Since cement-based composites have been used for more than one century in civil and other engineering areas, a relevant number of international and local standards has been produced in order to ensure the quality and durability of employed materials and, so, structural safety for users. Among all meaningful chemical, physical and mechanical properties early age properties represent a key parameter to predict the extent of early age cracking risk, which is one of the main causes of reduction in service life (the so-called "Vita Nominale" in Italian Structural Code Ministerial Decree 14/01/2008) respect to design hypothesis. The knowledge of shrinkage phenomena, which are deformations associated to the complex chemical reactions of cementitious materials, is related to the reliability of the measurement method and, if a proper measure is accomplished, an adequate mitigation strategy can be chosen among existing alternatives (shrinkage reducing admixtures, internal curing, superabsorbent polymers, etc.). Geopolymer matrices represent one of the main sustainable alternatives to traditional cementitious binders such as ordinary Portland cement (OPC) and other clinker-based materials offering several potential advantages like higher fire resistance, durability, etc. At the moment, real scale applications are limited and, so, a relevant amount of data is still needed to assess the actual early age and long-term behavior of these systems. Particularly, the early-age monitoring of geopolymers represent a key parameter for mix design optimization. In order to assist in describing these processes, which are related to complex chemistry and drying phenomena, in this paper we have simultaneously measured the early-age shrinkage and temperature changes of metakaolin-based geopolymers by using Fiber Bragg Grating FBG-based sensors. Furthermore, we have evaluated workability limits respect to designed layout, in order to reduce the risk of excessive entrapped air, which could affect measurement accuracy. The use of this technique allowed optimizing filler content in order to minimize shrinkage and, at the same time, respect the criterion of resource efficiency.
|Titolo:||Fiber Bragg Grating sensors: A reliable method for the measurement of early age properties of traditional and innovative cements|
|Autori interni:||CAMPOPIANO, Stefania|
|Data di pubblicazione:||2015|
|Appare nelle tipologie:||4.1 Contributo in Atti di convegno|