Fabric-formed concrete formwork bags

Fabric-formed concrete formwork bags (also known as formwork bag concrete) are protective structures made of continuous bag-shaped flexible templates constructed from double-layered high-strength woven chemical fiber fabrics. Concrete is poured into the bags using a high-pressure pump.

I. Basic Structure and Principle The formwork bags are woven from high-strength filaments such as nylon, polypropylene, and polyester. The upper and lower layers of fabric are connected by nylon ropes to control the pouring thickness (typically 12-20cm). The formwork bags are permeable to water but impermeable to concrete slurry. During concrete pouring, excess water seeps out through the fabric pores, rapidly reducing the water-cement ratio to below 0.4, accelerating concrete setting, and increasing compressive strength.

II. Main Application Scenarios

Mortared concrete is mainly used in:

Hydraulic engineering: Earth-rock dams, dike slope protection, river, lake and coastline revetment and bottom protection projects

Transportation engineering: Slope protection on both sides of highways and railways

Environmental engineering: Large-area slope protection and seepage prevention for reservoirs, harbors, and waterway remediation

Special environments: Deep-water revetment and bottom protection can be directly constructed underwater without the need for cofferdams

III. Construction Process

Slope treatment: Level the slope surface, remove debris, and ensure the slope flatness is no more than 10cm.

Mortared concrete bag laying: Lay the bags from the toe of the slope to the top, leaving a longitudinal shrinkage allowance, with an overlap width of no less than 30cm between adjacent bags.

Concrete filling: Use a concrete pump, with a pumping distance not exceeding 50 meters, an outlet pressure of 0.2-0.3MPa, and pour in layers from bottom to top.

Curing: Cure for at least 7 days after filling. Keep the surface moist.

IV. Technical Advantages

Convenient Construction: One-time spraying molding, fast construction speed, and high degree of mechanization.

Strong Adaptability: Adaptable to various complex terrains, especially suitable for deep-water bank protection, and can be directly constructed underwater.

Stable Quality: Good integrity, good durability, and long service life (underwater formwork concrete can last up to 100 years).

Good Economy: Saves labor and time, low maintenance costs, and high overall benefits.

V. Key Points for Quality Control

Slope flatness error ≤ 5 cm

Thickness deviation controlled within -5% to +8%

Concrete strength grade C15 to C30

Slump controlled within 18 to 25 cm

Filling speed should be controlled within 10 m³/h

With its unique construction advantages and good protective effect, formwork concrete technology has become one of the preferred technologies for slope and bank protection in water conservancy projects.