Method For Monitoring Thixotropy In Concrete Mixing Drum
First Claim
1. A method for monitoring thixotropy of concrete, comprising:
- (A) rotating a concrete mix, or the components of a concrete, in a concrete mixing drum at a first mixing speed (S1) to mix completely the concrete mix components or otherwise to maintain the concrete in a completely mixed state; and
(B) measuring the thixotropy of the concrete mix by monitoring the reversible, time dependent change in viscosity occurring after rotational speed of the concrete mix in the mixing drum is altered by changing to another speed (S2) that is different from S1.
8 Assignments
0 Petitions
Accused Products
Abstract
The invention provides ‘thixotropy’ monitoring, by measuring the reversible, time-dependent reduction in viscosity occurring when concrete is subjected to mixing, and employs a mixing drum and conventional slump monitoring equipment as used on ready-mix trucks. In one embodiment, the drum is rotated until concrete is completely mixed; the speed is altered, such as by increasing it to a predetermined level; and the energy required to rotate the drum (ER) is monitored; the maximum (ER-MAX) and minimum (ER-MIN) values are recorded in computer memory; and these values are compared to pre-determined (target) values. Rheology factors (including viscosity, yield stress, and/or thixotropy) can be adjusted accordingly by adding liquid component(s) into the mix. This method, suitable for delivery of highly fluid concrete speed such as SCC, can involve transit and placement rheology targets during monitoring.
-
Citations
19 Claims
-
1. A method for monitoring thixotropy of concrete, comprising:
-
(A) rotating a concrete mix, or the components of a concrete, in a concrete mixing drum at a first mixing speed (S1) to mix completely the concrete mix components or otherwise to maintain the concrete in a completely mixed state; and (B) measuring the thixotropy of the concrete mix by monitoring the reversible, time dependent change in viscosity occurring after rotational speed of the concrete mix in the mixing drum is altered by changing to another speed (S2) that is different from S1. - View Dependent Claims (2, 3, 6, 7, 8, 9, 10, 13, 14, 15, 16, 17, 18, 19)
-
-
5. The method of claim 4 wherein a value determined by taking the difference between or ratio of ER-MAX and ER-MIN values is compared to a predetermined or target value stored in computer memory.
-
12. The method of claim 11 comprising determining when to adjust the concrete mix based on the comparison of the determined placement thixotropy to the predetermined value desired for the concrete at placement, said determination being based on at least one of factors selected from nature of the concrete mix components, volume of concrete mix, the effect of liquid additions to the concrete mix, estimated transit time from batching plant or dispatch center to placement, estimated waiting time at placement site, traffic congestion, ambient temperature, concrete temperature, humidity, minimum time needed to mix separate components into uniform mix, minimum time needed to incorporate and to mix completely a liquid component introduced into the concrete, minimum time needed to convert the concrete mix from transit rheology to placement rheology, and topography.
Specification