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Ensuring quality control when building RCC dams
Published in L. Berga, J.M. Buil, C. Jofré, S. Chonggang, Roller Compacted Concrete Dams, 2018
Alberto Marulanda, Alvaro Castro, Fabio A. Sanchez
Most lab test results are available only after some RCC layers have been placed, when remedial measures are traumatic or less effective. An accelerated curing method can be developed to get early results of compressive strength, 24 h after a layer had been placed and enables the contractor to take effective corrective measures.
Controlling Corrosion in Steel Bars
Published in Mohamed Abdallah El-Reedy, Steel-Reinforced Concrete Structures, 2017
According to ACI clause 5.11, the curing of concrete should be maintained above 50°F and under moist conditions for at least the first 7 days after placement; high early-strength concrete should be maintained above 50°F and under moist conditions for at least the first 3 days. If it is necessary to accelerate curing by high-pressure steam, steam at atmospheric pressure, heat and moisture, or other accepted processes, it is allowable to accelerate strength gain and reduce the time of curing. Accelerated curing should provide a compressive strength of the concrete at the load stage considered to be at least equal to required design strength at that load stage. The curing process should produce concrete with durability at least equivalent to that required by the engineer or architect; strength tests should be performed to ensure that curing is satisfactory.
Microwave Processing of Fibre Reinforced Cement Composites
Published in R. N. Swamy, Fibre Reinforced Cement and Concrete, 1992
J. Pera, J. Ambroise, M. Farha
It is possible to use accelerated curing schedules, either by the use of chemical accelerators or by a higher curing temperature. Because F.R.C.C. are generally of thin section, they are prone to rapid drying and the curing conditions have to be carefully controlled to prevent thermal cracking (Proctor, 1977).
Effect of lime and cement fillers on moisture susceptibility of cold mix asphalt
Published in Road Materials and Pavement Design, 2022
Accelerated curing was also found to be useful as far as evaporation of water is concerned. It also accelerated the development of the bond between aggregate and bitumen but to develop the whole strength further curing duration was required. So, in the field also accelerated curing can be adopted to reduce the curing duration of CMAs. Generally, field accelerated curing procedures include higher temperature and higher relative humidity. Studies by Du (2018), Graziani et al. (2016) and Ojum et al. (2014) have concluded that temperature has a significant effect on the curing characteristics of CBEM. Elevated temperature shows faster curing rates. The effect of relative humidity was more significant in the case of cement incorporated mixes (García et al., 2013), such as CMA-2C. Kekwick (2005) found that the curing of three days at 40°C to be equivalent to the in situ curing of six months. Serfass and Henrat (2004) concluded that 14 days of curing at a temperature of 35°C and a relative humidity of 20% are comparable to the curing of one to three years in the field condition. A study conducted by National Roads Authority (2011), Ireland indicated that curing at 40°C for 28 days could be corresponding to one year of field curing.
Fast inductive curing of adhesively bonded glass-timber joints
Published in The Journal of Adhesion, 2022
Jonas Wirries, Michael Adam, Christian Tornow, Michael Noeske, Till Vallée, Morten Voß
One possibility to overcome aforementioned issue is to consider accelerated curing. Accelerated curing can be achieved in various ways, including UV,[16] radiation,[17] microwaves,[18] resistive heating,[19] etc.; however, heating is the most widely used method. The speed with which hardening of the adhesive progresses increases with temperature; a first approximation thereof is given by Arrhenius’s Law[20]; a review of more precise formulations for cure kinetics, respectively, curing progress, is summarised in [21]. An experimental approach to combine development of the mechanical properties during cure with curing kinetics of a structural adhesive is shown in [22]. In recent years, research on induction heating as a means to accelerate the curing of adhesive has regained momentum.[23–28] For adhesively bonded joints, two situations exist. Firstly, at least one of the substrates is susceptible to electromagnetic fields (usually metallic), in which case the induced heat is transferred via thermal conduction to the adhesive. Secondly, adherends inert to electro-magnetic fields (as timber and glass) are to be joined, in which case susceptibility can be provided by particles adjunct to the adhesive.[29,30] For both considered cases, temperature control is generally required, as the induction process can be extremely fast (from tens to hundreds K/s). Additionally, unless specifically designed for, induction equipment hardly achieves evenly distributed temperatures.
Accelerated curing of glued-in threaded rods by means of inductive heating — part IV: curing under low temperatures
Published in The Journal of Adhesion, 2022
N. Ratsch, M. Burnett-Barking, S. Böhm, M. Voß, M. Adam, M. Kaufmann, T. Vallée
To tackle the first drawback, accelerated curing has been considered as a possibility to shorten drastically curing times. Among the techniques considered, inductive heating appears an elegant method. The basic principles of electromagnetic induction go back to Faraday in the XXIth century.[51–53] Since then, Lenz[54] and Henry[55] have continued their work. Maxwell finally summarized the observed electromagnetic phenomena in four differential equations, [56] and most of the related technical aspects are presented in .[57] Since adhesives themselves are transparent to the electromagnetic (EM) field, curing relies on heat conduction, either from the (EM excitable) parts to be joined or from susceptors embedded in the adhesive.[58–60] Carbas et al. published a series of articles on inductively heated liner bonds of high strength steel substrates, [61,62] and showed that the technique provides sufficient control to expose the adhesive to different temperatures within the same tensile shear length to obtain graded adhesive layers. Induction heating was also investigated for GiR [,63,64] in combination with 1 K-EPX, where complete curing was achieved within 5 minutes. Regarding 2 K adhesives, the first three parts of this series of papers[18–20] have demonstrated that induction heating is indeed a practicable solution to significantly shorten induction time, and provided for methods to predict the duration of such induction processes to achieve full cure. Similarly, Voß et Vallée[65] reported on comparable tests involving G-FRP rods, for which susceptibility to the electromagnetic field was obtained through particles embedded in the adhesive.