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Maybe in Your Lifetime, People Will Live on the Moon and Then Mars
news.movim.eu / TheNewYorkTimes · Monday, 2 October - 16:07
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RAAC Crisis in U.K. Schools Hits Children With Special Needs
news.movim.eu / TheNewYorkTimes · Monday, 11 September, 2023 - 12:12
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Ready the Ig Nobel: Researchers incorporate used diapers into concrete
news.movim.eu / ArsTechnica · Sunday, 21 May, 2023 - 11:00 · 1 minute
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The road to low-carbon concrete
news.movim.eu / ArsTechnica · Saturday, 19 November, 2022 - 11:36
More than 100 schools have had to shut or close areas off because of dangerous lightweight concrete, leaving many parents, especially those whose children have special needs, scrambling for care.
Government building rules and regulations can be outdated and misguided, insisting upon conventional building materials with prices that aren’t compatible with building affordable housing. The building codes suggested by the United Nations decades ago often preclude using local, lower-cost, and environmentally friendly materials.
Of late, certain researchers have speculated that they might be able to solve two problems plaguing burgeoning cities—a glut of non-degradable waste and dearth of building materials—by folding the former into the latter. Now, a team in Japan reports that used, sanitized disposable diapers can be incorporated into concrete and mortar, which would still meet Indonesian building standards. Low-cost housing is desperately needed there as the urban population continues to bloom and housing is scarce. Obviously, all of the people moving to the cities bring more waste there, as well.
Diapers are substituted for the fine aggregates that are normally used in making concrete. The team determined that mortar for structural components, like load-bearing walls and public road pavement, could only tolerate a maximum of 10 percent added diaper material. But mortar and concrete for nonstructural components, like non-load-bearing wall partitions and low-impact floor pavers, could tolerate having up to 40 percent of their aggregates swapped for diaper material.
Nobody knows who did it first, or when. But by the 2nd or 3rd century BCE, Roman engineers were routinely grinding up burnt limestone and volcanic ash to make caementum : a powder that would start to harden as soon as it was mixed with water.
They made extensive use of the still-wet slurry as mortar for their brick- and stoneworks. But they had also learned the value of stirring in pumice, pebbles, or pot shards along with the water: Get the proportions right, and the cement would eventually bind it all into a strong, durable, rock-like conglomerate called opus caementicium or—in a later term derived from a Latin verb meaning “to bring together”— concretum .
The Romans used this marvelous stuff throughout their empire—in viaducts, breakwaters, coliseums, and even temples like the Pantheon, which still stands in central Rome and still boasts the largest unreinforced concrete dome in the world.