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K-175 concrete research has been carried out with two types of volcanic ash addition, namely variations of 0%, 6%, 8%, 10%, 12% (K-175 concrete) and 15%, 20%, 25%, 30% (density analysis XRD). K-175 concrete contributes to residential concrete. The making of K-175 concrete refers to SNI 7394: 2008 with compressive strength criteria of 14.53 Mpa. The method used is Precast concrete with sheet pile type. The making of concrete K-175 with the addition of cube-shaped volcanic ash with 15 cm sides consisting of cement, sand, broken stone, volcanic ash and water. After casting is done, the concrete is soaked in the tub and then removed from the soaking tub after 28 days of age dried for 24 hours. The following is the water absorption test and compressive strength test by selecting 3 samples which have the optimum compressive strength for XRD, SEM and FTIR tests to see the concrete characterization. Analysis of XRD, SEM, and FTIR are in the variation of 0%, 10% and 25% low absorption, compressive strength respectively 21.06 MPa, 21.16 MPa and 19.46 MPa. The pressure strength also fulfills the compressive strength of Portland cement type I which is 20 MPa.