Precast concrete with sacrificial anode cathodic protection

Abstract

All new precast concrete products such as precast concrete piles, precast prestressed concrete piles, precast concrete beams, and precast concrete wall panels can be embedded with sacrificial anode materials and withstand impact load during installation without any modification of the concrete material in TIS 396-2549 or equivalent to prevent corrosion of reinforcing steel. The key success is the total cross-section area of the zinc anodes covered with the activating cementitious material is equal to 10.28% of the cross-section area of the precast concrete products or less.

Description

[0001] PRECAST CONCRETE WITH SACRIFICIAL ANODE CATHODIC PROTECTION

[0002] Technical Field

[0003] This invention is related to the new design of sacrificial anode cathodic protection systems of reinforcing steel in the precast concrete products such as precast concrete piles, precast prestressed concrete piles, precast concrete beams, and precast concrete wall panels.

[0004] Background Art

[0005] There are two major causes of the deterioration of steel reinforced concrete. First is the carbonation problem which reduces the pH of the concrete from approximately 12-14 to about 8. The second is corrosion from chloride ions in saline soil or seawater. Both cause corrosion of steel in concrete. In corrosion process, high volume expansion of steel corrosion leads to cracking, spalling, and collapsing of concrete structures.

[0006] Sacrificial anode cathodic protection has been used to control corrosion of steel in concrete in the repair stage for more than 30 years. Many attempts have been made to embed sacrificial anode to new concrete structures also but only cast in place concrete structures are success. There are no new precast concrete structures with embedded sacrificial anode because of mechanical properties concern. The most concern is the precast concrete piles which will encounter impact load during installation.

[0007] In WO2010 / 043908 A 1 by Glass et al., high performance cementitious concrete or mortar and bonding agents developed for use as patch repair materials for corrosion damaged concrete to improve the performance of sacrificial anodes located within patch repair areas.

[0008] In WO2018 / 169495 by Mungsantisuk, the zinc or zinc alloy anode covered by the cementitious material with at least 4% lithium hydroxide (LiOH) by weight of the cementitious material and sand size control will improve the anodes performance and prevent them from passivation.

[0009] Disclosure of Invention

[0010] The present invention is the very new design to embed zinc anode covered with activating cementitious materials, which will be named in this invention as “concrete anode”, into new precast concrete products such as precast concrete piles, precast prestressed concrete piles, precast concrete beams, and precast concrete wall panels for cathodic prevention. The concrete anode used in this invention is related to that in WO2018 / 169495.

[0011] The precast prestressed concrete piles used in this invention are conformed to Thai Industrial Standard, TIS 396-2549 or equivalent. The dimensions of the concrete piles are 0.18x0.18x1.00 m. and 0.18x0.18x6.00 m. The description of 4 types of embedded concrete anodes in precast prestressed concrete piles are the following:

[0012] - Type CB20, bar shape, minimum net weight of zinc anode is 20 grams, total volume, and maximum cross-section area of zinc anode covered with the activating cementitious material are about 22.9 cm3and 14.3 cm2respectively. One of the CB20 was embedded in the 0.18x0.18x1.00 m. concrete pile and 8 of the CB20 were embedded in the 0.18x0.18x6.00 m. concrete pile.

[0013] - Type CR40, round shape, minimum net weight of zinc anode is 20 grams, total volume, and maximum cross-section area of zinc anode covered with the activating cementitious material are about 12.9 cm3and 6.2 cm2approximately. One of the CR20 was embedded in the 0.18x0.18x1.00 m. concrete pile and 8 of the CR20 were embedded in the 0.18x0.18x6.00 m. concrete pile.

[0014] - Type CR40, round shape, minimum net weight of zinc anode is 40 grams, total volume, and maximum cross-section area of zinc anode covered with the activating cementitious material are about 39.0 cm3and 12.6 cm2approximately. One of the CR40 was embedded in the 0.18x0.18x1.00 m. concrete pile and 4 of the CR40 were embedded in the 0.18x0.18x6.00 m. concrete pile.

[0015] - Type CR60, round shape, minimum net weight of zinc anode is 60 grams, total volume, and maximum cross-section area of zinc anode covered with the activating cementitious material are about 87.7 cm3and 28.3 cm2approximately. One of the CR60 was embedded in the 0.18x0.18x1.00 m. concrete pile and 3 of the CR60 were embedded in the 0.18x0.18x6.00 m. concrete pile.

[0016] All the concrete piles with embedded concrete anodes were driven into the soil by hammering. Concrete anodes were electrically connected to the steel in concrete with CVV cable 16x2.5 mm2via testing stations as described in figures 1 - 4. The cross-section area of CVV cable 16*2.5 mm2is about 5 cm2. The number of concrete anodes per precast prestressed concrete pile were calculated and determined using ISO standard 12696: Cathodic Protection of Steel in Concrete.

[0017] Ag / AgCl and stainless steel 304 reference electrodes were used to measure the change of corrosion potential of the reinforcing steel in concrete in saline soil. A minimum of 100 mV polarization decay is obtained from the measurement and the concrete piles are in good condition. The total maximum cross-section area of the anode CR60 and CVV cable is 33.3 cm2or 10.28% of the cross-section area of the concrete piles. This invention is the first success of the new precast concrete product with embedded sacrificial anode that can withstand impact load without any modification of concrete materials.

[0018] Description of the Drawing

[0019] Figure 1 shows the schematic drawing and wiring diagram of the CB20 in the 0.18x0.18x6.00 m. concrete pile.

[0020] Figure 2 shows the schematic drawing and wiring diagram of the CR20 in the 0.18x0.18x6.00 m. concrete pile.

[0021] Figure 3 shows the schematic drawing and wiring diagram of the CR40 in the 0.18x0.18x6.00 m. concrete pile.

[0022] Figure 4 shows the schematic drawing and wiring diagram of the CR60 in the 0.18x0.18x6.00 m. concrete pile.

[0023] RB, AN and RE are prestressed concrete wire (or steel rebar), sacrificial anode, and reference electrode respectively.

Claims

AMENDED CLAIMS received by the International Bureau on 30 January 2025 (30.01.2025)

1. Precast prestressed concrete piles with a minimum compressive strength of concrete 25 MPa embedded with zinc anode covered by cementitious-based materials, which the total cross-section area of the zinc anode and cementitious materials is not exceeding 10.28% that of the concrete piles, can endure impact load during pile installation without any critical damage and remain long durable in chloride-rich or marine environments.

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