Paper by SIEBEL from ISCR 6th 1990
To ensure that concrete has a high resistance to freezing and thawing it must contain small air voids which are produced by an air-entraining agent and which must be present in sufficient quantities to match the amount of fine mortar. The limits for the air content of unset concrete and the air-void parameters which have to be obser-ved when ensuring that concrete isproduced witha high resistance to de-icing salt are shown, parti-cular account being taken of concretes with super-plasticizers and wetting agents. Air-void measu-ring equipment developed in Denmark with whichthe air-void content L 300 and the spacing factorcan be determined even in unset concrete is alsoexamined. Trials carried out at the Research Ins-titute of the Cement Industry in Düsseldorf tocompare the parameter determined in unset andhardened concrete are discussed. In addition, pos-sibleways are indicated as to how the required air-void content can be achieved under practical cons-truction conditions by quality assurance methods.