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Fulltext Modal behaviour of vertical axis Wind Turbine Comprising Prestressed Rotor Blades: A finite element analysis

Torabi Asr, M., Masoumi, M.M., Mustapha, F.

Pertanika Journal of Science & Technology, 2017;25(3):977-982.
MyJurnal

Pre-stressing is a concept used in many engineering structures. In this study prestressing in the form of axial compression stress is proposed in the blade structure of H-Darrieus wind turbine. The study draws a structural comparison between reference and prestressed configurations of turbine rotor with respect to their dynamic vibrational response. Rotordynamics calculations provided by ANSYS Mechanical is used to investigate the effects of turbine rotation on the dynamic response of the system. Rotation speed ranging between 0 to 150 rad/s was examined to cover the whole operating range of commercial instances. The modal analysis ends up with first six mode shapes of both rotor configurations. As a result, the displacement of the proposed configurations reduced effectively. Apparent variations in Campbell diagrams of both cases indicate that prestressed configuration has its resonant frequencies far away from turbine operation speeds and thus remarkably higher safety factor against whirling and probable following failures.
Fulltext Wireless structural health monitoring (SHM) system for damage detection using ultrasonic guided waveform response

Shirazi, A.H.S., Muda, M.K.H., Thirumurthy, M.J., Mustapha, F.

Pertanika Journal of Science & Technology, 2017;25(1):283-292.
MyJurnal

This paper presents an improved version of a wireless device embedded with a smart PZT sensor to
detect flaws and structural defects on selected investigated structure. Smart PZT sensors were used as an
actuator and sensor, coupled with two XBee’s and one signal generator IC chip. Programme execution on
transmitting and receiving the ultrasonic guided wave via the PZT sensor had been written in MATLAB.
The developed source code is basically to receive serial data from one Xbee to another remote Xbee attached
to the investigated structural system. The refined waveform response is utilised for prognosis of the true
structural status. The 4-mm simulated holed into one of the aluminium structural plate is benchmarked
with its pristine condition in validating the effectiveness of the developed SHM wireless module. Results
showed that the wave is more even in non-defected area and disrupted in affected area. Ultrasonic waves
increase continuously for non-destructive evaluation and structural health monitoring in various structural
applications because the guided wave can propagate long distances and reach difficult-to-access regions;
for inspecting porous and some non-porous materials ultrasonic waves attenuate fast and are very useful.
Recent advances in ultrasonic wave application model and results are discussed in this paper.
Fulltext Drop-weight impact test on laminated composite plate of flax (Linum usitatissimum) using rice husk ash from paddy (Oryza sativa) as a natural binder

Yaakob, M.S., Abidin, N.A.Z., Abdullah, M.N., Muda, M.K.H., Mustapha, F.

Pertanika Journal of Science & Technology, 2017;25(1):317-326.
MyJurnal

Composite structures and materials are used in aerospace, marine and automotive applications due
to their light weight characteristics. By using rice husk ash (RHA) as natural binder to replace epoxy
resin, it improves the characteristic of the composite laminated structure. Rice husk has become an
important ingredient in silica, silicon carbide, and silicon nitride because of its high a silicon content.
This paper evaluates the performance of laminated composite plate in a drop-weight impact testing. Two
plates are attached to the test rig in the particular desired impact orientation. The main advantages of
this process are the plates provide more realistic drop-weight impact and data. Data from the impact test
was collected and analysed to evaluate the material properties of epoxy resin and RHA. Results show
RHA’s energy absorption is better and it has more deformation to prevent structure failures compared
with epoxy resin. This paper aims to evaluate the application of RHA as a geopolymer binder and flax
fibre as an alternative material to glass fibre in the composites industry.
Fulltext Simulating bio-composite cycling helmet performance through FEA and CFD approaches

Mohd Naim Abdullah, Mustapha, F., Muda, M.K.H., Arrifin, M.K.A., Rafie, A.S.M., Shamsudin, M.A.

Movement Health & Exercise, 2015;4(1):77-91.
MyJurnal

Finite Element Analysis (FEA) and Computational Fluid Dynamics (CFD) analysis were performed in this work in order to obtain the best design for safety and aerodynamic performance of the bicycle cycling helmet. FEA analysis was computed on two different helmet designs to determine the critical area subjected to impact. A pressure load was applied on the helmets’ outer surface to simulate oblique loading. The critical areas of the helmets were then highlighted and identified, enabling design improvements to be made on both designs. CFD analysis was then executed in order to obtain the lowest drag coefficient number in reducing the air resistance induced by both of the helmet designs, inherently increasing cyclist performance and ensuring competition success.
Fulltext Assessing The Medication Use Among Diabetic Patients With Comorbid Diseases

Azmi S, Mustapha FI, Abdul AS

Value Health, 2014 Nov;17(7):A359.
PMID: 27200726 DOI: 10.1016/j.jval.2014.08.776
Fulltext Rice Husk Ash-Based Geopolymer Binder: Compressive Strength, Optimize Composition, FTIR Spectroscopy, Microstructural, and Potential as Fire-Retardant Material

Mohd Basri MS, Mustapha F, Mazlan N, Ishak MR

Polymers (Basel), 2021 Dec 14;13(24).
PMID: 34960924 DOI: 10.3390/polym13244373

Compressive strength is an important property in construction material, particularly for thermal insulation purposes. Although the insulation materials possess high fire-retardant characteristics, their mechanical properties are relatively poor. Moreover, research on the correlation between fire-retardant and compressive strength of rice husk ash (RHA)-based geopolymer binder (GB) is rather limited. In addition, previous studies on RHA-based GB used the less efficient one-factor-at-a-time (OFAT) approach. In understanding the optimum value and significant effect of factors on the compressive strength, it was deemed necessary to employ statistical analysis and a regression coefficient model (mathematical model). The objective of the study is to determine the effect of different material behavior, namely brittle and ductile, on the compressive strength properties and the optimum material formulation that can satisfy both compressive strength and fire-retardant properties. The factors chosen for this study were the rice husk ash/activated alkaline solution (RHA/AA) ratio and the sodium hydroxide (NaOH) concentration. Compressive strength and fire-retardant tests were conducted as part of the experiments, which were designed and analyzed using the response surface methodology (RSM). The microstructure of geopolymer samples was investigated using a scanning electron microscope (SEM). Results showed that RHA/AA ratio was highly significant (p < 0.000) followed by NaOH concentration (p < 0.024). When the RHA/AA ratio was at 0.7 to 0.8 and the NaOH concentration was between 12 and 14 M, high compressive strength above 28 MPa was recorded. Optimum compressive strength of approximately 47 MPa was achieved when the RHA/AA ratio and NaOH concentration were 0.85 and 14 M, respectively. Brittle samples with low Si/Al ratio of 88.95 were high in compressive strength, which is 33.55 MPa, and showed a high degree of geopolymerization. Inversely, ductile samples showed low compressive strength and degree of geopolymerization. Water content within the geopolymer binder had a major effect on its fire-retardant properties. Semi-ductile GB showed the best fire-retardant properties, followed by semi-brittle and brittle GB. Using RHA as an aluminosilicate source has proven to be a promising alternative.
Fulltext Detection, Localisation and Assessment of Defects in Pipes Using Guided Wave Techniques: A Review

Ghavamian A, Mustapha F, Baharudin BTHT, Yidris N

Sensors (Basel), 2018 Dec 17;18(12).
PMID: 30563013 DOI: 10.3390/s18124470

This paper aims to provide an overview of the experimental and simulation works focused on the detection, localisation and assessment of various defects in pipes by applying fast-screening guided ultrasonic wave techniques that have been used in the oil and gas industries over the past 20 years. Major emphasis is placed on limitations, capabilities, defect detection in coated buried pipes under pressure and corrosion monitoring using different commercial guided wave (GW) systems, approaches to simulation techniques such as the finite element method (FEM), wave mode selection, excitation and collection, GW attenuation, signal processing and different types of GW transducers. The effects of defect parameters on reflection coefficients are also discussed in terms of different simulation studies and experimental verifications.
Fulltext Optimization of Adhesion Strength and Microstructure Properties by Using Response Surface Methodology in Enhancing the Rice Husk Ash-Based Geopolymer Composite Coating

Mohd Basri MS, Mustapha F, Mazlan N, Ishak MR

Polymers (Basel), 2020 Nov 16;12(11).
PMID: 33207752 DOI: 10.3390/polym12112709

As a result of their significant importance and applications in vast areas, including oil and gas, building construction, offshore structures, ships, and bridges, coating materials are regularly exposed to harsh environments which leads to coating delamination. Therefore, optimum interfacial bonding between coating and substrate, and the reason behind excellent adhesion strength is of utmost importance. However, the majority of studies on polymer coatings have used a one-factor-at-a-time (OFAT) approach. The main objective of this study was to implement statistical analysis in optimizing the factors to provide the optimum adhesion strength and to study the microstructure of a rice husk ash (RHA)-based geopolymer composite coating (GCC). Response surface methodology was used to design experiments and perform analyses. RHA/alkali activated (AA) ratio and curing temperature were chosen as factors. Adhesion tests were carried out using an Elcometer and a scanning electron microscope was used to observe the microstructure. Results showed that an optimum adhesion strength of 4.7 MPa could be achieved with the combination of RHA/AA ratio of 0.25 and curing temperature at 75 °C. The microstructure analysis revealed that coating with high adhesion strength had good interfacial bonding with the substrate. This coating had good wetting ability in which the coating penetrated the valleys of the profiles, thus wetting the entire substrate surface. A large portion of dense gel matrix also contributed to the high adhesion strength. Conversely, a large quantity of unreacted or partially reacted particles may result in low adhesion strength.
Fulltext Rice-Husk-Ash-Based Geopolymer Coating: Fire-Retardant, Optimize Composition, Microstructural, Thermal and Element Characteristics Analysis

Mohd Basri MS, Mustapha F, Mazlan N, Ishak MR

Polymers (Basel), 2021 Oct 29;13(21).
PMID: 34771303 DOI: 10.3390/polym13213747

Geopolymer using aluminosilicate sources, such as fly ash, metakaolin and blast furnace slag, possessed excellent fire-retardant properties. However, research on the fire-retardant properties and thermal properties of geopolymer coating using rice husk ash (RHA) is rather limited. Additionally, the approach adopted in past studies on geopolymer coating was the less efficient one-factor-at-a-time (OFAT). A better approach is to employ statistical analysis and a regression coefficient model (mathematical model) in understanding the optimum value and significant effect of factors on fire-retardant and thermal properties of the geopolymer coating. This study aims to elucidate the significance of rice husk ash/activated alkaline solution (RHA/AA) ratio and NaOH concentration on the fire-retardant and thermal properties of RHA-based geopolymer coating, determine the optimum composition and examine the microstructure and element characteristics of the RHA-based geopolymer coating. The factors chosen for this study were the RHA/AA ratio and the NaOH concentration. Rice husk was burnt at a temperature of approximately 600 °C for 24 h to produce RHA. The response surface methodology (RSM) was used to design the experiments and conduct the analyses. Fire-retardant tests and thermal and element characteristics analysis (TGA, XRD, DSC and CTE) were conducted. The microstructure of the geopolymer samples was investigated by using a scanning electron microscope (SEM). The results showed that the RHA/AA ratio had the strongest effect on the temperature at equilibrium (TAE) and time taken to reach 300 °C (TT300). For the optimization process using RSM, the optimum value for TAE and TT300 could be attained when the RHA/AA ratio and NaOH concentration were 0.30 and 6 M, respectively. SEM micrographs of good fire-resistance properties showed a glassy appearance, and the surface coating changed into a dense geopolymer gel covered with thin needles when fired. It showed high insulating capacity and low thermal expansion; it had minimal mismatch with the substrate, and the coating had no evidence of crack formation and had a low dehydration rate. Using RHA as an aluminosilicate source has proven to be a promising alternative. Using it as coating materials can potentially improve fire safety in the construction of residential and commercial buildings.
Fulltext A Rare Intraorbital Mass: An Isolated Mucocele

Che Mat CMH, Mustapha F, Noor RM, Ramli R, Mohamad I

Medeni Med J, 2020;35(4):344-348.
PMID: 33717628 DOI: 10.5222/MMJ.2020.01057

Mucocele is a mucous filled benign cystic lesion. It develops due to obstruction of any natural os-tium of the paranasal sinus. Even though being benign, it has capability to erode and cause thinning the adjacent bony structures. Isolated intraorbital mucocele without paranasal sinus disease is a rare condition. We present a 39-year-old female patient with right medial canthal swelling without any nasal symptoms, and normal nasoendoscopic finding. Imaging revealed the lesion as a right ethmoidal mucocele with normal paranasal sinuses. However intraoperatively, it was an isolated intraorbital lesion, lateral to lamina papyracea with thick-yellowish mucin discharge.
Endorsing the redefinition of fatty liver disease

Tan SS, Lee YY, Ali RAR, Mustapha F, Chan WK

Lancet Gastroenterol Hepatol, 2021 03;6(3):163.
PMID: 33581757 DOI: 10.1016/S2468-1253(21)00002-9
Fulltext Consideration of Lamination Structural Analysis in a Multi-Layered Composite and Failure Analysis on Wing Design Application

Basri EI, Sultan MTH, Basri AA, Mustapha F, Ahmad KA

Materials (Basel), 2021 Jul 02;14(13).
PMID: 34279278 DOI: 10.3390/ma14133705

A finite element (FE) model is developed to study the structural performance on a composite wing of a UAV with a tubercle design at the leading edge of the wing. The experimental study of the designation of the composite at the wing skin is carried out to prove the simulation validity through material characteristics. In this paper, the numerical modeling for simulation is highlighted to correlate the process parameter setting of simulation replicating the actual experimental tests. The percentage difference was calculated to be 11.1% by tensile and 10.47% by flexural. The numerical work applied the study of FE analysis and developed a standardized numerical approach for structural optimization, known as FE-ACP simulation. The significant findings of deformation are obtained according to Schrenk's aerodynamic loading, while the prediction of failure mode of Tsai-Wu under interaction among stresses and strains was acquired at the seventh and eighth layer of both spars.
Fulltext Study and Use of Rice Husk Ash as a Source of Aluminosilicate in Refractory Coating

Abdullah MN, Mustapha M, Sallih N, Ahmad A, Mustapha F, Dahliyanti A

Materials (Basel), 2021 Jun 22;14(13).
PMID: 34206150 DOI: 10.3390/ma14133440

The utilisation of rice husk ash (RHA) as an aluminosilicate source in fire-resistant coating could reduce environmental pollution and can turn agricultural waste into industrial wealth. The overall objective of this research is to develop a rice-husk-ash-based geopolymer binder (GB) fire-retardant additive (FR) for alkyd paint. Response surface methodology (RSM) was used to design the experiments work, on the ratio of RHA-based GB to alkyd paint. The microstructure behaviour and material characterisation of the coating samples were studied through SEM analysis. The optimal RHA-based GB FR additive was formulated at 50% wt. FR and 82.628% wt. paint. This formulation showed the result of 270 s to reach 200 °C and 276 °C temperature at equilibrium for thermal properties. Furthermore, it was observed that the increased contents of RHA showed an increment in terms of the total and open porosities and rough surfaces, in which the number of pores on the coating surface plays an important role in the formation of the intumescent char layer. By developing the optimum RHA-based GB to paint formulation, the coating may potentially improve building fire safety through passive fire protection.
Fulltext Testing of Silicon Rubber/Montmorillonite Nanocomposite for Mechanical and Tribological Performance

Shinde A, Siva I, Munde Y, Deore V, Hameed Sultan MT, Md Shah AU, et al.

Nanomaterials (Basel), 2021 Nov 12;11(11).
PMID: 34835814 DOI: 10.3390/nano11113050

Nanocomposite made by blending nano-montmorillonite (MMT) and Silicon Rubber (SR) for mechanical and tribological performance is explored in this work. Different configurations of MMT/SR nanocomposite, with 0, 0.5, 2 and 5 wt % of MMT are manufactured by two roll mixing methods. Noticeable improvement in the mechanical and tribological performance is observed, which is also justified by a morphological study of fractured and wear surfaces through SEM. Two percent of MMT loading is found to be the optimum content that shows excellent performance compared to other compositions. The performance improvement can be linked to the good interfacial interaction between the MMT and SR. Statistical modeling through ANOVA is carried out for tribological performance, which reveals the influence of load on the coefficient of friction (COF) and the influence of sliding distance on the wear rate.
Fulltext Rheological and Morphological Properties of Oil Palm Fiber-Reinforced Thermoplastic Composites for Fused Deposition Modeling (FDM)

Ahmad MN, Ishak MR, Taha MM, Mustapha F, Leman Z

Polymers (Basel), 2021 Oct 29;13(21).
PMID: 34771297 DOI: 10.3390/polym13213739

Fused deposition modelling (FDM) is a filament-based rapid prototyping technology that allows new composite materials to be introduced into the FDM process as long as they can be manufactured in feedstock filament form. The purpose of this research was to analyze the rheological behavior of oil palm fiber-reinforced acrylonitrile butadiene styrene (ABS) composites when used as a feedstock material, as well as to determine the best processing conditions for FDM. The composite's shear thinning behavior was observed, and scanning electron microscopy was used to reveal its composition. The morphological result found that there was a good fiber/matrix adhesion with a 3 wt% fiber loading, as no fiber pullouts or gaps developed between the oil palm fiber and ABS. However, some pores and fiber pullouts were found with a 5 and 7 wt% fiber loading. Next, the rheological results showed that the increment of fiber content (wt%) increased the viscosity. This discovery can definitely be used in the extrusion process for making wire filament for FDM. The shear thinning effect was increased by adding 3, 5, or 7 wt% of oil palm fiber. The non-Newtonian index (n) of the composites increased as the number of shear rates increased, indicating that the fiber loading had a significant impact on the rheological behavior. As the fiber loading increased, the viscosity and shear stress values increased as well. As a result, oil fiber reinforced polymer composites can be used as a feedstock filament for FDM.
Fulltext Mechanical Performance and Corrosion Behaviour of Diffusion-Bonded A5083 Aluminium and A36 Mild Steel with Gallium Interlayer

Ismail A, Othman NH, Mustapha M, Mohamed Saheed MS, Abdullah Z, Muhammed M, et al.

Materials (Basel), 2022 Sep 13;15(18).
PMID: 36143643 DOI: 10.3390/ma15186331

This article investigated the mechanical performance and corrosion behaviour of a diffusion-bonded A5083 aluminium/A36 mild steel dissimilar joint with a Gallium (Ga) interlayer. The bonding parameters were the bonding temperature (525 and 550 °C), holding time (60 and 120 min) and surface roughness (800 and 1200 grit). Property characterisation was achieved using Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDX) analysis, Vickers microhardness tester, Izod impact tester and potentiodynamic polarisation testing. The results revealed that the significance of the bonding parameters was in the order bonding temperature > surface roughness > holding time. Increasing the bonding temperature resulted in an increase in the impact strength and a corresponding reduction in the corrosion rate and microhardness. However, increasing the grit size decreased the microhardness and a corresponding increase in the impact strength and corrosion rate. The impact strength and corrosion rate decreased with the increasing holding time while the microhardness followed a reverse trend. It was also discovered that incorporating the Ga interlayer resulted in a 67.9% improvement in the degradation rate.
Fulltext Five-year LDL-cholesterol trend and its predictors among type 2 diabetes patients in an upper-middle-income country: a retrospective open cohort study

Wan KS, Hairi NN, Mustapha F, Ismail M, Mohd Yusoff MF, Moy FM

PeerJ, 2022;10:e13816.
PMID: 36317122 DOI: 10.7717/peerj.13816

BACKGROUND: Patients with diabetes have increased risks of cardiovascular diseases (CVD), and their LDL-cholesterol (LDL-C) has to be treated to target to prevent complications. We aim to determine the LDL-C trend and its predictors among patients with type 2 diabetes (T2D) in Malaysia.
METHODS: This was a retrospective open cohort study from 2013 to 2017 among T2D patients in public primary health care clinics in Negeri Sembilan state, Malaysia. Linear mixed-effects modelling was conducted to determine the LDL-C trend and its predictors. The LDL-C target for patients without CVD was <2.6 mmol/L, whereas <1.8 mmol/L was targeted for those with CVD.
RESULTS: Among 18,312 patients, there were more females (55.9%), adults ≥60 years (49.4%), Malays (64.7%), non-smokers (93.6%), and 45.3% had diabetes for <5 years. The overall LDL-C trend reduced by 6.8% from 2.96 to 2.76 mmol/L. In 2017, 16.8% (95% CI: 13.2-21.0) of patients without CVD and 45.8% (95% CI: 44.8-46.8) of patients with CVD achieved their respective LDL-C targets. The predictors for a higher LDL-C trend were younger adults, Malay and Indian ethnicities, females, dyslipidemia, and diabetes treatment with lifestyle modification and insulin. Longer diabetes duration, obesity, hypertension, retinopathy, statin therapy, achievement of HbA1c target and achievement of BP target were independent predictors for a lower LDL-C trend.
CONCLUSIONS: The LDL-C trend has improved, but there are still gaps between actual results and clinical targets. Interventions should be planned and targeted at the high-risk populations to control their LDL-C.
Fulltext A Review of Natural Fiber-Based Filaments for 3D Printing: Filament Fabrication and Characterization

Ahmad MN, Ishak MR, Mohammad Taha M, Mustapha F, Leman Z

Materials (Basel), 2023 May 29;16(11).
PMID: 37297184 DOI: 10.3390/ma16114052

Today, additive manufacturing (AM) is the most recent technology used to produce detailed and complexly built parts for a variety of applications. The most emphasis has been given to fused deposition modeling (FDM) in the development and manufacturing fields. Natural fibers have received attention in the area of 3D printing to be employed as bio-filters with thermoplastics, which have prompted an effort for more ecologically acceptable methods of manufacturing. The development of natural fiber composite filaments for FDM requires meticulous methods and in-depth knowledge of the properties of natural fibers and their matrices. Thus, this paper reviews natural fiber-based 3D printing filaments. It covers the fabrication method and characterization of thermoplastic materials blended with natural fiber-produced wire filament. The characterization of wire filament includes the mechanical properties, dimension stability, morphological study, and surface quality. There is also a discussion of the difficulties in developing a natural fiber composite filament. Last but not least, the prospects of natural fiber-based filaments for FDM 3D printing are also discussed. It is hoped that, after reading this article, readers will have enough knowledge regarding how natural fiber composite filament for FDM is created.
Fulltext Eighteen months into the COVID-19 pandemic: The prevalence of depression, anxiety, and stress symptoms in Southeast Asia and the associated demographic factors

Tay WWY, Jesuthasan J, Wan KS, Ong T, Mustapha F

Front Public Health, 2022;10:863323.
PMID: 35991032 DOI: 10.3389/fpubh.2022.863323

Mental health has become a growing concern in the wake of the COVID-19 pandemic. We sought to determine the prevalence of mental health symptoms 18 months after the pandemic's declaration. Our cross-sectional study conducted among 18- to 65-year-old adults (N = 33,454) in October 2021 using the Depression, Anxiety and Stress Scales (DASS-21) found a high prevalence of severe to extremely severe anxiety (49%), depression (47%) and stress (36%) symptoms in Malaysia, Indonesia, Thailand, and Singapore. Multiple logistic regression showed that female and non-binary genders were associated with increased odds of severe/extremely severe symptoms of anxiety (female: aOR 1.44 [95% CI 1.37-1.52]; non-binary aOR 1.46 [1.16-1.84]), depression (female: aOR 1.39 [1.32-1.47]; non-binary aOR 1.42 [1.13-1.79]), and stress (female: aOR 1.48 [CI 1.40-1.57]; non-binary aOR 1.42 [1.12-1.78]). In all three symptom domains, the odds of severe/extremely severe symptoms decreased across age groups. Middle- and high-income respondents had lower odds of reporting severe/extremely severe anxiety (middle-income: aOR 0.79 [0.75-0.84]; high-income aOR 0.77 [0.69-0.86]) and depression (middle-income: aOR 0.85 [0.80-0.90]; high-income aOR 0.84 [0.76-0.94]) symptoms compared to low-income respondents, while only middle-income respondents had lower odds of experiencing severe/extremely severe stress symptoms (aOR 0.89 [0.84-0.95]). Compared to residents of Malaysia, residents of Indonesia were more likely to experience severe/extremely severe anxiety symptoms (aOR 1.08 [1.03-1.15]) but less likely to experience depression (aOR 0.69 [0.65-0.73]) or stress symptoms (aOR 0.92 [0.87-0.97]). Respondents living in Singapore had increased odds of reporting severe/extremely severe depression symptoms (aOR 1.33 [1.16-1.52]), while respondents residing in Thailand were more likely to experience severe/extremely severe stress symptoms (aOR 1.46 [1.37-1.55]). This study provides insights into the impacts of the COVID-19 pandemic on the point prevalence of psychological distress in Southeast Asia one and a half years after the beginning of the pandemic.
Fulltext Thermal Properties and Drying Shrinkage Performance of Palm Kernel Shell Ash and Rice Husk Ash-Based Geopolymer Concrete

Abdullah MN, Mustapha F, Yusof N', Khan T, Sebaey TA

Materials (Basel), 2024 Mar 11;17(6).
PMID: 38541452 DOI: 10.3390/ma17061298

This study aims to develop suitable formulations of geopolymer concrete (GPC) by varying the percentages of the geopolymer with aggregates and evaluating the performances in thermal and mechanical properties of palm kernel shell ash (PKSA)-GPC compared to rice husk ash (RHA)-GPC and ordinary Portland cement concrete (OPCC). Preliminary tests were conducted to select the best mix design ratios before casting the specimens. Then, the performance of the PKSA-GPC, RHA-GPC and OPCC specimens was evaluated based on their thermal performance and drying shrinkage. The mix designs of PKSA-GPC 70:30, PKSA-GPC 60:40, PKSA-GPC 50:50 and PKSA-GPC 66.6:33.3 were found to produce an acceptable consistency, rheological and thixotropic behaviour for the development of the GPC. PKSA-GPC showed a better thermal performance than the RHA-GPC and OPCC due to their strong and dense intumescent layers and slow temperature increment upon exposure to a high flame temperature from ambient temperature to 169 °C. The low molar ratio of the Si/Al present in the PKSA-GPC created a thermally stable intumescent layer. In the drying shrinkage test, PKSA-GPC 60:40 and RHA-GPC 60:40 shared an equal drying shrinkage performance (5.040%) compared to the OPCC (8.996%). It was observed that microcrack formation could significantly contribute to the high shrinkage in the PKSA-GPC 50:50 and RHA-GPC 70:30 specimens. The findings of this study show that PKSA could be incorporated into GPC as a fire-retardant material due to its capability of prolonging the spread of fire upon ignition and acting as an alternative to the conventional OPCC.

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