No abstract

The eruption of Sidoarjo mud volcano that has been taken place since 2006 had caused significant damage to the local social environment, and until now there is no immediate solution that can be offered. Utilization of the Sidoarjo mud as construction material recently has gained some advancement by calcination of the mud, that make the previously inert material to become more reactive and to be more viable for its use as cement replacement or geopolymer precursor. This paper reports an on-going study to utilize the Sidoarjo mud as precursor of geopolymer by investigating the influence of particle size on the reactivity of the calcined Sidoarjo mud. Furthermore, durability properties of Sidoarjo mud-based geopolymer was also studied. The results show that making finer the mud particles by milling in longer period, using a rod-mill drum for 8 hours, can increase the reactivity of the mud. Compressive strength of geopolymer mortar can increase up to 155% when compared to the ones based on milling time of only 2 hours. Durability properties of sulphate acid resistance and chloride penetration are comparable to fly ash-based geopolymer, while the shrinkage measurement showing higher value.

Circulating fluidized bed combustion (CFBC) is a newer type of burner that employ a circulating process to burn fuel effectively. CFBC burning process is gaining more popularity due to its compact size, high efficiency and lower burning temperature compared to the pulverized coal combustion (PCC) burner. The CFBC burner produces fly ash with different physical properties compared to the PCC burner, i.e. the fly ash is not rounded, and required higher water content for comparable workability. The CFBC fly ash also has a high sulfur content that is detrimental for hardened concrete. Due to its drawbacks, the CFBC hardly used as cementitious material and geopolymer precursor. This study focuses on comparing variations in the concentration of NaOH solution and variations in the ratio of alkaline activators to the setting time and compressive strength of geopolymer mortars on a new class of CFBC fly ash, which have low sulfur content. The concentrations of NaOH solution were 6M, 8M, 10M, and 12M, while the alkaline activator ratios used were 3.0, 2.5, 2.0, 1.0, and 0.5. It was concluded that the low sulfur CFBC fly ash has a potential to be utilized as geopolymer precursor, however, with a shortcoming in its high water demand. The CFBC fly ash used in this study resulted in a geopolymer matrix with good compressive strength and stability. The water demand varies with the fly ash sampling time shows the challenges in the utilization of the fly ash. The highest mortar’s compressive strength, 33.4 MPa at 90 days was achieved at NaOH concentration of 8M and ratio of sodium silicate solution to sodium hydroxide solution of 2.5 with excellent stability.

Penelitian ini dilakukan untuk mengetahui sejauh mana responden memahami keberadaan kamera ETLE dan batas kecepatan di ruas jalan, serta faktor-faktor yang dapat memengaruhi pelanggaran batas kecepatan. Faktor-faktor yang digunakan dalam penelitian ini berbentuk 17 variabel. Penyebaran kuesioner dilakukan secara online dan didapatkan 117 responden. Sampel responden yang dibutuhkan untuk melakukan penelitian ini ditentukan dari hasil perhitungan uji slovin. Hasil dari jawaban responden diolah menggunakan SPSS, dan dilakukan beberapa uji seperti, uji validitas dan reliabilitas, dan dilakukan Categorical Principal Components Analysis. Hasil dari penelitian ini menunjukan jika jumlah responden yang mengetahui dan memahami tentang ETLE, jenis pelanggaran ETLE, dan batas kecepatan jalan perkotaan di Surabaya masih setara dengan jumlah responden yang ragu-ragu dan tidak mengetahui maupun memahami hal-hal tersebut.  Dan dari indikator, ke-17 variabel tersebut telah tereduksi dan terbagi menjadi 2 dimensi.