Investigation of waste products of boron and metakaolin utilizes in portland cement mortar

This study is concerned with an investigation of waste products of boron and metakaolin utilizes in cement mortar. The objective of this paper is to design the most appropriate composition, where colemanite, metakaolin and superplasticizer will take place along with Ordinary Portland cement. The outcome of this study will give us an opportunity to decrease cost of the final product without affecting properties of the construction material and contribute to less CO2 emission caused by Portland cement manufacturing. Metakaolin produced by Kaolin Endustriyel Mineraller A.S. (Istanbul / Turkey) is a pozzolanic material, but is not a cementitious material itself. By reacting with lime it forms a stable insoluble compound that possesses hydraulic properties. Production of metakaolin releases less CO2 in the atmosphere comparing to Portland cement clinker, and on the other hand, can partially substitute it. Colemanite waste materials figuring in this study have been provided by Eti Mine Bigadic Boron Inc. (Balıkesir/Turkey). Separate and joint application of 1% superplasticizer solution, colemanite and metakaolin was investigated. Physical and mechanical properties such as compressive and flexural strength, at the age of 2, 7, 28 and 90 days as well as unit weight, water absorption, porosity, flow table and setting time test were determined and compared with reference mix results. The general trend is the addition of colemanite to the cement mortar impairs compressive strength by up to 43% as well as increases its setting time on 215%. Introduction of 1% superplasticizer mitigates the presence of colemanite and improves the strength of the mortar comparing to reference. Metakaolin facilitates early hardening and with addition of superplasticizer it gains strength up to 12% more than the reference value, although its strength strongly depends on the water-to-cement ratio. Replacement of 25% of the Portland cement by 5% of colemanite and 20% of metakaolin with an addition of 1% super-plasticizer resulted in the almost same characteristics as reference values.