Inuence of Waste Clinical Mask Fiber on Interfacial Strength Parameters

To investigate the inuence of clinical mask bers on the geotechnical properties of different interfaces. In the present study different geotechnical tests like Triaxial Shear Tests, California Bearing Ratio Tests, and split tensile strength tests were done to understand the behavior of different mix propositions containing clinical mask ber. From the test result, it is clear that the addition of waste clinical mask ber in different mix proportions increases the overall shear strength of the material. Also, the percentage increases in CBR value were recorded by about 40% with the addition of clinical mask ber. In addition, from the split tensile tests results on different mix proportions, it is observed that the tensile strength value increases up to 45% to 50 % with the addition of mask ber to respective coarser and ne grain compositions. Thus, the study conrms that clinical mask bers have the potential to improve the geotechnical properties and can be used as ll material in different construction like retaining structures and earthen embankments.


Introduction
The municipal and Industrial waste problem is a major issue nowadays worldwide. The emergence of the novel Covid-19 virus (SARS-CoV-2) raises the waste clinical mask in the environment since December 2019. Due to the Covid-19 pandemic disposal of clinical masks and medical waste is a massive problem for municipalities. The health agencies of the country like India have advised or make it mandatory for the general public to wear masks in public places. Also, no one seems aware of what to do with these masks (especially single times use ones) after using these masks (Satpal Singh, 2020 used polypropylene (PP) ber with pond ash and Cement kiln dust to strengthen the structural ll. Different geotechnical tests like the Proctor test, California bearing ratio (CBR) test, direct shear test, and triaxial shear tests were conducted to investigate the geotechnical properties of mix containing polypropylene ber. Nezhad et al. 2021 investigated the effect of natural and synthetic bers on the tensile and bearing capacity of clay. The study reported that with the addition of basalt ber to clay, the angle of friction enhances up to 100% while further with the addition of synthetic polyester (PET) bers the cohesion value increased by 70%. In the present study, a small effort has been made to convert waste into resources by investigating the geotechnical properties of waste clinical mask ber with different industrial wastes. To investigate the effect of waste clinical mask ber on interfacial shear strength of different mix various consolidated drained triaxial shear tests were conducted. Also, a reference study has been conducted to investigate the California bearing ratio, and tensile strength testing using clinical mask ber, industrial waste, and locally available soil (c-ϕ soil). The present study proposed the waste clinical mask ber as construction material for structural ll, embankments construction, and back ll material in retaining material. In the present study, efforts have been made to replace conventional ber with waste clinical mask ber.
Clinical mask ber (CMF) has been used to impart tensile strength to a material. The addition of ber accounts for a signi cant alteration and recti cation in the engineering properties of materials. The e ciency of CMF in terms of strength parameters was checked along with the different industrial waste.

Experimental Methodology And Material
Based on reported literature different optimum mix percentages of soil, ber, and industrial waste were selected. The ber of the selected mix was then replaced with clinical mask ber (CMF) and investigated the interfacial shear strength parameters, California bearing ratio, and tensile strength for different mix compositions. The detail of proposed mix in the present study is given in Table 1.
The scheme of proportions for laboratory testing is given in Table 2. The tests included California bearing ratio tests (as per IS 2720-16 (BIS 1973)), triaxial shear tests (as per IS 2720-12 (BIS 1991)). The split tensile strength is calculated according to ASTM C 496-96.
T is split tensile strength;

Cement Kiln Dust
Cement kiln dust (CKD) is a waste dust product of the cement industry, has pozzolanic properties. In the present study, Cement kiln dust (CKD) has been collected from Ultra-tech Cement Grinding & Blending Unit, Bagheri, Himachal Pradesh (India). The properties of Cement kiln dust (CKD) are listed in Table 3 which is given by the cement industry.

Pond ash
Pond ash is collected from Guru Gobind Singh Super Thermal Power Plant, Roopnagar (Punjab) India. The physical and chemical properties of pond ash are presented in Table 4.

Clay and Expansive Clay
In the present study, clay has been collected from Tihra, Himachal Pradesh, India. The Geotechnical properties of clay are listed in Table 5.

Results And Discussion
To understand the effect of clinical mask ber of geotechnical properties of a different mix of industrial waste, clay, and expansive clay are presented in the following sections:

Triaxial Shear Tests
The Consolidated drained tests were conducted on the composition which contains pond ash, cement kiln dust, and clinical mask ber. The tests were conducted under different cell pressure i.e. 50, 100, and 150 kPa respectively. From the test result, the normal and shear stresses are plotted as shown in Fig.2. Evident from Table 6 that with the replacement of 25% of pond ash with cement kiln dust the cohesion and interface friction value increase from 0 to 16.66 kN/m 2 and 33.4° to 42°r espectively. With the addition of 1% of clinical mask ber the shear strength parameters i.e. c and ϕ increase to 30 kN/m 2 and 54.46° respectively. Evident that with the addition of waste clinical mask ber the cohesion value increases 80% and friction value increases up to 30% respectively. Similarly, the Unconsolidated un-drained tests were conducted on the composition which clay and expansive clay along with clinical mask ber. From the test result clear that with the addition of clinical mask ber to clay and expansive clay the cohesion and angle of friction increase signi cantly as shown in Fig.3 and Table 6. Clear from the test result that waste clinical mask ber has the potential to strengthen the retaining structure, soil subgrade, and earth embankment.

California Bearing Ratio Tests
To simulate the saturated soil conditions of a sub-grade the soaked California Bearing Ratio (CBR) tests were conducted on different mix proportions. Evident, from Fig.4 the CBR value of different mixes increases signi cantly with the addition of clinical mask ber. The CBR value of 75% pond ash mixed with 25% of cement dust was recorded 20%, while with addition on of clinical mask up to 1% it increases up to 28%. Evident that with the addition of 1% of waste clinical masks ber having aspect ratio up to 600, the percentage increases in CBR value was recorded about 40% respectively. With further increases in the percentage of masks ber (i.e. up to 1.5%), the soaked CBR value starts decreasing compared to the CBR value at 1% ber.
For clayey and expansive soil, the percentage increases in CBR% values were recorded at 25% and 37.5% with the addition of 0.5% and 1% masks ber respectively (Fig.4). Based on the tests result that waste clinical mask ber helps in increasing the bearing capacity of subgrade or embankment as well.

Split tensile strength (STS) test
Evident from Fig. 5, the result of split tensile test on different mix proportions containing waste clinical mask ber. It is observed that the tensile strength value increases up to 45% to 50 % with the addition of mask ber to respective coarser and ne grain compositions. From the comparison of soil samples containing mask ber and soil samples without mask ber, it is observed that samples containing mask ber show less deformation. Also, the sample containing mask ber re ects lesser tension cracks under applied load. This reduction in deformation and tension cracks is due to increases in the total contact area between the different materials. Similar kinds of results were reported by the different researchers using brous material in different soil compositions (Kumar and Sharma, 2018;Kumar and Gupta, 2015). Moreover, it is observed that with increases in curing period the split tensile strength of different mixes increases, which further increases with the addition of clinical mask ber. Also, evident (Fig.5) that beyond 20 days the increment in strength becomes constant with further increases in the curing period.

Conclusions
In the present study different geotechnical tests like Triaxial Shear Tests, California Bearing Ratio Tests, and split tensile strength tests were done to understand the behavior of different mix propositions containing clinical mask ber. The based on key observations from the present study it can be concluded that clinical mask ber has various construction bene ts. From the test result with the addition of waste, clinical mask ber in coarser mix proportion increases the cohesion value up to 80% and friction value increases up to 30% respectively. Similarly, from unconsolidated un-drained tests with the addition of clinical mask ber to clay and expansive clay the cohesion and angle of friction increases signi cantly. Also, the percentage increases in CBR value were recorded by about 40% with the addition of clinical mask ber. From the split tensile tests results on different mix proportions containing waste clinical mask ber, it is observed that the tensile strength value increases up to 45-50% with the addition of mask ber to respective coarser and ne grain compositions. Thus, the study con rms that clinical mask bers have the potential to improve the geotechnical properties.
Declarations Funding Not applicable.

Con icts of interest/Competing interests
The authors declare that they have no con ict of interest.

Data Availability Statement
Some or all data, models, or code that support the ndings of this study are available from the corresponding author upon reasonable request.        Variation of split tensile strength with time for different mix