Properties of sustainable concrete incorporating cold-bonded lightweight aggregate manufactured from expired cement, biopolymer, and various waste

This investigation aims to evaluate the performance of sustainable concrete incorporating artificial coarse aggregate in both its fresh and hard states. The dry reference aggregate mixture, containing 90% fly ash and 10% expired cement, was pelletized utilizing cold-bonded technology. Nine distinct types of aggregates were produced alongside a reference aggregate and subsequently categorized into three groups according to the curing method after a duration of 28 days. This was achieved using the same technique and a water quantity of 20–22% by weight after adding 0.5%, 0.75%, and 1% by weight for each starch, alginate, and tire waste. The reference aggregate categories containing 1% starch (RSS1, ROS1) and 0.75% tire waste (RWR0.75), subjected to self-curing, oven curing, and water curing, represent the optimal formulations of cold-bonded aggregates identified through physical and mechanical testing. Six varieties of sustainable concrete were made by increasing the amount of synthetic coarse aggregate used from 50% to 100%. The water-to-cement ratio stayed at 0.4, and the cement content was kept at 400 kg/m³. When 50% and 100% of the ROS1 class aggregate were replaced, the density of fresh and hard concrete dropped to its lowest levels, with rates of 7.95%, 16.27%, 10.69%, and 17.63%, respectively. ROS1 aggregate concrete presents exceptional performance across sustainable concrete classifications regarding mechanical characteristics, including compressive strength, splitting, flexural strength, and modulus of elasticity at a 100% replacement rate and an age of 28 days, with decreases of 28.47%, 27.42%, 18.11%, and 36.65% relative to ordinary concrete. Although a good assessment of sustainable concrete styles is according to water absorption test values, normal concrete continues to yield superior outcomes.