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Bound with animal fat, milk, or blood, Roman concrete is hardened over time Less water would ordinarily mean a less workable, yet stronger setting substance – concrete production being a tireless balance between liquid and solid against stability – but sanguine additives introduced bubbles of air, like tiny vehicles for the movement of solid materials through the cement, enabling flow and so multiplying the minutes between the mixing of the concrete and the moment it set for good A splash of water could be sacrificed without reduced workability Once the concrete set, each entrained microdwelling of air became a pore, allowing the now solid structure to absorb new water and for this to freeze, thaw, and exit the artificial stone without fracturing its temporary home In correspondence to the civilisation itself, strength was won and growth quickened with blood The first Pantheon was erected following the determining sea-fought battle of that last war of the Republic – the fight that saw Cleopatra exit, like a descendant of so many kings, with an asp to her breast Its replacement, built under Hadrian – concrete beneath brick – still stands The resistance of this ancient concrete was forged at scorching temperatures, the ash of Vesuvian eruptions precooked just as the limestone in Portland cement is sintered to clinker today Two parts volcanic mortar to one part lime; blood for tenacity; horsehair to reduce shrinking; laid by hand in line with its aggregate It built the Pantheon, the Colosseum, it rebuilt much of Rome and thousands of miles of road These days a soupier substance is needed to flow through machinery Watered down by industrialisation, and for the sake of economy, it is required to move faster, to build more It arrives ready mixed, slow-setting, weaker and bloodless Its quickflow corpus is reinforced now by steel; cracks begin to appear much earlier on   As the Empire faded, so too did the common use of concrete, its systematic application being the stuff of large-scale bureaucracy The Middle Ages had concrete, but not as much, nor as strong, nor so persistent In building material circles, it