REVEALED: New Technology KeNHA Is Using To Build Mombasa Road

The Kenya National Highway Authority (KENHA) on Sunday, December 15 opened up on a new technology being used to construct Mombasa Road in Nairobi, to lengthen the road's lifespan.

According to KeNHA, it has adopted Hand-Packed Stone (HPS) technology. "KeNHA has adopted Hand Packed Stone (HPS) technology in the construction of Mombasa Road to create a durable sub-base and extend the pavement's lifespan."

"This labour-intensive method enhances the road’s structural integrity, ensuring taxpayers get value for money," the highways authority explained.

Hand-packed stone (HPS) is a technique often used in road construction or drainage systems, particularly in areas requiring robust and cost-effective substructure or foundation stability solutions.

A photo collage of the Hand Packed Stone (HPS) used by Kenya National Highways Authority on the construction of Mombasa Road in Nairobi. /KENHA

It involves manually laying stones compactly and interlocked to create a stable base layer. This method is valued for its durability, load-bearing capacity, and resistance to erosion.

Key Characteristics of Hand-Packed Stone (HPS):

Material Used:

• Typically consists of hard, angular stones of various sizes.
• The stones are usually unshaped but fit tightly together when manually arranged.

Manual Process:

• Stones are carefully hand-packed to minimize voids between them.
• Smaller stones or gravel may be used to fill gaps and increase compaction.

Applications:

• Road bases in rural or hilly areas where machinery access is limited.
• Drainage structures, such as channels or culverts, to provide stability and reduce water erosion.
• Foundations for retaining walls, embankments, or other low-cost structural supports.

Advantages:

• Cost-effective compared to using concrete or asphalt in remote areas.
• Environmentally sustainable, as it often uses locally sourced materials.
• High load-bearing capacity and resistance to settling when properly executed.

Disadvantages:

• Labor-intensive and time-consuming due to the manual nature of the work.
• Requires skilled workers to ensure stones are packed effectively and interlocked.

Relevance in Modern Construction:

• HPS is often used in regions where resources are limited or as part of traditional construction practices.
• It may serve as a base layer for more modern road-building methods or as a standalone solution in rural infrastructure.

The hand-packed stone technique remains a practical approach in areas with challenging terrains, economic constraints, or a need for durable, low-maintenance solutions.

This technique is often used in infrastructure projects, especially in rural and low-traffic areas, due to its cost-effectiveness and simplicity. It will extend the road's lifespan as it will address challenges like drainage by the introduction of a rockfill base to stabilise the wet ground.

Mombasa Road is characterised by poorly drained black cotton soil, meaning that other technologies of road construction that do not address stagnant water are likely to be a waste of taxpayers' money. 

"To address drainage challenges caused by high water percolation, the contractor has also introduced a rockfill base to stabilise the wet ground. The road’s surface will feature a layer of Dense Bitumen Macadam and Asphalt Concrete for added strength and durability," added KeNHA.

The HPS technology is majorly used in the construction of roads within areas that have loose soils and as base layers for paved roads and pathways.

Mombasa Road has been targeted as one of the major highways that the government is currently struggling with to address the traffic jam issues within the Nairobi metropolitan, coupled with budget constraints to address damages.