In the underside of the existing concrete structure joint placing manner null of the newly founded concrete which is formed

摘要

PURPOSE:To strengthen the adhesion of concrete at a joint surface by arranging the upper end of a formwork via a small gap from the underside of concrete and pressing concrete containing a separation reducing agent and a swelling agent into the formwork via the concrete placing opening thereof. CONSTITUTION:When a division 14 is built between the first basement slab 10 and the second basement slab 12, for example, a reinforcement 16 is assembled and the upper end thereof is embedded in the slab 10 for connection to an anchor 18. Also, a swelling agent, a separation reducing agent and the like are added to jointing concrete. Thereafter, a pair of formworks 20 having a concrete placing opening 22 and a drain hole 2 is set at the outside of the reinforcement 16, and a small interval 28 is formed between the upper ends of formworks 20 and the slab 10. Then, the concrete after placed via the opening 22, is pressurized with a pump at an area reaching the underside of the slab 10. In addition, the concrete is kept under pressure due to the effect of the swelling agent until cured.