Using Existing Pavement in Place and Achieving Long Life (2014)

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103 A p p e n d i x C The decision tables developed for the R23 project were based on extensive literature review, on pavement design analysis, and in working with a number of engineers from state departments of transportation (DOTs) and industry. The guidelines were developed to help designers in selecting either a rigid or flex- ible reconstruction approach that can reasonably be expected to provide long-life pavement performance. For this project, long-life performance was defined as providing 50 years of service without major structural deterioration. It is antici- pated that any approach selected will require some form of rehabilitation or resurfacing during the service life of the pavement. The final selection of the most appropriate design should be based on a life-cycle cost analysis of the various approaches, including all rehabilitation or resurfacing costs over the life of the pavements. The development of the decision matrices followed more or less the standard process where team members laid out an outline of the decision process on a blackboard. The out- line had the basic form seen on the tables with pavement type, distress present, and potential renewal approaches for those conditions. The outline was circulated to the full team and modified as additional considerations were added. The outline was presented at the kickoff meetings and then cir- culated among the participating agencies for comment, and again adjustments were made to the outline. To make the process clearer, the decision matrix was put in a set of tables. The tables were then circulated again to the full R23 team and the participating agencies, which provided more com- ment (most likely because the tables were easier to follow than the outlines). The tables were then used to build an interactive Flash-based program that would simplify use of the decision matrix. In building the logic for the interactive program, a few more decision points were added based on the more rigorous nature of that process. After the program was developed, it was put through a series of trials on a wide range of potential applications, and the decision tables were adjusted again based on errors or omissions found in that process. The interactive program and the decision tables were again presented to the participating agencies for review and comment, and final adjustments were made to the pro- gram and the tables presented in this appendix. General guidance was also developed on layer thickness that would be required to provide long-life pavement renewal. A set of tables was developed as described in Appendix D. Since these design tables are linked to the actions included in the decision tables, a fifth column was added to the decision tables. The information in this column, called “Design Resources,” states the specific thickness design table to be used for those specific sets of conditions and renewal approach. These specific thick- ness design tables can be found in Appendix D. Where there was a clear repetition of actions and design resources, rules were used to reduce the verbiage in the columns. The decision tables have been incorporated into the interac- tive program to help users develop a list of feasible approaches based on existing site conditions. Table C.1 provides details on the decision matrix for existing flexible pavements. Table C.2 provides details on the decision matrix for existing JPCP and JRCP. Table C.3 describes the decision process for existing CRCP, while Table C.4 details renewal alternatives for exist- ing composite pavements. Three rules are commonly refer- enced in Tables C.2 through C.4 under the “Design Resources” column: • Rule 1: Rubblization of existing portland cement concrete (PCC) followed by application of asphalt concrete (AC) overlay from Tables D.37 through D.39 (Appendix D). Rubblization guidelines include the following: 44 If the subgrade MR < 6,000 psi or CBR < 4%, do not rubblize, thus defaulting to crack and seat only. 44 If the subgrade MR ≥ 6,000 psi but < 10,000 psi, consult the TTI rubblization guidelines as to whether rubbliza- tion is viable (Sebesta and Scullion 2006). 44 If the subgrade MR ≥ 10,000 psi, then rubblization is a viable option. Development of Rigid and Flexible Renewal Decision Matrices

104 The selection of the AC thickness is based on a drop-down menu of subgrade moduli equal to 5,000 psi, 10,000 psi, or 20,000 psi. The existing pavement shall be character- ized by one of four possible moduli: 30,000 psi, 50,000 psi, 75,000 psi, or 100,000 psi. It is recommended that an exist- ing pavement modulus of 50,000 psi be used to reflect rub- blized PCC. • Rule 2: Crack and seat existing PCC followed by applica- tion of AC overlay from Tables D.37 through D.39 (Appen- dix D). The selection of the AC thickness is based on a drop-down menu of subgrade moduli equal to 5,000 psi, 10,000 psi, or 20,000 psi. The existing pavement shall be characterized by one of four possible moduli: 30,000 psi, 50,000 psi, 75,000 psi, or 100,000 psi. It is recommended that an existing pavement modulus of 75,000 psi be used to reflect crack and seated PCC. • Rule 3: Use Table D.22 (Appendix D) for thickness deter- mination of an unbonded PCC overlay and place on a 2-in.-thick AC bond breaker. The unbonded PCC overlay thickness is independent of subgrade support conditions. Reference Sebesta, S., and T. Scullion. 2007. Field Evaluations and Guidelines for Rubblization in Texas. Report FHWA/TX-08/0-4687-2. Texas Trans- portation Institute.

105 Table C.1. Feasible Renewal Alternatives for Existing Flexible Pavements Distress Category Specific Distress Description Distress Present? Renewal Pavement Type Option Action Design Resources Environmental cracking Transverse or block cracking Yes Flexible Pulverize pavement structure full depth followed by a thick AC overlay. Pulverize and use residual material as untreated base (50 ksi). Apply AC thickness from Tables D.37–D.39. Pulverize and treat residual material with emulsion or foamed asphalt resulting in a treated base (100 ksi). Apply AC thickness from Tables D.37–D.39. Rigid No mitigation required, place an unbonded PCC overlay. Use Table D.22 for thickness determination of an unbonded PCC overlay. No — Continue to “materials-caused distress.” — Materials- caused distress Stripping Yes Flexible If stripping is found through all layers, pulverize pave- ment structure full depth followed by a thick AC overlay. Pulverize and use residual material as untreated base (50 ksi). Apply AC thickness from Tables D.37–D.39. Pulverize and treat residual material with emulsion or foamed asphalt resulting in a treated base (100 ksi). Apply AC thickness from Tables D.37–D.39. If stripping is found in specific layers, remove AC to maximum depth of stripping followed by a thick AC overlay. Use Tables D.37–D.39 with 30-ksi base and the subgrade MR to deter- mine total depth of AC thickness, then subtract remaining AC thick- ness to determine overlay thickness. Rigid Place unbonded PCC overlay. If grade limits require, mill existing pavement. AC overlay over stripped pavement may be required to stabilize HMA. Use Table D.22 for thickness determination of an unbonded PCC overlay. No — Continue to “full-depth fatigue cracking.” — Full-depth fatigue cracking Longitudinal or alligator cracking in wheelpaths Yes Flexible <15% fatigue cracking: patch and repair, moderate thickness AC overlay. Use Tables D.37–D.39 with 30-ksi base for AC overlay thickness, then subtract existing AC thickness to determine overlay thickness. >15% fatigue cracking: pulverize pavement structure full depth followed by a thick AC overlay. Pulverize and use residual material as untreated base. Apply AC thick- ness from Tables D.37–D.39 with 50-ksi base. Pulverize and treat residual material with emulsion or foamed asphalt, resulting in a treated base. Apply AC thickness from Tables D.37– D.39 with 100-ksi base. Rigid Patch severely cracked areas, place an unbonded PCC overlay. Profile elevation may require milling existing AC pavement. Use Table D.22 for thickness determination of an unbonded PCC overlay. No — Continue to “top-down cracking.” — Top-down cracking Longitudinal or alligator cracking in wheelpaths Yes Flexible <15% patch and overlay. Use Tables D.37–D.39 with 30-ksi base and the subgrade MR to deter- mine total depth of AC thickness, then subtract the thickness milled out to eliminate the top-down cracking (unless indicated, the assumed depth is 2 in.). Where patching only, subtract existing depth to calculate overlay. >15% mill down to bottom of cracking followed by a moderate thickness AC overlay. Rigid Place an unbonded PCC overlay. Use Table D.22 for thickness determination of an unbonded PCC overlay. Note: AC, asphalt concrete; HMA, hot-mix asphalt; PCC, portland cement concrete.

106Table C.2. Feasible Renewal Alternatives for Existing JPCP and JRCP Pavements Distress Category Specific Distress Description Distress Present? Renewal Pavement Type Option Action Design Resources Materials- caused distress D-cracking with light Severity Yes Flexible option for JPCP Rubblization or crack and seat JPCP followed by a thick AC overlay. For rubblization, apply TTI guide- lines (Sebesta and Scullion 2007). Apply Rule 1. Apply Rule 2. Flexible option for JRCP Rubblization or saw, crack, and seat JRCP with a thick overlay. For rubblization, apply TTI guidelines (Sebesta and Scullion 2007). Apply Rule 1. Saw, crack, and seat existing PCC followed by application of AC overlay from Tables D.37–D.39; otherwise, Rule 2 applies. Rigid option Apply 2 inch AC overlay bond breaker followed by an unbonded PCC overlay. Apply Rule 3. No — Continue to next level of “D-cracking.” — D-cracking with moderate to high severity Yes Flexible option with rubblization if subgrade meets TTI guidelines Rubblize followed by a thick AC overlay. For rubblization, apply TTI guidelines. Apply Rule 1. Flexible option if does not meet TTI guidelines for rubblization Do not use the existing pavement; requires all new pavement. — Rigid option Full-depth patch and apply 2-in. AC overlay bond breaker followed by an unbonded overlay. Apply Rule 3. No — Continue to “alkali-silica reactivity.” — Alkali-silica reactivity Yes Flexible option Rubblize followed by thick AC overlay. For rubblization, apply TTI guidelines. Apply Rule 1. Rigid option Patch plus 2-in. AC bond breaker followed by unbonded PCC overlay. Apply Rule 3. No — Continue to “pavement cracking.” — Pavement cracking % multiple cracked panels Yes Flexible option for low to moderate multiple cracked panels (1% to 10% of panels) Rubblization or crack and seat JPCP with a thick AC overlay. For rubblization, apply TTI guidelines (Sebesta and Scullion 2007). Apply Rule 1. Rigid option for low to moderate multiple cracked panels (1% to 10% of panels) Place a 2-in. AC bond breaker followed by an unbonded PCC overlay. Apple Rule 3. Flexible option for moderate to high multiple cracked panels (>10% of panels) If subgrade meets or exceeds TTI criteria, apply rubblization followed by a thick AC overlay. Apply Rule 1. If subgrade does not meet TTI criteria, options include crack and seat or do not use existing pavement. Apply Rule 2. Rigid option for moderate to high multiple cracked panels (>10% of panels) Replace rocking or shattered slabs followed by a 2-in. AC overlay bond breaker followed by an unbonded PCC overlay. Apply Rule 3. No — Continue to “joint faulting.” (continued on next page)

107 Table C.2. Feasible Renewal Alternatives for Existing JPCP and JRCP Pavements Distress Category Specific Distress Description Distress Present? Renewal Pavement Type Option Action Design Resources Joint faulting — Yes Flexible option for low faulting (< 0.25 inches) Rubblization or crack and seat JPCP with a thick AC overlay. For rubblization, apply TTI guidelines (Sebesta and Scullion 2007). Apply Rule 1. Apply Rule 2. Rubblization or saw, break and seat JRCP with a thick AC overlay. For rubblization, apply TTI guidelines (Sebesta and Scullion 2007). Apply Rule 1. Saw, crack, and seat existing PCC followed by application of AC overlay from Tables D.37–D.39; otherwise, Rule 2 applies. Rigid option for low faulting (< 0.25 inches) Place a 2 inch AC overly followed by an unbonded PCC overlay. Apply Rule 3. Yes Flexible option for high faulting (> 0.25 inches) Rubblization or crack and seat JPCP with a thick AC overlay. For rubblization, apply TTI guidelines. (Sebesta and Scullion 2007) Apply Rule 1. Apply Rule 2. Rubblization or saw, break and seat JRCP with a thick AC overlay. For rubblization, apply TTI guidelines (Sebesta and Scullion 2007). Apply Rule 1. Saw, crack, and seat existing PCC followed by application of AC overlay from Tables D.37–D.39; otherwise, Rule 2 applies. Rigid option for high faulting (> 0.25 inches) Place a 2-in. AC overlay followed by an unbonded PCC overlay. If joint deflections > 40 mils (0.040 in.), then consider crack and seat JPCP or saw, break, and seat JRCP to stabilize slabs. Apply Rule 3. No — Continue to “pumping.” — Pumping — Yes Flexible Crack and seat JPCP with a thick AC overlay if the drainage can be improved. Apply Rule 2. Saw, crack, and seat JRCP with a thick AC overlay if the drainage can be improved. Saw, crack and seat existing PCC followed by application of AC overlay from Tables D.37–D.39; otherwise, Rule 2 applies. If drainage cannot be improved, then AC based renewal should not be used. — Rigid If joint deflections >40 mils (0.040 in.), consider crack and seat followed by a 2-in. AC bond breaker fol- lowed by an unbonded PCC overlay. Drainage must be improved. Apply Rule 3. No — — — Note: AC, asphalt concrete; JPCP, jointed plain concrete pavement; JRCP, jointed reinforced concrete pavement; PCC, portland cement concrete. (continued)

108 Table C.3. Feasible Renewal Alternatives for Existing CRCP Pavements Distress Category Specific Distress Description Distress Present? Renewal Pavement Type Option Action Design Resources Punchouts — Yes Flexible option with ≤5 punchouts per mile Repair all punchouts; place thick AC overlay to achieve a longer service life. Apply AC overlay from Tables D.37–D.39. The selection of the AC thick- ness is based on a drop- down menu of subgrade moduli equal to 5,000 psi, 10,000 psi, or 20,000 psi. The existing pavement is characterized by one of four possible moduli to select from: 30,000 psi, 50,000 psi, 75,000 psi, or 100,000 psi. Rigid option with ≤5 punchouts per mile Repair major punchouts if slab load support in question. Follow repairs with a 2-in. AC bond breaker followed by an unbonded PCC overlay. Apply Rule 3. Flexible option with >5 punchouts per mile Rubblization of CRCP with a thick AC overlay. For rubblization, apply TTI guidelines (Sebesta and Scullion 2007). Apply Rule 1. Rigid option with >5 punchouts per mile Repair major punchouts if slab load support in question. Follow repairs with a 2-in. AC bond breaker followed by an unbonded PCC overlay. Apply Rule 3. No — — — Note: AC, asphalt concrete; CRCP, continuously reinforced concrete pavement; PCC, portland cement concrete. Table C.4. Feasible Renewal Alternatives for Existing Composite Pavements Distress Category Specific Distress Description Distress Present? Renewal Pavement Type Option Action Design Resources Surface course in fair to poor condition Can be a range of distress types. For the underlying PCC, these are mostly cracking related. Yes Flexible option Remove existing AC surface(s). Apply rubblization if meets TTI criteria. Remove existing AC surface(s). Use crack and seat or saw, crack, and seat. Apply Rule 1. Following crack and seat or saw, crack, and seat of existing PCC pavement, apply Rule 2. Rigid option Place unbonded PCC overlay. If grade limits require, mill existing AC pavement. Apply Rule 3. Surface course in very poor condition Can be a range of distress types. For the underlying PCC, these can include severe D-cracking and ASR. Yes Flexible option Remove and replace existing pavement structure. — Rigid option Place unbonded PCC overlay. If grade limits require, mill existing AC pavement. Apply Rule 3. Note: AC, asphalt concrete; ASR, alkali-silica reactivity; PCC, portland cement concrete.