Measurements of yield stress and plastic viscosity of cement-based materials via concrete rheometer

• US 7,624,625 B2
• Filed: 04/27/2007
• Issued: 12/01/2009
• Est. Priority Date: 04/29/2006
• Status: Active Grant

• Current Assignee: Wen-Chen Jau
• Original Assignee: Wen-Chen Jau
• Inventors: Jau, Wen-Chen
• Primary Examiner(s): Williams; Hezron
• Assistant Examiner(s): Gissel; Gunnar J
• Application Number:
  US11/790,880
• Publication Number:
  US 20080060423A1
• Time in Patent Office: 949 Days
• Field of Search: 73/543.1, 73/542.8, 73/542.3, 73/540.1
• US Class Current: 73/54.31
• CPC Class Codes: G01N 11/14 by using rotary bodies, e.g. vane G01N11/16 takes precedence
• CPC Class Codes: G01N 2203/0676 Force, weight, load, energy, speed or acceleration
• CPC Class Codes: G01N 33/383 Concrete, cement

Abstract

A rheometer can be used to measure yield stress and viscosity of a cement-based material with excellent results. It mainly includes a drum and at least one adaptive vane assembly. The adaptive vane assembly is replaceably connected to a shaft. The shaft rotates relative to the drum. The ratio of radius (r₁) of the adaptive vane assembly to radius (r₀) of the drum is between 0.1˜0.6. The shaft is rotated with a minimum rotational speed more than 0.001 rad/s, and then can measure its torque at constant speed. Accordingly, the rheometer can greatly reduce the disturbance of vanes of the adaptive vane assembly upon the cement-based materials and reduce the slippage among particles and the vanes. Moreover, the minimum shear stress is defined as a yield stress.

Claims

1. A rheometer (200,300) used to measure rheology of a cement-based material, comprising:

a drum (210,310) used to accommodate cement-based material;

a shaft (220,320) having one end pushed into the drum (210,310);

a rotational speed controller (230) configured to adjust rotational speed of the shaft (220,320) or the drum (210,310); and

at least one adaptive vane assembly (240,340,280,290), which is replaceably connected to the shaft (220,320), wherein the adaptive vane assembly (240,340,280,290) contains at least two vanes (241,281,291),

wherein the ratio (r₁/r₀) of radius (r₁) of the said adaptive vane assembly (240,340,280,290) to radius (r₀) of the drum (210,310) is between 0.1˜

0.6.

2. The rheometer (200,300) as claimed in claim 1, wherein the gap width (r₀−

r₁) is at least 2.5 times of maximum aggregate size.

3. The rheometer (200,300) as claimed in claim 1, wherein the vanes (241) of said adaptive vane assembly (240) are vertical vanes.

4. The rheometer (200,300) as claimed in claim 1, wherein the vanes (281,291) of said adaptive vane assembly (280,290) are oblique vanes with included angle in horizontal plane that rotates clockwise or counter-clockwise.

5. The rheometer (200,300) as claimed in claim 1, wherein there are a plurality of said adaptive vane assembly (280,290) mounted onto the shaft (220,320) side-by-side.

6. The rheometer (200,300) as claimed in claim 1, wherein the said cement-based material is selected from the group consisting of concrete, mortar and cement paste.

7. The rheometer (200,300) as claimed in claim 1, wherein the adaptive vane assembly (240,340,280,290) is assembled in a manner to measure viscosity and yield stress of concrete and to determine corresponding slump and slump flow.

8. The rheometer (200,300) as claimed in claim 1, wherein the adaptive vane assembly (240,340,280,290) is assembled in a manner to qualify SCC by measuring torque and rotational speed of concrete.

9. The rheometer (200,300) as claimed in claim 1, wherein the shaft (220) is rotatable.

10. The rheometer (200,300) as claimed in claim 1, wherein the drum (310) is rotatable.