Workability maintenance of water-reducing admixtures in high-performance pastes produced with different types of Portland cement

Matos, Paulo Ricardo de; Sakata, Rafael Dors; Foiato, Maiara; Repette, Wellington Longuini; Gleize, Philippe Jean Paul

doi:10.1590/s1517-707620210001.1225

Cited by 2 publications

(1 citation statement)

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“…For UHPC, where w/b ratio is lower than 0.20, homogeneous microstructure of the concrete is also achieved by use of high silica fume and superplasticizer content and employment of pressure during early age curing (before setting) [32]. Since superplasticizer effectively improves workability [33], it also permits to use very little water in UHPC, thus limiting cement hydration and resulting in changes in the concrete microstructure. Existing research has focused extensively on the effects of w/b on concrete mechanical and transport properties, the latter of which controls by concrete pore structure.…”

Section: Introductionmentioning

confidence: 99%

Evaluating the effect of autoclave curing on the microstructure and compressive strength evaluation of a high strength concrete

et al. 2022

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High strength concrete is usually cast with low water-to-binder ratio (w/b) in order to produce a compact microstructure with high strength and durability. Autoclave curing can accelerate cement hydration and pozzolanic reactions and further modify microstructure of cement pastes (such as decreasing the Ca/Si ratio and forming crystallized calcium silicate hydrate). The present paper evaluates the effect of w/b ratio, in the range 0.20 -0.40, on compressive strength, porosity and microstructure of a high strength concrete. Some samples were subjected to autoclave curing in order to evaluate the effect of this process on the parameters evaluated. The microstructure was evaluated using X-ray diffraction and scanning electron microscopy. The results show the porosity decreased when w/b ratio decreased from 0.40 to 0.30 and thereafter the total porosity remained virtually constant while the water permeable porosity increased. An inverse relationship is observed between the porosity and the compressive strength. Autoclave curing affects significantly the phases developed in hardened concrete. It accelerates hydration and pozzolanic reactions, affects the interfacial transition zone and triggers the formation of crystalline C-S-H. These changes reflect in improved compressive strength at a low w/b but its effect is negligible at moderate w/b ratios.

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Section: Introductionmentioning

confidence: 99%