Umum mengetahui bahawa sifat mekanik struktur konkrit merosot selepas didedahkan kepada api. Kerja- kerja pembaikkan dan pengukuhan adalah penting bagi meningkatkan ketahanan struktur ini. Oleh yang demikinan, Konkrit Gentian Bertetulang Prestasi Tinggi (UHPFRC) telah digunakan sebagai bahan pembaikkan kerana ianya mempunyai kekuatan yang sesuai. Kajian ini, menyiasat ciri-ciri ikatan muka antara konkrit biasa (NC) yang tededah kepada api manakala UHPFRC sebagai bahan pembaikkan. Sebagai permulaan, konkrit biasa akan didedahkan kepada suhu 600 °C suhu selama 2 jam. Kemudian, substratum tersebut akan tertakluk kepada syarat-syarat kelembapan permukaan substrat yang berbeza yang sebelum ikatan UHPFRC membentuk komposit pembaikkan. Ketiga-tiga jenis keadaan kelembapan tersebut adalah Udara Kering (AD), Permukaan tepu kering (SSD) dan basah (W). Konkrit berkeadaan udara kering dicapai dengan meletakkan substrat yang rosak di dalam makmal . Permukaan tepu kering pula dicapai dengan merendamkan spesimen konkrit lama dalam air selama satu hari, dikeluarkan dari air, dan permukaannya dilap sebelum UHPFRC dituang. Keadaan basah disediakan dengan meletakkan konkrit lama di dalam air selama tiga hari, dikeluarkan sebelum konkrit baru dituang tanpa mengelap air permukaan. Sebahagian ujian yang dijalankan bagi menentukan kekuatan antara muka adalah , ujian ricih condong dan ujian silinder belah. Ujian ricih condong dilakukan untuk menilai kekuatan ikatan ricih, manakala ujian tegangan silinder dijalankan untuk mengukur kekuatan ikatan ketegangan tidak langsung. Secara umumnya, keputusan kajian menunjukkan bahawa, keadaan kelembapan permukaan memberi kesan ketara kepada kekuatan ikatan antara NC dan UHPFRC. Substratum dengan keadaan permukaan tepu kering mempamerkan kekuatan ikatan yang tinggi. Oleh itu, UHPFRC berpotensi besar untuk digunakan sebagai bahan dalam kerja-kerja pembaikkan dan pemulihan semula struktur konkrit.
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It is well known that the mechanical properties of concrete structure deteriorate after exposure to fire. Repair and strengthening in order to improve the performance of the affected structure has become critical. Ultra High Performance Fibre Reinforced Concrete (UHPFRC) has been used as repair material due to its superior properties. However, the bonding characteristics are still not well known. The aim of this study is to investigate the interfacial bond characteristics between fire damaged normal concrete substrate and UHPFRC as a repair material. Firstly, normal concrete were exposed to 600°C temperature for 2 hours. Then, with as cast surface, the substrate was then subjected to different substrate surface moisture conditions prior to bonding of UHPFRC to form repair composites. Three types of moisture condition prepared were Air Dry (AD), Saturated Surface Dry (SSD) and Wet (W). Air dry condition of old concrete was achieved by placing the fire damaged substrate in a laboratory. The SSD condition was achieved by immersing the old concrete specimen in water for one day, removing the specimen from the water, and wiping out the moisture at the surface before placing UHPFRC. Wet condition was achieved by placing the old concrete in water for three days, removing the specimen from the water immediately before casting new concrete without wiping the surface water. In order to determine the interfacial bond strength of the composite, slant shear test and splitting cylinder test were carried out. Slant shear test was performed to evaluate the bond strength in shear, while splitting cylinder test was conducted to quantify the bond strength in indirect tension. Generally, the result indicates that, surface moisture conditions give significant impact on the bond strength. The substrate with Saturated Surface Dry condition exhibits the highest bond strength. This study shows that, the UHPFRC performed well as a choice of material for repair and rehabilitation of fire damaged concrete structures.
Evaluation of bond strength between fire damaged normal concrete substrate and ultra high performance fibre reinforced concrete as a repair material / Nur Khaida Baharuddin