Mitigation of plastic shrinkage in fly ash concrete using basalt fibres

Abstract

Many durability related problems in concrete structures are caused due to early-age cracking. Though early-age cracking is not detrimental to the structure, this will open up the way for the long-term durability issues, hence, needs to be mitigated. Cracking of such types in concrete is commonly prevented by adding fibres. Present work aims at studying the potential use of basalt fibres in controlling the shrinkage cracks at early age, otherwise this fibre is considered not suitable for use in concrete as it would degrade under alkaline environment. Further, to sustain the long-term durability, an attempt has been made to reduce the alkalinity of the concrete by replacing the cement with fly ash up to 50%. Concrete specimens made with two water to binder ratios (w/b), six replacement levels of fly ash, and one type of fibre are used for this study. Crack width and crack area generally used for evaluating the extent of shrinkage cracks are measured and analyzed. As the shrinkage cracks are very thin to measure manually, image analysis technique has been employed to measure the crack widths. Results indicate that to a greater extent cracks developed during early age has been effectively mitigated with the incorporation of fly ash. Further, it is found that basalt fibres are effective in arresting the shrinkage cracks. Furthermore, it is concluded that manual measurement will under or overestimate the crack width, hence, image analysis technique can be successfully used for measuring the crack widths.

Fractal Dimension of Basalt Fiber Reinforced Concrete (BFRC) and Its Correlations to Pore Structure, Strength and Shrinkage

“…Owing to its apparent advantages, such as environmental friendliness, cost effectiveness, light weight, high modulus, and excellent thermal and chemical stability [ 8 , 9 , 10 , 11 , 12 ], basalt fiber has recently been considered an alternative to other fibers. Previous studies on basalt fiber reinforced concrete (BFRC) paved a solid foundation in understanding the effect of basalt fiber length and dosage on the strength [ 13 ], fracture properties [ 14 , 15 ] and shrinkage performance [ 16 , 17 ] of concrete. It has been acknowledged from the aforementioned investigations that basalt fiber distinctly improved the anti-cracking and load-bearing ability of concrete.…”

Investigation of plastic shrinkage cracking in fiber-reinforced concrete and shrinkage-compensating cement concrete

“…Unlike the above methods of crack mitigation, which aim to address the root cause of shrinkage cracking directly (i.e. water loss through evaporation and consumption by cement hydration reactions), fiber reinforcement helps to mitigate shrinkage cracking by increasing the tensile strength of the concrete element (Banthia and Gupta 2006, Hemalatha and Ramesh 2019. In addition, the even distribution of fibers throughout the entire concrete element tends to improve crack distribution (see Fig.…”

“…Fibers offer their own tensile strength, much larger than that of early-age concrete, for immediate help in reducing plastic shrinkage cracking (Banthia and Gupta 2006, Hemalatha and Ramesh 2019. While the tensile strength of typical fiber reinforcement is likely well above the tensile stresses induced by plastic shrinkage, the mechanical strength of fiber reinforcement alone is not enough to eliminate plastic shrinkage cracking.…”

“…While the tensile strength of typical fiber reinforcement is likely well above the tensile stresses induced by plastic shrinkage, the mechanical strength of fiber reinforcement alone is not enough to eliminate plastic shrinkage cracking. Due to the semiplastic nature of concrete during the early stages of hydation, it is not fully bonded to the fiber reinforcement during the time that plastic shrinkage cracking may occur (Hemalatha andRamesh 2019, Sayahi 2019). However, in addition to crack-bridging behavior, evenly distributed fiber reinforcement helps to achieve a more uniform crack pattern.…”

“…Aggregate interlock may still be sufficient to bridge the macro-cracks at this point, allowing the concrete to retain a small amount of tensile strength. However, once the macro-cracking progresses and exceeds the aggregate interlock, the concrete has lost all tensile capacity at the crack location and, if unreinforced, the concrete would fail in tension at this point (Dopko 2018, Hemalatha andRamesh 2019).…”