THE ITZ MICROHARDNESS OF POROUS CONCRETE UNDER ALTERNATION OF WETTING AND DRYING

摘要

The failure mechanism of porous concrete (POC) under alternation of wetting and dryingwas studied by observing the change of ITZ microhardness (IMH) of different specimensunder different drying conditions. The results show that the influence of drying conditions onthe change of IMH is slight; When the paste W/C is in the range of 0.25-0.29, the influenceof W/C on the change of IMH is slight; IMH of the sample whose fly ash quantity is 40% ofthe cement quantity falls down continuously during alternation of wetting and drying whileIMH of other samples rises first and falls later; The admixture of slag added into the cementincreases IMH, but excessive amount of slag will reduce the increment. The admixture of flyash added into the cement has no great effect on IMH value, and Large amount of fly ashadded into the cement decreases IMH value; When the mixing of slag and fly ash is addedinto the cement, IMH increases remarkably. The combination of the wet-dry experimentalresults of POC in past studies and the experimental results in this paper implies that theresistance property of alternation of wetting and drying of porous concrete falls down if theIMH is too high or too low.