How to monitor the modulus of elasticity of concrete, automatically since the earliest age?

Abstract

Monitoring the evolution of an early age set of parameters on concrete is necessary to predict the early age behaviour of structures. The difficulty lies in the fact that this monitoring must be automatic because the concrete hardening process takes place over a long period after the casting. This paper presents a new methodology and an apparatus, specifically designed at IFSTTAR, to monitor the hardening process of a concrete. Mainly, the Young’s modulus can be monitored in compression. Measurements start soon after having cast the concrete and the sample temperature is completely controlled so that the concrete maturity is well mastered. The performances of this apparatus, obtained on an ordinary concrete, are compared to more classical measurements using an extensometer mounted on the sample just after the setting time and to ultrasonic measurements. In these cases, the temperatures were not controlled and results have to be expressed in equivalent time. A comparison with another method developed and used at ULB by using the same concrete, in the frame of a joined cooperation between our two laboratories is achieved. This test set up is based on the so called Temperature Stress Testing Machine (TSTM). This device has been specifically designed with a control of the concrete maturity by the use of a dummy specimen only submitted to free deformations (thermal, shrinkage). The TSTM allows compressive and tensile testing starting just after the setting time. In addition, concrete properties, such as compressive and tensile strength, have been characterized at early age. These values have been used for the design of the loading histories applied in the automatic tests. The heat released by the cement hydration has also been measured in order to express the results on a maturity scale

Viscoelastic Behavior of Polymer-Modified Cement Pastes: Insight from Downscaling Short-Term Macroscopic Creep Tests by Means of Multiscale Modeling

“…For each one of these values, all 168 creep tests are analyzed, in order to identify optimal values of shear creep moduli that minimize the error between experimental and modeled viscous creep functions. Interestingly, the obtained total mean errors, according to Equation (17), are virtually constant for power-law exponents within the interval β pol ∈ [0.4, 0.8]; see Figure 5. As for the further steps of the analysis, we choose the central value β P1 = β P2 = 0.6.…”

“…The power-law creep exponents, in turn, are virtually constant, β P1 ≈ β P2 ≈ 0.9, at material ages of less than 100 h. Subsequently, they decrease and finally stabilize around β P1 ≈ 0.3 or β P2 ≈ 0.4, respectively. The corresponding mean errors, according to (17), amount to 2.0 × 10 −7 for paste P1 and 2.2 × 10 −7 for paste P2. These values are approximately 25% smaller compared to that obtained with a constant power-law exponent; see Table 2.…”

Influence of cyclic movement on the hardening process of grout: case of offshore wind turbine installation

“…Then loads are applied at ages of 2, 3, 7, 14 and 28 days. A complete description of the device, the test protocol and the data processing is indicated in [4,17,18].…”

Comparison Between Different Experimental Techniques for Stiffness Monitoring of Cement Pastes

“…This paper is focused on non-destructive approaches for characterization of the cement paste hardening, particularly on setting and stiffness monitoring. To evaluate these properties, several non-destructive methods can be found in the literature, namely: mechanical methods (Chamrová 2010;Maia et al 2012b;Boulay et al 2010;Staquet et al 2012;Boulay et al 2013b); wave propagation methods (Voigt 2005;Reinhardt and Grosse 2004;Song et al 2008;Zhu and Kee 2010;Zhu et al 2011a;Zhu et al 2011b;Voigt et al 2005;Kim et al 2009); resonance methods (Kim et al 2009, Malhotra andSivasundaram 2003;Wang et al 2010;Shin et al 2008;Azenha et al 2012); and methods based on dielectric properties (Beek 2000Princigallo et al 2003). The Cyclic Compression (CC) method is the oldest and the most accepted method for characterizing the elastic modulus of concrete.…”

“…To overcome this limitation, Boulay et al (2010) developed a new method called BTJASPE, based on a specially devised mould and testing rig, which allows the application of compression cycles without demoulding the specimen. Another method, which also allows the evaluation of elasticity modulus through cyclic mechanical testing, is the Temperature Stress Testing Machine (TSTM) Boulay et al 2013b). Even though this method was de-veloped for monitoring creep of concrete in tension under controlled temperature, it also allows the application of loading cycles along the curing period of the material, without removing the specimen from the mould.…”