Abstract
Abstract The concrete’s performance depends on its behavior in the fresh and hardened states, since the workability corroborates for the transport and application processes of the material, while the mechanical strength guarantees structural effectiveness and functionality. Generally, studies of nanosilica (nS) are focused on performance analysis in the hardened state and they are founded on the use of the mineral admixture in dry grains. Thus, this article aims to evaluate the effects of superplasticizer admixture use with nanosilica in colloidal suspension in the consistency and mechanical strength of the concrete. Two concrete mixtures were produced with the same materials and identical proportions, however with different superplasticizes, one with nanosilica (CnS) and the other without nanosilica (CC) used as reference to analyse the effects of the presence of mineral admixture in the development of the consistency and the mechanical strength of the concrete. For evaluation of these properties were carried slump tests as a function of time and compressive strength at 28 days, according to ABNT NBR 10342 and NBR 5739, respectively. The results showed that the concrete without nanosilica presented longer time available for handling, achieving 135 minutes, extending its period of slump loss for fifteen minutes besides the concrete with nanosilica, which reached 120 minutes; and, also presented higher slump values throughout the test, reaching up to 60.0 mm above at 75 minutes after the beginning of test. However, the CnS presented better performance in the hardened state, achieving the C70 high performance concrete class with 70.92 MPa; while the CC reached 65.57 Mpa, fitting within the C60 class.
Highlights
Fresh concrete hardens over time, especially if mixed continuously, the result of prolonged mixing is associated with accelerated loss of slump of the mixture
It can be noted that the mixture with colloidal suspension nanosilica, industrially incorporated to the superplasticizer admixture, presented lower workability time than the conventional concrete
Based on the results previously showed, the effect of the chemical admixture incorporated with nanosilica on the slump loss and mechanical strength of concretes can be noted
Summary
Fresh concrete hardens over time, especially if mixed continuously, the result of prolonged mixing is associated with accelerated loss of slump of the mixture. One of the most used products is the nanosilica (nS) and, it is widely used for improving the properties of mixtures, e.g. decreasing the porosity of the cementitious material, its applications and effects on concretes have not been fully known yet. It is known that the performance of the concrete depends on its behavior both in the hardened and fresh states, since the mechanical strength guarantees structural effectiveness and functionality, while the workability corroborates with the transport and application processes. Most studies of concrete with nanosilica are focused on the analysis of its impacts on the hardened mixture and little is known about the impacts on the fresh mixture. This paper aims to evaluate the effects of using superplasticizer admixture with nanosilica in colloidal suspension on the consistency and mechanical strength of the concrete
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