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 REPORT This report is an archived publication and may contain dated technical, contact, and link information
 Publication Number:  FHWA-HRT-12-031    Date:  August 2012
 Publication Number: FHWA-HRT-12-031 Date: August 2012

# User’s Guide: Estimation of Key PCC, Base, Subbase, and Pavement Engineering Properties From Routine Tests and Physical Characteristics

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## PCC Tensile Strength Models

### PCC Tensile Strength Model Based on Compressive Strength

This model development served as both a validation and development of a new correlation using the LTPP database. The model form used was a power equation and can be expressed as follows:

Figure 68. Equation. Prediction model 12 for ft.

Where:

ft = Indirect tensile strength of the PCC material.
f'c = Compressive strength of the mix determined at the same age.

The model statistics are presented in table 23. The model was developed using 541 data points with an R2 value of 42.09 percent and an RMSE of 61 psi. Table 24 provides details of the range of data used to develop the model.

Table 23. Model statistics for tensile strength prediction model.

 Parameter Estimate Standard Error 95 Percent Confidence Limits Coefficient 8.9068 2.0204 4.9381 to 12.8756 Power 0.4785 0.0256 0.4282 to 0.5288

Table 24. Range of data used for tensile strength prediction model.

 Parameter Minimum Maximum Average Compressive strength 1,990 12,360 6,763 Tensile strength 316 1,012 600

Figure 69 and figure 70 show the predicted versus measured plot and the residual errors plot, respectively. Figure 71 shows the sensitivity of the model to compressive strength. The relationship developed shows that for typical ranges of compressive strength (i.e., 3,000 to 6,000 psi), the PCC tensile strength varies from about 400 to 570 psi, which is a reasonable range for this strength parameter.

Figure 69. Graph. Predicted versus measured for tensile strength model.

Figure 70. Graph. Residual errors plot for tensile strength model.

Figure 71. Graph. Sensitivity of tensile strength prediction model to change compressive strength.

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