Creep Properties of Cementitious Materials from Indentation Testing: Significance, Influence of Relative Humidity, and Analogy Between C-S-H and Soils

Abstract

Concrete creeps, and this creep must be well characterized and modeled to properly design civil engineering infrastructures. Here, we present some results on the creep properties of cementitious materials obtained by using the indentation technique. Firstly, we show that minutes-long microindentations on cement paste yield a quantitative measurement of their long-term logarithmic creep kinetics, which can be used to predict the rate of long-term creep of concrete. Then, by performing microindentations, we study the effect of relative humidity on the long-term creep properties of hydrated C 3 S samples, compacted samples made of pure C-S-H, and compacted samples made of pure CH. The last part is dedicated to a study by nanoindentation of the creep properties of C-S-H phases directly within a hydrated cement paste. We identify scaling relations independent of mix proportion and heat treatment, which we can explain by drawing a thorough analogy between the mechanical behavior of C-S-H and that of clays.

Concrete creep modelling for structural applications: non-linearity, multi-axiality, hydration, temperature and drying effects

“…Water effect on basic creep C-S-H interlayer cohesion and disjoining forces are sensitive to the water saturation degree as explained in [1], or at lower scale, in [9] and [18]. In a structural model, as suggested in [19], only a macroscopic approximation of these complex underlying phenomena can be envisioned.…”

Statistical filtering of useful concrete creep data from imperfect laboratory tests

“…0 is still a power law, which again satisfies the functional equation (1). However, reanalysis of Vandamme et al's [11] data in [9] revealed that the best fit of these data is obtained by a power law with n = 0.08, as stated above, although visually the difference from the logarithmic curve is quite small (later it was proposed that the nearlogarithmic creep in the ten-second nanoindentation test explains why multidecade creep is logarithmic; The second regime is the present case. The third regime with n % 0:10 was identified by statistical optimization of large databases for the purpose calibration of RILEM creep prediction models B3 [6] and B4 [5] and was incorporated into a general expression of d Jðt; t 0 Þ=dt, which also covers the transitions between the regimes with n = 0.10 and 0.…”

“…It may be noted that recently some researchers [11] interpreted their micro-indentation creep tests during the initial few seconds as approximately logarithmic, which would correspond to n ! 0; but their data were later found to be fitted slightly better by a power law with n ¼ 0:08 (see Fig.…”

“…The transition between the subsequent regimes are very gradual, spread-out, and the above-mentioned times are those at which the transitions are centered. The initial regime for t À t 0 less than about 10 s was studied by means of creep micro-indentation tests of hardened cement paste by Vandamme et al [11]. They proposed to represent their data by a logarithmic curve, which corresponds to n !…”

A review of the potential impacts of climate change on the safety and performance of bridges

“…It is well established in the literature that one of the factors governing long-term deformations of concrete, i.e., creep, is the ambient environmental conditions. The projected lower relative humidity over land, along with higher temperatures are identified in the literature as resulting in a higher creep rate for concrete; see, e.g., Bažant and Panula (1978), England and Ross (1962), Geymayer (1972), Nasser and Neville (1967), Razak (1986), and Vandamme et al (2013). In a recent study by Bažant et al (2011) it is noted that creep problems are of considerable significance for bridges.…”