The Effect Of Mixing Sequence On The Properties Of Concrete

Concrete is the most demanded material only second to water as a substance, with this, itcan only be imagined that huge expense and resources have been put into it. Inconsideration with the aforementioned fact on concretes‟ demands coming in tune withthe advancements of the 21st century production researches, cost free methods are beingoptimized to boost production efficiency. This research entitled “The effect of mixingsequence on the properties of concrete” is about the latter statement, as it deals directlywith finding the most suitable mixing sequence to optimize production efficiency withoutany added resources. The research focused on the fresh and hardened properties ofconcrete. British Research Establishment (BRE) Method of mix design was used. A totalof 720 cubes were cast for tests at the following ages of 7, 14, 28 and 56 days. Twentyfour (24) mixing sequences were assessed. Among the mixing sequences, twostandardized mixing sequences from the ASTM and ACI were chosen. It was found thatsamples mixed using the standard mixing sequences of the ASTM and ACI passed all thestandard requirements for all properties of concrete assessed. However the samplesproduced using ACI mixing sequence had better hardened concrete properties whencompared with the samples of concrete made using ASTM mixing sequence. All theconcrete batch samples from the various mixing sequences passed the standard conditionsfor compacting factor and plastic density. Samples mixed using mixing sequences (22, 19and 17) did not pass the standard condition for slump. Samples mixed using mixingsequences (14 and 17) did not pass the standard condition for air content. Samples frommixing sequence 24 had optimum compressive strengths of 23.40N/mm2, 25.52 N/mm2,30.84 N/mm2and 35.56 N/mm2for 7, 14, 28 and 56 days of testing respectively andpassed all the standard conditions for all properties tested. It surpassed samples from thestandardized mixing sequences in grade by at least 4.7% for every test age. Duringconcrete production, with all processes, materials and proportioning considered, two setsof concrete samples from two different mixing sequences can differ in average from0.91% to 41.85% under water absorption while two sets of concrete samples from twodifferent mixing sequences can differ in average from 0% to 100% under abrasionresistance. From the properties of concrete tested, the various mixing sequences usedhave the most positive effects on plastic density followed by air content then slump andfinally compressive strength. Due to the differences in the properties of concrete samplesunder the influence of different mixing sequence, it is recommended that good mixingsequences, when used should be consistent under a particular job. Mixing sequence 24had optimum compressive strengths and can be used to make the best concrete.Uniformity should be checked firstly for fresh concrete properties when determiningwhich or what mixing sequence to use.

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