Corrosion Study and Implementation Plan for NCHRP Report 597 (2008) / Chapter Skim
Currently Skimming:
Pages 1-48
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 1... ...
A-1 APPENDIX A CORROSION STUDY Introduction Controlled low-strength material (CLSM) is a cementitious, flowable, material, commonly made with cement, supplementary cementitious materials (SCMs)
|
From page 2... ...
A-2 ANSI/AWWA standard. California 643 estimates the maintenance-free service life of galvanized steel culverts in soils based on the pH and minimum electrical resistivity of soils.
|
From page 3... ...
A-3 Figure 1 California 643 chart to estimate years to perforation of steel culverts. Resistivity of the electrolyte can be an influencing parameter for most corroding systems.
|
From page 4... ...
A-4 would not occur in these environments. This would be typical of most CLSM mixtures as these mixtures are purposely designed for low strength.
|
From page 5... ...
A-5 In many instances when CLSM is used in the field, it may not be possible to embed a pipe entirely in CLSM. This could occur when a pipe undergoes localized repair or replacement and CLSM is used as a bedding and backfill material for the repaired area (scenario 1)
|
From page 6... ...
A-6 investigated the corrosion of steel reinforcement in concrete, due to the differences in the surrounding concrete environment, such as differential aeration, differential moisture content, differential salt concentrations, etc. (Mozer et al.
|
From page 8... ...
A-8 5 mm from the face of the CLSM. Six holes (4 mm diameter)
|
From page 9... ...
A-9 Table 2 Phase I CLSM mixture proportions and fresh characteristics. Mix No Cement Content (kg/m3)
|
From page 10... ...
A-10 Phase II Investigation Thirteen CLSM mixtures were cast to evaluate the corrosion of metals embedded in CLSM. The proportions of CLSM mixtures and their unit weights are shown in Table 3.
|
From page 11... ...
A-11 Table 3 CLSM mixture proportions and unit weights. Mix Cement Content (kg/m3)
|
From page 12... ...
A-12 Table 4 Chemical composition of Type 1 portland cement. Chemical compound % by weight Silicon Dioxide, SiO2 21.0 Aluminum Oxide, Al2O3 4.9 Iron Oxide, Fe2O3 2.3 Calcium Oxide, CaO 64.8 Magnesium Oxide, MgO 1.7 Sodium Oxide, Na2O 0.3 Compound composition C3S 62.0 C2S 13.0 C3A 9.0 C4AF 7.0 Table 5 Chemical composition of fly ashes and foundry sand.
|
From page 13... ...
A-13 Method for Density, Relative Density (Specific Gravity) , and Absorption of Fine Aggregate.
|
From page 14... ...
A-14 Figure 5 Resistivity measurement with Wenner Four-Electrode Method. The difference in measurement techniques is believed to be the reason for the different results obtained in the statistical analysis.
|
From page 15... ...
A-15 used to determine the chloride content of the CLSM and soil samples that were exposed to the chloride solution (Cady and Gannon 1992)
|
From page 16... ...
A-16 0 1 2 3 4 5 All CLSM samples Pe rc en t m as s l os s Mixture 23 Mixture 21 Figure 6 Phase I percent mass loss of ductile iron coupons embedded in all CLSM types. A multiple regression and analysis of variance was performed with the average percent mass loss data of the thirty-six CLSM samples as the response variable.
|
From page 17... ...
A-17 MSE is 0.0916. Appropriate coefficients should be used to predict the percent mass loss of a specific mixture.
|
From page 18... ...
A-18 where r is the resistivity (Ω-cm) and α and β are constants.
|
From page 19... ...
A-19 represent the actual in place resistivity of the exposed samples. In Phase 2 of this research program, the resistivity was measured from the actual exposed samples.
|
From page 20... ...
A-20 Figure 10 shows the influence of fly ash type on logarithm of the mass loss of the ductile iron pipe embedded in the various CLSM mixtures. The figure shows that the addition of fly ash reduces the logarithm of the percent mass loss of the ductile iron samples resulting from chloride-induced corrosion.
|
From page 21... ...
A-21 corrosion performance of the ductile iron pipe, the results do not indicate a significant decrease in the percent mass loss as a result of the increased pH. As such, the pH of the pore solution alone does not seem to reliably estimate the corrosion performance of ductile iron pipe embedded in CLSM.
|
From page 22... ...
A-22 -2.5 -2 -1.5 -1 -0.5 0 Bottom Ash Concrete Sand Foundry Sand None Lo g 1 0( P er ce nt M as s L os s) Figure 12 Logarithm of mass loss versus aggregate type.
|
From page 23... ...
A-23 outliers are not included in the analysis. It can be seen that the percent mass loss slightly increases with increasing w/cm.
|
From page 24... ...
A-24 0 2 4 6 8 10 12 14 -0.2 0 0.2 0.4 0.6 0.8 1 Log 10 (Average Percent Mass Loss) Distribution Normal p=0.83 Fr eq ue nc y Figure 14 Histogram of the transformed percent mass loss of coupons embedded in sand section of coupled samples.
|
From page 25... ...
A-25 materials. Figure 15 compares the logarithm of the distribution of percent mass loss of uncoupled samples (specimens embedded only in CLSM)
|
From page 26... ...
A-26 -2.5 -2 -1.5 -1 -0.5 0 0.5 1 BA-C BA CS-C CS FS-C FS None-C None Control Lo g 1 0( Pe rc en t M as s L os s) BA: Bottom Ash CS: Concrete Sand FS: Foundry Sand None: No Fine Aggregate Control: Sand -C: Indicates Coupled Samples Figure 16 Uncoupled versus coupled log mass loss versus CLSM mixtures containing various fine aggregate types.
|
From page 27... ...
A-27 0 10 20 30 40 50 Pe rc en t m as s l os s Uncoupled samples Figure 17 Percent mass loss distribution of metallic coupons Evaluation of different possible models for coefficient of multiple determination (R2) , the Cp statistic, and the error sum of squares indicated that the best model had a square root of the percent mass loss values as the response variable.
|
From page 28... ...
A-28 defined in the model for the main effects of continuous variables represent the amount of change in the expected value of the response variable for each unit change of the corresponding continuous variable, all other factors being the same. The interaction parameters in the model define how the response reacts to one variable based on the value or level of another variable.
|
From page 29... ...
A-29 Table 8 Parameters and their standard errors of the model Main effect Parameter Standard Error Intercept 4.4030 0.6610 Environment (α ) Chloride 0.7270 0.2780 Fine Aggregate type (β )
|
From page 30... ...
A-30 0 1 2 3 4 5 0 1 2 3 4 5 6 Pr ed ic te d sq ua re ro ot o f p er ce nt m as s l os s Observed square root of percent mass loss Figure 18 Observed percent mass loss values vs. the predicted values from the model.
|
From page 31... ...
A-31 Comparison of transformed percent mass loss means for the different levels of classification variables was performed using the Bonferroni comparison of means method. The transformed mean percent mass loss values for the samples exposed to chloride solution and distilled water were 2.765% and 2.291%, respectively.
|
From page 32... ...
A-32 needed to initiate the corrosion, and the actual amount of chloride ions did not have a significant effect. Resistivity of CLSM samples was a statistically significant continuous variable included in the model.
|
From page 33... ...
A-33 Comparison of the transformed mean percent mass loss for the four different fly ash types indicated that only the mean of the samples containing Class C fly ash were significantly different (in this case lower) from the other fly ashes.
|
From page 34... ...
A-34 0 1 2 3 4 5 6 7 Sq ua re ro ot o f p er ce nt m as s l os s none high carbon Class F Class C high carbon Class F Class C Class C 30 kg/m3 15 kg/m3 0 kg/m3 Fly ash type and cement content Figure 23 Square root of percent mass loss box plot for samples containing sand as fine aggregate. The figures show that among the samples with the same amount of cement content, samples with Class F and high-carbon fly ashes have lower pH values compared to the samples with Class C fly ash and samples without fly ash.
|
From page 35... ...
A-35 0 1 2 3 4 5 6 Bottom ash Foundry sand None Sand Sq ua re ro ot o f p er ce nt m as s l os s Figure 24 Box plots of transformed percent mass loss separated by fine aggregate type. Although the samples shown in each box plot have different values of other significant variables determined by the model, the Figure 24 shows that the samples containing foundry sand as the fine aggregate exhibited the highest mean percent mass loss.
|
From page 36... ...
A-36 -20 0 20 40 60 80 Embedded in Soil Embedded in CLSM Pe rc en t M as s L os s Figure 25 Percent mass loss box plots of coupons embedded in CLSM and soil. Figure 26 compares the percent mass loss box plots of the phase II uncoupled coupons and the phase II coupled coupons.
|
From page 37... ...
A-37 Multiple regression analysis and analysis of variance were performed on the percent mass loss data of metallic coupons that were embedded in the soil section of the coupled samples. The environment, metal type, soil type, fine aggregate type, fly ash type, resistivity of CLSM, resistivity of soil, pH of CLSM, pH of soil, chloride content of the CLSM, and chloride content of the soil were the regression variables examined.
|
From page 38... ...
A-38 Figure 27 shows the observed percent mass loss values against the percent mass loss values obtained from the model. The overall model is statistically significant and the linear correlation coefficient (R)
|
From page 39... ...
A-39 pH values could be due to the interaction of pore solutions at the CLSM/soil interface of the coupled samples. The model shows that the type of environment is a statistically significant factor.
|
From page 40... ...
A-40 -2 104 0 2 104 4 104 6 104 8 104 1 105 1.2 105 1.4 105 Soil/Cl Soil/DW CLSM/Cl CLSM/DW R es is tiv ity (O hm -c m ) Cl: Chloride Solution DW : Distilled Water Figure 29 Resistivity box plots of soils and CLSM separated by environment.
|
From page 41... ...
A-41 -0.5 0 0.5 1 1.5 2 Clay Sand lo g 1 0( Pe rc en t M as s L os s) Figure 30 Logarithm of percent mass loss values of coupons embedded in sand and clay.
|
From page 42... ...
A-42 -0.5 0 0.5 1 1.5 2 Ductile Iron Galvanized Steel lo g 1 0( Pe rc en t M as s L os s) Figure 32 Logarithm of percent mass loss box plots separated by metal type.
|
From page 43... ...
A-43 the effect of foundry sand is an indicator that in the coupled condition the main driving force of corrosion is the potential difference between the CLSM and soil environments. The fly ash type was another statistically significant variable in the model.
|
From page 44... ...
A-44 -0.5 0 0.5 1 1.5 2 Class C Class F High Carbon None lo g 1 0( Pe rc en t M as s L os s) Figure 34 Box plots of LPML values for coupled samples with sand as fine aggregate separated by fly ash type.
|
From page 45... ...
A-45 been performed on the influence of CLSM on the corrosion of embedded metals, engineers and owners are often reluctant to use CLSM. This research program presented findings on the corrosion of coupled and uncoupled galvanized steel and ductile iron coupons embedded in various CLSM mixtures and exposed to various environments.
|
From page 46... ...
A-46 References Association of Water Technologies, "White Rust: An Industry Update and Guide Paper 2002," Retrieved October 13, 2004 from Association of Water Technologies web site: www.awt.org/AWT_WHITE%20RUST%20PAPER_2002.pdf Abelleira, A., N.S. Berke, and D.G.
|
From page 47... ...
A-47 Escalante, E., "Measuring the Corrosion of Steel Piling at Turcott Yard, Montreal, Canada- A 14 Year Study," Corrosion Forms and Control for Infrastructure, ASTM STP 1137, Victor Chaker, Ed., ASTM, Philadelphia, 1992, 339-355 Folliard, K.J., et al., Controlled Low-Strength Material for Backfill, Utility Bedding, Void Fill, and Bridge Approaches, in NCHRP 24-12 Interim Report.
|
From page 48... ...
A-48 Sarhan, H.A., M.W. O'Neill, and P.D.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.