Wall Tie Screw

Wall Tie Screw is an independent steel structural component widely used in concrete formwork fastening systems. It is composed of screw body, threaded sections and matched fastening nuts. Each structural part bears separate mechanical functions, and the whole assembly can realize formwork tensioning and positioning independently without extra auxiliary hardware. Carbon structural steel serves as the main raw material. Two common structural forms are integral full‑thread type and segmented assembled type. Integral wall tie screw is wholly embedded in concrete for one‑time application. Assembled wall tie screw consists of middle embedded section and detachable outer threaded segments. The outer threaded parts can be unscrewed and recycled after concrete hardening. Thread sections are processed by thread rolling technology, improving thread‑tooth surface hardness and wear resistance for repeated assembly and disassembly. Fastening nuts are produced by forging or casting crafts, and their structural integrity guarantees stable clamping force under lateral pressure from fresh concrete. Positioning cones and plastic sleeves can be equipped to accurately control wall thickness and reduce subsequent surface repairing workload. For waterproof working conditions, a water‑stop plate can be fully welded on the middle of screw body to cut off capillary water seepage passages through wall penetration points.

Multiple surface anti‑corrosion treatments adapt to various construction environments. Hot‑dip galvanizing forms compact zinc‑iron alloy protective layers covering screw body and thread teeth. This coating provides reliable resistance against rainwater, humid air and salt‑fog corrosion, suitable for long‑term outdoor and underground construction projects. Electro‑galvanizing creates relatively thin zinc layer on steel surface, applicable for short‑cycle construction projects with low corrosion risk. Black oxide finish applies to temporary dry‑environment projects without high anti‑corrosion requirements. Paint finishing is rarely adopted for threaded parts, since paint layers are easy to peel off under thread friction and concrete impact. Ordinary wall tie screw without water‑stop plate is mainly applied for non‑waterproof concrete wall structures. It bears expanding lateral force generated during concrete pouring, keeps fixed gap between opposite formwork panels, and prevents formwork bulging, shifting and deformation.

Core dimensional parameters determine practical mechanical performance. Screw body diameter is a critical tensile‑load indicator, larger diameter corresponds to higher ultimate tensile capacity. Total effective length shall match designed wall thickness together with formwork panel thickness and on‑site operating space. Thread specifications must be consistent with supporting nuts. Mismatched threads will cause poor meshing, insufficient clamping force and component slipping. This accessory is compatible with timber formwork, steel formwork and multiple combined formwork assemblies. Dimensional tolerances shall comply with corresponding international technical specifications to achieve reliable physical fitting during on‑site assembly. For waterproof‑type wall tie screw, the size of water‑stop plate and welding quality need to meet anti‑seepage requirements under designed water head.

Prior to construction deployment, visual inspection and sampling mechanical tests shall be carried out as independent inspection workflows. Visual examination covers screw body bending deformation, surface cracks, thread‑tooth damage and anti‑corrosion‑layer peeling. Recycled outer screw segments require stricter inspection standards. Even with intact outer appearance, invisible metal fatigue may accumulate after repeated load cycles and cannot be judged merely through surface observation. Sampling tensile tests verify ultimate bearing capacity and anti‑deformation performance. Components with permanent bending, thread slipping and structural cracks must be screened out and scrapped, and shall not be mixed into construction usage. Secondary modification operations such as cutting, welding and hole‑drilling on finished wall tie screw are prohibited. Unauthorized alteration will change original steel section characteristics and weaken overall tensile performance of the component.

Assembled wall tie screw supports cyclic reuse. After concrete curing and formwork dismantling, detachable outer threaded segments can be unscrewed and recovered. Concrete mortar, dust and foreign residues attached to thread grooves need thorough cleaning before next installation. Impurities trapped inside thread gaps will cause nut jamming and interfere with normal assembling and clamping effect in subsequent service cycles. Finished components shall be stored in dry and ventilated surroundings, sorted and stacked by specification, avoiding long‑term rain soaking and direct contact with damp soil. Improper on‑site operations include selecting insufficient screw diameter, mismatching screw length with wall thickness, insufficient tightening of nuts and applying load exceeding rated limit. These improper practices may trigger formwork bulging, component fracture and dimension deviation of concrete walls. As an independent tension‑bearing fastening unit for formwork systems, its structural integrity and mechanical stability directly affect formwork safety and concrete forming accuracy, and constitute essential preconditions for cast‑in‑place concrete wall construction.