Evaluation of Palm Kernel Shell Concrete Strength for Various Mixes and Water/Cement Ratios using Non Destructive (UPV) Method

Ultrasonic Pulse Velocity (UPV) measurement is one of the most popular non-destructive techniques used in the indirect assessment of mechanical properties of concrete. This paper investigates the compressive strength-UPV relationship of palm kernel shell concrete (PKSC) to develop strength based quality assurance model for construction of vegetative lightweight concrete pavement. A total of 420 cubes (150mm) and 28 PKSC slabs were casted for nominal mixes of 1:1:1, 1:1:2, 1:11/2:3 and 1:2:4 and varying water/cement (w/c) ratios of 0.3-0.7. The PKSC elements were cured in water at laboratory temperature for 3, 7, 14, 21, 28, 56 and 91 days, and then subjected to nondestructive testing using the Pundit apparatus for determination of the respective ultrasonic wave velocity and elastic modulus at the various ages. The unconfined compressive strength of the PKSC was determined after the pulse velocity to establish a velocity-strength data set, which was employed for the development of statistical model. Results show that the UPV and the compressive strength of PKSC increased with age but decreased with increase in w/c ratio and mixes. The strength-UPV models developed for all mixes were in the form of logarithm equation, at R2 values between 94.9 – 99.3 %. The application of the developed model as rigid pavement maintenance/deterioration planning and design was demonstrated in the paper. Keywords: Compressive strength, Palm kernel shell concrete, Nondestructive technique, Rigid pavement maintenance, Ultrasonic pulse velocity.

Synthesis, physico-chemical and antimicrobial evaluation of Co(II) and Ni(II) complexes with Schiff base derived from sulphanilamine and salicylaldehyde

Schiff base derived from sulphanilamine and salicylaldehyde was synthesized, its reaction with nickel(II) and cobalt(II) chloride in 2:1 mole ratio yielded Ni(II) and Co(II) complexes respectively. The synthesized compounds were characterized based on melting point/decomposition temperature, solubility, molar conductance, magnetic susceptibility and infrared spectral analyses. The complexes have low molar conductance value (31.4-32.6Ω- 1cm2mol-1), indicating that they are non-electrolytes. The magnetic moment values (2.50- 3.54B.M) showed that, the metal ions in the complexes are paramagnetic in nature. Decomposition temperatures of the complexes were found to be in the range of (275 – 283ºC). Job’s method of continuous variation revealed that, the metal complexes are in 1:1 Metal- Ligand ratio. The physical and analytical data coupled with shift of spectral peaks of the Schiff base in the complexes suggested that the Schiff base act as tetradentate ligand towards metal ion and coordinated via the azomethine-N, deprotonated phenolic-O and S=O group of the sulphanilamine. The synthesized ligand and its respective metal complexes were screened for their antibacterial activity against Staphylococcus aureus (Gram-positive), Escherichia coli, (Gram-negative) bacterial strains and antifungal activity against Mucor inducus spp and Aspergillus fumigatus. The results revealed that, the Schiff base and the metal complexes showed significant antibacterial and antifungal strength at high concentrationsKeyword: Synthesis, characterization sulphanilamine, salicylaldehyde, Schiff bas

Creep and morphological evaluation of polypropylene waste modified asphalt for pavement applications

Synoptic findings by researchers have revealed tremendous physic-chemical improvements of polymer modified mixes over the conventional asphalt. Traditionally, laboratory mechanical properties were carried out for asphalt testing, but cannot calibrate simple performance test (SPTs) criteria for fatigue and field performance. Marshall test-sized specimens of polymer asphalt mixtures were engineered with arbitrary contents of 0 to 3.0% polypropylene waste admixed with 4.5 to 6.5% bitumen contents based on relevant literature. Creep deformation involves uniaxial static creep (USC) test using BS 598-111. Morphological examinations were test with Hitachi S-4700 field-emission scan-electron-microscope (FE-SEM). Thirdly, thermal degradation was determined using Shimadzu TGA-50 thermo-gravimetric analyzer. The results showed creep resistivity with fatigue recovery of 23.2% and 28.9% strain reduction at 10oC and 60oC respectively from the optimal 2.0% polypropylene and 6.0% bitumen compared to the control mix. Also, the same mix produced well dispersed and better enhanced pore packaging micro-structure capable of resisting ageing volatization under severe traffic and environmental loading conditions considered. Keywords: Asphalt pavement, polypropylene, creep deformation, age volatization and microstructur

In silico and in vitro screening of antipathogenic properties of Melianthus comosus (Vahl) against Pseudomonas aeruginosa

Bacterial quorum sensing (QS) system regulates pathogenesis, virulence, and biofilm formation, and together they contribute to nosocomial infections. Opportunistic pathogens, such as Pseudomonas aeruginosa, rely on QS for regulating virulence factors. Therefore, blocking the QS system may aid management of various infectious diseases caused by human pathogens. Plant secondary metabolites can thwart bacterial colonization and virulence. As such, this study was undertaken to evaluate three extracts from the medicinal plant, Melianthus comosus, from which phytochemical compounds were identified with potential to inhibit QS-dependent virulence factors in P. aeruginosa. Chemical profiling of the three extracts identified 1,2-benzene dicarboxylic acid, diethyl ester, neophytadiene and hexadecanoic acid as the common compounds. Validation of antibacterial activity confirmed the same MIC values of 0.78 mg/mL for aqueous, methanol and dichloromethane extracts while selected guanosine showed MIC 0.031 mg/mL. Molecular docking analysis showed anti-quorum sensing (AQS) potential of guanosine binding to CviR’ and 2UV0 proteins with varying docking scores of 5.969 and 8.376 kcal/mol, respectively. Guanosine inhibited biofilm cell attachment and biofilm development at 78.88% and 34.85%, respectively. Significant swimming and swarming motility restriction of P. aeruginosa were observed at the highest concentration of plant extracts and guanosine. Overall, guanosine revealed the best swarming motility restrictions. M. comosus extracts and guanosine have shown clear antibacterial effects and subsequent reduction of QS-dependent virulence activities against P. aeruginosa. Therefore, they could be ideal candidates in the search for antipathogenic drugs to combat P. aeruginosa infections.The South African National Research Foundation (NRF) Thuthuka Grant, South African Medical Research Council–Self Initiated Research (SAMRC-SIR), NRF Incentive Funding for Rated Researchers, Research Development Grants for Y-Rated Researchers and equipment subsidy from the Alexander von Humboldt Foundation.https://www.mdpi.com/journal/antibioticsam2022BiochemistryGeneticsMicrobiology and Plant PathologyZoology and Entomolog