Pengaruh Substitusi Cangkang Kerang Dengan Agregat Halus Terhadap Kuat Tekan Beton

Penelitian ini dilakukan untuk memanfaatkan limbah cangkang kerang sekaligus menyelamatkan lingkungan pantai dari pencemaran sekaligus mencari inovasi baru pada tehnologi beton, dan ingin mengetahui bagaimana pengaruhnya sebagai bahan substitusi agregat halus pada campuran beton.Substitusi cangkang kerang halus dengan variasi 5% , 10% dan 15 % dari volume agregat halus, dengan FAS 0,5 dan sampel berbentuk kubus 15 x 15 x 15 cm masing-masing 5 buahsehingga berjumlah 20 buah sampel. Sampel-sampel tersebut akan dilakukan pengetesan setelah berumur 28 hari. Pengukuran slump pada masing-masing campuran menunjukkan nilai slump yang bervariari :beton normal = 7,5 cm, beton substitusi 5 % = 8,0 cm, beton substitusi 10 % = 7,5 cm, danbeton substitusi 15 % = 8,5 cm. Hasil pengetesan beton diperoleh kuat tekan sebesar: 20,6 MPa , 26,3 MPa , 23,4 MPa , dan 19,7 MPa. Dari hasil di atas dapat disimpulkan bahwa substitusi cangkang kerang optimum 5 % meningkatkan kuat tekan maksimum(27,7 %) dari beton normal, sedangkan substitusi cangkang kerang 10% terhadap agregat halus meningkatkan kuat tekan beton 23,3 % dari neton normal, maka substitusi serbuk cangkang kerang 5 % dan 10 % dapat memberikan dampak positif terhadap peningkatan kuat tekan beton, sedangkan substitusi 15% mengalami penurunan kuat tekan sebesar 4,4 % dari beton normal.Kata Kunci: Cangkang Kerang, Agregat dan Kuat tekan BetonPENDAHULUANBetonmerupakan bahan konstruksi yang banyak digunakan karena beton banyak memiliki kelebihan jika dibandingkan dengan bahan lain, harganya yang relatif murah, mudah dikerjakan/dibentuk, bahan baku penyusun mudah didapat, tahan lama, tahan terhadap api, tidak mengalami pembusukan. Secara teknik beton selalu dituntut untuk memenuhi tantangan akan kebutuhan bahan konstruksi, dimana beton yang dihasilkan biasanya diharapkan mempunyai kwalitas dan daya tahan/kekuatan yang tinggi dengan mengabaikan nilai ekonomis dan lingkungannya. Untuk mendapatkan beton yang ekonomis sekaligus menjaga lingkungan tetap lestari, penulis mencoba membuat beton dengan memanfaatkan bahan hasil limbah yang adadi sepanjang pantai yang didiami oleh para nelayan (kampong nelayan) sehingga dapat menjaga ekosistem pantai yang bersih, aman, dan lestari.Bahan-bahan limbah di sekitar ling-kungan mungkin dapat dimanfaatkan sebagai bahan substitusi dalam campuran beton.Sebagian besar Wilayah Indonesia adalah daerah perairan laut oleh karena itu perlu mencari inovasi baru untuk campuran beton dengan menggunakan hasil laut yang tidak dimanfaatkan lagi berupa limbah. Dalam hal ini dapat memberikan alternatif untuk memanfaatkan limbah dari hasil laut yang dibuang masyarakat pesisir

Hubungan Antara Tegangan-regangan (Stress - Strain Relationships) Pada Beton

Thereinforced concrete structures has been used more of structureswhere the compressive force was endured by concrete coused compressive stress and steel has tensile strength so it be coused tensile stress be holded by steel.The compressive strength concrete is usually obtained from cylinders with a hight to diameter ratio of 2. The cylinders are loaded longitudinally at a slow strain rate to reach maximum stress in 2 0r 3 minutes. The stress-strain curves obtained from concrete cylinders loaded in uniaxial compression in a test conducted over several minutes. The stress-strain relationships can be showed at stress-strain curve , where this curve can be obtained from cylinders test with uniaxial compressive test, biaxial compressive test and triaxial compressive test, with high intensity repeated axial compressive cycle loading. The axial stress-strain curve obtained by Richart at all for compression test conducted on concrete cylinders. The cyliders confined laterally by fluid pressure. For each curve the fluid pressure held constant while the axial compressive stress was increased to failure and the axial strain measured.The tensile strength of concrete generally less than 20 % of compressive strength, can be obtained direcly from tension specimens. Tensile strength of concrete may be measured indirectly in term of the computed stress at wich a cylinder placed horizontally in a testing machine and loading along the loaded diameter will split, and can be also be evaluated by means of bending test conducted on plane concrete beams.The tension stress-strain relationships can be obtained from those testings.Key Words: Stress - Strain Relationships PENDAHULUAN Beton merupakan bahan konstruksi yang banyak digunakan, baik untuk bangunan ringan maupun bangunan berat, karena beton mempunyai kuat tekan yang besar sedangkan gaya tarik sangat kecil. Jika dilihat dari komposisi beton terdiri dari campuran agregat, semen dan air atau bahan tambahan lainnya, bahan-bahan tersebut menjadi padat dan keras karena semen dan air mengalami proses kimia mengikat agregat sampai menjadi sangat keras. Dalam struktur bangunan, beton dipercayakan untuk menahan gaya tekan sedangkan gaya tarik ditahan oleh tulangan baja, maka beton yang diberi tulangan disebut beton bertulang (reinforced concrete). Beton yang mengalami gaya tekan tentunya menimbulkan tegangan (stress)di dalam beton. Tegangan ini menyebabkan bahan beton mengalami regangan (strain), sehingga perlu kiranya untuk mengetahui hubungan antara tegangan dan regangan pada beton.Sifat Tegangan Satu arah (Uniaxial Stress Bihavior)Dalam praktek beton jarang menunjukkan tegangannya dalam satu arah (uniaxial stress), untuk ini banyak dari konstruksi beton structural, tegangan yang yang terjadi bersamaan dengan arah gaya yang diberikan, dengan kata lain suatu uniaxial stress dapat terjadi dalam segala arah

Buletin Pa'biritta LPMP Sulawesi Selatan nomor 19 tahun X 2017

Buletin Pa'birita nomor 19 ini terbit setelah beberapa lama berhenti selama beberapa waktu. Penerbitanya merupakan permintaan dari widyaiswara, guru dan tenaga kependidikan yang ingin karyanya di publikasikan. Buletin ini menyajikan tulisan yang membahasa penjaminan mutu pendidikan, program induksi, efek samping haemodialisis, teknologi pembelajaran, Praktikum pembelajaran IPA, Fungsi dan ragam bahasa, Penyelesaian perkalian, dan pappaseng toriolota

The impact of surgical delay on resectability of colorectal cancer: An international prospective cohort study

AIM: The SARS-CoV-2 pandemic has provided a unique opportunity to explore the impact of surgical delays on cancer resectability. This study aimed to compare resectability for colorectal cancer patients undergoing delayed versus non-delayed surgery. METHODS: This was an international prospective cohort study of consecutive colorectal cancer patients with a decision for curative surgery (January-April 2020). Surgical delay was defined as an operation taking place more than 4 weeks after treatment decision, in a patient who did not receive neoadjuvant therapy. A subgroup analysis explored the effects of delay in elective patients only. The impact of longer delays was explored in a sensitivity analysis. The primary outcome was complete resection, defined as curative resection with an R0 margin. RESULTS: Overall, 5453 patients from 304 hospitals in 47 countries were included, of whom 6.6% (358/5453) did not receive their planned operation. Of the 4304 operated patients without neoadjuvant therapy, 40.5% (1744/4304) were delayed beyond 4 weeks. Delayed patients were more likely to be older, men, more comorbid, have higher body mass index and have rectal cancer and early stage disease. Delayed patients had higher unadjusted rates of complete resection (93.7% vs. 91.9%, P = 0.032) and lower rates of emergency surgery (4.5% vs. 22.5%, P < 0.001). After adjustment, delay was not associated with a lower rate of complete resection (OR 1.18, 95% CI 0.90-1.55, P = 0.224), which was consistent in elective patients only (OR 0.94, 95% CI 0.69-1.27, P = 0.672). Longer delays were not associated with poorer outcomes. CONCLUSION: One in 15 colorectal cancer patients did not receive their planned operation during the first wave of COVID-19. Surgical delay did not appear to compromise resectability, raising the hypothesis that any reduction in long-term survival attributable to delays is likely to be due to micro-metastatic disease

Simple method for the growth of 4H silicon carbide on silicon substrate

In this study we report thermal evaporation technique as a simple method for the growth of 4H silicon carbide on p-type silicon substrate. A mixture of Si and C60 powder of high purity (99.99%) was evaporated from molybdenum boat. The as grown film was characterized by XRD, FTIR, UV-Vis Spectrophotometer and Hall Measurements. The XRD pattern displayed four peaks at 2Θ angles 28.550, 32.700, 36.100 and 58.900 related to Si (1 1 1), 4H-SiC (1 0 0), 4H-SiC (1 1 1) and 4H-SiC (2 2 2), respectively. FTIR, UV-Vis spectrophotometer and electrical properties further strengthened the 4H-SiC growth

The impact of surgical delay on resectability of colorectal cancer: An international prospective cohort study

AimThe SARS-CoV-2 pandemic has provided a unique opportunity to explore the impact of surgical delays on cancer resectability. This study aimed to compare resectability for colorectal cancer patients undergoing delayed versus non-delayed surgery.MethodsThis was an international prospective cohort study of consecutive colorectal cancer patients with a decision for curative surgery (January-April 2020). Surgical delay was defined as an operation taking place more than 4 weeks after treatment decision, in a patient who did not receive neoadjuvant therapy. A subgroup analysis explored the effects of delay in elective patients only. The impact of longer delays was explored in a sensitivity analysis. The primary outcome was complete resection, defined as curative resection with an R0 margin.ResultsOverall, 5453 patients from 304 hospitals in 47 countries were included, of whom 6.6% (358/5453) did not receive their planned operation. Of the 4304 operated patients without neoadjuvant therapy, 40.5% (1744/4304) were delayed beyond 4 weeks. Delayed patients were more likely to be older, men, more comorbid, have higher body mass index and have rectal cancer and early stage disease. Delayed patients had higher unadjusted rates of complete resection (93.7% vs. 91.9%, P = 0.032) and lower rates of emergency surgery (4.5% vs. 22.5%, P ConclusionOne in 15 colorectal cancer patients did not receive their planned operation during the first wave of COVID-19. Surgical delay did not appear to compromise resectability, raising the hypothesis that any reduction in long-term survival attributable to delays is likely to be due to micro-metastatic disease

Global Incidence and Risk Factors Associated With Postoperative Urinary Retention Following Elective Inguinal Hernia Repair

Importance Postoperative urinary retention (POUR) is a well-recognized complication of inguinal hernia repair (IHR). A variable incidence of POUR has previously been reported in this context, and contradictory evidence surrounds potential risk factors.Objective To ascertain the incidence of, explore risk factors for, and determine the health service outcomes of POUR following elective IHR.Design, Setting, and Participants The Retention of Urine After Inguinal Hernia Elective Repair (RETAINER I) study, an international, prospective cohort study, recruited participants between March 1 and October 31, 2021. This study was conducted across 209 centers in 32 countries in a consecutive sample of adult patients undergoing elective IHR.Exposure Open or minimally invasive IHR by any surgical technique, under local, neuraxial regional, or general anesthesia.Main Outcomes and Measures The primary outcome was the incidence of POUR following elective IHR. Secondary outcomes were perioperative risk factors, management, clinical consequences, and health service outcomes of POUR. A preoperative International Prostate Symptom Score was measured in male patients.Results In total, 4151 patients (3882 male and 269 female; median [IQR] age, 56 [43-68] years) were studied. Inguinal hernia repair was commenced via an open surgical approach in 82.2% of patients (n = 3414) and minimally invasive surgery in 17.8% (n = 737). The primary form of anesthesia was general in 40.9% of patients (n = 1696), neuraxial regional in 45.8% (n = 1902), and local in 10.7% (n = 446). Postoperative urinary retention occurred in 5.8% of male patients (n = 224), 2.97% of female patients (n = 8), and 9.5% (119 of 1252) of male patients aged 65 years or older. Risk factors for POUR after adjusted analyses included increasing age, anticholinergic medication, history of urinary retention, constipation, out-of-hours surgery, involvement of urinary bladder within the hernia, temporary intraoperative urethral catheterization, and increasing operative duration. Postoperative urinary retention was the primary reason for 27.8% of unplanned day-case surgery admissions (n = 74) and 51.8% of 30-day readmissions (n = 72).Conclusions The findings of this cohort study suggest that 1 in 17 male patients, 1 in 11 male patients aged 65 years or older, and 1 in 34 female patients may develop POUR following IHR. These findings could inform preoperative patient counseling. In addition, awareness of modifiable risk factors may help to identify patients at increased risk of POUR who may benefit from perioperative risk mitigation strategies