Mechanical properties of high strength concrete containing different cementitious materials

الملخص EN

High strength concrete has strength significantly beyond what is used in normal practice.

According to American Concrete Institute (ACI), high strength concrete revised the definition to cover mixtures with specified design strength of 55 MPa or more.

The main objective of this investigation is to study the effect of using different supplementary cementitious materials in binary blends on mechanical properties of high strength concrete.

The experimental work includes three stages: firstly, preparation of cementitious materials (metakaolin and pumice) from local materials, second involves conducting several trial mixes to choose the best of superplasticizer that satisfies the required properties and to specify the optimum water content which is designed in laboratory by 0.3 W/Cm ratio, to achieve workability with (60- 80mm) slump and the best compressive strength which was 64.6 at 28 days.

Thirdly carrying out tests to find out the compressive strength, splitting tensile strength, modulus of rupture, on binary concretes including mixes containing silica fume as cement replacement at percentages of 8 %, 10 % and 15 %, mixes containing metakaolin as cement replacement levels of 10 %, 15 %, and 20% and mixes containing pumice at cement replacement of 10 %, 15 %, and 20%.These properies were measured at ages ranging from7 days to 180 days.

The results indicate that the silica fume performs better than other supplementary cementitious materials (metakaolin or pumice) in terms of the compressive strength, splitting tensile strength and modulus of rupture development at ages of 7,28,60,90and180 days where the average percentage of increase when using 8 %,10% and 15 % of silica fume was about (19 %,23 % and 18.7 %) ,respectively, while when using 10%,15 % and 20% metakaolin the average percentage of increase was (10 %,12.6% and 4%) respectively, also when using 10 %,15% and 20% of pumice the average percentage of increase was (2.6 %, 6% and 1.5 %), respectively.