Roman Construction Engineering
The Romans had engineers and they worked out designs ahead of construction like we do today. Yet, unlike our modern methods that seem to change by the week, Roman construction technology grew over the course of many centuries and they didn’t go straight from pounded-earth huts to the Coliseum overnight. In some ways Roman civil engineering was more like the rise of the dinosaurs than our current notions of technological development – inching ever larger and further into specific niches — given many generations for this to develop.
The first Roman arches were not 30-meter spans — rather more like those I’ve seen crossing mountain streams on trade routes through the Alps. The first large Roman bridges were wooden piers like those later built by Julius Caesar to invade Germanic tribes north of Rome’s mid-life frontiers — not the huge aqueduct bridges crossing major rivers seen on page 1 of many Roman history texts.
The Romans slowly blended methods from earlier centuries with practices invented more recently. As a result, how they went about building their great monuments differs from how we build our own structures today. Since the advent of the Industrial Revolution we’ve emphasized speed and ease of construction whereas the technological pace and disposition of the Romans resulted in structures that emphasized permanence.
Chemically, most Roman concrete is about the same as modern concrete. The main difference is how the pre-industrial Romans hand-mixed their concrete in much smaller batches and hand-pounded each batch into forms — just like how civilizations had been pounding raw earth for as long as civilizations have existed.
To facilitate this sort of hand-tamping, Roman concrete was mixed with less water (not the soupy mix needed for industrial-scale pouring). Very likely the Romans had no idea how the pounding and tamping removes air-gaps and interlocks the mixture mechanically on a molecular level. The Romans only cared that it made the concrete strong — resulting in the sort of strength we can only attain today via steel rebar reinforcing.
The chemical composition of modern concrete keeps rebar rust-free for about 50 years in typical outdoor applications. After that, it oxidizes, expands and breaks the concrete to bits. Rebar is a modern cheat, and if not for how we tend to replace outdoor concrete structures before they wear out, rebar would put an end to much of our civil engineering in the span of a human lifetime.
If we made and applied concrete the way the Romans did, we could have the same sort of permanence in concrete structures. Yet it won’t happen because it would be cheaper to replace buildings and bridges every 50 years than to gather an army of laborers to hand-make and pound concrete into place.
If people were to vanish from our current age — one that now seems so indelibly substantial and permanent — we would be amazed to see what lasts and what crumbles. After just 200-300 years the majority of human endeavor still intact and visible would be those things made by the ancient Romans, Greeks and Egyptians, and there would be little superficial evidence to say that modern society ever existed.
