The present disclosure relates to a medical cement composition containing calcium silicate in an amount of less than 20 wt % of a total weight of the composition, with a lithium salt being added thereto. The medical cement composition of the present disclosure has a low compressive strength of 12 MPa or less, after being hardened, for easy removal, excellent stability in storage, and high bioactivity.

Mineral fines reduce OPC content in concrete, mortar and other cementitious compositions, typically in combination with a pozzolanically active SCM. Mineral fines can replace and/or augment a portion of hydraulic cement and/or fine aggregate. Mineral fines can replace a portion of cement binder and fine aggregate as an intermediate that fills a size void between largest cement particles and smallest fine aggregate particles. Supplemental lime can enhance balance of calcium ions in the mix water and/or pore solution. Supplemental sulfate can address sulfate deficiencies caused by high clinker reduction, use of water reducers and/or superplasticizers, and SCMs containing aluminates. Concentrated or pure carbon dioxide (CO.sub.2) can be used to passivate alkaline values in highly alkaline materials, such as concrete washout fines, CKD, class C flyash, incinerator ash, bottom ash, or biomass ash. CO.sub.2 passivation or sequestration can be carried out before, during or after forming an initial concrete mix.

Mineral fines reduce OPC content in concrete, mortar and other cementitious compositions, typically in combination with a pozzolanically active SCM. Mineral fines can replace and/or augment a portion of hydraulic cement and/or fine aggregate. Mineral fines can replace a portion of cement binder and fine aggregate as an intermediate that fills a size void between largest cement particles and smallest fine aggregate particles. Supplemental lime can enhance balance of calcium ions in the mix water and/or pore solution. Supplemental sulfate can address sulfate deficiencies caused by high clinker reduction, use of water reducers and/or superplasticizers, and SCMs containing aluminates. Concentrated or pure carbon dioxide (CO.sub.2) can be used to passivate alkaline values in highly alkaline materials, such as concrete washout fines, CKD, class C flyash, incinerator ash, bottom ash, or biomass ash. CO.sub.2 passivation or sequestration can be carried out before, during or after forming an initial concrete mix.

A highly thixotropic 3D printing concrete and a manufacturing method therefor are provided. The weight percentage of each component calculated per cube of concrete is: 35-40% of cement, 0.1-0.4% of polycarboxylate superplasticizer, 0.1-0.4% of polypropylene fiber, 1.0-3.0% of special thixotropic agent for 3D printing concrete, and 12.5-14.5% of water, and the remainder is sand.

A highly thixotropic 3D printing concrete and a manufacturing method therefor are provided. The weight percentage of each component calculated per cube of concrete is: 35-40% of cement, 0.1-0.4% of polycarboxylate superplasticizer, 0.1-0.4% of polypropylene fiber, 1.0-3.0% of special thixotropic agent for 3D printing concrete, and 12.5-14.5% of water, and the remainder is sand.

A method of designing a cement slurry may include: (a) selecting at least a cement and concentration thereof, water and concentration thereof, and, optionally, at least one supplementary cementitious material and a concentration thereof, such that a cement slurry comprising the cement, the water, and, if present, the at least one supplementary cementitious material, meet a density requirement; (b) calculating a thickening time of the cement slurry using a thickening time model; (c) comparing the thickening time of the cement slurry to a thickening time requirement, wherein steps (a)-(c) are repeated if the thickening time of the cement slurry does not meet or exceed the thickening time requirement, wherein the selecting comprises selecting different concentrations and/or different chemical identities for the cement and/or the supplementary cementitious material than previously selected, or step (d) is performed if the thickening time of the cement slurry meets or exceeds the thickening time requirement; and preparing the cement slurry.

A method of designing a cement slurry may include: (a) selecting at least a cement and concentration thereof, water and concentration thereof, and, optionally, at least one supplementary cementitious material and a concentration thereof, such that a cement slurry comprising the cement, the water, and, if present, the at least one supplementary cementitious material, meet a density requirement; (b) calculating a thickening time of the cement slurry using a thickening time model; (c) comparing the thickening time of the cement slurry to a thickening time requirement, wherein steps (a)-(c) are repeated if the thickening time of the cement slurry does not meet or exceed the thickening time requirement, wherein the selecting comprises selecting different concentrations and/or different chemical identities for the cement and/or the supplementary cementitious material than previously selected, or step (d) is performed if the thickening time of the cement slurry meets or exceeds the thickening time requirement; and preparing the cement slurry.

A method of designing a cement slurry may include: (a) selecting at least a cement and concentration thereof, a water and concentration thereof, and one or more chemical additives and a concentration thereof such that a cement slurry formed from the cement, water, and the one or more chemical additives meet a density requirement; (b) calculating a thickening time of the cement slurry using a thickening time model; (c) comparing the thickening time of the cement slurry to a thickening time requirement, wherein steps (a)-(c) are repeated if the thickening time of the cement slurry does not meet or exceed the thickening time requirement, wherein the step of selecting comprises selecting concentrations and/or different chemical identities for the one or more chemical additives, cement, or water, or step (d) is performed if the thickening time of the cement slurry meets or exceeds the thickening time requirement; and (d) preparing the cement slurry.

A method of designing a cement slurry may include: (a) selecting at least a cement and concentration thereof, a water and concentration thereof, and one or more chemical additives and a concentration thereof such that a cement slurry formed from the cement, water, and the one or more chemical additives meet a density requirement; (b) calculating a thickening time of the cement slurry using a thickening time model; (c) comparing the thickening time of the cement slurry to a thickening time requirement, wherein steps (a)-(c) are repeated if the thickening time of the cement slurry does not meet or exceed the thickening time requirement, wherein the step of selecting comprises selecting concentrations and/or different chemical identities for the one or more chemical additives, cement, or water, or step (d) is performed if the thickening time of the cement slurry meets or exceeds the thickening time requirement; and (d) preparing the cement slurry.

A concrete composition and method include a portion of fine aggregate bearing a coating of a polymer or an admixture, which may be a continuous coating layer or a layer of powdered, discrete particles embedded in a binder. The polymeric coating may be an admixture in powdered form, a super absorbent polymer (insoluble in water, but absorbing water), or another polymer such as the acrylamides, co-polymers thereof, polyacrylamides, or the like (soluble in water). The coating absorbs water, but particles are too small to form significant voids. Water is absorbed into the concrete mix in far greater proportions (e.g. w/c ratio over 0.5) improving workability, doubling workability time, and improving ultimate compressive stress (strength).