Modelling early age cracking in blended cement concrete [thesis]

Yingda Zhang
Concrete is one of the most commonly used building materials in the world because of its excellent versatility. The concrete consumption has increased considerably because of the rapid urbanisation development. Annual cement consumption is expected to increase to 5.2 billion tons by 2050. An average of 850 kg of carbon dioxide can be released into the environment to produce one tone of clinker. To minimise the disadvantages of cement production, one option is to use Supplementary Cementitious
more » ... terials (SCMs) such as fly ash and ground granulated blast furnace slag (GGBFS) to partially replace cement in concrete. Accordingly, this thesis extensively focuses on the research of time-dependent behaviour such as shrinkage and creep of blended cement concrete containing high volume of fly ash and GGBFS. To advance the understanding of volumetric changes in concrete mixes with high volume of fly ash and GGBFS, the presented research focused on five areas: (a) autogenous, drying and total shrinkage of concrete; (b) tensile stress development of concrete in restrained ring test; (c) tensile creep of concrete; (d) nonlinear tensile creep of concrete; and (e) thermal cracking of concrete. The first part of this dissertation reports the autogenous, drying and total shrinkage results of a total of 21 concrete mixes with a high volume of fly ash and GGBFS using concrete prisms. The experimental results were also compared to the predictions by Australian Standard AS3600 (2009 and 2018 versions) and Eurocode 2. Additional tests on pastes with the same SCM content were conducted to investigate both autogenous and chemical shrinkage in relation to their time-dependent pore structure refinement assessed using the nitrogen adsorption isotherm technique. For concrete with a characteristic compressive strength lower than 50 MPa, the autogenous shrinkage of concretes with 40-60% GGBFS was significantly higher than that of reference concretes mostly due to a later increase in the autogenous shrinkage between 28 and 100 days. No clear d [...]
doi:10.26190/unsworks/24411 fatcat:u72pqak6xvebrj3bwwvnblegee