Abstract
Alkali-activated slag (AAS) binders show in general larger autogeneous shrinkage strains than ordinary Portland cement (OPC) based binders. However, AAS can be a relevant alternative to OPC, if, for example low hydration heat release and fine pores, are required. This study proposes an evaluation of the advantage of using AAS materials in small-sized or massive structures with regard to cracking risk by autogeneous shrinkage and thermal strains. A cracking risk index is calculated; this risk is defined as the ratio between stress generated by full restraint and tensile strength. All required experimental data were investigated in an OPC and AAS mortar, these are: heat release, autogeneous shrinkage, Young’s modulus, tensile strength and basic creep evolutions. The material parameters of a rate-dependent model developed in 1D were then identified. Numerical simulations were then performed for different thicknesses in full-restraint conditions. These show that, as expected, basic creep is a very important material parameter to assess. Indeed, basic creep enables the significant reduction of the generated stresses. Besides, it is found that the more the structure is large (and sensitive to cracking by risk by thermal strain), the more the AAS material is becoming appropriate compared to the OPC material.
Highlights
Shrinkage and creep may significantly affect the behaviour of concrete structures
As shown in Eq (2) and (3), the cracking risk by autogeneous shrinkage restraint is highly related to the evolution of autogeneous shrinkage strains, thermal strains, Young’s modulus, basic creep and tensile strength
The study presented here was essentially related to the comparison of cracking risk at an early-age by autogeneous shrinkage restraint between different mix designs of cement and alkali-activated slag in autogenous conditions
Summary
Shrinkage and creep may significantly affect the behaviour of concrete structures. From early-age to long term, stresses occur in the restraint of autogeneous, drying and thermal strains. Self-restraint is due to the temperature and relative humidity gradients occurring inside concrete members This may lead to cracking and is highly dependent upon the concrete mix (shrinkages, Young modulus, creeps etc.) and on the mechanical and ambient (temperature, relative humidity, wind etc.) boundary conditions. It is very time consuming to make structural finite element calculations with several concrete mixes to assess the cracking risk In this contribution, a simple tool is proposed to compare two different mixes for the prediction of cracking risk by autogeneous shrinkage and thermal strain at early-age due to hydration heat release. All relevant parameters are taken into account: autogenous shrinkage, Young modulus, basic creep and tensile strength evolutions This approach uses an experimental data set (combined with identification) for the prediction of mechanical properties, shrinkage and creep evolutions. Calculations are performed for two mortar mixes with different binders: an alkali-activated slag (AAS) and an ordinary Portland cement (OPC)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
