Metakaolin based geopolymer concrete with recycled geopolymer concrete dust

Mechanical analyzes were carried out on the recycled concrete samples

obtained by preparing different mixtures of geopolymer powder,

metakaolin, aggregates and alkali activator as sodium silicate (Na2SO3)

and sodium hydroxide (NaOH) solution, which were formed by grinding

the geopolymer concrete samples prepared with certain temperature and

low curing times. In order to determine the contribution of metakaolin

and ground geopolymer powders to the mechanical properties of

geopolymer concrete, three different mixtures were prepared. In the

three mixtures, ground geopolymer powder of 33.8%, 29.6% and 25.4% by

volume, respectively, was used. In addition, metakaolin was used in

the three mixtures at a rate of 0%, 4.2% and 8.4% by volume,

respectively. The mixtures formed were kept in a curing environment at

45 and 75 ℃ for 8 hour, and mechanical properties (flexural and

compressive strength), capillary water absorption and dry unit weights

were determined by performing some experiments. The test results showed

that the highest compressive strength of the mixture in the curing

environment at 75 degrees was 46.3 MPa. The test results showed that

the lowest capillary water absorption (0.7 kg/m2) was in the mixtures

with the highest metakaolin content. In addition, it was shown that

the highest dry unit weight (2354 kg/m3) was obtained in the mixture

with the highest metakaolin content kept at 45 ℃. At the end of the

study, it has been suggested that recycled geopolymer powders and

metakaolin can be used together to make high strength concrete without

consuming too much natural resources and energy.