EXPERT ADVICE
A Small Investment in Crack Sealing Yields a Large Return
Study shows Crack Sealing as Pretreatment Improves other Surface Treatments
S imply put , crack sealing works .
Few resources impact society more than roads . Roads supply access to the world and are the arteries through which economies pulse . And like arteries transporting oxygenated blood to the body ; roads do not last forever but have a time from original construction to terminal condition , or design life . “ For a typical highway , we generally design an asphalt pavement for 20 years ,” said ADOT Pavement Design Group Manager Paul Burch . “ It does not mean the road ’ s going to fall apart in 20 years .”
Roads are designed to serve for a specific length of time and once constructed deterioration begins . Preventive maintenance requires an early adoption of routine measures to ensure road systems continue to perform to their design life and beyond .
Preventive Treatment Is Not a One and Done Application
Preventive pavement treatments are low-cost maintenance treatments designed to preserve or improve functional condition . Pavement preservation is not a one and done application . Rather , much like preventive healthcare , pavement preservation is a series of treatments applied continually across a pavement ’ s service life . Multiple pavement preservation treatments are far more cost effective than the “ built it and forget it ” cost of total reconstruction or rehabilitation .
Pavement preservation treatments include chip seal , slurry seal , micro surfacing , thin hot mix overlays , fog seal , and crack seal . Pavement preservation treatments are generally used to restore pavement surface characteristics . However , the performance and effectiveness of any preservation treatment is dependent on the condition of the existing pavement . Studies show preservation treatments are most effective when applied earlier in a structure ’ s service life . While there is benefit to preserving older , further degraded roads , preserving early and continually throughout a pavement ’ s service life is the most cost-effective way to maintain .
First Step , Crack Seal
Cracking is a primary mode of distress in asphalt pavements with approximately 75 % of cracks developing into potholes within 3 years if not sealed . According to the National Center for Asphalt Technology ( NCAT ), “ if left untreated , cracks can lead to accelerated deterioration and potholing , further reducing pavement serviceability .” When the right preventive treatment is applied to the right road at the right time , roads can be kept in
By Ade Craig
good condition eliminating the need for costly rehabilitation alternatives later in the pavement ’ s life when the structure has deteriorated ,” NCAT adds .
As soon as the first crack appears , water and debris permeate the pavement structure . Crack sealing should begin early after the first formation of cracks on a road surface .
Cracks are Inevitable , but Not Potholes
Crack sealing is the process of installing crack sealant ( specialized material ) into a crack for the purpose of preventing the intrusion of water and incompressible materials into the pavement . Crack sealing is the most common pavement preservation approach with the highest-benefit-to-cost ratio . Research demonstrates a dollar spent on early preventive maintenance , such as crack sealing ; can delay , or altogether eliminate spending $ 6 to $ 14 in future rehabilitation costs . Compared to 75 % of unsealed cracks becoming potholes in 3 years , when cracks are sealed early , only 1 % will develop into potholes within the same length of time .
Cracks are going to develop as asphalt pavement naturally oxidizes and deteriorates . Before initiating a preventive preservation treatment , it is important to ensure all cracks in the existing pavement are properly sealed . Sealing cracks promptly as part of a pavement preservation program prevents water infiltration , loss of load-carrying capacity and is the most important step in preventing potholes , ultimately ensuring a smooth ride for motorists .
Crack Sealing Provides Immediate Value to Other Surface Treatments
Pavement preservation study proves crack sealing improves performance of other surface treatments .
To answer the question of how much life-extending benefit can be gained from crack sealing-and other preservation treatments , the Minnesota DOT Road Research Project ( MNROAD ) and NCAT evaluated 25 treatments from 2012-2015 using field performance data of test sections on Lee Road 159 , a two-lane road near NCAT .
As shown in the table on the next page , sections were divided into three categories ( stand alone crack seal / fill , chip seal , and micro surfacing ) to allow direct comparisons among pairs of treatment . The control in this study is defined as normal cracking as if no treatment were applied . The results generated in the following sections ( L5 , L6 , L7 , L11 , and L12 ) were from the changes in pavement vs . the control .
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