The effect of yield shear stress on flow resistance Autumn 2016: Overview of laboratory and numerical results Evgeny Ramenskiy

Laboratory results – Autumn 2016 Mix number Sequence number w/c SP (SR-N) fi/c Filler Grading Solid volume fraction, Φs Mini-slump flow Bingham parameters Herschel–Bulkley parameters Measured Flow resistance, λQ Flow-3D Flow resistance, λQ Deviation [cm] τ0 [Pa] µ [Pas] τHB [Pa] c [Pas] p [Pa] [m-% of cem.] [m-%] [%] 10 0.4 0.75 % 0.25 Intermediate 0.516 19.40 11.04 0.84 9.26 1.26 0.91 0.861 2.4 % 1 79 1.00 %   4 82 1.25 % 0.515 7 85 1.50 % 88 1.75 % 11 0.32 0.531 15.85 16.79 1.09 14.34 1.67 0.90 0.89 0.905 1.7 % 2 80 20.80 8.32 0.97 8.59 0.92 1.01 0.86 0.880 2.7 % 5 83 0.530 24.75 4.42 0.68 5.53 0.47 0.80 0.827 3.3 % 8 86 26.70 1.69 0.62 3.32 0.33 1.15 0.805 0.4 % 89 28.60 1.63 0.49 2.68 0.30 1.12 0.76 0.766 0.3 % 12 0.39 0.545 13.15 3 81 6 84 9 87 0.544 90 13 0.55 0.45 0.450 26.65 2.73 2.14 0.57 0.605 5.8 % 91 16 94 19 97 22 100 14 0.52 0.490 26.20 3.73 0.27 2.75 0.85 0.618 7.8 % 92 30.15 1.64 0.20 1.30 0.28 0.558 0.7 % 17 95 32.00 1.00 0.17 0.73 0.23 0.93 0.53 0.529 -0.8 % 20 98 35.10 0.14 0.18 0.94 0.503 -3.0 % 23 101 0.489 37.70 0.43 0.10 0.16 0.48 0.446 -7.0 % 15 0.59 0.502 25.05 4.40 3.22 0.56 0.81 0.596 7.7 % 93 18 96 21 99 24 102 Text in white – is data from Summer 2016 cement paste mixes. Torjus – sick. Several mixes are not included as they don’t represent the whole series overview. Two series were completed with Rolands help.

Exponential reduction of Bingham yield stress with increased SP dosage This graph describes relationship between yield stress and SP dosage. As expected…

Linear reduction of Bingham plastic viscosity with increased SP dosage Here we see correlation of plastic viscosity and SP dosage.

Linear reduction of flow resistance with increased SP dosage As a result we see the linear reduction of workability parameter lambda Q with increasing SP dosage.

Linear increase of mini slump flow with increased SP dosage

Flow resistance deviation varies in matrices with varying w/c ratio On this graph we see flow resistance deviation of two series of cement paste (i.e. with w/c-ratio 0.4 and 0.55). Effect of SP dosage on the cement paste varies with varying w/c-ratio. In case of mixes with w/c-ratio = 0.4, reduction of lambda Q deviation is approximately 1.4%. For w/c=0.55, it is 14.8%. What can contribute to this variation?

Objective of the numerical DOE study The objective of this study is to find out how the flow resistance behaves when simulating concrete matrixes that have a yield stress and plastic viscosity combination that cannot be described by the linear relationship. The idea with the simulated matrixes is that they could for instance represent a situation where a matrix is not fully saturated with superplasticizer, so that the plastic viscosity could be relative low, but the yield stress could be relatively high.

Numerical DOE setup and results (τ0; µ) 1 2 3 4 5 6 - 1.19; 1.37 6; 1.37 11; 1.37 16.45; 1.37 1.19; 0.84 6; 0.84 11; 0.84 16.45; 0.9 1.19; 0.52 3.5; 0.52 6.13; 0.52 11; 0.5 16.45; 0.5 1.19; 0.38 3; 0.38 4.85; 0.38 6.13; 0.3 11; 0.07 16.45; 0.07 1.19; 0.23 2.64; 0.23 4.85; 0.2 6.13; 0.07 2.64; 0.07 4.85; 0.07 (λQ) 1 2 3 4 5 6 - 0.886 0.901 0.911 0.921 0.822 0.848 0.871 0.743 0.760 0.776 0.838 0.686 0.696 0.712 0.685 0.541 0.601 0.598 0.607 0.490  - 0.452 0.479 - 

Numerical DOE results (λQ) 1 2 3 4 5 6 - 0.886 0.901 0.911 0.921 0.822 0.848 0.871 0.743 0.760 0.776 0.838 0.686 0.696 0.712 0.685 0.541 0.601 0.598 0.607 0.490  - 0.452 0.479 -  Jon’s conclusion is: Flow resistance can be used as a single parameter to describe the flow behavior of concrete matrixes if the shear rates of cement paste is of the order of 200 s-1 (Per second) or higher.

FlowCyl nozzle analysis? The pressure gradient created by the fluid weight above the nozzle may not be sufficient for the shear stress to overcome the yield stress in the nozzle. The FlowCyl nozzle size analysis could be carried out via numerical simulation of matrix with high yield (e.g. <20Pa). Marsh Cone has two nozzle sizes. The FlowCyl nozzle size analysis could be carried out via numerical simulation of matrix with high yield (e.g. <20Pa). The reference distance form the cone to the container of the FlowCyl setup. It would be advantageous to establish the reference distance as it determines the length of the stream, possibly affecting the results.

Other concerns Torque of the mixer isn’t constant for mixes with high viscosity leading to improper mixing of the cement pastes. Can this contribute to the found inconsistency in the flow resistance deviations?

Flow-3D Numerical DOE overview Mix number Sequence number Mix density Bingham parameters Flow-3D Flow resistance, λQ [g/cm3] τ0 [Pa] µ [Pas] 1_4 103 1930 1.19 0.38 0.887 1_5 104 0.23 0.906 2_3 105 0.52 0.929 2_4 106 3.00 0.605 2_5 107 2.64 0.647 2_6 108 0.07 0.693 3_1 109 1.37 0.458 3_2 110 0.84 0.474 3_3 111 3.50 0.473 3_4 112 4.85 0.861 3_5 113 0.20 0.905 3_6 114 0.927 4_1 115 6.00 4_2 116 0.618 4_3 117 6.13 0.596 4_4 118 0.30 0.397 4_5 119 0.431 5_1 120 11.00 0.521 5_2 121 0.917 5_3 122 0.50 0.950 5_4 123 0.987 6_1 124 16.45 0.764 6_2 125 0.90 0.796 6_3 126 0.842 6_4 127 0.551 The results of the numerical simulation indicates that the flow resistance is a good measure if the shear rates is of the order of 200 s-1 or higher.