Pengaruh Variasi Kadar Limbah Wire Rope sebagai Serat dan Silica Fume terhadap Kuat Tekan High Performance Concrete (HPC)

Abstract

Abstract: High-Performance Concrete (HPC) offers superior compressive strength, durability, and microstructural density compared to conventional concrete; however, it remains inherently brittle and susceptible to crack propagation. While the addition of steel fibers can enhance crack resistance, the use of waste wire rope from discarded steel cables as an alternative fiber has not been extensively studied in high-grade HPC—specifically at a target strength of 60 MPa. This study aims to analyze the effects of adding silica fume and varying dosages of waste wire rope on the compressive strength of HPC, determine the optimum dosage, and identify the cracking patterns of the test specimens. An experimental laboratory approach was employed targeting a design strength of 60 MPa; a control mix was designed based on SNI 03-2834-2000 and subsequently modified with 10% silica fume and a superplasticizer to achieve HPC characteristics, with the addition of 30 mm-long waste wire rope at dosages of 0%, 0.75%, and 1.25% by weight of cement. Testing included slump tests on fresh concrete and compressive strength tests on 150×300 mm cylindrical specimens at 3 days of age, with values converted to 28-day strength in accordance with ACI Committee 209R-92 guidelines. The results indicate that the average compressive strength of the control concrete was 75.79 MPa; this increased to 83.18 MPa (a 9.7% rise) at the 0.75% dosage but decreased to 76.92 MPa at the 1.25% dosage due to a tendency for the "balling effect." All variations met the target strength of 60 MPa. Regarding cracking patterns, Type 5 failure was observed in the 0% and 0.75% variations, whereas the 1.25% variation exhibited Type 4 failure, classified according to ASTM C39/C39M-23 standards. Thus, a wire rope waste content of 0.75% represents the optimum variation for use as a fiber additive in HPC, supporting the sustainable utilization of industrial waste.

Abstrak: High Performance Concrete (HPC) merupakan beton berkinerja tinggi yang menawarkan kuat tekan, durabilitas, dan kepadatan mikrostruktur yang lebih baik dibandingkan beton normal, namun umumnya masih bersifat getas (brittle) sehingga rentan mengalami propagasi retak. Penambahan serat baja dapat memperbaiki ketahanan retak beton, sementara pemanfaatan limbah wire rope dari kabel baja bekas sebagai serat alternatif belum banyak dikaji pada HPC bermutu tinggi, khususnya pada mutu rencana 60 MPa. Penelitian ini bertujuan menganalisis pengaruh penambahan silica fume dan variasi kadar limbah wire rope terhadap kuat tekan HPC, menentukan kadar optimum, serta mengidentifikasi pola retakan benda uji. Penelitian menggunakan metode eksperimen laboratorium dengan mutu rencana 60 MPa; campuran kontrol dirancang berdasarkan SNI 03-2834-2000 kemudian dimodifikasi dengan silica fume 10% dan superplasticizer untuk mencapai HPC, ditambah limbah wire rope panjang 30 mm dengan variasi kadar 0%, 0,75%, dan 1,25% terhadap berat semen. Pengujian meliputi slump test pada beton segar serta kuat tekan benda uji silinder 150×300 mm pada umur 3 hari yang dikonversi ke umur 28 hari mengacu ACI Committee 209R-92. Hasil penelitian menunjukkan kuat tekan rata-rata beton normal sebesar 75,79 MPa, meningkat menjadi 83,18 MPa (naik 9,7%) pada variasi 0,75%, kemudian menurun menjadi 76,92 MPa pada variasi 1,25% akibat kecenderungan balling effect. Seluruh variasi memenuhi mutu rencana 60 MPa. Pola retakan menunjukkan keruntuhan Tipe 5 pada variasi 0% dan 0,75%, sedangkan variasi 1,25% mengalami keruntuhan Tipe 4 berdasarkan ASTM C39/C39M-23. Dengan demikian, kadar limbah wire rope 0,75% merupakan variasi optimum sebagai bahan tambah serat pada HPC yang mendukung pemanfaatan limbah industri secara berkelanjutan.