A hydraulic composition includes in relative parts by mass with respect to the cement 100 parts of cement the particles of which have a BET specific surface area comprised from 1.20 to 5 m.sup.2/g; 32 to 42 parts of water; 5 to 50 parts of a mineral addition A1 the particles of which have a D50 less than or equal to 6 m and selected from silica fume, metakaolin, slag, pozzolans or mixtures thereof; 90 to 230 parts of sand the particles of which have a D50 greater than or equal to 50 m and a D90 less than or equal to 3 mm; 0.0001 to 10 parts of a superplasticizer, the active material concentration of which is 15% by mass.

Provided are early-strength and quick-setting ultra-high performance concrete (UHPC), and a preparation method and use thereof. The early-strength and quick-setting UHPC includes, in parts by mass: 110 parts to 180 parts of a red mud, 70 parts to 80 parts of a silica fume, 130 parts to 290 parts of a cement, 400 parts to 500 parts of a quartz sand, 10 parts to 15 parts of a water-reducing agent, 80 parts to 100 parts of water, and 50 parts to 75 parts of a steel fiber. The preparation method includes: subjecting the silica fume, the cement, the quartz sand, and the red mud to first mixing to obtain a first premix; subjecting the first premix, the water, and the water-reducing agent to second mixing to obtain a second premix; and subjecting the second premix and the steel fiber to third mixing to obtain the early-strength and quick-setting UHPC.

A method for producing a flexural hybrid span beam includes casting a first layer of ultra-high performance concrete (UIHPC) into a bottom of a mold, the first layer comprising steel fibers that are randomly oriented and dispersed. The method includes self-curing the first layer for at least 48 hours to form an unfinished top surface of the first layer. The method includes casting a second layer of plain concrete, over the unfinished top surface of the first layer, in the mold, wherein the second layer of plain concrete is not reinforced by steel bars. The method includes curing the first layer and the second layer to form the flexural hybrid span beam. An interface between the first layer and the second layer is substantially flat and has a periphery conforming to a shape of the mold.

A hydraulic binder includes in mass percent from 20 to 82% of a Portland cement the particles of which have a D.sub.50 comprised from 2 m to 11 m; from 15 to 56% of a non-pozzolanic mineral addition A1, the particles of which have a D.sub.50 from 1 to 150 m and selected from among limestone additions, siliceous additions, siliceous limestone mineral additions, calcined shales, zeolites, burnt plant ashes, and mixtures thereof; from 4 to 30% of pozzolanic mineral addition A2, the particles of which have a D.sub.50 from 1 to 150 m; a sum of the percentages of the Portland cement, the non-pozzolanic mineral addition A1 and the pozzolanic mineral addition A2 being comprised from 90 to 100%.

A concrete product is produced by providing red dune sand having a particle size of 45 microns or less and mixing the red dune sand with hydraulic cement in a ratio of about 30% of the cement being replaced by the red dune sand. The cement and red dune sand are then mixed with fine and course aggregate, water and a superplasticizer and cast after pouring into a mold cavity. Then within 24 hours of casting, the cast article is steam cured for 12 hours under atmospheric pressure, demolded and placed in an auto clave at 100% humidity. The temperature in the auto clave is raised to 180 C. within one to two hours and maintained at that temperature for 4 to 5 hours. The temperature also increases the pressure to about 10 bars. The pressure is released to reach atmospheric pressure within 20-30 minutes and the temperature reduced gradually, so that the article can be removed.

Class C fly ash-based cementitious materials, concretes, and related techniques are disclosed. In accordance with some embodiments, an activated class C fly ash-based cementitious material may be produced by intergrinding class C fly ash (e.g., classified to remove quartz and/or other contaminants and, thus, increase the reactive materials present), an activator, sodium citrate, borax, and a polycarboxylate material. The class C fly ash may have an amorphous glass content of about 60 wt % or more, a calcium oxide (CaO.sub.2) content of about 20 wt % or more, and a quartz content of about 10 wt % or less. The activator may be a chemical which reacts with class C fly ash to form strtlingite structures therein when introduced with water. In some cases, the cementitious material may be provided as an all-in-one powder blend. In some cases, techniques disclosed herein may be utilized in providing a fast-setting flowable fill material.

A method for designing a cement composition may include: providing a target compressive strength and a target composition density; selecting at least one cementitious material from a plurality of cementitious materials; calculating a required amount of water to produce a cement composition with the target composition density, the cement composition comprising the water and the at least one cementitious material; calculating a compressive strength of the cement composition based at least in part on a model of compressive strength; comparing the calculated compressive strength to the target compressive strength; and preparing the cement composition with the calculated compressive strength.

Fly ash, a byproduct of coal combustion, has extensive and beneficial use in concrete and cement mixes. Closure of coal-powered power plants has caused a significant reduction in live fly production ash and turned attention of concrete producers to harvested fly ash, which can be excavated from closed coal powered plant's impoundment to satisfy the need in the industry for fly ash. However, challenges arise from the unique qualities of harvested fly ash, which according to the art requires extensive grinding and other processing measures to render it suitable for concrete applications. This invention discloses the use of harvested fly ash in concrete where the particle size percentage of the fly ash is greater than that generally accepted in the art. Also disclosed is a method for use of this harvested fly ash as a supplementary cementitious material in concrete mixes.

The present invention discloses a crack-resistant ultra-high performance concrete (UHPC) for underground engineering in water-rich strata, preparation method, and application thereof, belonging to the technical field of building materials. The concrete is prepared from the following raw materials in parts by weight: 550-650 parts of cement, 140-180 parts of fly ash, 120-150 parts of silica fume, 200-300 parts of calcined shield tunnel slag, 30-50 parts of micron-scale magnesium oxide, 30-50 parts of nano-scale magnesium oxide, 30-50 parts of rheology-modifying material, 800-1000 parts of lightweight aggregate, 4-8 parts of water reducer, and 50-200 parts of water. The rheology-modifying material has a fluidity ratio of 106%. The present invention incorporates calcined shield tunnel slag, micron/nano-scale magnesium oxide, and lightweight aggregate into the UHPC, which effectively suppresses shrinkage and reduces crack formation.

The present disclosure relates to cement compositions including Portland cement and volcanic ash. An exemplary cement composition includes about 10 wt % to about 85 wt % of Portland cement, and about 10% by weight of cement (BWOC) to about 70% BWOC of volcanic ash.