▁rein for ced ▁concrete ▁construction , ▁whether ▁it ▁is ▁a ▁building , ▁a ▁bridge , ▁a ▁bearing ▁wall ▁or ▁other ▁structure , ▁predict s ▁the ▁position ing ▁of ▁steel ▁reb ars ▁at ▁specific ▁positions ▁in ▁the ▁volume ▁of ▁concrete ▁( pred icted ▁concrete ▁cover ▁of ▁steel ▁rein for cement ▁bars ). ▁This ▁cover ▁typically ▁var ies ▁between ▁ 1 0 ▁and ▁ 1 0 0   mm . ▁The ▁stat ics ▁of ▁every ▁concrete ▁construction ▁are ▁designed ▁in ▁such ▁a ▁way ▁that ▁steel ▁and ▁concrete ▁properties ▁are ▁combined ▁in ▁order ▁to ▁achieve ▁the ▁maximum ▁possible ▁strength ▁for ▁the ▁particular ▁construction ▁( e . g . ▁anti - ear th qu ake ▁protection ) ▁as ▁well ▁as ▁to ▁prevent ▁the ▁long - term ▁cor ros ion ▁of ▁steel ▁that ▁would ▁weak en ▁the ▁construction . ▁Reb ar ▁spac ers ▁secure ▁the ▁correct ▁position ▁of ▁steel , ▁thus ▁assist ing ▁in ▁the ▁practical ▁application ▁of ▁the ▁theoretical ▁specific ations ▁of ▁concrete ▁construction . ▁The ▁cover ▁of ▁the ▁steel ▁of ▁a ▁particular ▁construction ▁element ▁( for ▁example ▁in ▁a ▁concrete ▁sl ab ▁or ▁a ▁beam ) ▁should ▁be ▁generally ▁uniform ▁within ▁the ▁element . ▁ ▁The ▁use ▁of ▁spac ers ▁is ▁particularly ▁important ▁in ▁areas ▁with ▁high ▁earth qu ake ▁activity ▁in ▁combination ▁with ▁cor ros ive ▁environment ▁( like ▁proxim ity ▁to ▁salt ▁water ▁of ▁sea ), ▁as ▁for ▁example ▁Japan , ▁Iran , ▁Greece , ▁California ▁etc . ▁ ▁Pl astic ▁versus ▁concrete ▁spac ers ▁and ▁bar ▁supports ▁ ▁Pl astic ▁spac ers ▁and