Utilization of bantak and Merapi volcanic ash for porous paving block as drainage control in the Prambanan Temple Yard

Ponding area occurred in the main yard of Prambanan Temple during rainfall is very bothering visitor activities. Some improvements have ever conducted but no longer effective. This paper shows the application of porous paving blocks to reduce the puddle. This porous paving block was made using waste materials from Mount Merapi eruption, such as bantak and volcanic ash. Volcanic ash was substituted for cement and bantak would replace the aggregate. Aggregate ratio used on this research is 1:5 and 0,4 for water-cement ratio. Characterization testing of porous paving block consists of density, compressive strength, porosity, and coefficient of permeability. The result shows that the optimum mixture of porous paving block is the mixture with 30% volcanic ash, strength capacity 6.05 MPa, porosity 28.4%, and coefficient of permeability 1.93 cm/s or 8 times faster than normal paving block and 18 times faster than the soil of Prambanan Temple yard. The infiltration analysis indicated that runoff level in the main yard of Prambanan Temple is 8.8 cm and ponding time is 3.2 hours. When using normal paving blocks, ponding can be reduced up to 81.6%, however when porous paving blocks was used, the ponding was not occurred because coefficient of permeability of porous paving blocks is faster than intensity rainfall at Prambanan Temple area (1.5×10-3 cm/s). From the evaluation of porous paving blocks strength against forklift load shows that total forklift load allowed to work on porous paving blocks is 9 tons' load.