Protesters chased a contractor from Kathageri-Kanyuabora road in Embu East on Wednesday, saying his materials were substandard.
The residents claimed that contractor Jim Njamiu intended to use red soil instead of murram to grade the road.
This, they noted, would cause more damage on the dilapidated road especially with the rains.
"Red soil turns into mud whenever it rains. We wonder why any contractor would think of using soil to grade a road," Isaac Murimi said.
Murimi added that three weeks ago, road users took it upon themselves to repair the road.
"We pooled resources and unclogged culverts, cleared roadside bushes and covered potholes."
Motorist Jonathan Kinyua said they would rather continue repairing the road than watch a contractor do a shoddy job.
The road is the link to one of the major livestock markets in the region.
Boda boda operators at Kathageri said the contractor delivered the soil by lorry at night while telling residents that it was murram.
Reached for comment, Njamiu said the people had not been given the details of the project.
"I have been delivering soil but it will be used to raise the road before murram is used as a top layer," he said by phone.
"We will use the red soil to raise the road especially at the Kathageri boda boda stage which floods during the rainy season."
The work began after months of a push and pull between residents and area legislator Eric Muchangi.
The Member of Parliament said grading will take place once it stops raining.