Based on the concept of energy saving and environmental protection

it is proposed to treat the soft soil foundation using cement fly-ash construction waste pile. The coarse aggregate（particle size: 4. 75—9. 5 mm） made from construction waste is used instead of gravel and fine aggregate（particle size: 0. 075一0. 6 mm） instead of medium coarse sand. The feasibility of the proposed scheme is verified through laboratory tests

field tests and quality inspection

etc. Results show that a mixing ratio of 15 % cementitious materials and a 2 : 1 cement to fly ash ratio（E group） is the optimum combination for the design of recycled aggregate concrete with construction wastes. The unconfined compressive strength of recycled aggregate concrete increases by 19. 5%-26. 5% after 90 days of curing compared with 28-day curing

which is higher than that of ordinary concrete. The unconfined compressive strength value with 28-day curing is used as the standard one for recycled aggregate concrete

which is relatively low. The bearing capacity of a single pile composite foundation reaches 487. 7 kPa

which is 3. 8 times higher than that of a natural soft foundation

which can meet design requirements.