Comparison of test methods on the compressive strength of fly ash blended cements /

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2014
Tunç, Hasan
In Turkey the compressive strength of cements are determined according to TS EN 196-1. That standard suggests the use of a constant water-cement ratio of 0.50 in preparation of mortar specimens for all types of cements. On the other hand, in USA cement producers use ASTM C 109 to determine the compressive strength of cements, which is based on a constant consistency of cement mortars for blended cements only. The main difference of these methods is the needed amount of water to produce cement mortar. When a constant w/c is used to prepare mortar specimens as specified by TS EN 196-1, especially for certain blended cements insufficient compaction may occur and compressive strength may not be obtained in a standard repeatable manner. On the other hand, when ASTM C 109 is used, higher amount of water may be used to obtain a constant consistency and the compressive strength can be lower. Therefore, in this study, unlike EN 196-1 and ASTM C 109, a constant water/cementitious by volume method is suggested to prepare mortar specimens to determine their strength. vi The aim of this thesis is to demonstrate the variabilities that can be confronted with the determination of compressive strength of fly ash blended cements. For this purpose, portlant cement clinker was replaced with fly ash (FA) at 20 %, 35 %, 55 % replacement levels, by using three different methods which are acquired by the constant water/cementitious by mass (EN 196-1), constant flow (ASTM) and constant water/cementitious by volume methods,7-day and 28-day compressive strength of mortars were obtained. Then, coefficient of variation (CoV) of the results obtained by three different methods were compared. After the experimental study, it was observed that a less deviation in the compressive strength results were obtained by constant water/cementitious by volume method and ASTM C109 method. However, for the constant water/cementitious by mass method (EN 196-1), higher deviance in the compressive strength results were obtained. As a result, it was determined that the constant water/cementitious by mass method (EN 196-1) is not proper for fly ash blended cements.
Citation Formats
H. Tunç, “Comparison of test methods on the compressive strength of fly ash blended cements /,” M.S. - Master of Science, Middle East Technical University, 2014.