Self-Reinforcing Cementitious Composites for 3D Printing
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Solution Overview
Problem
Conventional 3D printing of concrete structures faces challenges due to concrete's low tensile strength and brittle nature, which leads to premature degradation, and the need for steel reinforcement, which contradicts the automated and freeform nature of 3D printing.
Innovation Solution
A printable cementitious composition that is self-reinforcing, composed of Portland cement, calcium aluminate cement, fine aggregate, water, high-range water reducing agent, and polymeric fibers, exhibiting strain hardening behavior, eliminating the need for steel reinforcement and allowing for large-scale, durable, and complex structure creation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If steel reinforcement is added to printed concrete structures, then tensile strength is improved, but device complexity and contradiction with automated 3D printing paradigm increase
Solution Approach 1:
The cementitious composition is formulated to be self-reinforcing through internal polymeric fiber reinforcement, eliminating the need for external steel reinforcement and manual insertion processes. The fibers are uniformly distributed within the matrix, providing tensile strength automatically as the material is extruded and cured.
Solution Approach 2:
The invention uses a composite cementitious composition combining cement matrix with polymeric fibers (such as PVA, polypropylene, or polyester fibers). This composite structure provides both compressive strength from the cement matrix and tensile strength from the fibers, resolving the need for separate steel reinforcement.
2Strength
If steel reinforcement is used in concrete structures, then tensile strength is improved, but corrosion resistance deteriorates due to corrosion products introducing additional tensile forces
Solution Approach 1:
The invention replaces durable but corrosive steel reinforcement with non-corrosive polymeric fibers. While steel offers high strength, it suffers from corrosion over time. The polymeric fibers, though potentially less strong individually, provide sufficient reinforcement without the corrosion problem, ensuring long-term reliability in various environmental conditions.
3Ease of manufacture
If conventional concrete is used for 3D printing, then ease of manufacture is improved, but tensile strength and durability deteriorate due to low tensile strength and brittle nature
Solution Approach 1:
The invention formulates a specialized cementitious composite material that maintains the workability and printability of conventional concrete while incorporating polymeric fibers to dramatically improve tensile strength. The fiber-reinforced composite allows the material to be extruded through nozzles and layered during 3D printing while resisting cracking and failure under tensile stresses.
Solution Approach 2:
The invention modifies the chemical and physical parameters of conventional concrete by adding specific fiber types, volumes, and distributions. This changes the material's rheological properties and mechanical behavior, enabling it to maintain flowability for printing while developing high tensile strength during curing.
4Strength
If manual reinforcement insertion is performed after printing, then tensile strength is improved, but productivity and adherence to automated paradigm deteriorate
Solution Approach 1:
The cementitious composition is formulated to be self-reinforcing through internal polymeric fiber reinforcement, eliminating the need for external steel reinforcement and manual insertion processes. The fibers are uniformly distributed within the matrix, providing tensile strength automatically as the material is extruded and cured.
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 composition achieves high uniaxial tensile strength, tensile strain capacity, and compressive strength, enabling the construction of durable concrete structures without steel reinforcement, suitable for building-scale 3D printing and resistant to corrosion.
Implementation Method 1
The composition comprises Portland cement, a calcium aluminate cement, a fine aggregate, water, a high range water reducing agent, and a polymeric fiber
Implementation Method 2
In the hardened state, the composition may exhibit a uniaxial tensile strength of greater than or equal to about 2.5 MPa, a tensile strain capacity of greater than or equal to about 1%
Data Source
AI summary
Printable cementitious compositions for additive manufacturing are provided, that have a fresh state and a hardened state. In fresh state, the composition is flowable and extrudable in the additive manufacturing process. In the hardened state, the composition exhibits strain hardening. In one variation, the strain hardening is represented by a uniaxial tensile strength of ≥about 2.5 MPa, a tensile strain capacity of ≥about 1%, and a compressive strength at 100 hours of ≥about 20 MPa. In other variations, the composition includes Portland cement, a calcium aluminate cement, a fine aggregate, water, a high range water reducing agent (HRWRA), and a polymeric fiber, as well as one or more optional components selected from: fly ash, silica flour, microsilica, attapulgite nanoclay, and/or hydroxypropylmethyl cellulose (HPMC). Methods of additive manufacturing with such compositions are also provided.