Strength development of GGBS and fly ash concretes and applicability of fib model code’s maturity function – A critical review

Abstract

This paper is the joint work of working group 4 of the RILEM TC 238-SCM and the fib Task Group 4.6. It was the aim of this literature study to quantify the effect of ground granulated blast furnace slag (GGBS) and silicious fly ash (sFA) on strength development of concrete. For the strength development the approach of the fib Model Code was chosen, which is based on an e-function that can be adapted to the strength development of an individual binder by selecting the so-called s-value based on the strength class of the Portland cement used. No guidance is provided for s-values for supplementary cementitious materials (SCMs). In order to determine the s-values for mixes with SCMs, a database was set up with results of material testing from literature. A relationship between s-values and w/b plus SCM/b ratios has been determined. This has been tested on laboratory cast specimens with 50 and 30 % cement replacement with GGBS and FA respectively. These were cured at 20 0 C. The s-values from this relationship were compared to those obtained from regression analysis and they were found to be satisfactory. This increased confidence in their use for predicting the strength development of other curing regimes, i.e. adiabatically cured concrete cubes, using the maturity function in the fib Model Code. Predictions of the effect of curing temperature, i.e. the adiabatic temperature history, on the strength development were again satisfactory. These were not significantly affected by the fib model code's use of one value of "apparent" activation energy.

Frost resistance of concrete with high contents of fly ash - A study on how hollow fly ash particles distort the air void analysis

“…The conclusion is that there is no systematic difference between the two curing conditions. The difference in curing conditions in [29] is similar to the difference in curing conditions for specimens for compressive strength testing and accelerated freeze/thaw testing, respectively in the present study. If strength reduction due to drying should explain the poor salt frost scaling resistance for mixtures 044 and 050, then the strength reduction should be approximately 30% to match the strength of mixture 000.…”

“…However, it also has to be taken into account that the outdoor temperature was lower than the temperature in the fog room. In a recent review [29], results are compared for concrete with fly ash, where the specimens are either moist cured (20°C, in water bath or in fog room) or moist cured for 7 days and then air dried (20°C, 65% RH). The review comprises more than 100 concrete mixtures with low calcium fly ash (up to 50% of the binder content) for each drying condition.…”

Hardening Concrete Exposed to Realistic Curing Temperature Regimes and Restraint Conditions: Advanced Testing and Design Methodology

“…e s values were in the same order of magnitude as found in other studies (e.g., [51,61]). e 28-day tensile strength was also decreasing with increasing amount of fly ash (Figure 4(d)).…”

Transition coefficients between compressive strengths of samples with different shape and size in mass concrete and use of weight maturity method in dam construction

“…Figure 12 shows the compressive strengths measured over concrete samples and estimated through weight maturity method or maturity method. In Figure 12, the difference between the compressive strengths of concrete samples and predicted maturity method is in the range of 1–5% 12,15,48,49 . Yıkıcı and Chen 16 used the maturity method in C20/C25 class MC and calculated 15% lower strength than in fresh concrete 50 .…”