No abstract

No abstract

Four-point bending fatigue experimental work was conducted on specimens that were cut from slabs to examine the fatigue life of concrete pavements. The variables considered were the volume fraction of fibres added in plain or steel bar reinforced concrete. It was found that the strain-based approach to fatigue testing on scaled-down concrete pavements is suitable to investigate the fatigue performance of scaled-down thin rigid pavements. The addition of fibres at 0.5% volume fraction in concrete improved the fatigue life by at least 135% and reduced the energy dissipated per cycle by 74%. As the volume fraction of fibres increased, it was found that the fatigue life of rigid pavements improved; total energy dissipation also increased but the energy dissipated per cycle was reduced in concrete pavements. This is due to the crack bridging effect of fibres that reduces the microcracking of concrete. The energy dissipation per cycle from fracture energy does not remain constant for rigid pavements under fatigue testing as it was found that the type of reinforcements influences the quantity of energy dissipated. Finally, hybrid reinforced pavements with both steel bars and fibres yielded the best performance in fatigue, with the highest number of fatigue cycles and lowest energy dissipated per cycle.

Nine alkali-activated concrete beams were produced and tested under pure torsional load to failure. The alkali-activated concrete beams were produced with following variables: (i) fibres only, (ii) conventionally reinforced or (iii) a hybrid of both fibres and conventional steel reinforcement. The fibres only beams were found to have approximately 20% higher cracking torque than conventionally reinforced beams. However, fibres only beams were observed to have lower post crack ductility and inconsistent post crack behaviour, in comparison to conventionally reinforced alkali-activated concrete (AAC) beams. On the other hand, the hybrid reinforcements in AAC beams were found to demonstrate more ductile post crack behaviour consistently of the beams tested. Hybrid reinforcement was also shown to have 20% and 25% improvement in cracking and ultimate torque compared to conventionally reinforced, which suggests that it is suitable for industrial applications to improve structure capacity. The ultimate torque results of the beams were compared to an analytical model that considered the contribution of fibres. It was found that the ultimate torque of the hybrid reinforced beam has good correlation with the model but overestimated conventionally reinforced beams.

Sulphate attack is one of the key issues in geotechnical engineering. This study aims to investigate the efficacy of the seashell to reduce negative impacts of the magnesium sulphate concentration on the cement-stabilized clay mixtures by performing a series of unconfined compressive strength (UCS) tests. Three percent of cement (3, 5 and 7%) was utilized in this study. In addition, the benchmark and exposed specimens were cured for 7, 14, and 28 days before testing and exposure, respectively. A series of the compaction tests were conducted and the optimum moisture content (OMC) and maximum dry density (MDD) values were achieved. In the next stage, the UCS tests were performed on the specimens containing 10, 20, or 30% seashell contents and the specimens were exposed to sulphate concentration. Scanning electron microscope morphology had indicated that seashells are a suitable replacement for cement. Qualitative X-ray diffraction had shown that the presence of magnesium sulphate reduces the formation of calcium silicate hydrate, which causes durability issues in cement-stabilized soils. The results indicated that seashell is effective to improve the sulphate resistance of cement-stabilized soil.