Expansive Grout Joint Seal for Concrete Modules
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing joint seals between precast concrete modules for underground water storage structures are prone to leaks due to imperfections in the joint surface and the inherent creep and relaxation properties of rubber sealants, leading to instability and watertightness issues over time.
Innovation Solution
A joint seal system utilizing high-strength precast concrete, post-tensioning technology, and expansive grout injection through internal ducts, where continuous closed-cell neoprene sealing strips are bonded to the module edges, and non-shrink grout is injected to support pre-stress loading and provide long-term watertightness, reducing the reliance on rubber seals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If rubber seal strips are used for joint sealing between precast concrete modules, then initial watertightness is achieved, but long-term watertightness deteriorates due to creep and relaxation of the rubber material
Solution Approach 1:
The patent changes the physical state of the sealing material from flexible rubber to rigid cementitious grout. The grout is injected in a plastic state and then cures to a rigid state, eliminating the creep and relaxation issues inherent in rubber sealants while maintaining the sealing function.
Solution Approach 2:
The patent creates a composite sealing system combining cementitious grout with embedded fibers (such as polypropylene or steel fibers) to achieve both the flowability needed for injection and the structural integrity needed for long-term sealing performance. This composite approach allows the material to be injected through narrow ducts while providing durable, crack-resistant sealing.
2Stability of the object's composition
If conventional grout is used to fill joint cavities, then structural stability is improved, but watertightness deteriorates due to shrinkage and cracking
Solution Approach 1:
The patent modifies the grout composition to include expansive agents that cause controlled expansion during curing. This compensates for the natural shrinkage of cementitious materials, preventing crack formation while maintaining structural stability and ensuring long-term watertightness.
Solution Approach 2:
The patent uses non-metallic ducts (such as plastic or coated ducts) that are left in place to serve as permanent formwork and injection channels. These ducts are designed to be compatible with the grout material and remain intact during the grouting process, eliminating the need for temporary forms and ensuring complete cavity filling.
3Force
If post-tensioning cables are used to compress joint segments, then initial joint compression is achieved, but long-term pre-stress is lost due to relaxation of the compression system
Solution Approach 1:
The patent replaces the mechanical post-tensioning system with a chemically-bonded grout system. The cementitious grout creates permanent bonds between concrete segments through adhesion and cohesion, eliminating the need for ongoing mechanical tension and avoiding the relaxation issues inherent in cable-based systems.
Solution Approach 2:
The patent applies the compressive force through the grout material itself during the grouting process. The grout is injected under pressure and cures in place, pre-compressing the joint surfaces and creating permanent bonds before the structure is subjected to service loads, thereby eliminating future settlement and leakage issues.
4Reliability
If impermeable membranes are used for joint sealing, then watertightness is improved, but flexibility and adaptability to joint movement deteriorate
Solution Approach 1:
The patent uses a cementitious grout with controlled expansion properties that allows for minimal movement accommodation through the expansion mechanism while maintaining impermeability. The grout can expand to fill voids and accommodate minor dimensional changes in the concrete segments without compromising the sealing function.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system achieves long-term watertightness by curing the grout under pressure, eliminating creep and relaxation issues that cause leaks in conventional joints, ensuring stable and efficient water retention and discharge control.
Implementation Method 1
a non-shrink, expanding, cementitious grout is injected into the joint
Implementation Method 2
The modules are then aligned and compressed against each other by tightening the post tensioning cables
Data Source
AI summary
The invention is a watertight joint seal for precast concrete box modules used to form underground enclosures to control the discharge of water runoff from roads and parking areas. The modules become sections of a tunnel structure, and the joint seal of the invention is constructed by forming the end of the walls of each module with mating offset inside and outside edge surfaces that are joined by an intermediate surface, applying sealing strips to the inside and outside edge surfaces of one end wall, compressing the modules against each other, and injecting an expansive grout into the cavity formed by the sealing strips and the modules' end surfaces. After the grout cures under the pressure resulting from its own expansion, the joint is watertight and does not suffer from leakage through cracks caused by the creep and relaxation characteristics which generally occur in joints formed with conventional grout or only rubber gaskets.