"Round Robin Testing" (RRT) is a well-known method for assessing the reproducibility of a test or verification of a new test procedure of almost any kind. In the EU funded network COST Action TU1404 Towards the next generation of standards for service life of cement-based materials and structures, an Extended "Round Robin Testing" program (RRT+) was planned as a fundamental tool to obtain input data for a range of concrete properties and validate non-standardised testing techniques. In this paper, detailed information on the planning, conduction and analysis of Phase 1 of the RRT+ is presented. The aim of Phase 1 was to define and confirm the best practice for creating a comparable reference concrete mix for RRT programmes. With a total of 45 laboratories from Europe, Japan and Canada, RRT+ was one of the most extensive round robin testing programmes targeting cement-based materials.
COBISS.SI-ID: 9108577
The feasibility of estimation of mechanical properties of limestone concrete after exposure to high temperatures, using nondestructive methods, was investigated. Experimental study was carried out on two concrete mixtures that differed in water to cement ratio (w/c). After standard curing time, specimens were exposed to various temperature levels, i.e. 20°C, 200°C, 400°C, 600°C or 800°C. Basic mechanical properties of concrete specimens were determined prior heating at ambient temperature. Once the specimens were cooled down to the ambient temperature, various nondestructive tests including ultrasonic (US) method, determination of rebound number, and resonant frequency method were performed. Further on, specimens were visually inspected to assess the damage of the concrete surface. To determine the residual mechanical properties of specimens after exposure to high temperature, the compressive and flexural strengths were determined on cubic and prismatic specimens, respectively. The main goal of presented research was the estimation of the compressive and flexural strengths of limestone concrete after fire based on developed relationships between results of destructive and nondestructive measurements performed on limestone concrete mixtures 1 and 2. The best relationship for estimation of compressive strength was determined based on measured fundamental torsional frequency, whereas the best relationship for estimation of flexural strength was determined based on combination...
COBISS.SI-ID: 8878945
The paper presents a study about differences and similarities in alkali-carbonate reaction (ACR) process inside concrete prepared with the same carbonate aggregate and different cement binders. Used aggregate is typical Slovenian late digenetic dolomite. The first cement binder is pure Portland cement (CEM I) and the second one is Blastfurnace cement (CEM III). The study of the ACR progress was carried out under accelerated conditions simulated by the 1 M aqueous NaOH solution at 60°C, up to 1 year. Analyses on the micro level were carried out using a petrographic microscope and scanning electron microscopy with X-ray microanalysis (SEM/EDS). On the macro level, measurements of specimens length and mass changes as well as compressive and flexural tests were carried out parallel to the microscopic investigations. The first results of the study show that the ACR process is slower in concrete with Blastfurnace cement. However, for both compositions the same products that are results of the ACR are formed. We can conclude that the replacement of the CEM I cement with the CEM III cement does not hinder the initialisation and progress of the ACR. It only shifts the formation of the reaction products to a later time.
COBISS.SI-ID: 8763745