Experimental Investigation of CFRP Confined Columns Damaged by Alkali Aggregate Reaction

Fiber reinforced polymer is the most effective repair material in use to enhance the strength and ductility of deteriorated reinforced concrete columns. Often, fiber reinforced polymer (FRP) provides passive confinement to columns until the dilation and cracking of concrete occurs. In the case of concrete suspected of Alkali Aggregate Reaction (AAR) where concrete undergoes expansion, FRP wrap provides active confinement to the expanded concrete. In this study, the performance of carbon fiber reinforced polymer (CFRP) wrapped columns damaged by AAR is evaluated based on the number of FRP layers and the time of the polymer application which provides two types of confinement: active or passive. The columns were tested under axial compression to evaluate the residual strength of the columns in comparison with unwrapped columns. The results reveal that the strength of the wrapped columns is enhanced with an increase in the number of CFRP layers. The strength of the columns under passive confinement is higher than the columns under active confinement. Under active confinement, early CFRP wrapping leads to improvement in the strength of the columns

Relationship between ae signal strength and absolute energy in determining damage classification of concrete structures

The most efficient tools in real monitoring system is acoustic emission (AE). This technique can be used to identify the damage classifications in RC structure. This research paper will mainly focus on the utilization of signal strength and Absolute energy (AE signal) in determining on the damage quantification for RC beam subjected to cyclic load test. The beam specimens size (150 X 250 X 1900) mm were prepared in the laboratory and tested with the four point bending test using cyclic loading together with acoustic emission monitoring system. The results showed that the analysis of AE data parameters is capable of determining the damage classification in concrete structures and the data corresponded to the visual observations during the increased loading cycle

Strength and Quality Assessment of Recycled Aggregate and Crumb Rubber Concrete Using the Ultra Pulse Velocity Method

This study focuses on the strength and quality of concrete incorporated with recycled aggregate and crumb rubber through the compressive strength test and the Ultra Pulse Velocity (UPV) test. RA was used to replace coarse aggregate while CR was used to replace fine aggregate in concrete production. A total of 36 specimens consisting of cubes (100 mm 100 mm 100 mm) with partial replacements of 50% RA and 0, 1, 2, 3, 4, and 5% CR were prepared, subjected to water curing for 7 and 28 days and tested in terms of compressive strength and quality using the compressive strength test and the UPV method. The UPV test and the compressive strength test were conducted at day 7 and day 28. The results show that the compressive strength of concrete decreased slightly with the increase of rubber content. Additionally, the quality of concrete slightly decreased as the percentage of rubber content increased. Finally, the optimum percentages for partial replacement of concrete suggested based on the results are 3% CR and 50% RA as this concrete mix achieved the highest velocity in the UPV test and the highest compressive strength compared to the control mix

Shear Capacity of Reinforced Concrete Beam with an Opening Retrofit Using Steel Fiber and Metakaolin

This study presents the experimental work of reinforced concrete beam with opening at shear zone and added with steel fibre and metakaolin to increase the shear capacity of the beam. A total of five (5) beams were casted and tested under four-point bending test. One beam served as the control specimen, two beams were beams with one and two opening respectively while the other two beams were beams with added steel fibre and metakaolin. The type of steel fibre used was a hooked-end steel fibers with the dimensions of 0.9mm in diameter, 60mm in length, and 0.5% of steel fiber was added by volume of beam, and 5% of metakaolin by volume of beam were used. From the experimental results, it was found that the two beams with added steel fibre and metakaolin shows an increase in shear capacity compared with the beams with opening without the steel fibre and metakaolin. The highest shear force recorded was 79.11 kN (beams with added steel fibre and metakaolin) which shows an increase for about 54.3 % compared with the same beam with opening without added steel fibre and metakaolin

Fresh Properties and Compressive Strength of 3D Printing Concrete Containing GGBS as Partial Cement Replacement

3D printed concrete is a particular mix of concrete that has been specially prepared to flow easily through the printing nozzle. The foundations of 3D printed concrete constructions are stacked, with each layer put on top of a preceding layer of pumped concrete. Despite its potential, the construction industry has been confronted with several material issues. The cement replacement in the concrete has also been intensively studied, but in 3D printed concrete, this matter has not been seen clearly. It still cannot be seen whether the cement replacement produces a good result for the 3D printed concrete. This research investigated the fresh characteristics and compressive strength of 3D printed concrete using GGBS as a partial cement replacement in the mixture. In addition, the optimal proportion of GGBS as a partial cement replacement in 3D printed concrete is also evaluated. In this study, the fresh properties of 3D printing were examined by a flow table test, a buildability test, and an extrudability test, while compression strength was assessed for the mechanical properties. The percentage of GGBS used will vary from 20% to 50% with a 10% increment by weight of cement, and the water-cement ratio was fixed at 0.5. The cube specimen for the compression test was 50 mm x 50 mm x 50 mm and was cured for 7 and 28 days. The findings show that the flowability of this 3D printed concrete increased as the percentage of GGBS increased. All of the specimens also passed the buildability and extrudability tests. The compressive strength of this 3D printed also increased as the percentage increased, but it decreased back at 50% GGBS replacement. Overall, this experiment shows that 40% GGBS replacement is the optimum proportion as cement replacement in 3D printed concrete as it shows the highest compressive strength, which is 57.3 MPa

Modified Epoxy for Fibre Reinforced Polymer Strengthening of Concrete Structures

Fibre-Reinforced Polymer (FRP) is a preferable material for repairing concrete structure due to excellent material properties and effective installation cost over the long-term maintenance of structures. The successful application of FRP strengthening system very much depends on the bond between the concrete substrate and the FRP material using epoxy adhesive. Epoxy acts as a bridge to transfer stress from the concrete to the FRP material. The use of wet lay-up technique to apply FRP onto concrete structure requires epoxy to undergo a curing process normally referred to as cold curing. This paper intends to give a review of the problems with cold-cured epoxy and its effect on structural performance. Cured epoxy is characterised as brittle; therefore, modifications of epoxy are required to toughen the epoxy to suit the purpose of repairing a concrete structure. The methodological approaches from previous studies on modified epoxy were collected and reviewed in this paper. This review also offers some important insights regarding the use of sustainable materials, as well as recommendations for new epoxy in the future. &nbsp

Pendatang asing di Kedah: Impak jenayah

Pergantungan Malaysia terhadap tenaga kerja asing disebabkan kekurangan tenaga kerja dalam kebanyakan sektor ekonomi terutamannya perladangan, pembuatan, perkhidmatan dan pembinaan. Kini terdapat kira-kira dua juta pendatang asing di negara ini dan 500,000 daripada mereka merupakan pendatang tanpa izin. Kebanyakan mereka adalah rakyat Indonesia, Bangladesh, Thailand, Filipina dan Myanmar. Di Kedah, kehadiran pendatang asing disebabkan oleh: kegiatan pertanian bermusim, sektor perindustrian,sektor perkhidmatan, sektor pembuatan

Implikasi sosial kemasukan pendatang asing di Kedah

Peranan yang dimainkan oleh pendatang asing di negara ini dari segi pembangunan ekonomi tidak dapat dinafikan.Namun begitu, kemasukan mereka telah memberi kesan terhadap beberapa aspek sosial seperti jenayah, kesihatan awam dan pendidikan.Kajian ini meneliti kesan kemasukan pendatang asing di Kedah dalam aspek-aspek sosial yang dinyatakan di atas.Dapatan kajian menunjukkan bahawa walaupun Kedah turut terdedah kepada masalah kemasukan pendatang asing, namun ia tidak memberi impak yang besar terhadap keadaan sosial di negeri ini

Masalah kesihatan di kalangan pendatang asing dan implikasinya di Kedah Darulaman

Sumbangan pendatang asing dalam pembangunan ekonomi dan negara tidak dapat disangkal terutama dalam sektor-sektor penting seperti perladangan, pembuatan dan perindustrian yang ketandusan tenaga kerja bukan profesional. Namun, kehadiran mereka turut membawa beberapa implikasi terhadap struktur sosial, ekonomi dan politik. Kedah yang turut menumpukan perhatian kepada sektor pembuatan dan perindustrian dalam Rancangan Tindakan Pembangunan Negeri Kedah 1991-2000 juga tidak terlepas daripada masalah ini. Kajian yang dijalankan untuk melihat sejauhmana seriusnya masalah sosial, yang antaranya menyentuh aspek kesihatan, mendapati bahawa sungguhpun negeri ini bebas daripada ancaman penyakit baru tetapi ia merekodkan peningkatan kes penyakit merbahaya seperti HIV/AIDS, hepatitis, batuk kering dan penyakit kelamin di kalangan pendatang asing. Pendatang asing yang mendapatkan rawatan di hospital-hospital awam dan pejabat kesihatan daerah (PKD) ini tidak dinafikan kemudahan kesihatan atas sifat kemanusiaan. Kajian ini mendapati bahawa, pada amnya, jumlah bayaran perkhidmatan yang diterima daripada mereka adalah kurang berbanding kos yang ditanggung oleh hospital-hospital dan PKD. Ini bermakna kerajaan tcrpaksa menanggung subsidi kesihatan awam bagi pendatang asing sepertimana penduduk tempatan walaupun jumlah peratusan pesakit asing yang menggunakan perkhidmatan awam di Kedah adalah kurang daripada satu peratus daripada jumlah keseluruhan pesakit

Copy number variation of CNVesv27061 analysis among young adults with high blood pressure using optimized droplet digital polymerase chain reaction (ddPCR) method

Several reports and databases on genomic variants have associated variation in DNA sequences (≥ 1kb), or copy number variation (CNV), with susceptibility to common diseases. However, very few reports are found on hypertension and no study has been reported on CNV in prehypertensive and hypertensive young adult Malaysians. In this comparative cross-sectional study, 133 young adults were recruited, comprising of normotensive (45 subjects), prehypertensive (40 subjects) and mild hypertensive (48 subjects) subjects. DNA for CNV determination was extracted from 3 ml of blood samples collected. CNV esv27061 was analysed using optimized droplet digital polymerase chain reaction (ddPCR) method which has enhanced sensitivity and precision. Frequency distribution patterns of CNV among mild hypertensives showed highest peak copy-number-gain (number of copies more than 2) particularly in copy numbers 3 and 5. The prehypertensive subjects exhibited marked increase in copy number 5 when compared with normotensives. All the subjects in this study showed low frequency distribution pattern for copy numbers 2, 6 and 7. This discovery emphasizes the importance of frequency patterns in determining CNV status of prehypertensive and mild hypertensive subjects. Optimization method in this study showed that the detection of CNV esv27061 is possible in our sample population