Ресурсоэффективные системы в управлении и контроле: взгляд в будущее: сборник научных трудов VI Международной конференции школьников, студентов, аспирантов, молодых ученых, 9 -14 октября 2017 г., г. Томск

В сборнике представлены материалы VI Международной конференции школьников, студентов, аспирантов, молодых ученых "Ресурсоэффективные системы в управлении и контроле: взгляд в будущее". Более 500 авторов из 35 вузов, предприятий и научных исследовательских университетов России, ближнего и дальнего зарубежья представили тезисы своих докладов, в которых рассматриваются актуальные проблемы неразрушающего контроля и технической диагностики, внедрения систем менеджмента, качества образования, управления в современной экономике. Материалы предназначены для специалистов, преподавателей, аспирантов и студентов вузов, а также для всех интересующихся проблемами ресурсоэффективных технологий

A new performance test to evaluate the sulfate resistance of concrete by tensile strength measurements

Concrete structures without sufficient durability can be damaged by sulfates in groundwater and from surrounding rock layers. To evaluate the performance of a concrete mixture, precise and performance-oriented test methods are a must. Therefore, a new a performance oriented concrete test procedure based on tensile strength measurements was developed considering experiences reported in international literature and recommendations of state-of-the-art reports. A vast parameter study with approx. 3850 tensile tests on ASTM briquets, 1900 flexural tensile tests on standard prisms and 2100 expansion tests on mortar flat prisms of different ages and with different storage conditions was statistically assessed. Based on the results a performance-oriented test method could be defined which considers not only the chemical, but also the physical resistance of a concrete against sulfate attack. The method was verified by 23 concretes with different cements or cement fly ash combinations and additional field tests. It could clearly be demonstrated that the results represent the performance of a practical concrete in case of sulfate attack. Furthermore, it leads much faster to an evaluation of the sulfate resistance compared to the most other practical oriented methods

TC 238-SCM: hydration and microstructure of concrete with SCMs State of the art on methods to determine degree of reaction of SCMs

This paper is the work of working group 2 of the RILEM TC 238-SCM. Its purpose is to review methods to estimate the degree of reaction of supplementary cementitious materials in blended (or composite) cement pastes. We do not consider explicitly the wider issues of the influence of SCMs on hydration kinetics, nor the measurement of degree of reaction in alkali activated materials. The paper categorises the techniques into direct methods and indirect methods. Direct methods attempt to measure directly the amount of SCM remaining at a certain time, such as selective dissolution, microscopy combined with image analysis, and NMR. Indirect methods infer the amount of SCM reacted by back calculation from some other measured quantity, such as calcium hydroxide consumption. The paper first discusses the different techniques, how they operate and the advantages and limitations along with more details of case studies on different SCMs. In the second part we summarise the most suitable approaches for each SCM, and the paper finishes with conclusions and perspectives for future work

Report of RILEM TC 281-CCC: outcomes of a round robin on the resistance to accelerated carbonation of Portland, Portland-fly ash and blast-furnace blended cements

Many (inter)national standards exist to evaluate the resistance of mortar and concrete to carbonation. When a carbonation coefficient is used for performance comparison of mixtures or service life prediction, the applied boundary conditions during curing, preconditioning and carbonation play a crucial role, specifically when using latent hydraulic or pozzolanic supplementary cementitious materials (SCMs). An extensive interlaboratory test (ILT) with twenty two participating laboratories was set up in the framework of RILEM TC 281-CCC ‘Carbonation of Concrete with SCMs’. The carbonation depths and coefficients determined by following several (inter)national standards for three cement types (CEM I, CEM II/B-V, CEM III/B) both on mortar and concrete scale were statistically compared. The outcomes of this study showed that the carbonation rate based on the carbonation depths after 91 days exposure, compared to 56 days or less exposure duration, best approximates the slope of the linear regression and those 91 days carbonation depths can therefore be considered as a good estimate of the potential resistance to carbonation. All standards evaluated in this study ranked the three cement types in the same order of carbonation resistance. Unfortunately, large variations within and between laboratories complicate to draw clear conclusions regarding the effect of sample pre-conditioning and carbonation exposure conditions on the carbonation performance of the specimens tested. Nevertheless, it was identified that fresh and hardened state properties alone cannot be used to infer carbonation resistance of the mortars or concretes tested. It was also found that sealed curing results in larger carbonation depths compared to water curing. However, when water curing was reduced from 28 to 3 or 7 days, higher carbonation depths compared to sealed curing were observed. This increase is more pronounced for CEM I compared to CEM III mixes. The variation between laboratories is larger than the potential effect of raising the CO concentration from 1 to 4%. Finally, concrete, for which the aggregate-to-cement factor was increased by 1.79 in comparison with mortar, had a carbonation coefficient 1.18 times the one of mortar

Reactivity tests for supplementary cementitious materials: RILEM TC 267-TRM phase 1

A primary aim of RILEM TC 267-TRM: “Tests for Reactivity of Supplementary Cementitious Materials (SCMs)” is to compare and evaluate the performance of conventional and novel SCM reactivity test methods across a wide range of SCMs. To this purpose, a round robin campaign was organized to investigate 10 different tests for reactivity and 11 SCMs covering the main classes of materials in use, such as granulated blast furnace slag, fly ash, natural pozzolan and calcined clays. The methods were evaluated based on the correlation to the 28 days relative compressive strength of standard mortar bars containing 30% of SCM as cement replacement and the interlaboratory reproducibility of the test results. It was found that only a few test methods showed acceptable correlation to the 28 days relative strength over the whole range of SCMs. The methods that showed the best reproducibility and gave good correlations used the R3 model system of the SCM and Ca(OH)2, supplemented with alkali sulfate/carbonate. The use of this simplified model system isolates the reaction of the SCM and the reactivity can be easily quantified from the heat release or bound water content. Later age (90 days) strength results also correlated well with the results of the IS 1727 (Indian standard) reactivity test, an accelerated strength test using an SCM/Ca(OH)2-based model system. The current standardized tests did not show acceptable correlations across all SCMs, although they performed better when latently hydraulic materials (blast furnace slag) were excluded. However, the Frattini test, Chapelle and modified Chapelle test showed poor interlaboratory reproducibility, demonstrating experimental difficulties. The TC 267-TRM will pursue the development of test protocols based on the R3 model systems. Acceleration and improvement of the reproducibility of the IS 1727 test will be attempted as well