SELECTION OF MIX PROPORTION BASED ON STRENGTH OF LOW-STRENGTH MORTAR WITH RECYCLED MATERIALS FOR BACKFILLING

摘要

Production of low-strength mortar with the recycled materials such as cullet, recycled fine aggregate, and fly ash produced in Akita Prefecture was tried. This mortar is normally placed for the backfilling which will be mechanically excavated in the future. The compressive strength of this low-strength mortar was tested at the age of 2 to 365 days for each curing conditions such as a) wet sand curing, b) lay underground of about 40cm depth, c)-1 wet sand curing in excessive water at 20 deg C, and c)-2 wet sand curing in excessive water at 10 deg C to simulate construction site. The compressive strength of the low-strength mortar increased until the age of 91 days, after that the strength was almost constant in each curing condition and 91 days strength was an aim to obtain the target strength ranging from 0.3 to 2.0 N/mm~2. The compressive strength in each curing condition at the age of 91 days was condition a) > condition b) > condition c)-1 > condition c)-2 in order of magnitude. It was clarified that the strength of low-strength mortar for backfilling depended on the existence of underground water and temperature. In order to obtain the mix proportion with target strength in situ, the existence of underground water and temperature in the construction site have to be confirmed. The strength test results in the appropriate laboratory curing condition corresponding to the site will enable us to select the mix proportion.