Controlled low strength material (CLSM) is self-compacting flowable fill which is primarily used as backfill. This book presents the investigation done on CLSM mixtures made using NaOH, lime, bottom ash, fly ash, and water. A series of experiments on fresh state, viz. flowability, fresh density, segregation resistance and bleeding were conducted. The CLSM mixtures were also tested for water absorption, hardened density, ultrasonic pulse velocity and compressive strength at hardened state. The flowability of all samples is 300 ± 20 mm and increase in FA/binder ratio reduces the flowability of mixture. All the CLSM mixtures were classified as normal weight. All samples had good segregation resistance with non-corrosive behavior. Durability properties of CLSM were satisfactory. Compressive strength of mixtures varied between 1.1 MPa to 3.35 MPa. Increment of lime and NaOH leads to increment in strength only at certain ratios. It is concluded that the CLSM mixtures produced in the investigation are cement-free, has good mechanical and durability properties and can be used in practical applications.