Recycling of waste PET granules as aggregate in alkali-activated blast furnace slag/metakaolin blends

In this study the utilization of waste PET aggregate in alkali-activated slag and slag/metakaolin blended mortar was investigated. Sodium hydroxide (NaOH) pellets and liquid sodium silicate were used as activators. Eighteen different mortar mixtures were prepared for the laboratory tests. In the reference mixture, unground slag (max Size of 4 mm) was used as aggregate. In PET aggregate mixtures, slag aggregate was replaced with waste PET aggregate, in amount of 20%, 40%, 60%, 80% and 100% by volume. The water-binder (w/b) ratio and aggregate-binder ratio used in the mixtures were 0.50 and 2.75, respectively. The unit weight, compressive strength, flexural tensile strength, ultrasonic wave velocity and water absorption and porosity ratios of the mixtures were measured. The test results showed that, using PET aggregate contributed to decrease of unit weight of alkali-activated mortars due to the low density of PET aggregate. Although the strength values of the specimens decreased depending on increasing waste PET aggregate amount, the compressive strength values of the alkali-activated slag mortars containing waste PET aggregate were satisfactory. In addition, alkali-activated slag mixtures containing 60% and 80% waste PET aggregate were drop into structural lightweight concrete category in terms of unit weight and strength properties. However, the compressive strengths of alkali-activated slag/metakaolin blended mixtures were lower than alkali-activated slag mixtures at the same cure condition. It is concluded from the test results that there is a potential for the use of waste PET as aggregate in the production of alkali-activated slag mortar. Because of using waste materials as binder and aggregate for mortar production in this study, alkali-activated slag mortar with PET aggregate is thought to be a good alternative for recycling of waste materials. (C) 2014 Elsevier Ltd. All rights reserved.