Effects of fruit juice extracts as natural admixture on setting time and hardened properties of concrete

Admixtures are vital in modern cement-based materials, enhancing workability, strength, and setting time. However, the high cost of commercially available admixtures has driven the search for more affordable alternatives. Traditionally, both organic admixtures, derived from organic sources like plants and inorganic ones, like natural and artificial pozzolanic materials, have been used. In this context, using fruit extracts as retarding admixtures offers a promising solution to reduce reliance on imported retarders, lower production costs, and increase the overall performance of concrete. This study investigates the incorporation of natural fruit juice extracts—specifically Pineapple Extract, Tangerine Extract, and Grape Extract—into concrete, with concentrations ranging from 5% to 25% of the water mix weight. The effects on setting time, workability, and compressive strength of the concrete were evaluated. The results indicated that Pineapple, Grape, and Tangerine juices effectively reduced both the initial and final setting times of fresh concrete. Although workability diminished, only slight reductions in slump (2–5 mm) were observed at dosages between 0 and 10%. However, more noticeable, non-linear effects were seen at higher dosages, ranging from 15 to 25%, compared to the control. Elevated extract dosages (> 15–20%) reduce compressive strength as excess organic compounds interfere with hydration reactions, while high acidity contributes to the breakdown of hydration products. The extracts further reduce the compressive strength of concrete, with the optimal dosage identified as 15%, achieving strength of 31.5 N/mm2.