The dynamics of the development of the Mamminasata Metropolitan new city area has an impact on environmental quality degradation. The increase in development activities causes land use conversion and contributes to an increase in energy demand. This study aims to analyze: the allocation of work space utilization as a determinant of environmental quality degradation in the Mamminasata new city area, the effect of controlling space utilization, renewable energy utilization, and transportation management on improving the environmental quality of the Mamminasata new city area; and formulate a model for the use of renewable energy and the sustainable development of the Mamminasata Metropolitan new city area. This study uses an explanatory suqiental approach. Data were obtained through observation, surveys, in-depth interviews, and documentation. The results of the study indicate that the allocation of land for the development needs of socio-economic activities in the new city area has an impact on increasing the burden of pollution on soil, water, and air as well as the complexity of the transportation system in the direction of decreasing environmental quality. Control of space utilization, renewable energy utilization, and transportation management simultaneously have an effect on improving the environmental quality of the Mamminasata new city area with a coefficient of determination of 94.84%. This study recommends the use of renewable energy in supporting socio-economic activities towards the sustainability of the Mamminasata Metropolitan new city area development.

This study aims to analyze the behaviour of hollow core placing in the tension zone of reinforced concrete beams. The hollow was filled with plastic bottle waste. The partial replacement of concrete below the neutral axis by using a different layer of plastic bottles was discussed. The cross-section is filled with plastic bottles, in order to get a lighter structure, reduce the volume of concrete/cement and the reduction of environmental pollution. This study used RC beams with concrete strength of 25 MPa and dimensions of 150 x 350 mm, with 3D16 mm longitudinal reinforcement with the yielding strength of 475 MPa. Four type specimens are tested, consisting of control beam and hollow beams type with the height variation of 600 mm (BR1C), and 1800 mm (BR3C). The length of the hollow for each type was 1760 mm (8 bottles) The results indicated that the flexural capacity of the reinforced concrete beam with hollow-core using plastic bottles was almost same with the normal beam. Moreover, the effect of the height of the hollow core was also insignificant on the flexural capacity, where the beam with higher hollow-core showed similar flexural capacity with the beam having a lower hollow. However, the stiffness of reinforced concrete beam was affected by the height of the hollow core, inherent the higher the hollow core, the smaller the stiffness of the beams.

Concrete is the most widely used construction material in the world, including in areas around the sea. Several previous studies have shown that sea water can reduce the strength of concrete. Therefore, research is needed to overcome this. This study aims to obtain the compressive strength of concrete treated in seawater by substituting portland cement with white cement, which is 10%, 20% and 30%. The results showed that the substitution of White Cement could increase the compressive strength of the concrete, both cured with fresh water and cured with seawater. The decrease in compressive strength of concrete that does not contain white cement is 11.28% greater than that of concrete containing white cement which is only around 4% on average.

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