The Effect of the Addition of Coal Fly Ash (CFA) on the Control of Water Movement within the Structure of the Concrete

Abstract

Studies were carried out to find a relation between the important physical property, i.e., water absorption and the main mechanical parameter, i.e., compressive strength (fcm), of concretes containing coal fly ash (CFA) in the amounts of 0% (CFA-00), 20% (CFA-20%), and 30% (CFA-30). The methodology of the water absorption tests reflected the conditions prevailing in the case of reinforced concrete structures operating below the water table. The microstructure of all materials was also assessed. Based on the conducted studies, it was found that both the fcm of concretes with the addition of CFA and its water absorption depended on the percentage of waste used, whereas both analyzed parameters were closely related to the structure of the cement matrix and interfacial transition zone area between the coarse aggregates and the paste. It should be stated that at the content of 20% CFA in the binder composition, an increase in the fcm of the material is observed, with a simultaneous increase in its water absorption. On the other hand, the addition of 30% CFA results in a significant decrease in both the strength of the composite and its water absorption. Thus, it was found that in the case of concretes with the addition of CFA, the strength of the material is directly proportional to the level of its water absorption. Moreover, the concrete including 30% CFA may increase the durability of reinforced concrete structures subjected to immersion conditions. From an application point of view, the obtained research results may be helpful in understanding the impact of the CFA additive on the level of water absorption in cement concretes with this waste.

Influence of pozzolanic addition on strength and microstructure of metakaolin-based concrete

“…In addition, the performance of the MB-4 specimens containing 10% MS provided superior characteristics with 28.99% reduction in the water absorption compared with MB-1 ( Fig 7C ). This is evident from the observation that these specimens displayed the highest compressive strength, indicating the enhanced durability with lesser penetrability [ 77 ]. This reduced penetrability further confirms the active participation of MS in the pozzolanic reaction [ 72 ].…”

Coprecipitation of Crystalline Calcium Silicates and Carbonates from the Hydrothermal Reaction of Pseudowollastonite

“…Slags from ore refinement or metal manufacturing and ashes from combustion are widely abundant and underutilized resources in the cement industry . A large body of literature explores mix designs and curing techniques that incorporate waste slags and ashes to further improve OPC hydration. − The waste products can improve the compressive strength and other properties by increasing the formation of calcium silicate hydrate (CSH) gel, the key reaction product of OPC hydration . These materials are rich in calcium silicates, which are generally not hydraulically activated, like OPC, but they can be reacted to form cementitious materials on their own using alkali or temperature activation. − As one example, the calcium silicate pseudowollastonite (α-CaSiO 3 ) can be carbonated in alkaline conditions and elevated temperatures to produce crystalline calcium silicate hydrate (CCSH) phases alongside calcium carbonates. − …”

Multi-Scale Analysis of the Damage Evolution of Coal Gangue Coarse Aggregate Concrete after Freeze–Thaw Cycle Based on CT Technology

“…To mitigate the environmental impact of the construction sector, researchers have proposed a series of eco-friendly solutions. Some have suggested using additives with active volcanic ash to replace cement during concrete production to reduce cement consumption [ 7 , 8 , 9 , 10 ], whereas others suggest modifying concrete using nanomaterials to increase its durability [ 11 , 12 , 13 , 14 ]. To reduce the demand for natural aggregates and to mitigate the environmental burden, people have started to study the use of recycled aggregates, industrial waste, and mineral tailings as alternatives to natural aggregates in concrete [ 15 , 16 , 17 , 18 , 19 ].…”