Various concretes have been developed to meet the principles of sustainability. High volume fly ash-self compacting concrete (HVFA-SCC) is one example. The utilization of HVFA-SCC for structural applications, however, raises a concern among designers: that HVFA-SCC may not be as strong as conventional concrete when carrying shear forces. This concern is related to slow strength development and relatively smoother crack surface formation in HVFA-SCC, which, consequently, reduces the aggregate interlock mechanism contribution to the shear strength. In this respect, the design code for estimating the shear strength of HVFA-SCC may not be valid for the reason that the code was developed on the basis of the conventional concrete database. Previous research on the shear strength of HVFA-SCC was limited and no database can be extracted to justify the validity of the shear design code. This research was conducted to clarify the suitability of shear design code for HVFA-SCC. The research began with a limited laboratory investigation, followed by a numerical investigation to expand the range of results. Two types of HVFA-SCC beams with dimensions of 100 mm × 150 mm × 1700 mm were prepared, utilizing 50% and 60% fly ash. The shear behavior obtained from the laboratory investigations was then numerically modeled with the help of 3D ATENA Engineering software. The numerical model was used to explore the influence of reinforcement ratio, shear span to beam effective depth ratio, and beam size on the shear strength of the HVFA-SCC beam. The results were compared with the shear strength database of conventional and unconventional concrete beams to judge if the provisions in the design code can be applied to the shear design of an HVFA-SCC beam. The results confirm that the ACI shear design code is applicable for HVFA-SCC.

ABSTRACT:Complete stress-strain behavior is a fundamental characteristic of concrete from which principle parameters in the analysis and design of structural concrete elements are developed. It is recognized that the stress-strain behavior of concrete under uniaxial compressive loading is influenced by the concrete constituents. A special type of concrete, i.e. self-compacting concrete (SCC) incorporating high-volume fly ash, has different constituents to that of conventional concrete. For this reason, characterization of the complete stress-strain behavior of this type of concrete is necessary for reliable analysis, design, and utilization of this concrete as a structural element. This research aims to investigate the complete stress-strain behavior of SCC, incorporating a variety of high-volume fly ash (50-70% by weight of total binder) under uniaxial compressive loading. The compression tests were carried out on cylinder specimens of 75×150 mm, where the deformation was controlled at a rate of 1.5mm/min. The results show that at a stress below 60% of peak value, there is a linear relationship of stress and strain. In this state, both global and local longitudinal deformation is quite similar. However, above this stress level, a nonlinearity of the stress and strain relationship exists and local deformation at the fracture zone is higher than global deformation. Various stress-strain models have been used to capture the complete stress-strain diagram of the investigated concrete, using key parameters of the diagram as inputs. Most of the models give a better prediction in the ascending part compared to that of the descending branch. In general, Samani and Attard's model gives the lowest coefficient of variation of error than other models.

Bamboo is one of the potential material as a substitute for steel reinforcement. This paper will discuss the flexural capacity of concrete beam with

<p class="Default"><em>Fly ash </em>merupakan limbah pembakaran batu bara yang memiliki kandungan kimia berupa silika dan alumina mencapai 80%. Senyawa tersebut bereaksi dengan Ca(OH)₂ hasil proses hidrasi semen dan membentuk C₃S₂H₃ atau <em>tubermorite</em> yang dapat menambah kekuatan beton. Secara fisik <em>fly ash </em>memiliki bentuk yang hampir bulat semppurna sehingga memiliki <em>ball bearing effect </em>pada bidang gelincir adukan mortar atau semen. <em>Fly ash </em>sebagai subtituen semen sering digunakan dalam jumlah besar (&gt;50%). Konsep tersebut dikenal dengan <em>High Volume Fly Ash Concrete (HVFAC)</em>. Untuk mengatasi permasalahan terbentuknya rongga pada beton bertulang, konsep HVFAC dipadukan dengan <em>Self Compacting Concrete (SCC). </em>Penelitian ini mengkaji pengaruh persentase <em>fly ash</em> terhadap kuat tekan pada beton HVFA-SCC. Metode penelitian ini adalah eksperimen, dimana digunakan 3 variasi kadar <em>fly ash </em>pada beton HVFA-SCC yaitu 50%, 60%, 70% serta beton normal. Tiap variasi terdiri dari 3 sampel berukuran 75 mm x 150 mm. Pengujian beton segar HVFA-SCC dilakukan dengan 3 metode yaitu : <em>flow table test, L-box test, </em>dan <em>V-funnel test. </em>Hasil pengujian menunjukkan bahwa semakin bertambahnya kadar <em>fly ash </em>maka <em>workability </em>dari beton segar tersebut semakin baik. Pengujian beton keras dilakukan untuk mendapatkan nilai kuat tekan beton. Kuat tekan yang dihasilkan HVFA.28.50, HVFA.28.60, HVFA.28.70, dan NC.28 berturut turut adalah 49,86 MPa, 39,16 MPa, 23,71 MPa, dan 47,78 MPa. Dari hasil pengujian tersebut dapat disimpulkan bahwa semakin banyak penambahan kadar <em>fly ash </em>maka kuat tekan semakin menurun. Hal tersebut diakibatkan karena tidak hanya menurunnya bahan ikat utama beton tetapi juga <em>fly ash </em>belum bereaksi secara optimal pada usia 28 hari.</p>

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