Guidelines for Detection, Analysis, and Treatment of Materials-Related Distress in Concrete Pavements

Previous | Table of Contents

Equation 1-1: Equation. Equation to determine the sample size necessary to obtain an estimate of a pavement section's PCI. Lowercase N equals uppercase N multiplied by lowercase S squared all divided by the following: the quotient of lowercase E squared and four multiplied by uppercase N minus 1 and added to lowercase S squared.

Equation 1-2: Equation. Equation to determine the PCI procedure sampling interval. Lowercase I equals uppercase N divided by lowercase N.

Figure 1-5: Graphic. Example of PCI sample unit inspection form (Shahin and Walther 1990). This form is used to record the inspection of a sample unit of a concrete surfaced road or parking lot. The right side of the form has a space for sketching out any distressed areas of the sample unit and is marked with an 11 by 5 grid. The top left part of the form has a list of distress types. Below the list of distress types is a table for the inspector to denote information about any distressed areas found on the sample unit. The table contains columns for the inspector to indicate the distress type number, level of severity, slab number, density, and deduction value.

Figure 1-6: Flowchart. Fundamental process for analyzing a concrete MRD sample. The flowchart shows the steps involved in diagnosing an MRD. The steps are as follows:

1.)    Perform visual observation.

2.)    Perform either wet chemistry analysis, stereo OM observation, or use staining techniques.

3.)    If wet chemistry analysis or staining techniques are chosen, follow both with stereo OM observations

4.)    Diagnose the MRD after the stereo OM observations if possible or perform further wet chemistry analysis or staining, or conduct petrographic OM or SEM/EDS observations.

5.)    Diagnose the MRD if possible or conduct more stereo OM observations or X-ray diffraction analysis. In some cases, if petrographic OM observation was performed first, researchers might want to follow that with SEM/EDS observation. The same goes for if SEM/EDS observations was performed first.

6.)    Once all appropriate observation techniques are conducted and X-ray diffraction has been performed, diagnose the MRD.

Equation 1-3: Equation. Equation showing relationship between total points, total line length, area fraction, and volume fraction during phase of interest. Uppercase P subscript uppercase P equals uppercase L subscript uppercase L equals uppercase A subscript uppercase A equals uppercase V subscript uppercase V.

Equation 1-4: Equation. Equation for calculating total specific surface of air voids. Alpha equals four divided by lowercase L bar or the average chord length.

Equation 1-5: Equation. Equation number one for calculating the Powers spacing factor. The Powers spacing factor is noted as uppercase L bar and equals lowercase P divided by the product of alpha and uppercase A.

Equation 1-6: Equation. Equation number two for calculating the Powers spacing factor. Uppercase L bar equals three divided by the following: the sum of one and lowercase P divided by uppercase A all to the one-third power, all of which is multiplied by 1.4 and then minus 1 and then multiplied by alpha.

Figure 1-7: Graph. Effect of treatment with lithium hydroxide solution (Stark et al., 1993). This chart presents the results of a study to determine the effect of treating hardened concrete with a lithium concrete solution. Overall, the treatment caused the concrete to stop expanding or reduced the rate of expansion. The chart indicates that when concrete was treated with a lithium hydroxide soak, expansion within the concrete continued for approximately 90 days after the treatment. At 90 days, expansion leveled off at slightly more than 0.40 percent. For concrete soaked with lithium hydroxide at 32 days and then resoaked at 90 days, expansion occurred at a steady rate until the first soaking and then at a slower rate until the second soaking. After the re-soak, expansion stopped at 0.20 percent. Expansion increased steadily throughout the entire time period for the control sample of concrete.

Figure 1-8: Graph. Effect of various lithium treatments. This chart presents the results of a study to determine the effect of treating hardened concrete with various lithium treatments. The chart indicates the following effects for three different treatments and a control sample: Concrete treated with lithium carbonate at the 90-day mark expanded rapidly until the four-month mark to approximately 0.30 percent. After the four-month mark, the concrete expanded at a slower rate to a maximum of 0.40 percent by the 25-month mark. Concrete soaked with lithium fluoride expanded to 0.55 percent during the first 15 months after treatment, after which time expansion leveled off. Concrete treated with lithium hydroxide expanded rapidly, by more than 0.40 percent, during the first 90 days prior to treatment. After the 90 days and the treatment occurred, expansion leveled off at approximately 0.43 percent for the remainder of the time period. The control sample continuously expanded throughout the 25-month time period to a maximum of approximately 0.78 percent.

Figure 1-9: Flowchart. Flowchart for selecting preferred treatment and rehabilitation options. This flowchart shows the process for selecting treatment and rehabilitation options for MRDs. When selecting the preferred treatment and rehabilitation options, the following steps should be followed:

1.)    Identify the extent and severity of the durability distress.

2.)    Identify potential treatment or repair options. To do this, see the tables for each distress type.

3.)    Identify appropriate materials and equipment for use with the identified treatment or repair options

4.)    Determine if other durability distress exists. (If other durability distress exists, then go back to step one and identify the extent and durability of the distress. If the answer is no and no other durability distress exists, then continue to the next step.)

5.)    Evaluate overall pavement conditions. Note that at this point, other types of distress than durability distress should be identified, along with their severity and extent. Regardless of whether durability or other types of distress are identified, continue with the following steps.

6.)    Identify comprehensive feasible treatment or rehabilitation alternatives by evaluating potential constraints and the performance of each alternative and by conducting a life cycle cost analysis for each alternative.

7.)    Select the preferred alternative.

8.)    Develop a detailed treatment and rehabilitation plan.

Figure 1-10: Diagram. A holistic model of concrete deterioration from environmental effects (Mehta 1997). The starting point of this flow chart indicates that deterioration begins when cracks, microcracks, and pores start to form within a watertight, reinforced concrete structure pores. At this point, the surrounding environment can impact the concrete causing no visible damage but effecting the concrete through either weathering such as cyclic heating and cooling or wetting and drying or from loading such as cyclic loading or impact loading. This stage is known as Stage 1 environmental action. This environmental action leads to the gradual loss of watertightness as cracks, microcracks, and pores become more interconnected. Stage 2 environmental action then occurs, which can cause initiation and propagation damage from either the penetration of water, the penetration of oxygen and carbon dioxide, or the penetration of acidic ions such as chlorine or sulfate ions. Stage 2 environmental action can simultaneously cause two problems. First, it can result in the expansion of the concrete due to increasing hydraulic pressure in pores caused by the corrosion of steel, sulfate attack on aggregates, alkali attack on aggregates, or the freezing of water. Second, it can lead to a reduction in concrete strength and stiffness. Both of these problems can lead to cracking, spalling, and a loss of mass, which can lead once again lead to the gradual loss of watertightness as cracks, microcracks, and pores become more interconnected. If this happens, the cycle begins again.

Equation 1-7: Equation. Equation to calculate the scale code from one to five. Uppercase SC equals negative 4.187 plus the product of 7.313 and the Powers spacing factor or uppercase L bar plus the product of 8.939 and the water-concrete ratio plus the product of 0.372 and uppercase VR or the void removal parameter.

Equation 1-8: Equation. Ratios indicating sulfate attack resistance. This equation is divided into two parts. In the first part, the percent tricalcium aluminate divided by the sum of the percent sulfur trioxide and sodium oxide at equilibrium is less than three. One is less than the percent sulfur trioxide divided by the percent sodium oxide at equilibrium, which are less than 3.5.

Equation 1-9: Equation. Equation to determine the R-factor as it relates to fly ash and sulfate resistance. Uppercase R equals the quotient of the percent of calcium oxide minus 5 and the percent ferric oxide.

Equation 1-10: Equation to determine the oxide durability factor. Uppercase ODF equals the quotient of total calcium oxide multiplied by the total free calcium oxide and the sum of the amount of silica, aluminum oxide, and ferric oxide.

Figure 1-11: Graphic. General location of projects included in study. This map shows the location of the six projects (four primary and two secondary) conducted for this study. On the map, circles indicate primary project sites and are located along State Route 68 in Boron, California, along I 90 in Spearfish, South Dakota, TH 65 in Mora, Minnesota, and along I 440 in Raleigh, North Carolina. Triangles indicate secondary project sites and are located along State route 14 in Mojave, California and along State route 2 in Nebraska City, Nebraska.

Equation: Method used to assign project identification numbers. The project identification numbers are the two letter state abbreviation followed by a dash and then the three digit highway number followed by a dash and then the beginning milepost number followed by a dash and then the section number.

Equation: Method used to assign core sample identification numbers. The core sample identification numbers are the two letter state abbreviation followed by a dash and then the three digit highway number followed by a dash and then the beginning milepost number followed by a dash and then the section number followed by a dash and then the one letter code designation that indicates core location.

Equation A-1: Equation. Chemical equation showing the dissolution of calcium hydroxide from treatment with sodium chloride. Two sodium chloride plus calcium hydroxide reacts to form calcium chloride and two sodium hydroxide.

Equation A-2. Equation. Chemical equation showing the reaction between soluble calcium chloride and aluminate. Calcium chloride plus tricalcium aluminate reacts to form chloroaluminate crystals, which is the chemical compound uppercase C subscript 3 uppercase A bonded to uppercase C lowercase A uppercase C lowercase L subscript 2 bonded to ten uppercase H subscript 2 uppercase O.

Equation A-3. Equation. Chemical equation showing the reaction of calcium chloride on concrete. Three calcium hydroxide plus calcium chloride plus 12 water reacts to form hydrated calcium oxychloride, which is denoted as three uppercase C lowercase A uppercase O bonded to uppercase C lowercase L subscript 2 bonded to fifteen uppercase H subscript 2 uppercase O.

Equation A-4: Equation. Chemical equation showing dedolomization, in which M represents potassium, sodium, lithium or other alkali elements. Calcium magnesium carbonate or dolomite plus two uppercase MOH reacts to form magnesium hydroxide plus calcium carbonate plus uppercase M subscript two carbonate.

Equation A-5: Equation. Chemical equation showing production of alkali hydroxide. Sodium carbonate plus calcium hydroxide reacts to form two sodium hydroxide plus calcium carbonate.

Equation A-6: Equation. Chemical equation showing the formation of the high sulfate form of ettringite. Tricalcium aluminate bonded to uppercase CS bar bonded to uppercase H subscript 18 plus two uppercase CH plus two uppercase S bar plus twelve hydrogen react to form tricalcium aluminate monosulfate hydrate, the chemical compound for which is uppercase C subscript 3 uppercase A bonded to three uppercase C uppercase S bar bonded to uppercase H subscript 32.

Equation A-7: Equation. Chemical equation showing the formation high sulfate ettringite. Tricalcium aluminate bonded to uppercase CH bonded to uppercase H subscript 18 plus two uppercase CH plus three uppercase S bar plus eleven hydrogen react to form tricalcium aluminate monosulfate hydrate, the chemical compound for which is uppercase C subscript 3 uppercase A bonded to three uppercase C uppercase S bar bonded to uppercase H subscript 32.

Equation A-8: Equation. Chemical equation for the formation of the high sulfate form of ettringite by Bickley et al (1994). Six calcium ions with a superscript positive two charge plus 2 aluminum hydroxide ions with superscript negative charge and subscript four plus four hydroxide ions with a superscript negative charge plus three uppercase S bar plus twenty-six water molecules react to form uppercase C subscript six uppercase AS bar subscript three uppercase H subscript thirty-two.

Equation A-9: Equation. Chemical equation for sodium sulfate gypsum corrosion (Mehta and Monteiro 1993). Sodium sulfate plus calcium hydroxide plus two water reacts to form gypsum, which is the chemical compound uppercase C lowercase A uppercase S uppercase O subscript four, bonded to two uppercase H, subscript two uppercase O, plus two sodium hydroxide.

Figure A-1: Diagram. The electrochemical process of steel corrosion. (Mehta and Monteiro 1993). At the top of the diagram are the reaction equations for the cathode and anode processes. The reaction equation for cathode process is one oxygen molecule plus two water plus four free electrons reacts to form four hydroxide. The reaction equation for the anode process is iron represented by uppercase F lowercase E reacts to form iron denoted as uppercase F lowercase E with two positive charges in the superscript plus two free electrons. The graphic depicts oxygen flowing into moist concrete as an electrolyte. Below the moist concrete is a layer of steel where the cathodes and anodes are located. The concrete and steel are separated by a surface film of ferric oxide. A current flows through the steel from the cathodes into the anodes resulting in the release electrons from the anodes into the cathodes and iron molecules back into the moist concrete.

Equation A-11: Equation. Steel corrosion anode reaction. Uppercase F lowercase E reacts to form two free electrons plus iron denoted as uppercase F lowercase E with two positive charges in the superscript.

Equation A-12: Equation. Steel corrosion cathode reaction. One-half oxygen plus water plus two free electrons reacts to form two hydroxide ions.

Equation A-13: Equation. The sum of the anode and cathode reactions. Iron plus one-half oxygen plus water react to form iron with two positive charges plus two hydroxide ions, which then reacts to forms iron oxide.

Previous | Table of Contents