Abstract: 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.

Abstract: An automated robotic printing device for additive manufacturing or three-dimensional printing of an engineered cementitious composite (ECC) structure is provided. The device has a feeding system and an automated extrusion system configured to receive the ECC composition from the feeding system and deposit the ECC composition onto a target. The automated extrusion system comprising at least one robotic device comprising a tiltable and steerable deposition head that comprises an extrusion nozzle having a substantially rectangular opening and at least one shaping blade at a terminal end to shape and deposit the cementitious composition onto a target. Methods of additive manufacturing of a structure from the ECC compositions are also provided.

Abstract: Methods of preparing engineered cementitious composite precursors include carbonating a fly ash comprising >about 25% by weight of calcium oxide (CaO) and having a water content of >about 12% to <about 18% by weight of water by exposing the fly ash to a first gas stream comprising carbon dioxide to form a carbonated fly ash. A steel slag is also carbonated that comprises >about 40% by weight of calcium oxide (CaO) and having a water content of >about 12% to <about 18% by weight of water by exposing the steel slag to a second gas stream comprising carbon dioxide to form a carbonated steel slag. The carbonated fly ash and the carbonated steel slag are suitable for use as engineered cementitious composite precursors in a bendable engineered cementitious composite composition that further comprises Portland cement, a polymeric fiber, and a superplasticizer.

Abstract: Methods of preparing engineered cementitious composite precursors include carbonating a fly ash comprising >about 25% by weight of calcium oxide (CaO) and having a water content of >about 12% to <about 18% by weight of water by exposing the fly ash to a first gas stream comprising carbon dioxide to form a carbonated fly ash. A steel slag is also carbonated that comprises>about 40% by weight of calcium oxide (CaO) and having a water content of >about 12% to <about 18% by weight of water by exposing the steel slag to a second gas stream comprising carbon dioxide to form a carbonated steel slag. The carbonated fly ash and the carbonated steel slag are suitable for use as engineered cementitious composite precursors in a bendable engineered cementitious composite composition that further comprises Portland cement, a polymeric fiber, and a superplasticizer.

Abstract: Methods of preparing a cementitious structure for carbon dioxide (CO2) sequestration are provided. The cementitious structure may be a cast in a mold. First, a cementitious composite material comprising binder and water is conditioned, for example, in a mold by exposing the cementitious composite material to ?about 50% to ?about 80% relative humidity for ?about 3 hours to ?about 24 hours. The cementitious composite material is then dried to remove ?about 10% by weight of initial water in the cementitious composite material. The cementitious structure formed is capable of a carbon dioxide uptake level of greater than or equal to about 6% by weight binder. The cementitious structure has a tensile strain capacity of ?about 1% and a uniaxial tensile strength of ?about 1 MPa. The method may also include carbonating the cementitious structure, following by an optional further hydration process.

Abstract: A new civil infrastructure construction scheme is provided that is capable of meeting various objectives, including reducing climate change, addressing labor shortage issues, and enhancing construction productivity. Methods of forming load-bearing structures include placing a first reusable load-bearing element adjacent to a second reusable load-bearing element. The first reusable load-bearing element is fixed with respect to the second reusable load-bearing element without any adhesive or mortar. The first reusable load-bearing element and the second reusable load-bearing element respectively have a compressive strength of greater than or equal to about 25 MPa. The first and second reusable load-bearing elements optionally may be formed by additive manufacturing with a printable cementitious composition, such as an engineered cementitious composite.

Abstract: 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.

Abstract: A railway tie being constructed of an engineered cementitious composite (ECC) material having: (1) a minimum of 2% tensile ductility of ECC, (2) complete absence of alkali-silica reaction (ASR), (3) high fatigue resistance of ECC at least five times that of normal concrete, (4) self-healing ability of ECC requiring only water and air, and (5) customization of ECC for lower stiffness in the tie (60% that of normal concrete) and higher abrasion resistance in the seat (three times that of normal concrete).

Abstract: A railway tie being constructed of an engineered cementitious composite (ECC) material having: (1) a minimum of 2% tensile ductility of ECC, (2) complete absence of alkali-silica reaction (ASR), (3) high fatigue resistance of ECC at least five times that of normal concrete, (4) self-healing ability of ECC requiring only water and air, and (5) customization of ECC for lower stiffness in the tie (60% that of normal concrete) and higher abrasion resistance in the seat (three times that of normal concrete).

Abstract: A Thermally Adaptive Ductile Concrete (PCM-ECC) having a tensile ductility ceramic with 5 times the thermal resistance, 2 times the specific heat capacity, and 400 times the tensile strain capacity of regular concrete.

Abstract: A formulation of a spray applied fire-resistive engineered cementitious composite (SFR-ECC) which is made by addition of polymeric fibers, vermiculite, bonding agent and lightweight aggregates to cement and water. The SFR-ECC formulation is made in wet cement and can be spray-applied. The durable SFR-ECC exhibits thermal conductivities sufficient for fire resistance with increased tensile ductility and impact resistance.

Abstract: A Thermally Adaptive Ductile Concrete (PCM-ECC) having a tensile ductility ceramic with 5 times the thermal resistance, 2 times the specific heat capacity, and 400 times the tensile strain capacity of regular concrete.

Abstract: A formulation of a spray applied fire-resistive engineered cementitious composite (SFR-ECC) which is made by addition of polymeric fibers, vermiculite, bonding agent and lightweight aggregates to cement and water. The SFR-ECC formulation is made in wet cement and can be spray-applied. The durable SFR-ECC exhibits thermal conductivities sufficient for fire resistance with increased tensile ductility and impact resistance.

Abstract: A new class of ultra-high performance concrete with very high strength and very high tensile ductility (High Strength High Ductility Concrete) is provided that represents the culmination of two high performance cement-based composite systems, namely those of very high strength, and those of very high tensile ductility into a single composite system. The integration of high strength and ductility has been attained via the adoption of micromechanical analysis and design of fiber reinforced brittle matrix composites. In doing so, the new High Strength High Ductility Concrete material dramatically increases the energy absorption capabilities of structural systems employing this material, making it a very good candidate material where hurricanes, earthquake, impact and blast loads are a concern.

Abstract: Rapid repair and retrofit of existing infrastructures demand durable high early strength materials that not only deliver sufficient strength within a few hours of placement but also significantly prolong the maintenance interval. The invention comprises a class of newly developed polyvinyl alcohol (PVA) fiber-reinforced high early strength engineered cementitious composites (ECC) materials featuring extraordinary ductility. The tailoring of preexisting flaw size distribution through non-matrix interactive crack initiators in the composite matrix results in high tensile ductility. The resulting high early strength ECC materials are capable of delivering a compressive strength of 21 MPa (3.0 ksi) within 4 hours after placement and retaining long-term tensile strain capacity above 2%.

Abstract: Railway tie is based upon a fiber-reinforced brittle matrix composite material. The composite material is isotropic, demonstrating pseudo-strain hardening behavior in uniaxial tension, and material ductility by design, not relying on reinforcing bars or mesh embedded within concrete or other brittle cementitious matrices for durability, abrasion resistance, or crack width control. Reinforcing bars or mesh, pretensioned or otherwise, may be used within the tie to control the load capacity and load-deformation response. The properties of this fiber-reinforced brittle matrix composite material are adjusted to preferably work with casting, injection molding, or extrusion manufacturing methods.

Abstract: Cementitious composites engineered for self-healing, combining self-controlled tight crack width and extreme tensile ductility. Self-healing takes place automatically at cracked locations without external intervention. In the exemplary embodiment, fiber-reinforced cementitious composites with self-controlled tight crack width less than 50 ?m and tensile ductility more than 2% are prepared. Self-healing in terms of mechanical and transport properties recovery of pre-damaged (by pre-cracking) composite is revealed in a variety of environmental exposures, include wetting and drying cycles, water permeation, and chloride submersion.

Abstract: An extremely ductile fiber reinforced brittle matrix composite is of great value to protective structures that may be subjected to dynamic and/or impact loading. Infrastructures such as homes, buildings, and bridges may experience such loads due to hurricane lifted objects, bombs, and other projectiles. Compared to normal concrete and fiber reinforced concrete, the invented composite has substantially improved tensile strain capacity with strain hardening behavior, several hundred times higher than that of conventional concrete and fiber reinforced concrete even when subjected to impact loading. The brittle matrix may be a hydraulic cement or an inorganic polymer. In an exemplary embodiment of the teachings, the composites are prepared by incorporating pozzolanic admixtures, lightweight filler, and fine aggregates in Engineered Cementitious Composite fresh mixture, to form the resulting mixtures, then placing the resulting mixtures into molds, and curing the resulting mixtures.

Abstract: Pipe cladding is based upon a fiber-reinforced brittle matrix composite material. The coating is isotropic, demonstrating pseudo-strain hardening behavior in uniaxial tension, and damage tolerance by design, not relying on stratified layers of reinforcing mesh embedded within concrete or other brittle cementitious matrices for impact resistance, fracture toughness, or crack width control. The fiber reinforced brittle matrix composite cladding protects both the pipe and inner thin, anti-corrosion layer (if present) from impact or abrasion damage while permitting bending of coated and clad pipe. The finished composite clad can be in a simple circular form alone the pipe or in some complex form providing an integrated housing for electrical or optical fiber cables, or optical sensing sensors for continuous or intermittent sensing of pipeline leakage or failure.