Concrete compressive strength depend on many factors, one of the critical factor is fineness of sand, one material component of concrete. This study aims to quantify effect of the sand fineness to the concrete compressive strength by using sand with zone I and zone III. Kata kunci: kehalusan pasir, faktor air semen, kuat tekan beton.

The waste of the concrete tile production factory (LPPGB) is the waste obtained from the concrete tile production result at PT. Varia Usaha Beton which is located in Sidoarjo regency. The waste has element SiO2 that reactively reacts with calcium hidroxyde into calcium silicate hydrate, so that it increases the concrete compessive strength. In this research, the waste of the concrete tile production factory is added as a substitute for part/some fly ash in concrete mix. The design of concrete mix composition uses the procedure of the normal concrete mixed design, SNI 03-2834-1993. The cylinder speciment used has 15 cm in diameter and 30 cm in height. The percentages of additional LPPGB in the concrete mix composition are 0%, 5%, 10%, to 15 % by substituting some of the fly ash. The reseach result indicates that the addition of LPPGB influences the concrete pressure strength; the more the LPPGB content used in concrete mix, the less the concrete pressure strength. For example for K225 concrete strength with the waste proportion of 0% the 28 days old compressive strength is 350.91 kg/cm 3 . However for the same concrete strength with waste composition of 5%, the compressive strength decreases to 296.22 kg/cm 2 . This indicates 16% dcrease of the compressive strength.Keywords: pressure strength, tile factory waste, chemical element. AbstrakLimbah pabrik produksi genteng beton (LPPGB) adalah limbah yang didapatkan dari hasil sisa produksi genteng beton di PT. Varia Usaha Beton yang terletak di daerah Sidoarjo. Limbah ini memiliki unsur oksida SiO2 yang reaktif bereaksi dengan kalsium hidroksida menjadi kalsium silikat hidrat sehingga menambah kuat tekan beton. Dalam penelitian ini, Limbah pabrik produksi genteng beton ditambahkan sebagai pengganti sebagian abu terbang (fly ash) pada campuran beton. Desain komposisi campuran beton menggunakan tata cara pembuatan rencana campuran beton normal, SNI 03-2834-1993. Benda uji silinder yang digunakan dengan ukuran diameter 15 cm, dan tinggi 30 cm. Variasi porsentase tambahan LPPGB pada komposisi campuran beton mulai dari 0%, 5%, 10%, dan 15% dengan menggantikan sebagian fly ash. Dari hasil penelitian ini menunjukkan bahwa tambahan LPPGB mempunyai pengaruh pada kuat tekan beton, semakin banyak kadar LPPGB yang digunakan dalam campuran beton semakin turun kuat tekan beton. Seperti pada mutu K225 dengan proporsi limbah 0% (Umur 28 hari) menghasilkan kuat tekan sebesar 350.91 kg/cm² dibandingkan dengan komposisi limbah 5% kuat tekan turun menjadi 296.22 kg/cm². Hal ini menunjukkan kuat tekan turun sebesar 16%.Kata kunci: kuat tekan, limbah pabrik genteng, unsur kimia.