This study examined HDPE (high-density polyethylene) plastic waste as an added material for concrete mixtures. The selection of HDPE was based on its increased strength, hardness, and resistance to high temperatures compared with other plastics. It focused on how HDPE plastic can be used as an additive in concrete to increase its tensile strength and compressive strength. 156 specimens were used to identify the effect of adding different percentages and sizes of HDPE lamellar particles to lower, medium, and higher strength concrete for non-structural applications. HDPE 0.5 mm thick lamellar particles with sizes of 10 × 10 mm, 5 × 20 mm, and 2.5 × 40 mm were added at 2.5%, 5%, 10%, and 20% by weight of cement. The results showed that the medium concrete class (with compressive strength equal to 10 MPa) had the best response to the addition of HDPE. The 5% HDPE addition represented the optimal mix for all concrete types, while the 5 × 20 mm size was best.

The role of the circular economy has attracted increased attention amongst practitioners and policymakers in recent years. It has been broadly developed and applied at different levels (micro, meso and macro) in developed countries. However, to date, the possibility of a circular economy in Indonesia has not been widely explored or discussed by city actors. This gap in research represents an opportunity to investigate options that may foster the adoption of circular economy principles and practices. Which aspects of the circular economy should be of primary concern, considering Indonesia’s current situation? In response to this question, this paper offers a systemic process of lessons learnt as developed from the literature, identifying certain key aspects that could benefit Indonesia. This study mapped important factors and key indicators that have been claimed to have beneficial effects in the application of circular economy principles in cities. The authors developed a protocol to systematize the literature review process to illustrate gaps and to provide and recommend indicators for circular cities. These are equally applicable to the local situation in North Kalimantan, which we selected as a showcase medium-sized city. Empirical data was collected by interviewing different stakeholders to enrich the theoretical set of circular economy indicators. This case study offered the opportunity to gain a more realistic understanding of what circular cities might look like in the Indonesian situation. The findings allowed us to explore and describe the current circular economy city-level discussion. They also provide insight and information for decision-makers and city actors on how to collaborate to develop a framework to advance circular city initiatives.

Distribusi air di Kota Samarinda masih belum optimal dikarenakan factor tekanan air di dalam pipa yang rendah pada waktu tertentu dan kehilangan air fisik karena kebocoran. Artikel ini memuat analisis jaringan perpipaan distribusi air bersih di Kelurahan Harapan Baru, Kota Samarinda menggunakan perangkat lunak EPANET 2.0. Hasil simulasi dibandingkan dengan hasil pengukuran tekanan air di lapangan pada kran pelanggan menggunakan manometer. Dari hasil penelitian, diketahui terdapat sebanyak 7 junction yang nilai tekanan airnya di bawah batas minimum kriteria pipa distribusi dari Peraturan Menteri Pekerjaan Umum No.18/PRT/M/2007 sebesar 0,5 atm, serta sebanyak 11 pipa yang nilai kecepatan aliran airnya di bawah batas minimum kriteria yang sama sebesar 0,3 m/s. Rekomendasi perbaikan jaringan perpipaan distribusi air bersih berupa tekanan minimum sebesar 0,5 bar pada pelanggan dan kontinuitas, yakni perubahan pengaturan tekanan pada valve existing, dan penambahan pompa booster pada beberapa titik. Terdapat perbedaan nilai tekanan air yang cukup signifikan antara hasil simulasi model EPANET dengan pengukuran langsung pada kran pelanggan.

Sopialena, Suyadi, Sahil M, Nurdiana J. 2018. The diversity of endophytic fungi associated with Piper nigrum in the tropical areas: a recent study from Kutai Kartanegara, Indonesia. Biodiversitas 19: 2028-2034. This research aimed to identify the diversity of endophytes fungal in the root and leaves of Piper nigrum Linn. This research contributes to the knowledge gaps by focusing the discussion on the Endophytic fungal communities of Piper nigrum Linn in tropical areas at Kutai Kartanegara, Indonesia. Two certain plots within the study area were selected based on the different characteristics of topographic contours. The locations, named Plot A was characterized by ramps area, while plot B was sloping or hilly area. A total of 55 isolates were obtained from the root and the leaves of healthy plants, 35 isolates were from Plot A and the other 20 isolates were from plot B. Based on Shannon index (H’), both of the plots corresponded to the same genus; namely Aspergillus sp., Fusarium sp., Nigrospora sp., and Trichoderma sp, and categorized as medium diversity. In this regards, this study confirms that the genus Aspergillus sp. and Fusarium sp. represent a large part of the diversity of Endophytes fungi. As the study indicates that plot B has higher diversity of endophytic fungi compared to plot A, it shows that the hilly area turns out to be a better location for Piper nigrum Linn.

HDPE (high-density polyethene) plastic waste is stronger, harder, and more resistant to high temperatures than other plastics. Using it as an additive in a concrete mixture is one solution to reduce this type of waste. We examined how HDPE-type plastics can be used as an additive material in the manufacture of concrete to improve its hardness, tensile strength and compressive strength. Using 156 samples, we aimed to identify the effect of HDPE plastic fibres on concrete of three qualities; B0, f'c10 MPa (low quality), and f'c25 MPa (medium and high quality). We added four compositions (2.5%, 5%, 10% and 20% by weight of cement) of HDPE plastic fibre to each quality of cement, with HDPE plastic fibre sizes of 1 x 1 cm, 0.5 x 2 cm or 0.25 x 4 cm. We found that the addition of 5% HDPE plastic fibre with a 0.5 x 2 cm cross-sectional shape to the f'c10 MPa concrete gives the best result, with increased tensile and compressive strength of the concrete.