Abstract
This paper presents test results of the impact of chemical admixtures used in the underwater concrete technology, i.e. a superplasticizer (SP), an anti-wash admixture (AWA) and SiO2 nano- particles (NP) on the cement hydration process, rheological properties and the setting time. The impact of admixtures was tested in combination and separately, with the use of microcalimetry, X-ray diffraction (XRD) and rheology. It was demonstrated that AWA and SP admixtures caused a delay of the hydration process, while the impact of SP was much greater. The above statement was also confirmed by results of rheological tests. Combined application of AWA, SP and NP causes even a larger delay of the hydration process and the increase of paste rheological parameters, with the impact of the superplasticizer particularly visible.
Highlights
IntroductionProperties of the concrete mix are very important. Its composition has to ensure suitable rheological properties, as well as the lowest washout tendency [1]
During underwater concrete work, properties of the concrete mix are very important
Results of hydration heat tests are presented for CEM I 42.5 R (CEM I) with and without chemical admixtures applied separately in different quantities: anti-washout admixture (AWA) - Fig. 1 and SP - Fig. 2
Summary
Properties of the concrete mix are very important. Its composition has to ensure suitable rheological properties, as well as the lowest washout tendency [1]. Reduction of water amount in a concrete mix, while keeping the resistance of the cement paste to washout, requires simultaneous application of both the superplasticizer and anti-washout admixture (AWA) [2]. Suitable water reduction of underwater concretes recently installed is reached by application of a new-generation polycarboxylate-based superplasticizers. Ramachandran [4] classifies high surface area inorganic materials that swell in water, as well as materials that increase the content of fine particles in pastes. They are fly ash, hydrated lime, diatomaceous earth. Chains of polymers interlace fine particles of the cement, which in consequence increases the paste viscosity, which grows along with the increase of the admixture content [5]
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