Tensile performance of cast-in headed anchors in geopolymer concrete
Date of Award
Edith Cowan University
Doctor of Philosophy
School of Engineering
Geopolymer concrete is an ecofriendly alternative to normal concrete and its use in construction industry is growing due to the increased awareness of global warming. The relationships between the mechanical properties, such as the compressive strength, elastic modulus and mode I fracture energy of geopolymer concrete are not similar to those of normal concrete; these are specifically important for the prediction of the tensile capacity of structural anchors in a concrete substrate. As there are limited studies on the fracture energy of ambient-temperature cured geopolymer concrete, experiments are conducted to study the fracture energy and compressive strength of geopolymer concrete and compare the results with the respective properties of normal concrete. The results show that the ambient-temperature cured geopolymer concrete provides approximately 85% lower fracture energy than normal concretes of comparable compressive strengths. Based on the experimental results, a new fracture energy prediction equation is proposed for ambient-temperature cured geopolymer concrete.
In the current research study, the tensile behaviour of cast-in headed anchors in ambient-temperature cured geopolymer concrete is studied using the results of over 100 experimental tests and over 90 numerical simulations. There are 3 sets of experiments on anchors, which are differentiated based on the mix design of concrete. In each set of experiments, cast-in headed anchors of sizes 1.3T, 2.5T and 5T are embedded at effective embedment depths of 40 mm, 70 mm and 90 mm. In addition to the above sets, anchors of 2.5T and 5T sizes at embedment depths of 40 mm and 70 mm are also installed in normal concrete for comparison purposes. The difference in the capacity of anchors due to the variations in fracture energy of geopolymer concretes of the same compressive strength as well as the influence of anchor head size ratio is investigated using experimental tests.
Numerical simulations are used to complement and expand the results from the experimental study. Nonlinear Finite-Element analyses are conducted to study the influence of surface cracking of the substrate material and the effect of anchor head profile on the tensile capacity of anchors.
The experimental and numerical results are compared with two of the currently available prediction models namely: Concrete Capacity Design (CCD) and Linear Fracture Mechanics (LFM) models. It is shown that on average, the CCD model overestimated the tensile capacities by 10% to 40%, depending on the anchor embedment depth, and the LFM model accurately predicted the capacity of anchors at 40 mm embedment depth, and underestimated the results by 40% at 90 mm embedment depth.
In comparison to similar anchors embedded in a normal concrete of a comparable compressive strength, the capacity of anchors in geopolymer concrete is on average 35% lower. Hence, new modification factors are proposed to extend the application of CCD and LFM models to anchors installed in geopolymer concrete. The modification factors are validated using 60 numerical simulations whereby the effective embedment depth ranges between 40 mm and 180 mm.
Access to this thesis is embargoed until 11th May 2025.
Karmokar, T. R. (2023). Tensile performance of cast-in headed anchors in geopolymer concrete. Edith Cowan University. https://doi.org/10.25958/pah8-jn15