8 Jurnal Sains Materi Indonesia Vol. 22, No. 1, Oktober 2020, hal. 8-15 THE EFFECT OF REVERSE FLOTATION METHOD ON SILICA SAND AS WATERPROOFING MORTAR Okky Putri Prastuti 1 , Ayu Tri Septianingrum 1 , Elisya Dianty Fatmala 1 , Ufafa Anggarini 1 , Tri Eddy Susanto 2 , Nuvixca Dewi Milangsari 1 1 Universitas Internasional Semen Indonesia, Jl. Veteran, Gresik, 61122 2 PT.Semen Indonesia, Jl. Veteran, Gresik, 61122 E-mail: okky.prastuti@uisi.ac.id Received: 15 July 2020 Revised: 14 October 2020 Accepted: 21 October 2020 ABSTRACT THE EFFECT OF REVERSE FLOTATION METHOD ON SILICASANDAS WATERPROOF- ING MORTAR. Waterproof fabrication mortar cement by silica sand using reverse flotation silica (RFS) method was evaluated by waterproof absorption coefficient, compressive strength test, attrac- tive test, and contact angle. RFS is used to replace waterproof agent and aggregate mortar to reduce cost. The aims of this experiment are to know RFS process, ratio between waterproof mortar cement with RFS and mortar, to determine performance and characteristic waterproof mortar cement. Methods used are prepare RFS, mortar cement fabrication, and testing (compressive strength, tensile strength, permeability, contact angle, XRF, FTIR, SEM, BET). Variable used are ratio cement/silica sand, concen- trations of CaCl 2 , curing time, oleic acid and sodium oleate addition. Optimum collector addition is obtained by oleic acid with compress strength 167.65 kg/cm 2 , tensile strength 0.16 MPa, permeability 4.6cm, and contact angle 95 0 . Curing inside water effect and outside temperature give compress strength 167.65 kg/cm 2 and 163.24 kg/cm 2 , permeability curing inside water and outside temperature are 4.6cm and 12cm. Optimum CaCl 2 addition is gained at CaCl 2 1.8 M with compress strength 64.29 kg/ cm 2 , tensile strength 0.15 MPa, permeability 2.4 cm, contact angle 95 0 . Optimum ratio cement/RFS is 1:1 with compress strength 167.65 kg/cm 2 , tensile strength 0.16MPa, permeability 4.6 cm, and contact angle 95 0 . Keywords: Mortar, Reverse flotation, Silica sand, Tailings, Waterproof ABSTRAK PEMANFAATAN PASIR SILIKAPT. SEMEN INDONESIASEBAGAI MOTAR WATERPROOF DENGAN PROSES REVERSE FLOTATION. Fabrikasi waterproof berbasis semen mortar dengan bahan baku pasir silika menggunakan metode reverse flotation silica (RFS) dievaluasi dengan koefisien penyerapan tahan air, kekuatan tekan, daya tarik dan sudut kontak. RFS digunakan untuk menggantikan sifat waterproof dan agregat mortar untuk mengurangi biaya. Tujuan dari penelitian ini adalah mengetahui proses RFS, mengetahui perbandingan mortar waterproof berbasis semen dengan RFS dan mortar, mengetahui kinerja dan karakteristik waterproof mortar RFS. Metode yang digunakan adalah persiapan RFS, fabrikasi mortar semen, dan pengukuran (kuat tekan, kuat tarik, permeabilitas, sudut kontak, XRF, FTIR, SEM, BET). Variabel yang digunakan adalah perbandingan semen/pasir silika, konsentrasi CaCl 2 , waktu curing, penambahan asam oleat dan sodium oleat. Penambahan kolektor paling optimal adalah asam oleat dengan kuat tekan sebesar 167,65kg/cm 2 , kuat tarik sebesar 0,16 MPa, permeabilitas 4,6 cm dan sudut kontak 95°. Pengaruh curing dalam air memiliki kuat tekan 167,65 kg/ cm 2 , curing suhu luar sebesar 163,24 kg/cm 2 , permeabilitas curing dalam air sebesar 4,6 cm, sedangkan Akreditation No : 36/E/KPT/2019 Date 13 Dec 2019 ISSN 1411-1098 E-ISSN 2614-087X