Product | Application of New Synthetic "Spherical Sand" in UHPC
1. An introduction to ultra-high performance concrete
Ultra-high-performance concrete (UHPC for short) refers to the general term for cement-based composite materials with a compressive strength of more than 150 MPa, ultra-high toughness and ultra-long durability, including ultra-high-performance fiber reinforced concrete (UHPFRC), reactive powder concrete (RPC), ultra-high-performance fiber-reinforced cementitious composites (UHPFRCC), etc.
2. Baseline mix ratio
3. Specimen preparation and maintenance
Specimen preparation method and maintenance system: stir the dry mix except fibers for 5 minutes, add water and superplasticizer mixture and stir to form a slurry, gradually add steel fibers by sieving method, add and stir for 5 minutes, then discharge into the mold ; Normal temperature curing 8h-12h demoulding, 90 ℃ steam curing 72h, normal temperature curing to 28d test.
4. The introduction of special aggregate sand
Sunshine sand (HYTIDE SF series) is made from a variety of raw materials after mixing, refining, granulation and other special processes and then sieving. Its dense crystal phase structure ensures high hardness and high strength, perfect spherical body and glass body surface and other characteristics are rich its application areas.
Meet the standard of Jiangsu Engineering Quality Inspection Center - "Sand for Construction"
HYTIDE SF005, mesh: 40-140 mesh;
HYTIDE SF520, mesh, 8-40 mesh;
Fineness modulus: 2.5;
The total crushing value index of artificial sand: 12.2%;
Radioactivity: Internal/External Exposure Index 0.1;
Alkali silicic acid reactivity (14d expansion rate): 0.07%;
5. Application and construction
At present, the most mature application of UHPC is steel bridge pavement. The steel-UHPC composite bridge deck greatly improves the stiffness of the bridge deck, and solves the problem of “steel bridge deck pavement damage” and “steel structure fatigue cracking”—two major steel bridges. Typical projects: Jinan Fenghuang Road Yellow River Super Bridge paving 21,000 square meters (2021-8 CCCC Second Harbor Bureau Wuhan Harbor New Material Construction), 2017 Hangrui Expressway Dongting Lake Bridge (Suspension Bridge) Pavement in 48 days UHPC (STC) 65000 ㎡ (Huacheng Middle Road in Hunan/Guangdong Guansheng Civil Construction).
6. Answers to questions
1. What is the particle size range of sunshine sand? Water absorption index?
The particle size of sunshine sand is 8-140 mesh (excluding powder), which can be sieved into two specifications: SF520 (8-40 mesh) and SF005 (40-140 mesh), water absorption rate <0.5%;
2. What are the advantages of sunshine sand in UHPC?
A. Sunshine sand is a regular spherical shape, and the water absorption rate is less than 0.5%. It does not contain powder, which can reduce the water-to-binder ratio of UHPC, improve the strength, and at the same time improve the fluidity of UHPC and improve the pumping performance;
B. Due to the reduced water-binder ratio, the concrete is denser, which improves the durability of UHPC;
3. What is the bulk density of sunshine sand? Usage in UHPC?
The bulk density of sunshine molding sand SF005 is 2200KG/m³, and the bulk density of SF520 is 2100KG/m³; in UHPC, it is recommended to use SF005 molding sand.
4. Is the sunshine sand stable in concrete?
A. Pressure steaming pulverization rate test: pressure steaming at 215℃ and 2.0MPa for 48h, the pulverization rate is 1.86%, which is better than the standard (the standard is <5.9%, pressure steaming for 3h);
B. Micropowder substitute for glue strength test, the specific gravity of micropowder replacing cement is increased, the flexural and compressive strengths drop sharply, and the spherical aggregate is inactive and has strong stability;
C. Strong alkali excitation: soak molding sand powder with 10% concentration NaOH aqueous solution for 72H, no hardening phenomenon;
D. SGS test report: magnetite: 40%, dicalcium silicate: 59%, hematite: 1%; a complex of calcium silicate and calcium ferrite is formed during high temperature smelting.