Pregrouted PC steel material and curing method for pregrouted layer therein
A pregrouted PC steel material ( 10 ) includes a 19-wire-twisted PC strand ( 1 ), a pregrouted layer ( 2 ) disposed on an outer periphery of the PC strand ( 1 ), and a sheath ( 3 ) configured to cover an outer periphery of the pregrouted layer ( 2 ). A filling resin ( 4 ) is filled between steel wires (side wires) ( 1 b, 1 c, 1 d ). Since the filling resin ( 4 ) does not exude to the pregrouted layer ( 2 ) before tensioning of the PC strand ( 10 ), an operation of tensioning the PC strand ( 1 ) is not hindered by curing of the pregrouted layer ( 2 ). In contrast, since the gap between the steel wires is reduced when the PC strand ( 1 ) is tensioned, the filling resin ( 4 ) flows out (exudes) from between the steel wires to the pregrouted layer ( 2 ) to cure the pregrouted layer ( 2 ) only after the reduction.
1. A pregrouted PC steel material comprising: a PC strand formed by twisting a plurality of steel wires; a pregrouted layer disposed on an outer periphery of the PC strand to contain the PC strand; and a sheath configured to cover an outer periphery of the pregrouted layer,
wherein
in a cross section perpendicular to a longitudinal direction, the PC strand has a steel wire forming a core wire, steel wires forming an inner layer provided on the core wire, and steel wires forming a continuous outer layer provided on the inner layer,
a filling resin configured to promote curing of the pregrouted layer is filled between the steel wires in the PC strand, and the filling resin does not exude to the pregrouted layer before tensioning of the PC strand, and exudes to the pregrouted layer owing to a tensioning force during the tensioning,
the filling resin is only filled between the steel wire forming the core wire and the steel wires forming the inner layer and/or between the steel wires forming the inner layer and the steel wires forming the outer layer, and
the filling resin exudes to the pregrout layer along with contraction of a gap between the steel wires of the PC strand due to tensioning of the PC strand.
2. The pregrouted PC steel material according to claim 1 , wherein a gap filled with the filling resin between layers of the steel wires is widened by interposing a spacer between the layers.
3. The pregrouted PC steel material according to claim 1 , wherein the pregrouted layer is formed of epoxy resin or a resin mainly composed of epoxy resin, and the filling resin is a curing agent for the epoxy resin.
4. The pregrouted PC steel material according to claim 1 , wherein the pregrouted layer is formed of epoxy resin or a resin mainly composed of epoxy resin, and the filling resin is a mixture of epoxy resin and a curing agent for the epoxy resin.
5. The pregrouted PC steel material according to claim 1 , wherein a filler is added to the filling resin to achieve thickening, to improve a thixotropic property, or to prevent dripping.
6. A curing method for the pregrouted layer in the pregrouted PC steel material according to claim 1 , wherein the pregrouted PC steel material is buried in concrete, and the filling resin is caused to flow into the pregrouted layer to cure the pregrouted layer by the tensioning force when the PC strand is tensioned to apply compressive force to the concrete.