TxDOT Research Library - TxDOT Research Project

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Research on Joint Seal Materials to Improve Installation and Performance

What Was the Need?

Joints in Portland cement concrete (PCC) pavement are sealed with proper sealant materials to prevent intrusion of water and incompressible materials. Intrusion of water could result in corrosion of dowels or tie bars in CPCD, and tie bars or longitudinal steel in CRCP. Intrusion and collection of incompressible materials could cause surface spalling. Another important failure mechanism in PCC pavement in Texas is erosion of base materials caused by water infiltration along longitudinal joints between the outside concrete lane and asphalt shoulder. Currently, joint design is dictated in the joint design standards, JS-94. Joint seal material quality is controlled by DMS-6310. Joint sealant installation is governed by Item 438. There are discrepancies between TxDOT requirements and actual practice, potentially compromising the effectiveness of joint performance. The discrepancies need to be identified and design standards or specifications revised or field practices modified.

What's the Solution?

The objectives of this project were to (1) identify failure modes and their mechanisms in joint seals in Texas, and to (2) identify what needs to be done to minimize the failures and improve joint seal performance. The findings from this study included (1) joint sealant performance period is much shorter than the current pavement design period, which is 30 years, (2) it is quite rare to observe pavement distresses that can be solely attributable to poor joint sealant condition, (3) there are other variables that have more significant effects on PCC pavement performance than joint seal condition, (4) most of the joint seal failures appear to be due to hardening of the sealant over time, or aging effect, (5) discrepancies exist between TxDOT requirements in design standards and field practice, and (6) continued concrete drying shrinkage increases joint width over time. It appears that the condition of joint sealant does not have substantial effects on overall performance of PCC pavement in Texas. This finding is in line with the findings in several state DOTs. However, joint sealing has its own merit, such as keeping incompressible materials out of the joints.

Project Number

0-6826

Status

Completed

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