Nov 13, 2025
Week 8 – Pavements, Performance and the Science of the Ground Plane
Across centuries of craft and failure, pavements reveal the hidden engineering that underpins every step we take.
Technical
From Roman roads to modern streets - the long history beneath our feet.
This week’s session was led by Steven Burton and Phil Crichton of Steintec, a company known for producing high-performance paving materials used globally across bound, unbound, permeable and impermeable construction systems. Their portfolio demonstrates longevity, structural stability and a high degree of technical reliability - unsurprising given their deep emphasis on research, testing and material science.
We began with a historical overview of paving, tracing its lineage back to Roman engineering, where layered road construction (statumen, rudus, nucleus and summum dorsum) created one of the most durable transport infrastructures in history. Roman systems relied on carefully graded aggregates, tight jointing and an understanding of drainage far ahead of their time.
Fast-forward to the present and contemporary failures often occur where this ancient logic is ignored. Steven and Phil presented case studies from Dundee, Edinburgh, Galway and Oxford, where repeated paving collapses and joint failures provoked detailed forensic analysis. Across the sites, a consistent pattern emerged:
Poor-quality mortars leading to joint failure
Insufficient compaction in bedding layers
Incorrect moisture content during installation
Freeze–thaw damage caused by water retention
Incompatibility between bedding material and paving stone
Inadequate support for point loads (bins, vehicles, bollards)
The key message: paving rarely fails because of the surface. It fails because of the layers beneath. Steintec’s work is rooted in diagnosing these problems and creating systems that perform reliably under extreme conditions - from heavy vehicle loading to pedestrian abrasion and climate exposure.
Bound vs unbound construction - and the science that separates stability from failure.
In the second half of the lecture, we were introduced to the specifics of modern pavement design and the crucial distinction between bound and unbound systems.
Unbound construction relies on:
A compacted granular sub-base
A loose laying course (typically grit sand)
Pavers laid without mortar
Joints brushed with sand
Its benefits include:
High flexibility
Ability to tolerate minor ground movement
Easier maintenance and replacement
Good permeability
Lower embodied carbon
However, it has weaknesses:
Vulnerable to deformation under heavy, concentrated loads
Susceptible to rutting and joint loss if not compacted perfectly
Poor performance on steep gradients
Bound construction, in contrast, uses:
Cementitious or polymer-modified mortars
Rigid bedding layers
Fully bonded joints
Often reduced permeability
Its benefits include:
Exceptional resistance to shear forces and point loading
Increased lifespan in urban centres with heavy traffic
Superior structural rigidity
Better aesthetic retention (joints stay crisp and defined)
Drawbacks include:
Increased risk of cracking when ground movement occurs
More complex installation requiring precise moisture control
Higher embodied carbon
Limited permeability unless combined with SuDS systems
Steintec specialise in hybrid systems, where mortar performance, permeability requirements and load expectations are calibrated to the specific site condition. They emphasised the importance of understanding:
Sub-base specification (Type 1, Type 3, recycled aggregate)
Laying course gradation
Moisture content during mixing
Joint width tolerance
Thermal expansion
Long-term freeze–thaw cycling
This was a reminder that paving is not a surface treatment - it is a structural system.
Laying patterns, structural logic and the aesthetics of load.
We concluded by studying laying patterns not simply as aesthetic choices but as load-bearing strategies.
Different patterns distribute force differently:
Herringbone (45° or 90°)
Best interlock and rotational restraint
Ideal for vehicular traffic
High shear resistance
Stretcher bond
Visually clean
Least effective structurally
Susceptible to tracking under wheels
Basketweave
More decorative
Creates visual rhythm
Better for small-scale courtyards
Random or mixed courses
Requires precise sizing and joint control
Can manage variable site geometries
Steven and Phil stressed that the decision is not merely visual - it defines:
How loads travel
Where failure may occur
The lifespan of the surface
The maintenance regime
Accessibility and comfort for users
In good pavement design, pattern is structure.
Reflection: This week highlighted how paving is a deeply engineered system rather than a decorative layer. Understanding mortar science, bedding composition, structural interlock and historical precedent revealed that durability is never accidental - it’s designed, tested and built from the ground up.