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Assessment, Testing and Specification
Published in Ian Sims, Alan Poole, Alkali-Aggregate Reaction in Concrete: A World Review, 2017
These are generally regarded as being the laboratory methods most likely accurately to reflect the behaviour in real structures. A number of standards bodies have published methods, e.g., RILEM as AAR-3 (in Nixon & Sims, 2016), ASTM C1293-8b (2014), CSA A23.2-14A (2014), BS 812-123 (1999), Norway (Norwegian Concrete Association, 2005), Germany (Deutscher-Ausschuss fur Stahlbeton, 2001) and AS 1141 60.2 (2014). The most usual specimen size is 75x75x250-300 mm, though in the German and Norwegian methods, larger specimens are used, e.g., 100x100x500 mm in the Norwegian CPT. Generally, a high content (420 – 440 kg/m3) of a high alkali cement (≈ 0.8 – 1.3% Na2Oeq, depending on the standard method) is used to produce a high alkali level in the concrete; in some methods [e.g., CSA A23.2-14A (2014), ASTM C1293-8b (2014), AS 114 60.1 (2014)], NaOH pellets are dissolved in the mix water in order to increase the total alkali content in the concrete to 1.25% Na2Oeq by mass of cement. The specimens are then stored at an elevated temperature (generally 38oC) and in high humidity. Any expansion is monitored and typically the test period is one year. Pessimum effects can be identified by varying the proportion of the test aggregate. The expansion limits used in the test vary based on local experience, but generally range between 0.03% and 0.05% for non-reactive aggregates.
Multiple Choice Questions and Answers for Chapter 6
Published in Ghazi G. Al-Khateeb, Traffic and Pavement Engineering, 2020
The appropriate SGC operation mode that should be used to prepare specimens for research purposes or further performance testing is: “number of gyrations” mode“height” mode“angle of gyration” mode“rate of gyration” modeAny of the above
Assessing the effect of moulding water content on the behaviour of lime-stabilised an expansive soil
Published in Geomechanics and Geoengineering, 2021
Abdelmoumen Aala-Eddin Driss, Khelifa Harichane, Mohamed Ghrici, Hamid Gadouri
The UCS tests were performed according to ASTM D2166 (2000) on several samples stabilised with different lime contents. The water content calculated according to the method explained in the ‘compaction’ section was added to the soil-lime mixture in order to prepare the deferent moulding moisture contents (DMC, OMC and WMC) for the UCS tests. Samples are preserved in the airtight container for about 1 h of curing prior to the preparation of specimens by static compaction using a static press. Figure 6 exhibits both the scheme of the static compaction mould and the dimensions of the studied specimens. However, the obtained specimens were prepared by compaction at different water contents (WMC, OMC and DMC) and their corresponding dry unit weights deduced from compaction tests (Table 3). After curing, all the specimens were statically compacted when the calculated amount of mixture was placed into the cylindrical mould (Figure 6). During filling, the treated soil was tamped gently and uniformly so that the upper and lower plug could be inserted in about 5 mm. The assembled static compaction mould was then placed on a hydraulic jack to gently force the upper and lower-plug in contact with the barrel of the mould. This was held for about 1 minute before the specimens were dismantled. The samples were considered suitable for testing if the variations in their physical and geometric properties meet the following tolerances: γd ±1%, ω ± 0.5% of target value, diameter 38 ± 0.5 mm and height 76 ± 1 mm. The specimens were stored in plastic boxes to prevent possible loss of moisture which were kept in the laboratory at the temperature of 25°C and the relative humidity of 50%. Furthermore, after 1, 7 and 28 days of curing, the specimens are tested. The tests of all samples were repeated on three identical specimens and the peak stress accepted was the average of the three tests carried out on each sample type.
A comprehensive overview of genotoxicity and mutagenicity associated with outdoor air pollution exposure in Brazil
Published in Journal of Toxicology and Environmental Health, Part B, 2023
Vera Maria Ferrão Vargas, Flavio Manoel Rodrigues da Silva Júnior, Tatiana da Silva Pereira, Cristiane Silva da Silva, Mariana Vieira Coronas
In the case of investigations using specimens, it is important to find out whether it is necessary to have authorizations to use these models for example, a collection license, a license for the use of genetic heritage, or approval of ethics committees for animal experimentation. These licenses are important to guarantee the authorization to use the specimens (plants/animals) in research and that the study is carried out following ethical and moral principles.