Hydration of Hardened Cement Paste Incorporates Nano-Palm Oil Fuel Ash at Later Age: The Microstructure Studies

Cement replacement using pozzolanic materials in nano-sized particles could improve the mechanical and durability of concrete. A study on the hydration of cement in hardened cement paste (HCP) could assist the investigation of nano-POFA (nPOFA) as a potential supplementary cementing material (SCM). Hence, the present work aims to examine the hydration of HCP incorporates nPOFA and the pozzolanic activity of nPOFA in cement matrix through the microstructure studies. A set of nPOFA-HCP were prepared with a cement replacement in range of 10-60% and the paste were cured for 90 days. The microstructural investigation of nPOFAHCP was conducted via X-Ray diffraction (XRD) analysis, Field Emission Scanning Electron Microscope (FESEM) analysis, Thermogravimetric (TG) analysis and Fourier Transfrom Infrared (FTIR) spectroscopy analysis. The diffractogram show the calcium hydroxide (CH) peak at at 2θ = 18.1º and 34.0º in 30nPOFA and 40nPOFA HCP is low compare than other pastes. The 30nPOFA and 40nPOFA give a low value of the relative loss weight of CH at later age through the TG analysis. Meanwhile, the morphology study display 30nPOFA and 40nPOFA HCP possess a dense and compact microstructure. FTIR analysis study the peaks of O-H symmetric stretching, C-O asymmetric stretching, Si-O asymmetric stretching and C-O bending stretching. Overall, the findings reveals the presence of nPOFA in cement matrix enhance the microstructure of cement matrix through the acceleration of cement hydration and the pozzolanic reaction. The cement replacement up to 40% with nPOFA could give an optimum result to produce a better cement-based products

The performance of mortars incorporates nano-sized palm oil fuel ash on water absorption and soprtivity at early age of hydration

The durability performance of mortar at the early age of hydration is also affected by the pores system of the hardened cement matrix. The inclusion of supplementary cementing material (SCM) in nanosized particles might modify the durability behavior of mortars. Thus, the present study investigates the water absorption and sorptivity of mortar incorporates nano-sized palm oil fuel ash (nPOFA) at an early age of hydration. The Ordinary Portland Cement (OPC) cement was replaced with microsized palm oil fuel ash (mPOFA) and nPOFA in quantities ranging from 10% w/w to 30% w/w and 10% w/w to 60% w/w, respectively. The binder-to-sand ratio in mortar specimens was kept constant at 1:2.75. Water absorptivity and sorptivity tests were performed on the mortars at 28 days of curing age. It is observed that after 720 min of testing, the water absorption of 10nPOFA-40nPOFA mortars was found to be lower than that of 10mPOFA-30mPOFA mortars. Nonetheless, the water absorption for all mortars in the 720 min duration test was still above 10% by mass. According to the sorptivity test, the 20mPOFA mortar had the lowest sorptivity among the mPOFA mortars, while the 30nPOFA mortar had the lowest sorptivity among the nPOFA mortars. At this age, it is suggested that all mortar specimens are considered less durable due to the high-water absorption. It also suggested that as nPOFA is used in lieu of cement up to 40 % replacement by mass, the pores system of the hardened cement matrix improves when compared to mPOFA mortar

Pozzolanic activity assessment of a various palm oil fuel ash via lime consumption test

Palm oil fuel ash (POFA) is a conceivable cement substitute that could promote the strength and durability of cement-based products. However, the inconsistent burning conditions in mills result in POFA with different compositions. Therefore, the current study aims to evaluate the pozzolanic activity of POFA using the lime consumption test (LC). Five POFA'ss from different mills were designated as POFA1, POFA2, POFA3, POFA4 and POFA5. In the LC test, the hydroxide ion concentration of the saturated lime-POFA suspension was calculated by acid-base titration after 1, 3, 7 and 28 days of curing. The compressive strength of mortar with a mix design with a binder to sand weight ratio of 1:2.75 was carried out after 28 days of curing age to calculate the strength activity index (SAI). The results show that the LC for POFA1 was highest after 1, 3, 7 and 28 days compared to the other POFA samples. The mortar POFA1 also has the highest SAI value of 93.8% compared to the other mortars. The study has clearly shown that POFA from various sources has different pozzolanic performance due to inconsistent of chemical composition. The study suggests that POFA1 has higher pozzolanic activity than other POFAs due to its high reactivity with calcium hydroxide in the pozzolanic reaction

Effect of heat treatment on the physical and structural properties of tellurite glass

This study reports the spectroscopic properties of tellurite glass with a composition of 70TeO2-20ZnO-9.5Na2O-0.5Er2O3 synthesized using the melt-quenching technique. The physical and structural properties of glass heat treated at distinctive temperatures are found to vary due to the structural changes. The incorporation of erbium content into tellurite glass causes the glass to appear reddish in color and transparent. However, glass heat-treated at 400°C shows the tendency to become opaque due heat treatment near the crystallization temperature. XRD pattern indicated the amorphous nature of glass with the presence of a broad hump in the range 25° to 40°

Hydrothermal conversion of kaolin to kalsilite (kalSiO₄): the effect of K₂CO₃ concentrations

Kaolin was used as a silica and alumina precursor in the hydrothermal synthesis of kalsilite with the addition of potassium carbonate (K₂CO₃) as a potassium source. The effects of different K₂CO₃ concentrations have been studied. After a 24-hour hydrothermal reaction at 200°C, kaolin treated with 1.25M K₂CO₃ shows 28.7°, 34.2°, and 42.3° as the most significant peaks under X-ray diffraction (XRD) which corresponds to hexagonal kalsilite. In addition, Field emission scanning electron microscopy (FESEM) images also revealed hexagonal particles proving the formation of the desired kalsilite. At K₂CO₃ concentrations less than 1.0M, boehmite and bayerite were identified to be the primary products while kalsilite forms as a minor crystalline phase. Hexagonal kalsilite was observed as the major product at higher (>1.0M) K₂CO₃ concentration while the reaction kept constant at 200°C

Morphology of lightweight metakaolin-based geopolymer polystyrene composite paste at early ages

The integration of polystyrene foams as the lightweight agent in geopolymer is an alternative to produce a lightweight metakaolin-based geopolymer. Meanwhile, the microstructure studies assist to provide better understanding towards the formation of lightweight geopolymer. Hence, the present study examined the morphological characteristics of lightweight metakaolin-based geopolymer polystyrene composite at an early age. The lightweight metakaolin-based geopolymer paste is prepared at ratio 0.7 by using sodium hydroxide as an alkaline activator and the addition of polystyrene foams at ratio of 0.3. The morphology of the lightweight metakaolin-based geopolymer polystyrene paste was analyzed through SEM analysis at 14 days curing ages. The lightweight geopolymer at early ages consisted of the unresponsive metakaolin and porous gel as it gave less dense and compact microstructure. Meanwhile, the analysis showed that the polystyrene foams blended-well in the geopolymer matrix. However, the high temperature during the curing process damages the texture of some of the polystyrene foams. Yet, the utilization of the polystyrene foams as lightweight agents is believed to produce a lightweight metakaolin-based geopolymer

Impak modul pembelajaran berasaskan masalah-sains, teknologi, kejuruteraan dan matematik kepada pelajar sekolah menengah di luar bandar: Kajian perbandingan

Bilangan pelajar Sains, Teknologi, Kejuruteraan dan Matematik (STEM) semakin berkurang di Malaysia terutamanya pelajar luar bandar. Usaha dan kesedaran akan kepentingan STEM perlu digerakkan secara intensif dan ia harus dimulakan dari peringkat sekolah. Sehubungan itu, pihak STEM UMS Warriors, UMS melaksanakan program STEM AUMS Warriors dengan menggunakan modul pembelajaran berasaskan masalah (PBL)-STEM kepada pelajar luar bandar bagi mempromosikan pendidikan STEM. Justeru, kajian ini dilakukan untuk mengkaji impak modul PBL-STEM kepada pelajar luar bandar dalam aspek minat pelajar terhadap STEM, motivasi pembelajaran pelajar dan pembentukan kemahiran insaniah pelajar. Melalui program ini, empat modul PBL-STEM iaitu modul Seibutsu, modul Da Vinci Code, modul The Power of Atom dan modul Inception digunakan pada empat pertemuan yang disertai oleh 79 orang pelajar sekolah menengah luar bandar. Analisis kualitatif dilakukan menggunakan soal selidik yang merangkumi komponen yang berkaitan dengan minat pelajar terhadap STEM, motivasi pembelajaran pelajar dan pembentukan kemahiran insaniah pelajar diedarkan kepada pelajar setiap kali selesai modul dilaksanakan. Hasil kajian menunjukkan nilai purata bagi setiap pernyataan lebih dari 5.2000, iaitu kebanyakan pelajar memberi respon ‘Setuju’ dan ‘Sangat Setuju’ bagi setiap pernyataan. Hasil ini menunjukkan semua modul PBL-STEM memberi impak positif kepada pelajar luar bandar. Kajian perbandingan antara modul menunjukkan tidak ada perbezaan yang signifikan antara modul dan nilai purata bagi semua aspek yang dikaji menunjukkan peningkatan dari pertemuan pertama hingga pertemuan keempat. Hasil kajian menunjukkan semua aktiviti-aktiviti dalam modul berjaya meningkatkan motivasi pelajar untuk mempelajari subjek-subjek STEM dan seterusnya meningkatkan minat pelajar terhadap STEM. Pelaksanaan kaedah PBL dalam modul melalui aktiviti pembentangan dan kerja berkumpulan membantu meningkatkan kemahiran insaniah pelajar termasuklah kemahiran berkomunikasi, bekerjasama, keyakinan diri dan pembelajaran kendiri pelajar

Mental health crises among foundation level students during Covid-19 pandemic: an analysis of influencing factor

Quarantine, isolation, and social distancing were essential for preventing the transmission of the virus and protecting people's physical fitness during the ongoing COVID-19 pandemic. However, they may have had lasting negative impacts, notably on mental health and well-being, especially on higher education students, as they are in a pivotal life-transition stage linked to increased mental health crises. Therefore, the main objective of this study is to assess the influential factors associated with mental health crises among foundation-level students during the COVID-19 pandemic. This study involved 277 students from the foundation of science programme at the Preparatory Centre of Science and Technology, University of Malaysia Sabah. A questionnaire was originally constructed to analyse the factors impacting mental health crises. Overall results found that the range of the mean from the questionnaire was 4.56 to 4.80, indicating that depression, anxiety, stress, and eating disorders are undoubtedly the influencing factors of mental health crises among foundation-level students. The majority of students scored much higher on the items under the stress factor (4.73) compared to the other three factors, which suggests that most of the students suffered from stress during the COVID-19 pandemic. This is followed by depression (4.69), anxiety (4.64) and eating disorders (4.63). Thus, universities and lecturers play a crucial role in reducing stress, depression, and anxiety associated with academic commitment

A Preliminary Study on STEM Encouragement in Chemistry Subject: The Learning Experience of SMK Usukan Students in STEM AUMS Warrior Program

Currently, due to the lack of awareness in STEM education, the number of Science, Technology, Engineering and Mathematics (STEM) students in Sabah has been continuously decreasing. It is crucial to engage school in rural area of Sabah with STEM activities to boost their interest towards STEM education. The primary goal of this study is to establish effective Chemistry-STEM module, analyzing the preliminary effects of the integration on the interest of students, and encouraging STEM education to rural students through chemistry subject. Present study is the preliminary investigation on the learning experience of students in STEM through the Chemistry module. For the purpose of this study, a sample of 74 students from the lower secondary school of SMK Usukan, Kota Belud, Sabah participated in The Power of Atom Module developed by Preparatory Centre for Science & Technology (PPST), Universiti Malaysia Sabah (UMS). Student’s learning experience data was gathered through a questionnaire that results in statistically significant improvement in STEM learning and communication skills. The findings suggested that the Chemistry-STEM module developed by Chemistry lectures encourage and enhance self-learning, interest in learning Science (i.e. Chemistry), teamwork skills and communications skills of the students. It shows that this module is approachable to rural schools in learning STEM education

The effects of nanosized-palm oil fuel ash on early age hydration of hardened cement paste: The microstructure studies

Integration of cement-based products with nanosized-palm oil fuel ash as supplementary cementing material (SCM) amend its hydration's degree at early age phase and the microstructural groundworks are relevant to explain the findings. Hence, the present work investigates the microstructure properties of the hardened cement paste (HCP) incorporating nPOFA to study on the effect of nPOFA in cement hydration at an early age phase. An Ordinary Portland Cement (OPC) paste as a set of HCP blended with microsized-palm oil fuel ash (mPOFA) (10-30%) and nPOFA (10-60%) were prepared and cured for 28 days. The microstructural examination of OPC, mPOFA and nPOFA cement pastes at 28 days curing age via Thermogravimetric (TG) analysis, X-Ray diffraction (XRD) analysis, morphology study and Fourier transform infrared (FTIR) spectroscopy analysis. In TG analysis, the relative weight loss of calcium hydroxide (CH) of nPOFA pastes is lower than OPC and mPOFA. Based on the CH peaks at 20= 18.1°and 34.0° in the diffractogram, it shows that nPOFA pastes give the low CH peaks compare to OPC and mPOFA pastes. In addition, the nPOFA pastes form the dense and compact microstructure of HCP compare to other pastes. Observations from FTIR analysis, nPOFA pastes display a high frequency of Si-O band due to the high rate of pozzolanic reaction. Overall, the findings confirmed the contribution of nPOFA in accelerating the rate of cement hydration and pozzolanic reaction as it reduced the amount of CH in the cementitious matrix