Geopolymer is an inorganic polymer from activation of source materials that rich of silica and alumina with alkaline activator. Previous studies reveal that the geopolymer has engineering properties and durability, which is equivalent or higher than the Ordinary Portland Cement (OPC) concrete. This paper presents properties of geopolymer concrete prepared with local Palm Oil Fuel Ash (POFA) and Fly Ash (FA) from agro-industrial waste in Riau Province, Indonesia. The POFA and FA were activated by a combination of sodium hydroxide and sodium silicate. The specimens were cured at room temperature for 24 hours before steam cured for another 24 hours at 60OC. Hardened properties namely compressive strength, tensile strength, flexural strength and modulus of elasticity, and water penetration of both POFA and FA geopolymer concrete were determined at 7, 14 and 28 days. Results showed that local POFA and FA as geopolymer source materials could produce mix with strength 19-22.5 MPa at 28 days. The compressive strength, tensile strength, flexural strength and modulus of elasticity of both geopolymer tended to increase slightly with time. In general, the results suggest that the local POFA and FA are potential as source material to produce geopolymer concrete.

This research investigates the behaviour of non-engineered reinforced concrete (RC) beams strengthened with embedded steel bars. Two RC beams, namely control beam (Beam-A) and strengthened beam (Beam-B) were fabricated and tested under shear loading. Beam-B was strengthened with four 12 mm steel bars embedded in the core of the concrete beam. The results showed that Beam-A experienced shear failure while Beam-B failed in flexural tension where most cracks developed in the flexural span. The embedded steel bars were proven to shift failure mode from shear failure on Beam-A to flexural one on Beam-B. Furthermore, the shear capacity of the strengthened beam was enhanced by 31% compared to that of the control beam.

The concrete structure exposed to high temperatures can affect the strength of the structure. Limitations in the experimental method can be solved by mathematical modeling. This study aims to identify the stress and strain behavior that occurs at high-temperatures. The model is a cylindrical concrete with a diameter of 150 mm and a height of 300 mm. The concrete strength design is 25 MPa. The temperatures of the model are 100 °C, 200 °C, 300 °C, 400 °C, 500 °C, 600 °C, and 700 °C. The model analysis using LUSAS v. 16 Software to observe the properties of the concrete material due to exposure to high temperatures. The results of the study get the higher the temperature received by concrete, the strength of the concrete decreases. Concrete that burned to a temperature of 300 °C still had 82% available power, and at a temperature of 700 °C, the remaining concrete strength was 30%. The strain increases to 423% from normal conditions at a temperature of 700 ° C. Therefore, the results of the study can be used as a reference for structural engineers to know the behavior of the concrete that exposure to high temperatures.

Geopolymer hybrid concrete is prepared by activating fly ash bottom ash with an alkaline solution and curing with Ordinary Portland Cement (OPC). OPC could be added to the mixture to increase the reaction, promote hydration, and assist in curing at room temperature. Peat water is an acidic organic environment that may reduce the durability of concrete. The purpose of this research is to determine the effect of Portland cement on the properties of FABA geopolymer hybrid concrete exposed to peat water. Portland cement was used in geopolymer as an additive and a substitute. Compressive strength, porosity, and weight change were evaluated for both mixtures. The NaOH molarities were 10, 12, and 14M, the NaOH/sodium silicate ratios were 1.5, 2.0, and 2.5, and the Ordinary Portland Cement percentages were 0, 10, and 15%. Specimens were exposed to peat water for up to 91 days following 28 days of room temperature curing. The geopolymer mixture with 10M NaOH, 2.5M Ms, and 15% OPC had the highest compressive strength and the lowest porosity. The FABA geopolymer hybrid with OPC had a slightly greater compressive strength and a lower porosity than the geopolymer containing OPC as a cement replacement material. In addition, weight change is more stable in geopolymers containing OPC. Based on the performance of both mixes in peat water, it is recommended to use OPC as an additive in FABA geopolymer hybrid concrete.

Kayu adalah bahan yang umum digunakan baik secara struktural maupun non-struktural. Penggunaan kayu dalam bentuk struktural memerlukan spesifikasi tertentu. Kayu adalah bahan alami yang pertumbuhannya dipengaruhi oleh faktor lingkungan yang menyebabkan perbedaan kualitas kayu. Penelitian ini bertujuan untuk menguji dan memperoleh nilai kuat tekan sejajar serat kayu dan kuat geser kayu serta mengklasifikasikan kayu berdasarkan SNI 7973: 2013. Kayu tembusu (Fragraea fragrans) digunakan sebagai objek dalam penelitian ini. Hasil pengujian diperoleh nilai kuat tekan paralel kayu tembusu variasi A 16,31 MPa sehingga termasuk dalam kategori kayu dengan kode mutu E19. Nilai kuat tekan sejajar serat kayu kayu tembusu variasi B 16,26 MPa sehingga termasuk dalam kategori kayu dengan kode mutu E18. Modulus elastisitas kayu tembusu variasi A yang diperoleh adalah 3.555,95 MPa dan 5.324,24 MPa untuk variasi B. Nilai kuat geser kayu variasi A didapat sebesar 2,54 MPa dan untuk variasi B didapat 3,27 MPa. Penelitian ini bermanfaat untuk menganalisis kuat tekan sejajar serat, kuat geser kayu dan untuk penelitian lanjutan lainnya. Hasilnya diharapkan berkontribusi pada basis data ilmiah umum sifat mekanis kayu di Indonesia dan khususnya dalam desain komponen struktural tekan dan lentur serta untuk penelitian lebih lanjut.

Fiber Reinforced Polymer is a combination of two main materials Resin Polymer (plastic) as a binder matrix and Fiber (fiber) as reinforcement. This material has three fibers, namely Carbon, Glass, and Aramid. Glass fiber was used in this study, because it has a greater strain compared to other fibers. This study aims to design reinforced concrete structures using steel reinforcement and GFRP as well as to compare the reinforcement requirements of each reinforced concrete. Calculation of reinforcement for steel reinforced concrete refers to SNI 1726-2019, while for GFRP reinforced concrete it is based on ACI 440 1R-2015. This research begins by collecting data in the form of a design structure drawing of a 6-storey hypothetical building, with a total building height of 23 m. The hypothesis building has the number of spans in the X-axis direction is 5 with a distance between columns of 6 m, while the number of spans in the Y direction is 3 with a distance between columns of 5 m. The column dimensions for all floors are 60 cm x 60 cm, while the beam dimensions are 40 cm x 40 cm. The thickness of the floor and roof slabs is 12 cm and the concrete quality is 30 MPa. For the calculation of structural loading, dead load, live load and earthquake load are used and the design of reinforcement for conventional steel reinforced concrete structures and GFRP is carried out. Steel reinforced concrete structures with GFRP reinforced concrete have differences in the amount and diameter of reinforcement required. For beam elements bearing steel reinforcement, 24 pieces of flexural reinforcement are needed with a diameter of 19 mm, while for beam elements, GFRP reinforcement requires 12 pieces of flexural reinforcement with a diameter of 1 inch to 1,128 inches. For the field area, steel reinforcement beam elements need 12 pieces with a diameter of 19 mm, while for GFRP reinforcing beam elements require 8 pieces of flexural reinforcement with a diameter of 0.875 inch to 1.128 inch. In column elements, steel reinforcement and GFRP reinforcement require the same amount of main reinforcement, which is 32 pieces. However, in terms of diameter, steel reinforcement requires 25 mm diameter reinforcement, while GFRP is 1 inch in diameter.

Bridges are infrastructure buildings that are commonly used and very functional in everyday. One of the structural components of the bridge is a reinforced concrete beam as a load bearer that will be forwarded to the foundation. The shear capacity of reinforced concrete beam structures sometimes cannot meet the existing requirements. This can be caused by increased loads, inadequate shear strength in the initial design and material damage due to natural factors. There are several methods that have been carried out to overcome the decrease in shear strength in beam structures, namely reinforcement methods by externally bonded (EB) and near-surface mounted (NSM). In reality, shear reinforcement with EB and NSM methods in implementation only relies on epoxy adhesion and concrete blankets, which still causes structural failure. The deep embedment strengthening method (DE) can be proposed as a shear reinforcement for reinforced concrete beams to overcome the previous problems. Reinforcement with DE method is a shear reinforcement that is reinforced in the core of reinforced concrete beams. This research was conducted by embedding 8 reinforcements vertically with a distance of 200 mm along the shear span. In this study, finite element modeling was carried out using ABAQUS. The results of finite element modeling with the DE method showed that the maximum load was 30.646 kN and the maximum deflection was 13.00 mm. The collapse model that occurs from finite element modeling on test specimens with DE reinforcement experiencing flexural failure.

FABA is a by-product of coal combustion in power plants comprising fly ash (FA) and bottom ash (BA) in ratios of 80/20. Fly ash has great potential as a mineral ingredient in concrete, while bottom ash compromises its strength and durability. However, both materials are used to improve the strength and durability of structures in sulfate, chloride, and acidic environments. This research evaluated the properties of blended and high-volume FABA concrete, such as the strength, porosity, weight loss, and sorptivity in organic acidic peat water. OPC (Ordinary Portland Cement) was compared to the blended concrete containing 25% FABA and its high-volume containing 50% and 75% FABA with target strengths of 15, 21, and 29 MPa. The compressive strength of blended and high volume FABA increased during the immersion period, while the porosity and sorptivity rates decreased. Furthermore, the strength of the OPC concrete declined at 28 days, with a gradual marginal weight loss of 5% observed in all mixes. This research suggested that blended and high-volume FABA has potential as a construction material in an acidic peatland environment.