Khalid Al-Shamsi

Recycling of waste spent catalyst in road construction and masonry blocks

Waste spent catalyst is generated in Oman as a result of the cracking process of petroleum oil in the Mina Al-Fahl and Sohar Refineries. The disposal of spent catalyst is of a major concern to oil refineries. Stabilized spent catalyst was evaluated for use in road construction as a whole replacement for crushed aggregates in the sub-base and base layers and as a partial replacement for Portland cement in masonry blocks manufacturing. Stabilization is necessary as the waste spent catalyst exists in a powder form and binders are needed to attain the necessary strength required to qualify its use in road construction. Raw spent catalyst was also blended with other virgin aggregates, as a sand or filler replacement, for use in road construction. Compaction, unconfined compressive strength and leaching tests were performed on the stabilized mixtures. For its use in masonry construction, blocks were tested for unconfined compressive strength at various curing periods. Results indicate that the spent catalyst has a promising potential for use in road construction and masonry blocks without causing any negative environmental impacts.

Characterisation of asphalt mixes containing MSW ash using the dynamic modulus |E*| test

Municipal solid waste incinerator ash was used to replace fine aggregate in hot-mix asphalt concrete with up to 40% by aggregate weight in the mix. Mix design was performed according to the Marshall mix design method to find the optimum asphalt content for different mixes. The dynamic modulus |E*| test was conducted on all mixes. |E*| master curves were developed. The curves were compared with Witczaks predictive model. Shift factor equations were developed and compared with the proposed equation in the Mechanistic–Empirical Pavement Design Guide (M-E PDG). |E*|/sin δ was used as an indicator for the rutting potential of the mixes. The results indicated good agreement between the developed master curves and the predictive model for the control mix (conventional mix), while significant difference was noticed for the ash mixes. The M-E PDG shift factors were found to lie in the middle of the developed factors. The increase in ash content in the asphalt layer is expected to result in higher rutting.

Evaluation of rutting potential for asphalt concrete mixes containing copper slag

Abstract Copper slag (CS) is a by-product of the copper extraction process, which can be used as coarse and/or fine aggregate in hot mix asphalt (HMA) pavements. This study used CS as a replacement of the fine aggregate with a percentage of up to 40% by total aggregate weight. The objective of this study was to evaluate the effect of CS on the rutting potential of the asphalt concrete mix using two methods. One method is based on the Dynamic modulus |E*| testing result. Actual pavement temperature data from a test section were used with the developed |E*| master curves. EverStressFE finite element program was used to perform a linear elastic load-deformation analysis for a pavement section and to determine the vertical resilient strain in a 40-mm HMA surface layer. The M-E PDG permanent deformation model was used with and Excel Visual Basic for Applications code to predict the accumulated rutting for different CS mixes for 10 million ESALs. The other method used the data from the flow number (FN) test. Based on the |E*| approach, the results indicated that adding 5% CS in the mix increased the predicted rutting from 0.59 to 0.98 mm at 10 million ESALs (increase by 68%). When 40% CS was used, rutting increased by more than 700% compared with the control mix. After analysing the FN results with the Francken model, the results indicated a decrease in FN as CS content is increased, indicating higher rutting potential. The decrease in FN ranged from 9% for 5% CS to 95% for 40% CS. The mixes containing up to 10% CS satisfied the minimum FN criteria for rutting. A calibration process for the M-E PDG distress prediction models that allows the use of waste and by-product materials such as CS should be considered in the future.

Binder Contribution to Cracking of a Lightly Trafficked Asphalt Pavement Made with Clear Binder

This paper reports the findings of a technical investigation on the role of clear asphalt binder in the development of extensive block cracking in a lightly trafficked colored pavement. Visual inspection of the pavement surface was carried out together with detailed laboratory investigation on the rheological characteristics of the binder. The results showed that the tested clear binder is extremely viscous and harder than any bitumen grade specified by ASTM standards. Furthermore, the clear binder has much lower ductility compared to the conventional asphalt bitumen. The clear binder is almost 11 times more viscous than the conventional bitumen at the tested temperatures.

Effect of spent catalyst as a fine aggregate on the properties of concrete

Spent catalyst is a by-product generated by oil refineries. There are two types of spent catalysts produced from oil refineries in Oman; Zeolite catalyst generated at Sohar Refinery and Equilibrium catalyst generated at Mina Al-Fahl Refinery. Spent catalyst can be used in concrete applications due to its pozzolanic nature. This study investigates the potential use of spent catalysts in concrete as partial substitute of sand at w/c ratios of 0.5 and 0.7. Concrete mixtures with different proportions of spent catalyst (up to 25% as sand repalcement) were prepared. Concrete mixtures were evaluated for compressive strength, setting time, water absorption, and corrosion resistance. The results showed that using 25% of the Sohar refinery’s spent catalyst as sand replacement gave 73% increase in the cubes compressive strength at w/c ratio of 0.7. However, using spent catalyst from Mina Al-Fahl Refinery as sand replacement decreases the compressive strength gradually with the increase of spent catalyst percentage. The results also indicated that the elapsed time decreased as the quantity of spent catalyst from both refineries increases. Negligible increase in the total water absorption was observed in concrete when both spent catalysts were used. Concrete specimens made with spent catalyst from Sohar Refinery showed good corrosion resistance than the control mixture whereas spent catalyst from Mina AlFahl Refinery accelerated the corrosion process.