduces from 2.678 Â 10 À3 to 0.116 Â 10 À3 for pit A. With the addition of coconut shell powder 'CSP' the same trend is observed in pit B while it is 2.714 Â 10 À3 and 2.737 Â 10 À3 for ordinary soil in both pits A&B, and for Ado-Ilawe the value of 'k' reduces from 2.66 Â 10 À5 to 0.48 Â 10 À5 for pit A and the same trend is observed in pit B with 4.27 Â 10 À5 and 4.77 Â 10 À5 with ordinary soil in pits A&B. This implies that the soil is semi pervious to pervious with variation in addition of additive (CSP) in accordance to United State Bureau of Reclamation U.S.B.R.