ANALISIS PENGARUH FLY ASH SEBAGAI PENGGANTI PARSIAL SEMEN PADA PEMBUATAN BATA RINGAN CLC (CELLULAR LIGHTWEIGHT CONCRETE)

Abstract

Abstract: Cellular Lightweight Concrete (CLC) blocks are non-structural wall materials valued for their low weight; however, their characteristics require optimization to meet technical standards. Utilizing fly ash—a coal combustion byproduct—offers the potential to reduce cement consumption while supporting waste management and environmentally friendly, sustainable construction practices. This study aimed to analyze the effect of using fly ash as a partial cement replacement on the density, water absorption, compressive strength, and cracking patterns of CLC blocks, and to determine the appropriate replacement level based on SNI 8640:2018. An experimental study was conducted at the Civil Engineering Laboratory of Universitas Muhammadiyah Mataram, testing fly ash replacement levels of 0%, 5%, 10%, 15%, 20%, 25%, and 30% of the cement weight. Cubic specimens measuring 15 × 15 × 15 cm were used, with three samples per variation. Testing covered density, water absorption, and compressive strength at 28 days, as well as an analysis of cracking patterns following compression testing. The results showed that increasing the fly ash content reduced density from 713.58 kg/m³ (0% variation) to 645.93 kg/m³ (30% variation) but increased water absorption from 22.85% to 32.77%. The highest compressive strength was achieved at the 0% variation (3.881 MPa at 28 days), while the lowest was at the 30% variation (1.763 MPa). Based on SNI 8640:2018, variations ranging from 0% to 20% met the compressive strength requirements; therefore, a 20% fly ash replacement level is recommended as the optimum. Cracking patterns did not show consistent trends, likely due to inconsistencies in manual mixing.

Abstrak: Bata ringan Cellular Lightweight Concrete (CLC) merupakan material dinding non-struktural yang memiliki keunggulan berupa bobot ringan, namun karakteristiknya perlu dioptimalkan agar memenuhi persyaratan teknis. Pemanfaatan fly ash sebagai limbah hasil pembakaran batu bara berpotensi mengurangi penggunaan semen sekaligus mendukung pengelolaan limbah dan material konstruksi berkelanjutan yang ramah lingkungan. Penelitian ini bertujuan menganalisis pengaruh penggunaan fly ash sebagai pengganti parsial semen terhadap densitas, daya serap air, kuat tekan, dan pola retakan bata ringan CLC serta menentukan kadar penggunaan yang sesuai berdasarkan SNI 8640:2018. Penelitian dilakukan secara eksperimental di Laboratorium Teknik Sipil Universitas Muhammadiyah Mataram dengan variasi penggantian fly ash sebesar 0%, 5%, 10%, 15%, 20%, 25%, dan 30% dari berat semen. Benda uji berbentuk kubus berukuran 15 × 15 × 15 cm dengan tiga sampel pada setiap variasi. Pengujian meliputi densitas, daya serap air, kuat tekan pada umur 28 hari, serta analisis pola retakan setelah pengujian tekan. Hasil penelitian menunjukkan bahwa peningkatan kadar fly ash menurunkan densitas dari 713,58 kg/m³ pada variasi 0% menjadi 645,93 kg/m³ pada variasi 30%, tetapi meningkatkan daya serap air dari 22,85% menjadi 32,77%. Kuat tekan tertinggi diperoleh pada variasi 0%, yaitu 3,881 MPa pada umur 28 hari, sedangkan terendah pada variasi 30% sebesar 1,763 MPa. Berdasarkan SNI 8640:2018, variasi 0%–20% memenuhi persyaratan kuat tekan, sehingga penggunaan fly ash 20% direkomendasikan sebagai kadar optimum. Pola retakan tidak menunjukkan pengaruh yang konsisten akibat ketidakkonsistenan pencampuran secara manual.