This paper presents the results of tests on high performance concrete (HPC) prepared and cured at various ambient temperatures, ranging from 12 °C to 30 °C (the compressive strength and concrete mix density were also tested at 40 °C). Special attention was paid to maintaining the assumed temperature of the mixture components during its preparation and maintaining the assumed curing temperature. The properties of a fresh concrete mixture (consistency, air content, density) and properties of hardened concrete (density, water absorption, depth of water penetration under pressure, compressive strength, and freeze–thaw durability of hardened concrete) were studied. It has been shown that increased temperature (30 °C) has a significant effect on loss of workability. The studies used the concrete slump test, the flow table test, and the Vebe test. A decrease in the slump and flow diameter and an increase in the Vebe time were observed. It has been shown that an increase in concrete curing temperature causes an increase in early compressive strength. After 3 days of curing, compared with concrete curing at 20 °C, an 18% increase in compressive strength was observed at 40 °C, while concrete curing at 12 °C had a compressive strength which was 11% lower. An increase in temperature lowers the compressive strength after a period longer than 28 days. After two years of curing, concrete curing at 12 °C achieved a compressive strength 13% higher than that of concrete curing at 40 °C. Freeze–thaw performance tests of HPC in the presence of NaCl demonstrated that this concrete showed high freeze–thaw resistance and de-icing materials (surface scaling of this concrete is minimal) regardless of the temperature of the curing process, from 12 °C to 30 °C.

Rheological investigations were conducted into cement paste made of various cement types (CEM I 42.5 R, CEM II/B-S 42.5 R, CEM III/A 32.5 N LH/HSR/NA), with and without superplasticizer. The tests were performed at 15°C, 20°C and 25°C, for one hour. Rheological parameters (yield value and plastic viscosity) were designated according to the Bingham model. The influences of hydration time, the presence of superplasticizer and of temperature on the occurrence of the thixotropy phenomenon in cement paste were identified. The thixotropy was analysed by measuring hysteresis loops surfaces using a numerical integral method

Reducing CO₂ emissions from cement production is currently one of the major challenges faced by the cement industry. One approach to lowering these emissions is to reduce the clinker factor by incorporating alternative mineral additives into cement. Consequently, there is a growing interest in the use of copper slags (CSs) as supplementary cementitious materials. Therefore, this study investigates the properties of cements containing substantial amounts of copper slag (up to 60%) and, for comparison, the same proportions of granulated blast furnace slag. The inclusion of substantial amounts of CS results both from the lack of studies in this area and from the potential benefits associated with the utilization of larger quantities of copper slag. The chemical, phase, and particle size composition of CS and granulated blast furnace slag added to CEM I 42.5 cement from the Odra cement plant in amounts of 20%, 40%, and 60% by weight were compared. The pozzolanic activity index of the copper slag and the hydraulic activity index of the blast furnace slag were determined. The high pozzolanic activity of the CS was attributed to its high degree of vitrification (nearly 100%). In contrast, the lower hydraulic activity of the blast furnace slag was explained by its lower glass phase content (about 90% by mass). A gradual decrease in the total heat of hydration released within the first two days was observed with increasing slag content in the cement, slightly more pronounced for copper slags. However, at later stages (2–28 days), XRD analysis indicated higher hydration activity in cements containing copper slag, resulting from its strong pozzolanic reactivity. Cements with copper slag also showed slightly lower water demand compared to those with blast furnace slag. An increase in setting time was observed with higher slag content, more noticeable for blast furnace slag. The type and amount of slag in cement reduce both yield stress and plastic viscosity. Greater reductions were observed at higher slag content. Moreover, copper slag caused greater paste fluidity, attributed to the lower amount of fine particles fraction. The addition of slag decreased flexural and compressive strength in the early period (up to 7 days), this reduction being proportional to slag content. After 90 days, mortars containing 20% and 40% copper slag achieved strength values exceeding that of the reference mortar by 4%. In contrast, at a 60% CS content, a 5% decrease was observed, while for cement with 60% BFS the decrease was 11%. This indicates that a lower copper slag content in the cement (40%) is more favorable in terms of strength.

In this work, the evaluation of measurement uncertainty of concrete dynamic elastic modulus testing method was conducted. The dynamic test was carried out using impulse excitation and modal analysis method, which can be used to determine the compressive strength of concrete in a non-destructive way. The tests were conducted using concrete samples in order to determine the practical usefulness of the mentioned method. It has been demonstrated that the impulse excitation and modal analysis method is characterized by very good repeatability.

This paper presents test results of the impact of chemical admixtures used in the underwater concrete technology, i.e. a superplasticizer (SP), an anti-wash admixture (AWA) and SiO2 nano- particles (NP) on the cement hydration process, rheological properties and the setting time. The impact of admixtures was tested in combination and separately, with the use of microcalimetry, X-ray diffraction (XRD) and rheology. It was demonstrated that AWA and SP admixtures caused a delay of the hydration process, while the impact of SP was much greater. The above statement was also confirmed by results of rheological tests. Combined application of AWA, SP and NP causes even a larger delay of the hydration process and the increase of paste rheological parameters, with the impact of the superplasticizer particularly visible.