Composites Part B 216 (2021) 108880 Available online 16 April 2021 1359-8368/© 2021 Elsevier Ltd. All rights reserved. Effect of coarse aggregate size on non-uniform stress/strain and drying-induced microcracking in concrete Peng Gao a , Yang Chen a, c , Haoliang Huang a, b , Zhiwei Qian d , Erik Schlangen e , Jiangxiong Wei a, b, * , Qijun Yu a, b a School of Materials Science and Engineering, South China University of Technology, 510640, Guangzhou, China b Guangdong Low Carbon Technologies Engineering Centre for Building Materials, 510640, Guangzhou, China c Guangdong Provincial Academy of Building Research Group Co.Ltd, 510500, Guangzhou, China d FEMRIS, The Hague, 2497, CJ, the Netherlands e Microlab, Faculty of Civil Engineering and Geosciences, Delft University of Technology, 2628, CN, Delft, the Netherlands A R T I C L E INFO Keywords: Drying shrinkage Microcracks Tensile stress shell Aggregate size DIC Lattice modelling ABSTRACT Non-uniform stresses, strains and microcracking of the concretes with three coarse aggregate sizes (5–10 mm, 10–16 mm, 16–20 mm) dried under 40% relative humidity (RH) for 60 days were quantified using digital image correlation and lattice fracture modelling. The influencing mechanism of coarse aggregate size on the drying- induced microcracking of concrete was clarified: (1) As the coarse aggregate size decreases, propagation paths of microcracking are increased, which increase the number of small microcracks and release the drying shrinkage force from mortar phase. (2) Tensile stress shells surrounding the coarse aggregates become thinner, thereby decreasing the area of large microcracks. As the coarse aggregate size decreased from 16-20 mm to 5–10 mm, the average thickness of tensile stress shells decreased from 2.13 mm to 1.09 mm at the beginning of drying, and the area of the microcracks >5 μm in width decreased from 796.6 mm 2 /m 2 to 340.2 mm 2 /m 2 at 60 days since drying. 1. Introduction Drying shrinkage is a common issue of concrete structure [1–4]. Mortar phase and coarse aggregates are two main phases in concrete. The main components of the mortar phase consist of cement paste and fine aggregates. Being exposed to drying condition, the cement paste shrinks due to the moisture evaporation to environment, causing the shrinkage of the mortar phase. On the concrete scale, this shrinkage of the mortar phase is restrained by the coarse aggregates, which rises internal stresses in concrete. Once these internal stresses exceed the local strength in concrete, microcracking occurs and might lead to serious damage of concrete [5,6]. The drying-induced microcracking in concrete is influenced by many factors, such as the ambient relative humidity (RH) and temperature, the properties of binders, and the properties of aggregates. Because the aggregate size is an important parameter for concrete mix design, many studies concerned the drying-induced microcracking of the concretes with different aggregate sizes [5–9]. Bisschop and Van Mier [5] used the fluorescent epoxy impregnation method to observe the drying-induced microcracking of concrete. They found that the total length of micro- cracks increased with increasing the aggregate size. Also applying the fluorescent epoxy impregnation method, Wu et al. [6] observed that both the average width and total area of microcracks increased as the aggregate size increased. Numerical models are also attracting increasing interest in studying the drying-induced microcracking in concrete. By using a lattice approach, Grassl et al. [7] simulated the drying-induced microcracks in concrete and found that the concrete with larger aggregate size showed larger width of microcracks, while the microcracks’ density was smaller. By using a hygro-mechanical model, Idiart et al. [8,9] simulated the drying-induced microcracking of con- crete, and found that the concretes prepared with larger aggregates exhibited larger degrees of microcracking. These studies suggested that the drying-induced microcracking in concrete could be reduced by optimizing the aggregate size. However, there remains a need for clarifying the mechanism behind the effect of aggregate size on the microcracking of concrete under drying condition. Goltermann [10,11] calculated the stress distribution in the concrete based on classical elasticity theories. The calculation illustrated that * Corresponding author. School of Materials Science and Engineering, South China University of Technology, 510640, Guangzhou, China. E-mail address: [email protected] (J. Wei). Contents lists available at ScienceDirect Composites Part B journal homepage: www.elsevier.com/locate/compositesb https://doi.org/10.1016/j.compositesb.2021.108880 Received 11 December 2020; Received in revised form 4 April 2021; Accepted 5 April 2021
Effect of coarse aggregate size on non-uniform stress/strain and drying-induced microcracking in concrete
May 19, 2023
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