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Characterisation at the bonding zone between fly ash based Geopolymer Repair Materials (GRM) and Ordinary Portland Cement Concrete (OPCC)

2020 , Warid Wazien Ahmad Zailani , Mohd. Mustafa Al Bakri Abdullah , Mohd Fadzil Arshad , Rafiza Abd Razak , Muhammad Faheem Mohd. Tahir , Remy Rozainy Mohd Arif Zainol , Marcin Nabialek , Andrei Victor Sandu , Jerzy J. Wysłocki , Katarzyna Błoch

In recent years, research and development of geopolymers has gained significant interest in the fields of repairs and restoration. This paper investigates the application of a geopolymer as a repair material by implementation of high-calcium fly ash (FA) as a main precursor, activated by a sodium hydroxide and sodium silicate solution. Three methods of concrete substrate surface preparation were cast and patched: as-cast against ordinary Portland cement concrete (OPCC), with drilled holes, wire-brushed, and left as-cast against the OPCC grade 30. This study indicated that FA-based geopolymer repair materials (GRMs) possessed very high bonding strength at early stages and that the behavior was not affected significantly by high surface treatment roughness. In addition, the investigations using scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) spectroscopy have revealed that the geopolymer repair material became chemically bonded to the OPC concrete substrate, due to the formation of a C–A–S–H gel. Fundamentally, the geopolymer network is composed of tetrahedral anions (SiO4)4− and (AlO4)5− sharing the oxygen, which requires positive ions such as Na+, K+, Li+, Ca2+, Na+, Ba2+, NH4+, and H3O+. The availability of calcium hydroxide (Ca(OH)2) at the surface of the OPCC substrate, which was rich in calcium ions (Ca2+), reacted with the geopolymer; this compensated the electron vacancies of the framework cavities at the bonding zone between the GRM and the OPCC substrate.

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Optimizing of the cementitious composite matrix by addition of steel wool fibers (Chopped) based on physical and mechanical analysis

2021 , Akrm A Rmdan Amer , Mohd. Mustafa Al Bakri Abdullah , Liew Yun Ming , Jerzy J. Wysłocki , Wojciech Sochacki , Ikmal Hakem A Aziz , Muhammad Faheem Mohd. Tahir , Sebastian Garus , Joanna Gondro , Hetham A. R. Amer

The demand for durable, resistant, and high-strength structural material has led to the use of fibers as reinforcing elements. This paper presents an investigation into the inclusion of chopped steel wool fibers (CSWFs) in cement to form a high-flexural strength cementitious composite matrix (CCM). CSWFs were used as the primary reinforcement in CCM at increments of 0.5 wt%, from 0.5–6 wt%, with ratios of cement to sand of 1:1.5 and water to cement of 0.45. The inclusion of CSWFs resulted in an excellent optimization of the physicomechanical properties of the CCM, such as its density (2.302 g/cm3), compressive strength (61.452 MPa), and maximum flexural strength (10.64 MPa), all of which exceeded the performances of other reinforcement elements reported in the literature.