Improving the engineering and fluid transport properties of ultra-high strength concrete utilizing ultrafine palm oil fuel ash

Ground treated ultrafine-POFA obtained from palm oil industry was heat-treated to remove excess carbon. The varied proportion (17%, 30% and 40%) of UPOFA was incorporated into the ultra-high strength concrete (UHSC) to study its effects on the UPOFA-UHSC (U x-UHSC) in comparison with OPC-UHSC (U 0-UHSC) engineering and transport properties. The U x-UHSC has an increasing workability tendency with a retarded setting times as compared to U 0-UHSC. Besides, U x-UHSC registered higher compressive strength than the U 0-UHSC. The 90-d strength of 156 MPa was achieved in U 17-UHSC which was 4.7%, 7.5% and 12.2% higher than the values obtained for U 30-UHSC, U 40-UHSC and U 0-UHSC, respectively. The U 40-UHSC exhibited the greatest improvement at 90 days in transport properties such as porosity, water absorption, initial surface absorption, rapid chloride permeability, gas permeability and water permeability while the highest strength was recorded with U 17-UHSC. Thus, the pozzolanic UPOFA is capable of improving the engineering and transport properties of UHSC

Microstructural analysis of fired clay masonry brick under aggressive environment

The microstructural changes in fired clay masonry brick, exposed to various aggressive environments were studied. Test samples were subjected to sodium sulphate, sodium chloride and a combination of chloride-sulphate. Beside, for the durability of specimens exposed to chloride and sulphate attack, 5, 10, and 15% solutions were used. Micrographs of the internal structure were taken at the age of 180 days. Energy-dispersive X-ray spectroscopy (EDX) analyses were performed on scanning electron microscope (SEM) images. SEM/EDX studies revealed that halite is the main deterioration product for the samples exposed to sodium chloride where thenardite formations were dominant products of deterioration in the case of sulphate attack. However, the combination of sodium sulphate-chloride produced a double compound in the specimens