Enhancing the effectiveness of steam curing for cement paste incorporating fly ash based on long-term compressive strength and reaction degree of fly ash

Abstract

Steam-cured concrete plays an imperative role in contemporary construction, particularly in the urban region where the progress of the project is one of the main keys for cost savings. However, steam curing can cause several adverse impacts on the mechanical and durability performances of concrete in long term. The macroscale properties of concrete are mainly controlled by the properties of cement paste. This research aims to find out the appropriate treatment stage of steam curing on blended cement paste and the optimum quantity of fly ash substituted in the paste that not only can achieve the design strength in short term but also be able to alleviate the detrimental impacts of heat treatment in long term. Cement pastes incorporating 0, 20, 35, and 50 wt% fly ash were mixed at a water/binder ratio of 0.28 and cast into the mold with a size of 50 × 50 × 50 mm. Then, these paste specimens were treated with the treatment stage at 55 °C, 70 °C, and 85 °C for various hours. The compressive strength and the hydration degree of fly ash were measured over 545 days. The results indicated that the treatment stage with the temperature of 70 °C applied for 4 h existed to be adequate to promote the early strength while the substitution of 35% fly ash happened to be the optimum quantity.