Corrosion Evaluation on Fly Ash and Silica Fume Concrete Using NDT Methods

Abstract

ABSTRACT:  Corrosion of reinforced concrete is a major problem that can weaken a structure and even cause it to fail. On a macro level, this affects the safety and durability of important structures like bridges, buildings, and roads, leading to high repair costs and safety risks. On a micro level, corrosion begins with chemical reactions between steel and concrete, resulting in cracks, surface damage, and weakening of the concrete, which in turn reduces its strength and performance. This study examines the effects of using industrial waste, namely fly ash (FA) and silica fume (SF), as alternative solutions to improve reinforced concrete's corrosion resistance and mechanical performance. Concrete is made with FA substitutions of 10%, 20%, and 30% of the cement weight, and SF of 5%, 10%, and 15%, respectively. Compressive strength and flexural tests were performed to evaluate the mechanical properties, and corrosion analysis was conducted through non-destructive testing (NDT) to assess the corrosion resistance. Corrosion testing was carried out with accelerated corrosion for 48, 96, and 168 hours. Microstructural analysis using SEM was also performed to observe the effect of corrosion on the concrete. The results showed that the compressive strength of normal concrete and concrete with FA and SF decreased from 37 MPa to 25-35 MPa, respectively. The flexural strength of normal concrete and concrete with FA and SF decreased from 13 to 2 MPa due to increased corrosion rates, respectively. However, the normal concrete's resistivity value and impact echo frequency were lower than those of FA- and SF-mixed concrete. Significant resistivity values and frequency reductions were observed after corrosion, with V3 specimens (30% FA and 15% SF) showing the best corrosion durability performance.

ABSTRAK: Hakisan konkrit bertetulang merupakan masalah utama yang boleh melemahkan struktur dan bahkan menyebabkan kegagalan keseluruhan. Pada peringkat makro, ia menjejaskan keselamatan dan ketahanan struktur penting seperti jambatan, bangunan, dan jalan raya, sekali gus membawa kepada kos pembaikan yang tinggi serta risiko keselamatan. Pada peringkat mikro, hakisan bermula dengan tindak balas kimia antara keluli dan konkrit, menyebabkan rekahan, kerosakan permukaan, dan kelemahan pada konkrit, yang akhirnya mengurangkan kekuatan dan prestasinya. Kajian ini meneliti kesan penggunaan sisa industri iaitu abu terbang (FA) dan wap silika (SF) sebagai penyelesaian alternatif untuk meningkatkan rintangan hakisan dan prestasi mekanikal konkrit bertetulang. Konkrit dihasilkan dengan penggantian FA sebanyak 10%, 20%, dan 30% daripada berat simen serta SF sebanyak 5%, 10%, dan 15%. Ujian kekuatan mampatan dan lenturan dijalankan bagi menilai sifat mekanikal, manakala analisis hakisan melalui kaedah tanpa musnah (NDT) digunakan untuk menilai rintangan hakisan. Ujian hakisan dijalankan menggunakan kaedah hakisan dipercepat selama 48, 96, dan 168 jam. Analisis mikrostruktur menggunakan SEM turut dilakukan bagi memerhati kesan hakisan terhadap konkrit. Hasil kajian menunjukkan bahawa kekuatan mampatan konkrit normal serta konkrit dengan FA dan SF menurun daripada 37 MPa kepada 25–35 MPa. Kekuatan lenturan konkrit normal serta konkrit dengan FA dan SF juga menurun daripada 13 MPa kepada 2 MPa apabila kadar hakisan meningkat. Namun begitu, nilai rintangan dan frekuensi gema hentakan bagi konkrit normal adalah lebih rendah berbanding konkrit yang dicampur FA dan SF. Nilai rintangan serta pengurangan frekuensi yang ketara diperhatikan selepas hakisan, dengan spesimen V3 (30% FA dan 15% SF) menunjukkan prestasi ketahanan hakisan yang terbaik.