Method for adjusting concrete rheology based upon nominal dose-response profile

A method for controlling rheology of a hydratable cementitious composition in a rotatable mixer of a concrete delivery truck wherein the energy required for operating said rotatable mixer containing the cementitious composition is measured and correlated with a nominal rheology value and wherein a rheology-modifying agent or combination of rheology-modifying agents is added into the cementitious composition to modify its rheology, wherein the improvement comprises:

• (a) entering into a computer processor unit (“CPU”) a target rheology value (“TRV”) and load size for a hydratable cementitious composition placed into said truck rotatable mixer, said hydratable cementitious composition containing or intended to contain a particular rheology-modifying agent or combination of rheology-modifying agents;
• and
• (b) obtaining a current rheology value (“CRV”) of hydratable cementitious composition contained within said truck rotatable mixer;
• (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 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)”, said NDR profile is an average of a plurality of dose response curves for the particular rheology-modifying agent or combination of rheology-modifying agents, and at least two dose response curves of said plurality of 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;
• (d) dosing the hydratable cementitious composition in said truck rotatable 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);
• (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
• (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).