U.S. patent application number 13/649489 was filed with the patent office on 2017-10-19 for method for adjusting concrete rheology based upon nominal dose-response profile.
The applicant listed for this patent is Roy J. Cooley, Eric Koehler, Mark F. Robert, Steve Verdino. Invention is credited to Roy J. Cooley, Eric Koehler, Mark F. Robert, Steve Verdino.
Application Number | 20170297223 13/649489 |
Document ID | / |
Family ID | 50476108 |
Filed Date | 2017-10-19 |
United States Patent
Application |
20170297223 |
Kind Code |
A9 |
Koehler; Eric ; et
al. |
October 19, 2017 |
Method For Adjusting Concrete Rheology Based Upon Nominal
Dose-Response Profile
Abstract
The invention relates to a method for adjusting concrete
rheology requiring only that load size and target rheology value be
selected initially rather than requiring inputs into and
consultation of a lookup table of parameters such as water and
hydration levels, mix components, temperature, humidity, aggregate
components, and others. Dosage of particular rheology-modifying
agent or combination of rheology-modifying agents is calculated
based on a percentage of a nominal dose calculated with reference
to a nominal dose response ("NDR") curve or profile. The NDR
profile is based on a correlation between a rheology value (e.g.,
slump, slump flow, yield stress) and the rheology-modifying
agent(s) dose required to change rheology value by one unit (e.g.,
slump change from 2 to 3 inches) such that exemplary methods can
employ corrective dosing based on the NDR and the measured
deviation by the system.
Inventors: |
Koehler; Eric; (Boston,
MA) ; Robert; Mark F.; (North Andover, MA) ;
Cooley; Roy J.; (West Chester, OH) ; Verdino;
Steve; (Hamilton, OH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Koehler; Eric
Robert; Mark F.
Cooley; Roy J.
Verdino; Steve |
Boston
North Andover
West Chester
Hamilton |
MA
MA
OH
OH |
US
US
US
US |
|
|
Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 20140107844 A1 |
April 17, 2014 |
|
|
Family ID: |
50476108 |
Appl. No.: |
13/649489 |
Filed: |
October 11, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12821451 |
Jun 23, 2010 |
8311678 |
|
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13649489 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C04B 40/0032 20130101;
B28C 7/026 20130101; C04B 40/0032 20130101; G05D 21/02 20130101;
C04B 28/02 20130101; C04B 2103/0079 20130101 |
International
Class: |
B28C 7/02 20060101
B28C007/02; G05D 21/02 20060101 G05D021/02; C04B 40/00 20060101
C04B040/00 |
Claims
1-18. (canceled)
19. A method for controlling rheology of a hydratable cementitious
composition in a rotatable mixer drum on a concrete delivery
vehicle having an automated system for monitoring and adjusting
concrete rheology, wherein the improvement comprises: providing a
truck comprising a rotatable mixer in the form of a drum for mixing
and measuring rheology of a hydratable cementitious composition and
further comprising a computer processor unit ("CPU") programmed to
monitor and to adjust rheology of hydratable cementitous
composition contained within said mixing drum; and (a) entering
into said CPU a target rheology value ("TRV") and load size for a
hydratable cementitious composition containing or intended to
contain a particular rheology-modifying agent or combination of
rheology-modifying agents within said truck mixing drum; and (b)
obtaining a current rheology value ("CRV") of hydratable
cementitious composition contained within said truck mixing drum;
(c) comparing through use of said CPU the current rheology value
obtained in step (b) against a nominal dose response ("NDR")
profile stored in CPU-accessible memory and wherein said NDR is
based on at least one data set wherein various dose amounts of a
particular rheology-modifying agent or combination of
rheology-modifying agents and their correlative effect on rheology
value (such as slump, slump flow, or yield stress) is retrievably
stored, and determining the nominal dose of said particular
rheology-modifying agent or combination of rheology-modifying
agents required to change the obtained CRV to the TRV specified in
step "(a)"; (d) dosing the hydratable cementitious composition
contained in said truck mixing drum with a percentage of said
particular rheology-modifying agent or combination of
rheology-modifying agents that is selected or pre-selected from 5%
to 99% based on the nominal dose determined in step (c) required
for changing said obtained CRV to said TRV as specified in step
(a); (e) obtaining a subsequent CRV of the hydratable cementitious
composition contained in said truck mixing drum after the
percentage of the nominal dose of the particular rheology-modifying
agent or combination of rheology-modifying agents selected or
preselected in step (d) is added into and uniformly mixed with said
hydratable cementitious composition; comparing the dose selected or
preselected in step (d) to the dose according to the NDR profile
for the same change in the rheology value from step (b) to step
(e), and determining the scaling factor ("SF") by which to adjust
the dose from the NDR profile, where SF is defined as the actual
dose from step (d) divided by the nominal dose to achieve the same
change in rheology value indicated by the NDR profile; and (f)
mixing into the hydratable cementitious composition the particular
rheology-modifying agent or combination of rheology-modifying
agents in an amount calculated in terms of SF multiplied by the
dose from the NDR profile indicated to convert the current CRV
measured in step (e) to the TRV specified in step (a); and wherein
steps (a) through (f) are done by said CPU.
20. The method of claim 19 wherein steps (e) and (f) are repeated
whenever the CRV is less than or greater than the TRV by a
predetermined amount.
21. The method of claim 20 wherein said NDR profile described in
step (c) is derived as an average of a plurality of dose response
curves for the particular rheology-modifying agent or combination
of rheology-modifying agents.
22. The method of claim 21 wherein, in said NDR profile, at least
two dose response curves contains at least one non-homogeneous
parameter selected from concrete mix design, concrete mix
ingredient source, temperature, degree of hydration, water/cement
ratio, and aggregate amount.
23. The method of claim 22 wherein, in said NDR profile, at least
two dose response curves contains at least two non-homogeneous
parameters selected from concrete mix design, concrete mix
ingredient source, temperature, degree of hydration, water/cement
ratio, and aggregate amount.
24. The method of claim 19 wherein said at least one
rheology-modifying agent is a cement dispersant.
25. The method of claim 19 wherein said rheology value is slump
which is correlated with the slump of a standard 12-inch slump
cone.
26. The method of claim 19 wherein rheology value changes effected
by doses administered during a concrete mix delivery operation are
incorporated into said nominal dose response (NDR) curve or scaling
factor whereby said NDR curve or scaling factor (SF) is modified;
and subsequent rheology value changes in the same or a subsequent
concrete mix delivery operation are effected based on said modified
NDR curve or said modified SF.
27. The method of claim 21 wherein rheology value changes effected
by doses administered during a concrete mix delivery operation are
incorporated into said nominal dose response (NDR) curve or scaling
factor whereby said NDR curve or scaling factor (SF) is modified;
and subsequent rheology value changes in the same or a subsequent
concrete mix delivery operation are effected based on said modified
NDR curve or said modified SF.
28. The method of claim 22 wherein rheology value changes effected
by doses administered during a concrete mix delivery operation are
incorporated into said nominal dose response (NDR) curve or scaling
factor whereby said NDR curve or scaling factor (SF) is modified;
and subsequent rheology value changes in the same or a subsequent
concrete mix delivery operation are effected based on said modified
NDR curve or said modified SF.
29. The method of claim 27 wherein the concrete mixes have at least
two different parameters selected from group consisting of
temperature, mix design, water levels, hydration levels, and
humidity, whereby said concrete mixes have dose response
profiles.
30. The method of claim 29 wherein said at least two different
parameters includes temperature of the concrete mix.
31. The method of claim 19, wherein in more than one rheology
target can be inputted the CPU, wherein each target is defined for
a different time period in the same concrete mix delivery
operation.
32. The method of claim 31, including a slump target during transit
from batching or plant operation site to job site, and including a
placement slump target after the mix truck arrives at the job site
where the concrete mix is to be poured.
33. The method of claim 27, wherein a weighted average is used to
compute the said modified NDR curve or said modified SF.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to manufacturing of concrete,
and more particularly to a method for adjusting a rheological
property of concrete in a ready-mix truck or stationary mixer
through incremental doses of a rheology-modifying agent calculated
with reference to a nominal dosage response profile.
BACKGROUND OF THE INVENTION
[0002] It is known to control the "slump" or fluidity property of
concrete in ready-mix delivery trucks by using sensors to monitor
the energy required for rotating the mixing drum, such as by
monitoring the torque applied to the drum by measuring hydraulic
pressure (see e.g., U.S. Pat. Nos. 4,008,093, 5,713,663).
[0003] A hydraulic sensor coupled to the hydraulic drive and/or a
rotational speed sensor, for example, may be used for monitoring
mixing drum rotation. The monitoring of concrete slump involves
calibrating the outputs or values obtained from the hydraulic
sensor and/or electrical sensor on a mixing truck containing a
concrete mix and correlating these with slump values obtained using
a standard slump cone test. In the standard slump cone test, a
12-inch truncated cone containing the fresh concrete is removed to
permit the concrete to drop, and the vertical height drop of the
concrete is measured (e.g. ASTM C143-05). Concrete having this
known slump value is added into the drum mixer so that a hydraulic
or electrical value, which is obtained as an output from the
sensor, can be stored into a memory location and subsequently
correlated by computer processing unit (CPU).
[0004] During the delivery of the concrete to a customer, the
concrete stiffens with time as a result of hydration, evaporation,
and other factors, and the sensors detect this as increased
hydraulic or electrical energy required for turning the mixing
drum. The on-board CPU compares the detected energy value obtained
from the sensor or sensors and compares this to values stored in
memory. If the sensors and CPU detect that the concrete is
beginning to stiffen, the theory is that the CPU can be triggered
to activate metering or pumping devices to inject water or other
liquid (e.g., chemical dispersant) into the concrete to restore the
slump to the desired value.
[0005] It has long been desired to obtain the capability to add
water or chemical admixture to the concrete in an efficient way,
or, in other words, to add the precise quantity of admixture needed
to achieve the target rheology value while avoiding dosing errors
and lengthy trial and error. The presumption has been that because
highly sophisticated sensors and CPU can be used, then an accurate
and efficient methodology would inevitably result. However, prior
art cement mixing systems, for all of their evolving sophisticated
hardware, remain subject to variation in the mixture which they
control.
[0006] U.S. Pat. No. 5,713,663 of Zandberg et al. declared that
slump readings could be monitored in ready-mix trucks by inputting
information to an in-line CPU and that such information could
include the batch water amount, the amount of particulate material
ingredients, sand moisture content, time, "nominated" slump, and
other factors (See col. 8, lines 3-14). It was not specifically
explained by Zandberg et al., however, which of these factors were
to be included or how they were to be weighted. The patent stated
that such information could be stored into memory such that the CPU
could calculate from the inputted information the required liquid
component needed to arrive at a desired slump. It was alternatively
explained that the required liquid component could be
"pre-calculated" and loaded into the CPU with the other information
(Col. 8, lines 15-22). The patent further mentioned that the memory
may have stored information "in a look-up table" related to "a
range of possible mixes" and thus "for particular mix types and
particular slump values and particular amounts of mix ingredients,
the system will be able to compare measured values by the sensors
against known values for the mix to provide for an adjustment
either manually or automatically of the liquid component which is
added" (Col. 8, lines 29-36).
[0007] Despite reiterating that the objective was to enable
"maximization of mixing without an over-supply of liquid component"
which otherwise required the concrete mix to be returned rather
than delivered, Zandberg et al. did not specify what factors were
to be included in the "look-up" table. Nor did they set forth the
precise methodology for calculating the dose of the liquid
component to be administered.
[0008] Similarly, U.S. Pat. Nos. 6,042,258 and 6,042,259 of Hines
et al. (MBT Holding/BASF) disclosed an admixture dispensing system
for stabilizing the concrete either overnight, same day (as
delivery), or for long haul operations. In each of these modes,
admixture doses were to be calculated based on "internal charts"
located within computer-accessible memory (See e.g., U.S. Pat. No.
6,042,258 at Col. 9, lines 4-30; at Col. 9, lines 42-52; at Col.
10, lines 7-20; and also FIG. 2A at 128, 138, and 148). However,
the number of "variables" or conditions required for inclusion on
such internal charts or tables appeared to be rather extensive.
These variables included the amount of concrete in the mixer, its
temperature, the type of cement in the concrete, the amount of time
that the concrete is to be in transit in the delivery truck), the
amount of water required, and other factors. It was suggested that
a batchman or driver may generate his own specific charts or
look-up tables depending on the data chosen for entry into the
computer, and that the software provider could make adjustments
allowing for the driver or batchman "to compensate dosage values
for factors not considered in the data charts or look-up tables"
(See e.g., U.S. Pat. No. 6,042,258 at col. 9-10; See also U.S. Pat.
No. 6,042,259 at col. 9-10). Furthermore, it should be emphasized
that the intent of adding admixture was to control cement
hydration, rather than slump or other rheology value.
[0009] In US Patent Publication 2009/0037026, Sostaric et al. (RS
Solutions LLC) disclosed a system for adjusting concrete in
ready-mix delivery vehicles using water or chemical additives. This
system included sensors for detecting various parameters: such as
temperature, pressure, rotation (speed, energy), and
tilt/acceleration for calculating slump (See e.g., FIG. 4C; Para.
0071-0072). For example, the system could include sensors for
measuring load temperature as well as skin temperature of the
mixing drum. The system could also include sensors for measuring
"acceleration/deceleration/tilt." The system could even include
sensors for measuring vibration and environmental parameters, such
as humidity and barometric pressure. (See paragraph 0132).
Moreover, the system would automatically add water or other
admixtures based upon the measured output of the sensors used by
the system.
[0010] Despite increased technological sophistication for measuring
the ever-increasing number of parameters, as suggested by the
increasing number of sensors being deployed for measuring various
aspects of the cement during its delivery to a construction site,
the present inventors do not believe that the current state of the
prior art provides clear guidance about which parameters must be
considered and included in lookup tables or which parameters are
most important for calculating chemical admixture dosing
amounts.
[0011] Achieving accurate and efficient dosing of chemical
admixtures into concrete is presumed to be difficult in large part
due to the fact that the effect of added chemical admixtures on
rheology is altered to a greater extent than that of water on
rheology by the proportions (e.g. water to cement ratio),
characteristics (e.g. cement fineness), and condition (e.g.
temperature) of the concrete ingredients and history of the load
(age, temperature profile, etc.). These factors are likely to
change over the course of different loads of concrete batched over
the course of a day, week, month, etc. For instance, the concrete
temperature may increase with each batch during the day as the
ambient temperature increases. Different deliveries of cement may
vary in chemistry and fineness.
[0012] Rather than just adjusting slump, it is desired to adjust
other rheological properties of the concrete. Rheology deals with
the science of the flow and deformation of matter. The rheology of
concrete can be defined in terms of slump, slump flow, yield
stress, plastic viscosity, apparent viscosity, thixotropy, or flow
table test, among other factors. Therefore it is an object of this
invent to select the proper dose of chemical admixture to adjust
one or more of such concrete rheology parameters.
[0013] In view of the foregoing, the present inventors believe that
a novel method for adjusting concrete rheological properties in
mixing drums and other mixing devices is needed, a method that is
more efficient and practical to use than ones in current
practice.
SUMMARY OF THE INVENTION
[0014] In surmounting the disadvantages and increasing technical
complexity of prior art approaches to the problem of achieving
dosing accuracy and avoiding overdosing in concrete mixes, the
present invention provides a method wherein the dosing of a
particular rheology-modifying agent or combination of
rheology-modifying agents is calculated using a nominal dosage
response ("NDR") profile, one that surprisingly does not require
time-consuming compilations into a lookup table of parameters and
hence the inputting of numerous parameters at the outset of each
batch preparation or delivery.
[0015] A dose response curve relates the dose of a
rheology-modifying agent or combination of rheology-modifying
agents (such as water, a chemical admixture, or combination
thereof) to the rheology, strength, or some other characteristic of
the concrete that is modified by the effect of the
rheology-modifying agent. The dose response curve may be
represented in one of a number of forms, for clarity and
convenience, and for ease of CPU programming. For instance, a dose
response curve for a chemical admixture that modifies slump can be
represented as the dose of chemical admixture as a function of the
administered dose to the slump of the concrete. Alternatively, it
could be represented as the change in chemical admixture dose
needed to change the slump by one incremental unit (for example,
admixture dose needed to change slump by one inch).
[0016] It is common to establish a dose response curve for a given
set of materials under a certain set of conditions, which can be
later used to select the proper dose during concrete production.
This curve will be referred to herein as the nominal dose response
("NDR") curve. Because the dose response curve is a function of a
large number of variables (material properties, temperature, etc.),
it would be impractically complex to develop dose response curves
considering all relevant variables, program a CPU with look-up
tables or the like, measure all relevant variables, and select the
correct dose of the rheology-modifying agent (e.g., chemical
admixture) to achieve the desired response. It is an object of this
invention to provide a means for efficiently and accurately
updating the nominal dose response curve to meet changing external
variables, without the need to take these variables into account
explicitly. Therefore, nominal dose response curves are generated
and then adjusted by an adaptive control methodology.
[0017] The present invention arises from the surprising discovery
that concrete mixes having different parameters (e.g., temperature,
mix design, water levels, hydration levels, humidity, different
trucks) display "dose response" profiles that vary in amplitude but
otherwise have similar behavior in that their dosage response
curves do not intersect. The concept of "dose response" as used
herein shall mean and refer to the effect of a particular
rheology-modifying agent or combination of rheology-modifying
agents upon rheology (such as slump, slump flow, or yield stress)
as a function of the administered dose.
[0018] This unexpected dose response behavior is illustrated in
FIG. 1, wherein it is shown that different concrete mixes, into
which a rheology-modifying agent such as a polycarboxylate cement
dispersant admixture was admixed, show similar dose response curves
wherein slump is shown as a function of the dose amount (ounces of
admixture per cubic yard of concrete) required to change slump by
one unit (such as from 2 to 3 inches slump, and from 3 to 4 inches
slump, and so on). The calculation of a nominal dose response
("NDR") profile is basically illustrated in FIG. 2, in which at
least two profile curves (labeled "maximum dose" and "minimum dose"
for convenient reference) are considered to provide one NDR
profile.
[0019] The significance of the non-intersecting behavior of the
dose response curves (FIG. 1) led the present inventors to the
practical realization that one could adjust concrete rheology
through use of an NDR profile based on even one curve obtained form
only one data set, although using at least two curves is preferred
(e.g., FIG. 2) and using a plurality of curves (e.g., FIG. 1) is
more preferred from the standpoint of accuracy, the NDR profile can
be adjusted by scaling only one parameter--namely, a ratio
reflecting the actual admixture performance and that predicted by
the nominal dose response curve. Thus, an adaptive control
methodology is achieved to update the nominal dose response curve
based on actual admixture performance. Each dose of admixture is
selected by using the nominal dose response curve adjusted by the
scaling factor from previous additions of admixture into the same
load of concrete. Thus, the doses selected are adjusted to the
actual conditions associated with the concrete load without the
need to measure and adjust explicitly for these parameters. In such
case, the second and each subsequent doses of admixture within a
load are likely to be significantly more accurate than the first
dose. This eliminates a lengthy trial-and-error process where
previous performance of admixture in the load of concrete is not
considered.
[0020] It would be further possible to adjust the nominal dose
response curve based on admixture performance data from prior
loads.
[0021] Although the prior art methods have suggested that empirical
behavior of the concrete mix could be compensated for by use of
water or chemical admixture, until now it has not been taught or
suggested how this compensation was to be done. It is the
surprising aspect of the present invention that the rheology of the
concrete mix can be adjusted by inputting into a computer processor
unit (CPU) only the amount of the concrete (load size) and the
target rheology value (e.g., slump, slump flow, or yield stress),
and comparing the actual rheology to the NDR, adding a percentage
of the nominal dose the chemical admixture that would be
(theoretically) required to change the actual rheology to the
target rheology, measuring the resultant change in rheology value
and comparing this to the NDR value that would theoretically have
been obtained using the percentage nominal dose, and then adjusting
the rheology by adding a subsequent dose which takes into account
the deviation measured as a result of the first percentage
addition. Hence, the present invention takes into account a
"learning" step that is incorporated into the methodology, without
having to consider numerous parameters such as temperature, mix
design, humidity, and other factors.
[0022] Thus, an exemplary method of the present invention for
controlling rheology of a hydratable cementitious composition in a
mixer wherein the energy required for operating said mixer
containing the cementitious composition is measured and correlated
with a nominal rheology value and wherein a rheology-modifying
agent is added into the cementitious composition to modify its
rheology comprises:
[0023] (a) entering into a computer processor unit ("CPU") a target
rheology value ("TRV") and load size for a hydratable cementitious
composition containing or intended to contain a particular
rheology-modifying agent or combination of rheology-modifying
agents; and
[0024] (b) obtaining a current rheology value ("CRV") of hydratable
cementitious composition contained within a mixer;
[0025] (c) comparing through use of CPU the current rheology value
obtained in step (b) against a nominal dose response ("NDR")
profile stored in CPU-accessible memory and wherein said NDR is
based on at least one data set wherein various dose amounts of a
particular rheology-modifying agent or combination of
rheology-modifying agents and their correlative effect on rheology
value (such as slump, slump flow, or yield stress) is retrievably
stored, and determining the nominal dose of said particular
rheology-modifying agent or combination of rheology-modifying
agents required to change the obtained CRV to the TRV specified in
step "(a)";
[0026] (d) dosing the hydratable cementitious composition in a
mixer with a percentage of said particular rheology-modifying agent
or combination of rheology-modifying agents that is selected or
pre-selected from 5% to 99% based on the nominal dose determined in
step (c) required for changing said obtained CRV to said TRV as
specified in step (a);
[0027] (e) obtaining a subsequent CRV of the hydratable
cementitious composition after the percentage of the nominal dose
of the particular rheology-modifying agent or combination of
rheology-modifying agents selected or preselected in step (d) is
added into and uniformly mixed with said hydratable cementitious
composition; comparing the dose selected or preselected in step (d)
to the dose according to the NDR profile for the same change in the
rheology value from step (b) to step (e), and determining the
scaling factor ("SF") by which to adjust the dose from the NDR
profile, where SF is defined as the actual dose from step (d)
divided by the nominal dose to achieve the same change in rheology
value indicated by the NDR profile; and
[0028] (f) mixing into the hydratable cementitious composition the
particular rheology-modifying agent or combination of
rheology-modifying agents in an amount calculated in terms of SF
multiplied by the dose from the NDR profile indicated to convert
the current CRV measured in step (e) to the TRV specified in step
(a).
[0029] If the target rheology value such as slump is not attained
upon completion of the aforementioned steps (which can be due to
any number of factors, such as temperature or humidity change),
then process steps (e) and (f) can be repeated as required. In
addition, concrete rheology changes over time. Each time the
rheology value decreases by a certain amount, a rheology-modifying
agent (e.g., chemical admixture) must be added to restore the
rheology value. Steps (e) through (f) can be repeated to adjust the
rheology value.
[0030] In preferred methods of the invention, the NDR profiles are
calculated based on an average of at least two dose response curve
values (see e.g., FIG. 2), and, more preferably, an average of a
plurality dose response curve values obtained from trialing the
particular rheology-modifying agent or combination of
rheology-modifying agents (See e.g., FIG. 3).
[0031] In further exemplary embodiments, the system CPU can be
programmed to assume a learning mode, whereby batch histories can
be incorporated into the NDR profile which is then stored into
CPU-accessible memory, and/or the scaling factor can be redefined
so that dosing can be rendered more accurate. In other words, the
rheology value changes effected by doses of the rheology-modifying
agent administered during a concrete mix delivery operation are
incorporated into the nominal dose response (NDR) curve or scaling
factor whereby the NDR curve or scaling factor (SF) is modified;
and rheology value changes in a subsequent concrete mix delivery
operation or operations are effected based on the modified NDR
curve or modified SF.
[0032] Exemplary rheology modifying agents include water, a
chemical admixture (e.g., polycarboxylate water reducer,
naphthalene sulfonate formaldehyde condensate water reducer,
melamine sulfonate formaldehyde condensate water reducer,
lignosulfonate water reducer, or hydrocolloid viscosity modifying
admixtures such as welan gum or cellulose derivatives), or mixture
thereof. Preferred are chemical admixtures such as polycarboxylate
cement dispersants, which are commonly used as superplasticizers
(or so-called high range water reducers) in the concrete field. So
long as the same rheology-modify agent or combination of
rheology-modifying agent is being used as was previously trialed
for creating the nominal dosage response (NDR) profile, then other
variables such as concrete mix design, amount of water or cement or
water/cement ratio, aggregate selection or composition, degree of
hydration, do not necessarily need to be inputted into the CPU and
remain optional. Viscosity modifying admixtures primarily affect
the viscosity of the concrete, while having a relatively lesser
effect on other properties.
[0033] Further advantages and features of the invention may be
described hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0034] Further advantages and features of the present invention may
be more readily comprehended when the following detailed
description of preferred embodiments is taken in conjunction with
the appended drawings wherein
[0035] FIG. 1 is a graphic illustration of plurality of dose
response curves (profiles) of various concrete mixes, whereby the
effect of a particular rheology-modifying agent (e.g., chemical
admixture such as polycarboxylate water reducer) is measured upon
the slump of the concrete, as shown along the horizontal axis, is
measured against the dose of the rheology-modifying agent whose
amount, which is measured in terms of ounces per cubic yard
required to decrease the slump of the concrete by one unit, as
shown along the vertical axis;
[0036] FIG. 2 is another graphic illustration wherein at least two
dose response curves (labeled minimum and maximum for the sake of
illustration) of a particular rheology-modifying agent are used to
calculate an average dose response profile, which may function as a
nominal dose response profile used in exemplary methods of the
invention for automated control over concrete mix rheology; and
[0037] FIG. 3 is a graphic illustration wherein the theoretical (or
nominal) slump change is plotted against the actual slump change
when exemplary methods of the invention are used.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0038] The term "cementitious" as used herein refers to a material
that comprises portland cement and/or portland cement substitutes
that when mixed with water function as a binder to hold together
fine aggregates (e.g., sand), coarse aggregates (e.g., crushed
stone or gravel), or mixtures thereof.
[0039] Cementitious materials considered to be "hydratable" or
hydraulic are those which harden by chemical interaction with
water.
[0040] Such cementitious materials may further include fly ash,
granulated blast furnace slag, lime stone, or natural pozzolans,
which may be combined with portland cement or be used to replace or
substitute for a portion of the portland cement without seriously
diminishing hydratable properties. A "mortar" refers to cement or
cementitious mixture having a fine aggregate such as sand; while
"concrete" refers more accurately to a mortar that also contains a
coarse aggregate such as crushed stone or gravel.
[0041] The use of the term "cementitious material" may be used
interchangeably with the term "concrete," as concrete is most
commonly provided by ready-mix trucks which have rotatable mixing
drums. The term "concrete" as used herein does not necessarily
exclude the fact that the present invention can be used for
delivering materials that contain only cement or cement substitutes
(e.g., pozzolans) or mortars.
[0042] Hydratable cementitious materials, such as concrete mixes,
typically contain one or more rheology-modifying agents, which can
include water alone or chemical admixtures such as water-reducing
agents or high range water-reducing agents called
"superplasticizers," viscosity modifying agents,
corrosion-inhibitors, shrinkage reducing admixtures, set
accelerators, set retarders, air entrainers, air detrainers,
pigments, colorants, fibers for plastic shrinkage control or
structural reinforcement, and the like.
[0043] The phrase "rheology-modifying agent" will therefore be
understood to mean and include water, a chemical admixture, or a
mixture thereof. In many cases, a chemical admixture formulation
will comprise a dispersant and water, for example. The
rheology-modifying agent could well comprise one or more cement
dispersants (e.g., polycarboxylate water reducer), an air detrainer
or combination of detrainers, and other admixtures.
[0044] As mentioned in the background section, concrete delivery
mixing trucks having slump control monitoring and control
equipment, such as hydraulic and/or electric sensors for measuring
the energy for turning the mixing drum, speed sensors for measuring
the speed of rotation, temperature sensors for monitoring the
atmospheric temperature as well as the mix temperature, and
dispensing equipment, as well as the computer processing units
(CPU) for monitoring signals from the sensors and actuating the
dispensing equipment are by now relatively well known in the
industry. For example, such slump control systems, which can be
used in association with wireless communication systems, are
disclosed in U.S. Pat. No. 5,713,663; U.S. Pat. No. 6,484,079; U.S.
Ser. No. 09/845,660 (Publication no. 2002/0015354A1); U.S. Ser. No.
10/599,130 (Publication no. 2007/0185636A1); U.S. Ser. No.
11/764,832 (Publication no. 2008/0316856); U.S. Ser. No. 11/834,002
(Publication no. 2009/0037026); and WO 2009/126138. A further
exemplary system for monitoring and control using wireless
communications in combination with sensors for monitoring various
physical properties of the concrete mix is taught in U.S. Pat. No.
6,611,755 of Coffee. These teachings, as well as the patent
references as previously discussed in the background section above,
are expressly incorporated herein by reference.
[0045] Exemplary mixing drums contemplated for use in the present
invention may be ones that are customarily mounted for rotation on
ready-mix delivery trucks, as mentioned above, or on stationary
mixers which may be found in mixing plants. Such mixing drums may
have an inner surface upon which at least one mixing blade is
attached to the inner surface so that it rotates along with the
mixing drum and serves to mix the concrete mix, including the
aggregates contained within the mix.
[0046] It is believed that a number of exemplary embodiments of the
invention may be practiced using commercially available automated
concrete mix monitoring equipment with slight modifications as
would be apparent in view of the invention disclosed herein. Such
mix monitoring equipment is available under the VERIFI.RTM. name
from Grace Construction Products, Cambridge, Mass., and also from
RS Solutions LLC, West Chester, Ohio.
[0047] As previously described in the summary above, an exemplary
method of the invention for controlling rheology of a hydratable
cementitious composition in a mixer wherein the energy required for
operating said mixer containing the cementitious composition is
measured and correlated with a nominal rheology value and wherein a
particular rheology-modifying agent or combination of
rheology-modifying agents are added into the cementitious
composition to modify its rheology, comprises the following
steps:
[0048] (a) entering into a computer processor unit ("CPU") a target
rheology value ("TRV") and load size for a hydratable cementitious
composition containing or intended to contain a particular
rheology-modifying agent or combination of rheology-modifying
agents; and
[0049] (b) obtaining a current rheology value ("CRV") of hydratable
cementitious composition contained within a mixer;
[0050] (c) comparing through use of CPU the current rheology value
obtained in step (b) against a nominal dose response ("NDR")
profile stored in CPU-accessible memory and wherein said NDR is
based on at least one data set wherein various dose amounts of a
particular rheology-modifying agent or combination of
rheology-modifying agents and their correlative effect on rheology
value (such as slump, slump flow, or yield stress) is retrievably
stored, and determining the nominal dose of said particular
rheology-modifying agent or combination of rheology-modifying
agents required to change the obtained CRV to the TRV specified in
step "(a)";
[0051] (d) dosing the hydratable cementitious composition in a
mixer with a percentage of said particular rheology-modifying agent
or combination of rheology-modifying agents that is selected or
pre-selected from 5% to 99% based on the nominal dose determined in
step (c) required for changing said obtained CRV to said TRV as
specified in step (a);
[0052] (e) obtaining a subsequent CRV of the hydratable
cementitious composition after the percentage of the nominal dose
of the particular rheology-modifying agent or combination of
rheology-modifying agents selected or preselected in step (d) is
added into and uniformly mixed with said hydratable cementitious
composition; comparing the dose selected or preselected in step (d)
to the dose according to the NDR profile for the same change in the
rheology value from step (b) to step (e), and determining the
scaling factor ("SF") by which to adjust the dose from the NDR
profile, where SF is defined as the actual dose from step (d)
divided by the nominal dose to achieve the same change in rheology
value indicated by the NDR profile; and
[0053] (f) mixing into the hydratable cementitious composition the
particular rheology-modifying agent or combination of
rheology-modifying agents in an amount calculated in terms of SF
multiplied by the dose from the NDR profile indicated to convert
the current CRV measured in step (e) to the TRV specified in step
(a).
[0054] As described in Step (a), the first step of the exemplary
method requires inputting into a computer processor unit ("CPU")
only two pieces of information: the target rheology value ("TRV")
and the load size for the given hydratable cementitious composition
that will be placed into the mixer. The input of these two data
points may be performed by the batch master at the ready-mix plant,
by the truck driver, or foreman at the construction site. Indeed,
this input may be performed by anyone in charge of the concrete
delivery and does not require the inputting of other parameters
such as temperature, humidity, and other factors which are
optional.
[0055] The target rheology value (TRV) may be any of the rheology
factors whose measurement in unit values are customarily employed,
such as: slump (customarily measured in terms of length units,
e.g., inches); slump flow (length, e.g., inches); yield stress
(customarily measured in terms of stress, e.g., pounds per square
inch or pascals); viscosity (pascalsseconds); flow (length); and
thixotropy (pascals/second). Load size can be inputted into the CPU
in terms of total weight or volume of the batch concrete (e.g.,
cubic yards) including all of the components. If the TRV is defined
in terms of slump, then the measurement for slump can be done in
accordance with the following standards: ASTM C 143-05, AASHTO T
119, or EN 12350-2. If the TRV is defined in terms of slump flow,
then this measurement can be done in accordance with ASTM C1611-05.
If the TRV is defined in terms of the flow table test, then this
can be done in accordance with DIN EN 12350-5.
[0056] The rheology-modifying agent or combination of
rheology-modifying agents mentioned in Step (a) means and refers to
water, chemical admixture(s), or mixture thereof which are present
in the concrete that is used for generating the data set or sets
that provide the nominal dose response ("NDR") profile mentioned in
Step (c) as well as in the concrete being adjusted, i.e., whose
load size is inputted into the CPU in Step (a) and whose current
rheology value (CRV) is obtained in Step (b). It is important for
purposes of calibration (i.e., generating the NDR profile) to use
the identical or similar rheology-modifying agent(s) for the NDR
profile as for dosing into the concrete.
[0057] Preferred "chemical admixtures" suitable for use in methods
of the present invention include water-reducers and
superplasticizers commonly used in the concrete industry. Preferred
among these are cement-dispersing polymers which contain
(poly)carboxylic acid and/or salt groups and (poly)oxyalkylene
groups (herein referred to as "polycarboxlate polymers").
[0058] Thus, for example, the "rheology-modifying agent or
combination of rheology-modifying agents," as this phrase is
employed in Step (a), can refer to one or more active ingredients,
such as one or more polycarboxylate polymers, which, in turn, may
be used with air entrainers or other admixtures which may have an
effect on the rheology of the concrete. The concentration of the
one or more active ingredients is very important. One may need to
establish and use another nominal dose response (NDR) profile if
adding or omitting a particular active ingredient from the chemical
admixture(s) formulation. The dispersing polymers will be seen to
affect rheology and will be deemed to be "active ingredients" such
that it is preferable that the same polymers be used in the NDR
profile; this same reasoning applies for other components such as
air entraining and/or detraining components if by their amount
and/or nature they will have a profound effect on the rheology.
[0059] As one of the benefits of the present invention is that it
is self-correcting, it may be possible to achieve high accuracy
even where the cement-dispersing polymer is different and where
other active ingredients might be different in nature and amount.
However, when using the method of the present invention, it is
preferable to start with the same rheology-modifying agents or same
combination of rheology-modifying agents and to compensate for any
differences in their concentrations.
[0060] In Step (b) of the exemplary method, this second step
requires that the system determine the current rheology value
("CRV") of the hydratable cementitious composition contained within
the mixer. This is stored in CPU-accessible memory because it will
provide a reference point for later steps.
[0061] In Step (c) of the exemplary method, the CPU compares the
current rheology value (CRV) obtained in Step (b) with the nominal
dose response ("NDR") profile stored in CPU-accessible memory. As
previously mentioned, this NDR profile is based on at least one
data set wherein the effect of various dose amounts of a particular
rheology-modifying agent or agents on rheology (e.g., slump, slump
flow, yield stress, etc.) is measured. While the method of the
invention can work with one data set wherein the effect of the
rheology-modifying agent on rheology is correlated, it is preferred
to use an NDR profile that is generated using at least two data
sets, and it is most preferably to use an NDR profile that is
generated using a plurality of data sets.
[0062] For example, FIG. 2 illustrates two dose response curves
(labeled minimum and maximum) whereby the slump (inches) of a
concrete composition is plotted against the amount of the
particular rheology-modifying agent (a slump-modifying concrete
admixture) needed for changing slump by one unit (e.g., for
changing slump one inch, such as from 2 inches to three inches).
The nominal dose response profile (or curve) then is taken as the
average of the two dose response curves (minimum and maximum).
[0063] As a more preferred example, FIG. 1 illustrates a plurality
of dose response curves whose average provides a nominal dose
response ("NDR") profile that may be used as a reference during a
delivery operation.
[0064] In Step (d), the CPU is programmed to dose the hydratable
cementitious composition in the mixer using a selected or
pre-selected percentage of the ideal amount of the
rheology-modifying agent(s) that would be determined by the NDR
profile to change the current rheology value (CRV), as determined
in Step (b), to the target rheology value (TRV) entered in Step
(a). The percentage may be 50% to 95% of the ideal (or nominal)
amount, and more preferably would be about 50%-90%; and most
preferably would be 50%-80%. Generally, the lower percentage in
these ranges is preferable for this first dose until confidence is
obtained.
[0065] In Step (e), the CPU would be programmed to obtain a
subsequent current rheology value (CRV) of the hydratable
cementitious composition after the percentage of the nominal dose
of the particular rheology-modifying agent (e.g., chemical
admixture) administered in Step (d) was added into and uniformly
mixed with the hydratable cementitious composition. The CPU would
compare the nominal (or theoretical) effect on the rheology value
of the percentage dose selected or preselected in step (d) to the
subsequent current rheology value (subsequent CRV) and then
determine the scaling factor ("SF") by which to adjust the dose
from the NDR profile, where SF is defined as the actual dose from
step (d) divided by the nominal dose to achieve the same rheology
change indicated by the NDR profile.
[0066] In Step (f), the CPU would be programmed to mix into the
hydratable cementitious composition a subsequent dose of the
rheology-modifying agent.
[0067] The amount of this subsequent dose would be calculated by
multiplying the scaling factor (SF) calculated in Step (e) by the
amount theoretically needed, according to the nominal dose response
(NDR) profile, to change the subsequent current rheology value
(CRV) measured in Step (e) to the target rheology value (TRV)
specified in Step (a).
[0068] Steps (e) and (f) may be repeated whenever the current
rheology value (CRV) is less than or greater than the target
rheology value (TRV) by a predetermined amount. This may be done
automatically, for example, by programming the CPU to repeat this
steps when the difference between the CRV and TRV exceeds a
predetermined amount. If the difference between the CRV and TRV is
less than the predetermined amount, the CPU can be programmed to
trigger an alarm to indicate to the operator that the concrete mix
is ready to be discharged and poured.
[0069] As mentioned above, preferred methods of the invention
involve the use of a nominal dose response (NDR) profile which is
derived from an average of at least two sets of dose response
curves for the particular rheology-modifying agent(s), as
illustrated in FIG. 2; and, more preferably, from an average of a
plurality of dose response curves for the particular chemical
admixture(s), as illustrated in FIG. 1. The dose response curves of
FIG. 1 in particular suggests, by the varying curve amplitudes,
that various parameters such as concrete mix design, temperature,
degree of hydration, water/cement ratio, and aggregate amounts
might be varying slightly (or even significantly) from batch to
batch. Still, the fact that the various dose response curves did
not intersect led the present inventors to realize that these other
various parameters did not necessarily need to be kept constant in
order to establish a nominal dosage response (NDR) profile because
the average of these dose response curves would have similar
behavior in terms of calculating amounts of rheology-modifying
agent(s) needed for changing the rheology value (e.g., slump) from
one value to the next (e.g., from slump of 2 inches to, say, five
inches).
[0070] Hence, exemplary methods of the invention involve a nominal
dose response (NDR) profile involving the use of a plurality of
data sets having at least one non-homogeneous parameter. This
parameter may, for example, be the concrete mix design, temperature
of reaction, degree of cement hydration, the water/cement ratio,
and the aggregate amount or cement/aggregate ratio. These may be
varied from batch to batch in the data sets which go to make up the
NDR profile (See e.g., FIG. 1).
[0071] Thus, further exemplary methods of the invention comprise
the use of a nominal dose response (NDR) profile that is derived
from data sets having at least two non-homogeneous parameters, and
even more than two non-homogeneous parameters, such as different
concrete mix design, concrete mix ingredient source, temperature,
hydration, water/cement ratios, different aggregate amounts or
ratios, and concrete mix designs. So long as the particular
rheology-modifying agent(s) (e.g., water and/or concrete admixture
or combination of chemical admixtures) used for setting up the NDR
profile and for obtaining a current rheology value is/are identical
or substantially similar, the slope behavior of the dose response
curves is similar from one rheology value unit to the next. In
fact, even if two rheology-modifying agents vary in composition but
are similar in performance, it may be possible to use the same NDR
profile for both.
[0072] In further exemplary embodiments of the invention, the
process of monitoring rheology change can involve the use of more
than one type of rheology-modifying agent (or chemical admixture)
with each type of rheology-modifying agent having its own scaling
factor (SF), nominal dose response profile, or both. For example,
one can establish NDR profiles for combinations of chemical
admixtures such as: high range water reducer with viscosity
modifying admixture; normal range water reducer with high range
water reducer; water reducers with set accelerators, set retarders,
or combinations thereof; high range water reducers with thixotropy
modifying admixtures; and the like.
[0073] In still further exemplary embodiments, the method of the
invention can be modified so that more than one rheology target can
be specified and met within the same concrete mix delivery
operation. For example, one may use multiple rheology targets, such
as slump target during transit (from batching or plant operation to
job site) and during placement (after the truck arrives at the job
site where the mix is to be poured). As another example, one may
define two rheology targets that the concrete mix must attain
within the same delivery operation/process and at the same time,
such as slump flow and plastic viscosity. It is possible, in other
words, to have one rheology-modifying agent or combination of
agents (e.g., admixture packages) for modifying the slump flow
(characterized by the spreading of concrete from a removed slump
cone) and to have another rheology-modifying agent or combination
of agents for modifying the plastic viscosity (characterized by
shear stress divided by the shear rate).
[0074] In a further exemplary embodiment, the scaling factor is
calculated as a weighted average of all dose responses in a given
load or mix design. In other words, in a series of delivery
operations in which various scaling factors are derived, the
scaling factor used in the current delivery operation can be based
on an average of all scaling factors computed, but primarily based
on data obtained form the most recent delivery operations.
[0075] While the invention is described herein using a limited
number of embodiments, these specific embodiments are not intended
to limit the scope of the invention as otherwise described and
claimed herein. Modification and variations from the described
embodiments exist. More specifically, the following example is
given as a specific illustration of an embodiment of the claimed
invention. It should be understood, that the invention is not
limited to the specific details set forth in the example. All parts
and percentages in the examples, as well as in the remainder of the
specification, are by weight unless otherwise specified.
[0076] Further, any range of numbers recited in the specification
or claims, such as that representing a particular set of
properties, units of measure, conditions, physical states or
percentages, is intended to literally incorporate expressly herein
by reference or otherwise, any number falling within such range,
including any subset of numbers within any range so recited. For
example, whenever a numerical range with a lower limit, RL, and an
upper limit RU, is disclosed, any number R falling within the range
is specifically disclosed. In particular, the following numbers R
within the range are specifically disclosed: R=RL+k*(RU-RL), where
k is a variable ranging from 1% to 100% with a 1% increment, e.g.,
k is 1%, 2%, 3%, 4%, 5% . . . 50%, 51%, 52%, . . . 95%, 96%, 97%,
98%, 99%, or 100%. Moreover, any numerical range represented by any
two values of R, as calculated above, is also specifically
disclosed.
EXAMPLE 1
[0077] A concrete mixture was made in a laboratory mixer without
any chemical admixtures added. Slump was measured by removing
samples and placing them in a slump cone in accordance with ASTM
C143-05. When this test was done, the first mixture was discarded.
Immediately thereafter, another concrete mixture having the same
concrete mix design was made in the same laboratory mixer but this
time with a chemical admixture (polycarboxylate water reducer), and
slump was again measured using the same standard cone test). When
this test was done, the mixture was discarded. A plurality of
further successive concrete mixtures of the same concrete mix
design and identical mix factors (e.g., temperature, type of
cement, amount of air and water, water/cement ratio, etc.) were
also made in the laboratory mixer, but each varying only in the
dosage amount of the polycarboxylate polymer water reducer. Except
for the admixture dose of the water reducer, all other variables
were kept constant. Each successive mixture was discarded after
slump cone testing.
[0078] The data for the above concrete mixes is illustrated as one
plotted line shown in FIG. 1.
[0079] The above process was repeated, but for each reiteration one
of the mix factors was varied while all other mix factors were kept
constant. The varied mix factors included: temperature of the
materials, the amount and type of cement, type of fine aggregate,
type of coarse aggregate, amount of air in concrete, amount of
water, and ratio of water to cement.
[0080] The data for these concrete mixes having a varied mix factor
are also plotted as various lines shown in FIG. 1.
[0081] Surprisingly, the inventors discovered that the dosage
response curves, as shown in FIG. 1, did not intersect. The present
inventors thus discovered that the slump of the concrete mix could
be adjusted by reference to the behavior of any curve or an average
of all such dosage response curves, and that the behavior of such
curve or plurality of curves could serve as a nominal or reference
dosage response curve during real time production-operation.
[0082] FIG. 2 is a simplified version of FIG. 1 showing "minimum,"
"maximum," and average dosage response curves. The average dose
response curve shown in FIG. 2 can serve as a nominal dosage
response curve during real time production-operation.
EXAMPLE 2
[0083] The exemplary method of the invention was tested in the
field using a concrete mix truck having an automated monitoring and
dosing system provided by RS Solutions LLC of Ohio, commercially
available under the trade name VERIFI. This monitoring system could
measure slump based on hydraulic pressure and mix drum speed. This
system could also inject chemical admixture in liquid form into the
mix drum from a small chemical storage tank mounted on the fender.
(Reference is also made to US Patent Publication 2009/0037026,
Sostaric et al., described in the background section).
[0084] Over a period of months a variety of concrete mixes were
prepared in the concrete mix truck. Prior to this testing, a
nominal dose response profile was obtained, similar to the process
described above in Example 1, and this was used as the reference or
"nominal" reference dose ("NDR") profile.
[0085] A number of tests were run using the exemplary method of the
invention for different concrete mix delivery operations, wherein
the NDR was used by the computer processing unit of the automated
monitoring and dosing system for each successive concrete mix
sample prepared in the mix drum. Mixes produced in the drum over
the next few weeks experienced natural variations in terms of
temperature, raw materials, mixture proportions (e.g., water/cement
ratio, water/aggregate ratio, fine/coarse aggregate ratio,
etc.).
[0086] The amount of water reducing admixture (polycarboxlic
acid-based) was dosed in accordance with the method of the
invention as described in the foregoing summary section.
[0087] As shown in FIG. 3, the use of the method resulted in slump
changes in the concrete mix that were very close to the predicted
changes when the nominal dose response (NDR) curve was used as a
reference. See method steps (a) through (f) in Summary section
above. When the NDR curve is first applied, the slump change is
then used to develop the scaling factor (SF) which is then used on
the next addition of admixture. FIG. 3 illustrates that the actual
measured slump change values (shown by the dots) closely match the
theoretical slump change values.
[0088] The principles, preferred embodiments, and modes of
operation of the present invention have been described in the
foregoing specification. The invention which is intended to be
protected herein, however, is not to be construed as limited to the
particular forms disclosed, since these are to be regarded as
illustrative rather than restrictive. Skilled artisans can make
variations and changes without departing from the spirit of the
invention.
* * * * *