Summary This paper presents the results of an experimental study on the behaviour of high‐performance concretes after high temperature exposure. The high temperature exposure is related to the potential risk of fire, and mechanical properties analysis is needed afterwards to assess the residual strength of the material. The results presented in the paper show the properties evolution of four concretes made with four different aggregate types: basalt, granite, dolomite and riverbed gravel. The mix compositions allow comparisons, because the cement paste and mortar compositions and their volumes remain the same for all the four concretes. Moreover, the aggregate particle size distribution was chosen to be quasi identical so that this factor does not affect the concrete behaviour. The decrease of tensile strength value with the increase of temperature is more pronounced than compressive strength reduction thus, the exponential and power function equations were proposed to describe ftT–fcT relationship. The change of modulus of elasticity in relative values is similar, although the initial values of modulus are different and correspond to the aggregate type. Copyright © 2015 John Wiley & Sons, Ltd.

This paper presents the results of comprehensive cement paste porosity and gas permeability tests. The tests conducted concerned ordinary Portland cement (OPC) cement pastes with varying water-cement ratios ranging from 0.3 to 0.6. The tests were conducted after the curing of cement paste for 90 days and two years under laboratory conditions. Open porosity was determined using three methods: helium pycnometry, mercury intrusion porosimetry, and water saturation. Permeability was determined using a modified RILEM-Cembureau method. The results obtained demonstrated that permeability does not change significantly over time despite the observed material shifts in open porosity characteristics caused both by further progress in hydration and by the carbonation process that occurs. The results of the tests conducted also permitted the quantitative determination of the impact of the water-cement ratio, age, and the progress of carbonation on open porosity measured using different methods and also on the gas permeability of the pastes.

The paper presents experimental investigations concerning the influence of the cement type (CEMI 42.5 R Portland cement and CEMIII/A 42.5 N slag cement—with 53% granulated blast furnace slag) on the mechanical and transport properties of heated concretes. The evolution of properties due to high temperature exposure occurring during a fire was investigated. High temperature exposure produces changes in the transport and mechanical properties of concrete, but the effect of cement type has not been widely studied in the literature. In this paper, concretes were made with two cement types: CEMI and CEMIII, using basalt (B) and riverbed aggregates (RB). The compressive and tensile strength, as well as the static modulus of elasticity and Cembureau permeability, were tested after high temperature exposure to 200, 400, 600, 800, and 1000 °C. The evaluation of damage to the concrete and crack development due to high temperature effects was performed on the basis of the change in the static modulus of elasticity. The test results clearly demonstrated that permeability increases with damage, and it follows an exponential type formula for both types of cement.

Abstract. This paper presents the results of extensive research work on the open porosity and gas permeability of cement pastes. Tests were conducted on cement pastes with different water/cement ratios and types of cement. The three most popular cements in Poland from the CEM I, CEM II and CEM III groups were tested after the pastes had been cured for 90 days in laboratory conditions. The scope of experiments included the assessment of open porosity determined using three different methods: comparing the bulk and specific densities, mercury intrusion porosimetry and saturating the material with water. In addition, this article contains an analysis of the porosity characteristics based on the distributions produced by porosimetry examinations. Gas permeability was determined using the modified RILEM-Cembureau laboratory method. The results of the completed test allowed a quantitative determination to be made of the impact of water-cement ratio and type of cement used on open porosity assessed by various methods, and the influence of these parameters on the gas permeability of the paste. The quantitative changes in the content of capillary pores and meso-pores in the cement pastes analysed are also presented.

Abstract. This article presents results of fire spalling tests on small concrete slabs and studies of material parameters that may increase its occurrence. Experimental techniques enabling to study and determination of material features are presented and discussed. Experimental studies on spalling behaviour of elements were carried out on seven different concrete mixes with constant content of cement paste and mortar. Research aimed at determining influence of the following parameters: w/c ratio (0.30; 0.45; 0.60), cement type (CEM I, CEM III) and type of aggregates (riverbed gravel, granite, basalt) on fire concrete spalling. Paper discusses also the influence of cold rim that forms while testing slab-like element is subjected to one-side heating.

The paper presents the investigations related to concrete permeability change during heating and the contribution of polypropylene fibres melting at the temperature of 163°C to permeability. Permeability is an important parameter governing the occurrence of the explosive behaviour also known as concrete spalling due to fire. To limit the spalling of concrete, the polypropylene fibres are used to act as a fuse and, by melting, reduce gas pressure in concrete pore system. The investigations consisted of testing the permeability change of seven high performance concretes with polypropylene fibres. The permeability was measured after temperature exposure to temperature 140, 160, 180 and 200°C. The results have shown to what extent the fibre length and content affect the permeability when melting. Moreover the results have shown that the addition of polypropylene fibres had the desired impact causing a considerable increase in concrete permeability after fibre melting.

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A significant reduction in the CO2 emission associated with cement production is obtained by partially replacing Portland cement with supplementary cementing materials (SCM’s): e.g., siliceous fly ash or granulated blast furnace slag. In the near future, the limited availability of these materials will do more attractive to use ashes from combustion in fluidized bed boilers, which currently are mainly deposited in various landfills. Paper identifies the effect of Fluidized Bed Combustion (FBC) fly ash from both hard and brown coal combustion on the durability of mortars exposed to sodium and magnesium sulfate solution at different curing temperature: 20 and 5 °C. The evaluation was based on the results of long-term linear changes of mortar samples made with Portland cement and different amounts of FBC fly ash addition stored in a corrosive environment, as well as the evaluation of the type of formed corrosion products using XRD and microstructural studies (SEM/EDS). It has been shown that amount of FBC fly ashes used in binders significantly determines sulfate resistance of prepared cements as well as its chemical composition. By using fluidized ashes, the sulfate resistance of cement binders can be achieved with their content even of 15%.