Potential of Fe-Mn-Al-Ni Shape Memory Alloys for Internal Prestressing of Ultra-High Performance Concrete

Abstract

Prestressing of concrete is a commonly used technique in civil engineering to achieve long spans, reduced structural thicknesses, and resource savings. However, in terms of application, complex tensioning devices are necessary, and prestress losses due to shrinkage and creep of the concrete are unfavourable in terms of sustainability. In this work, a prestressing method using novel Fe-Mn-Al-Ni shape memory alloy rebars as a tensioning system in UHPC is investigated. A generated stress of about 130 MPa was measured for the shape memory alloy rebars. For the application in UHPC, the rebars are prestrained prior to the manufacturing process of the concrete samples. After sufficient hardening of the concrete, the specimens are heated inside an oven to activate the shape memory effect and, thus, to introduce the prestress into the surrounding UHPC. It is clearly shown that an improvement in maximum flexural strength and rigidity is achieved due to the thermal activation of the shape memory alloy rebars compared to non-activated rebars. Future research will have to focus on the design of the shape memory alloy rebars in relation to construction applications and the investigation of the long-term performance of the prestressing system.

Fibre reinforced ultra‐high performance concrete – Rheology, fibre bond strength and flexural strength

“…Shown are a reference (FMAN5_S1_Ref; non-prestrained and non heated), non prestrained but heated (FMAN5_S1_a) and prestrained and heated samples (FMAN_S1_p+a). Image from [43].…”

“…Prestrained rebars were fixed inside the moulds and after hardening of the concrete, the specimens were heated inside an oven. This increase was significantly higher compared to non activated rebars [43]. Furthermore, a sample with non-prestrained rebars was heated to exclude that the improvement is only because of the thermal treatment of the samples (Figure 9).…”

“…This work will connect and discuss the results of several investigations at the Department of Structural Materials and Construction Chemistry at the University of Kassel. These were carried out to get a better understanding of various aspects of fibre reinforced concrete [6][7][8][9][10][11][12][13][14][15]. This includes investigations regarding the bond behaviour of different fibre materials, fibre modifications and concrete mixtures as well as functionalization of the fibre reinforcement to improve concrete properties.…”

Development and Performance Evaluation of a Mechanical Connection for Steel and Shape Memory Alloy Bars

“…In addition, research has also pursued stress recovery and crack closure capabilities of cold-drawn and rolled wires [12,13]. Subsequent research has been conducted using SMA wires to prestress structural elements [14,15], and research continues to apply SMAs to structural members using various methods [16][17][18][19][20].…”