Concrete quality containing flash flood sands: A case study

In recent years in July 2020, harmful floods and landslides happened unpredictably in North Luwu Regency of South Sulawesi Province, Indonesia. This horrible event has been carrying millions of tons of flash flood sand (FFS) mixed with relatively small mud that spread along both sides of the Masamba and Radda rivers through over six districts area. Besides, if it is not used properly, this massive sand will be transformed into an environmental problem as material waste and disturbed human activities daily. However, the quality assurance of sand properties will play the main role in concrete strength and durability. The collection of the FFS sample began from upstream (Msb-Hu and Rda-Hu) and then to the middle stream (Msb-T and Rda-T) with a length distance of 200 meters through downstream (Msb-Hi and Rda-Hi) with similar lengths. The result shows that only Msb-T and Rda-Hi samples satisfy to meet a good standard of sand quality. Then we made concrete samples with a total of eighteen specimens consisting of two mixtures (M1-MsbT and M2-RdaHi) to evaluate their fresh and hardened properties. From the observations and discussions, we may conclude that the utilization of FFS in making concrete for material construction can be possible. Even so, there are some considerations in terms of the quality properties of FFS.