Fiber-Reinforced Self-Consolidating Concrete - Development and Use-Homogeneity of Self-Compacting Concrete Modified (PDF)

Homogeneity of Self-Compacting Concrete Modified (PDF)

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The study presented at the ACI Spring 2019 conference explores the effects of carbon nanotubes (CNTs) on self-compacting concrete (SCC), focusing on the technical challenges, key research efforts, and impacts on fresh and hardened properties of nanoengineered SCC. The concrete mix includes cement, water, limestone filler, CNTs, fine and coarse aggregates, and a superplasticizer. The introduction of CNTs enhances the mechanical properties of SCC, as shown by an increase in compressive strength from 37 MPa in standard SCC to 41.7 MPa in SCC with CNTs, and an increase in flexural strength from 5.9 MPa to 9.0 MPa.<br /><br />The evaluation of SCC's fresh state properties includes factors such as segregation resistance, flowability, and filling/passing ability using standardized tests like the J-ring and L and U-box methods. The homogeneity of SCC is critical in maintaining its compositional stability in the fresh state. Electrical resistivity and capacitance are used to evaluate the hydration process and the homogeneity of the concrete, with distinct resistivity profiles indicating different segregation levels—homogeneous SCC shows stable profiles, while segregated mixes display varying profiles over time.<br /><br />The study highlights how CNT-reinforced SCC exhibits high homogeneity and favorable filling and passing capabilities. Electrical resistivity and capacitance, which are affected by water distribution within the concrete, serve as indicators of segregation resistance and homogeneity. The rate of capacitance changes over time is particularly highlighted as a reliable measure of the homogeneity of SCC and is influenced by SCC’s ability to store electrical energy, affected by the material’s structure and dielectric properties. This research contributes to advancing the understanding of SCC’s properties and the potential benefits of using CNTs in concrete technology.

Keywords

carbon nanotubes

self-compacting concrete

mechanical properties

compressive strength

flexural strength

segregation resistance

electrical resistivity

capacitance

homogeneity

concrete technology