10-11-2014, 10:59 AM
Abstracts: Abstract This paper presents the results of aninvestigation on the use of metakaolin (MK) as asupplementary cementing material to improve theperformance of concrete. Two MK replacementlevels were employed in the study: 10% and 20%by weight of the Portland cement used. Plain and PCMKconcretes were designed at two water–cementitiousmaterials (w/cm) ratios of 0.35 and 0.55. Theperformance characteristics of the concretes wereevaluated by measuring compressive and splittingtensile strengths, water absorption, drying shrinkage,and weight loss due to the corresponding drying. Theporosity and pore size distribution of the concreteswere also examined by using mercury intrusionporosimetry (MIP). Tests were conducted at differentages up to 120 days. The results revealed that the inclusion of MK remarkably reduced the dryingshrinkage strain, but increased the strengths of theconcretes in varying magnitudes, depending mainlyon the replacement level of MK, w/cm ratio, and ageof testing. It was also found that the ultrafine MKenhanced substantially the pore structure of theconcretes and reduced the content of the harmfullarge pores, hence made concrete more impervious,especially at a replacement level of 20%. Dated this 6th day of April, 2013