Products | Application of new synthetic "spherical sand" in UHPC
Release time:
2022-04-15
Application of new synthetic "spherical sand" in UHPC
1. Introduction to ultra-high performance concrete
Ultra-high performance concrete (UHPC for short) is a general term for cement-based composite materials with a compressive strength of more than 150MPa, ultra-high toughness and ultra-long durability, including ultra-high performance fiber reinforced concrete (UHPFRC), reactive powder concrete (RPC), ultra-high performance fiber reinforced cement-based composites (UHPFRCC), etc.
2. Benchmark mix ratio
3. Specimen preparation and maintenance
Specimen preparation method and curing system: Stir the dry mix except the fiber for 5 minutes, add water and high-efficiency water-reducing agent mixture and stir until a slurry is formed, gradually add steel fiber by screening method, stir for 5 minutes after adding, discharge the material into the mold; cure at room temperature for 8h-12h and demould, steam cure at 90℃ for 72h, and cure at room temperature until 28d for testing.
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4. Introduction of special aggregate sand
Sunshine molding sand (HYTIDE SF series) is made from a variety of raw materials through special processes such as mixing, refining, granulation and screening. Its dense crystal structure ensures high hardness and high strength. Its perfect spherical shape and glass surface enrich its application areas.
Meet the standards of Jiangsu Provincial Engineering Quality Inspection Center - "Construction Sand"
Supply brand:
HYTIDE SF005, Number of stitches: 40-140 stitches;
HYTIDE SF520, stitch count, 8-40 stitches;
Typical data:
Fineness modulus: 2.5;
Total crushing value index of artificial sand: 12.2%;
Radioactivity: internal/external radiation index is 0.1;
Alkali-silica reactivity (14d expansion rate): 0.07%;
5. Application and construction
Currently, the most mature application of UHPC is steel bridge paving. The steel-UHPC composite bridge deck has greatly improved the stiffness of the bridge deck, and has effectively solved the "damage of steel bridge deck pavement" and "fatigue cracking of steel structure" - the pain points and difficulties of the two major steel bridges. Typical projects: 21,000 m2 of paving of the Yellow River Bridge on Fenghuang Road in Jinan (2021-8, China Communications Construction Second Engineering Bureau Wuhan Port New Materials Construction), 65,000 m2 of UHPC (STC) paved in 48 days on the Dongting Lake Bridge (suspension bridge) of Hangzhou-Ruili Expressway in 2017 (Hunan Zhonglu Huacheng/Guangdong Guansheng Civil Construction).
6. Questions and Answers
1. What is the particle size range of sunshine sand? Water absorption index?
The particle size of sunshine sand is 8-140 mesh (without powder), which can be screened into two specifications: SF520 (8-40 mesh) and SF005 (40-140 mesh). The water absorption rate is less than 0.5%.
2. What are the advantages of Sunshine Sand in UHPC?
A. Sunshine Sand is a regular spherical sand with a water absorption rate of less than 0.5% and does not contain powder. It can reduce the water-binder ratio of UHPC and improve its strength. At the same time, it can improve the fluidity of UHPC and improve its pumping performance.
B. As the water-binder ratio is reduced, the concrete becomes denser, which improves the durability of UHPC;
3. What is the bulk density of Sunshine Sand? How much is it used in UHPC?
The bulk density of Sunshine Sand SF005 is 2200KG/m³, and the bulk density of SF520 is 2100KG/m³. In UHPC, SF005 sand is preferred, and the amount is 30-50% of the total amount of sand. The amount of sand can also be adjusted appropriately according to the bulk density of concrete.
4. Is the sunlight sand stable in concrete?
A. Pressure steam pulverization rate test: Pressure steaming for 48 hours at 215℃ and 2.0MPa, the pulverization rate is 1.86%, which is better than the standard (the standard is <5.9%, pressure steaming for 3 hours);
B. Micro powder substitutes for glue strength test. The specific gravity of cement is increased by micro powder, and the flexural and compressive strengths drop sharply. This shows that spherical aggregates are inactive and have strong stability.
C. Strong alkali excitation: Soak the molding sand powder in 10% NaOH aqueous solution for 72 hours, and there is no hardening phenomenon;
D. SGS test report: Magnetite: 40%, Dicalcium Silicate: 59%, Hematite: 1%; Complexes of calcium silicate and calcium ferrite are generated during the high-temperature smelting process.
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