More time is needed for new Interstate 5 concrete to dry, which means the project will now take longer to complete.

Changes in the schedule announced Thursday will offer motorists a break from all I-5 shutdowns in downtown Sacramento from early Monday through July 8, providing relief to travelers over the busy July 4 holiday.

But the overall road repair effort will now take about nine weeks instead of roughly seven weeks, California Department of Transportation spokesman Mark Dinger said. But the number of road closure days will remain at about 35.

The next stage of the project will not begin until July 8 to allow thicker-than-anticipated concrete time to cure before a sealant is applied.

Southbound I-5 is currently shut down from Richards Boulevard south to the Highway 50 interchange for the project, which includes repaving and other improvements. The southbound lanes are set to reopen on Monday.

The project, which is billed as one of the biggest road repair efforts in the capital in decades, began May 30 and has involved alternating closures of northbound and southbound lanes in the so-called boat section of the freeway.

"It is critical that this concrete be completely dry before applying the sealant and the final driving surface," Caltrans District 3 Director Jody Jones said in a news release. "To ensure a quality, long-lasting product, Caltrans and our contractor determined the safest course of action was to move Stage 3 to July 8 and avoid impacting the public and downtown area businesses during the busy July 4 holiday."

Caltrans said the third stage will involve closing the southbound lanes of I-5 between Richards Boulevard and Highway 50 beginning at 8 p.m. July 8 through 5 a.m. July 15.

After a short break, Stage 4 of the project will include closing the northbound lanes of I-5 from Highway 50 to Richards Boulevard from 8 p.m. July 17 to 5 a.m. July 24.

When crews began removing the old pavement, they discovered it was much thicker than anticipated, Dinger said. In some places, concrete was as thick as 48 inches.

This discovery meant the preparation process for the new, fast-setting slag-based concrete is taking much longer than anticipated.