Experimental Study on Preparation and Performance of Concrete With Large Content of Fly Ash

Abstract

Producing concrete with large content of fly ash attracts increasing attention in low carbon building materials. In this paper, the fly-ash concrete (FAC) with a content of fly ash no less than 50% total weight of binders was developed. The adaptability of fly ash used for concrete was firstly examined by testing the water requirement of normal consistency and the setting time for cement fly-ash paste, and the strengths of cement fly-ash mortar at the curing age of 7 and 28 days. The factors of water-to-binder ratio from 0.3 to 0.5, the content of fly-ash from 40% to 80%, and the excitation measures with additional Ca(OH)2 and steam curing at initial were considered. After that, the FAC was designed by adding an excessive content of fly ash to reduce the water-to-binder ratio from 0.50 to 0.26, and the content of fly-ash varied from 52% to 60%. Results show that the cement fly-ash paste presented a reduction of water requirement and an elongation of setting time with the increased content of fly ash. This provides a foundation of maintaining the workability of fresh FAC with a decreased water-to-binder ratio by adding the excessive content of fly ash. The cement fly-ash mortar had a lower early strength due to the slow reaction of fly-ash with Ca(OH)2, which could be improved by steam curing at the initial 24 h due to the excitation of fly-ash activity. At curing age of 28 days, the FAC had the expected axial compressive strength and modulus of elasticity, but the tensile strength was lower than predicted. At the curing age of 56 days, all the basic mechanical properties of FAC reached the prediction. The resistances of FAC to chloride ion penetration and carbonization were realized at a very high level as specified in codes.

The Influence of Eco-friendly Ash on Sustainable Construction Material: A Review

“…LOI is lower in fly ash than the rice husk ask meanwhile LOI of wood ash varies according to the type of wood. Fly ash provides a better flowability of building motar (Li et al, 2022). Many varieties of ash have been used in cement industries; for the utilization of waste materials, decreasing energy consumption, reducing In Portland, cement silica compounds react with calcium hydroxide to form cementitious properties (Figure 1).…”

Case Study on the Performance of High-Flowing Steel-Fiber-Reinforced Mixed-Sand Concrete

“…For each kind of test, three specimens were tested per trial. As the normal content of fly ash has some influence on the strength development of concrete [20,21,33], all the mechanical properties were measured at the curing age of 28 days for the SFRMC with varying volume fractions of steel fibers. Meanwhile, considering that the concrete with a high content of fly ash has a lower strength at an early age but better long-term strength [21,31], the mechanical properties were measured at a curing age of 90 days for SFRMC with varying fly ash contents.…”

“…Meanwhile, as a commonly used mineral admixture of concrete, fly ash is limited to lower contents to avoid the drawback of decreased strength, especially at the early ages of the concrete [21,22]. As specified by China codes JGJ 52 [23] and GB/T 50146 [24], the fly ash content of concrete for reinforced concrete structures is less than 30-35% of the total mass of binders accompanying common Portland cement, whereas the fly ash content for prestressed concrete structures should be reduced by 10-15% for the same conditions as reinforced concrete structures.…”

Integrating Fly Ash-Controlled Surface Morphology and Candle Grease Coating: Access to Highly Hydrophobic Poly (L-lactic Acid) Composite for Anti-Icing Application

“…Fly ash (FA) mainly comes from the flue gas emitted by burning coal during the process of thermal power generation [ 30 ], metal smelting [ 31 ], heating for warmth, and so forth. FA usually exhibited a smooth surface like glass [ 32 ], with an average particle size of less than 20 microns [ 33 ], and contains a variety of active components such as unburned carbon and metal oxides (SiO 2 , Al 2 O 3 , and Fe 2 O 3 [ 34 , 35 ]). According to previous researches and reports, FA had been effectively and deeply applied in the fields of building materials [ 36 ], metallurgy [ 37 ], agriculture [ 38 ], and chemical industry [ 39 ] at home and abroad.…”