Abstract
The purpose of this experimental study is to obtain the reference value of workability characteristics, strength test age and curing method of low-strength mortar with self-compactability for backfill. Two types of ordinary cement（produced with and without burnt rubble caused by Tsunami）, two types of low quality recycled fine aggregate without treatment as fine aggregate, high volume fly ash and superplasticizers were used. The recycled fine aggregate was manufactured by only original crushing after demolishing old concrete bridge piers and buildings. The workability was measured by flow value and bleeding ratio. The target values were decided to be 250 to 300 and less than 3.0％ from many test results and references respectively. The target range of the compressive strength was 0.3 to 2.0N/mm2. It was clarified that the suitable age of strength test was 91 days cured in moist sand with excessive water in the laboratory because of showing almost constant strength after this age. The mortar prismatic test pieces were laid underground for three months and one year at two locations where weather condition was very different. The strength of test pieces laid underground at both locations showed that of target range. These results were previously confirmed by the laboratory cured test. The validity of laboratory cured strength test was verified from these results. These information will be able to make use of evaluating workability and strength of low- strength mortar with recycled fine aggregate for backfilling.
