Preparation of waste cooking oil emulsion as shrinkage reducing admixture and its potential use in high performance concrete: Effect on shrinkage and mechanical properties

Abstract This paper aims to use the waste cooking oil emulsions as shrinkage reducing admixture (SRA) to improve the durability of concrete, thus the recycling of the waste cooking oil is achieved. In order to make oils emulsions SRA (OSRA) capable of reducing shrinkage and enhance its dispersion and stability, oil-in-water emulsion was prepared by dispersing the waste cooking oil in water with the help of high efficiency mixed surfactants. The effects of different contents of OSRA on the autogenous and drying shrinkage and the compressive strength of the concrete were investigated. The addition of OSRA in concrete shows a significant reduction effect on shrinkage, especially in autogenous shrinkage. Moreover, the compressive strength of concrete is enhanced with OSRA incorporated, although a slight decrease is presented with increasing OSRA content. In addition, various characterization techniques such as MIP and SEM were utilized to discuss the effect of OSRA. The results indicate that the addition of OSRA reduced the total porosity and refined the pore size by reducing significantly Ca(OH)2 crystals, which may relate to the saponification reaction between OSRA and Ca(OH)2. This study provides new insights into the application of the waste cooking oil in concrete and a new way to alleviate the environmental pollution and health hazard caused by waste cooking oil.