During a fire, ordinary Portland cement (OPC) systems lose their mechanical properties. For this reason, it is important to find a way to protect it. This study suggested alternative uses of slag and phosphogypsum to produce coatings for fire-resistant applications. Five compositions of 10 mm thick alkali-activated slag coatings were investigated. In these compositions, different amounts of phosphogypsum (1%, 3%, 5%, 7%, and 10%) were used. In the first stage of this study, the residual compressive strength of samples with the coatings based on alkali-activated slag was compared to the results of OPC concrete samples without coatings. The experimental results showed that a higher residual compressive strength of 33.2–47.3 MPa OPC concrete was achieved for the samples with coatings. Meanwhile, the residual compressive strength of the uncoated samples was 32.37 MPa. In the second stage, OPC concrete samples were reinforced with fiberglass polymer (FRP) rods, and they had a similar positive effect on alkali-activated coatings. After exposure to higher temperatures, the pullout tests of the glass FRP bars showed that the adhesion strength was (9.44 MPa) 43.9% higher for the samples with coatings compared to the samples without coatings (6.56 MPa). Therefore, a higher bond strength can be maintained between concrete and FRP bars. Alkali-activated slag with 3% phosphogypsum can be used for the production of fire-resistant coating. These coatings could protect OPC concrete and reinforced concrete with glass FRP bars from fire.

The literature confirms that fine recycled concrete aggregate (fRCA) can be used as a replacement for natural soil in new concrete, offering many advantages. Despite these advantages, there are also critical barriers to the development of fRCA in new mixes. Among these, the first challenge is the variability of fRCA properties, in both physical, chemical, and mechanical terms. Many individual studies have been carried out on different RCA or fRCA properties, but little investigative work has been performed to analyze their dynamic properties. Therefore, the influence of the non-cohesive fine fraction content of RCA on the dynamic properties of this waste material, when used as a specific anthropogenic soil, has been studied in laboratory conditions, employing a standard resonant column apparatus, as well as piezoelectric elements. In the present research, special emphasis has been placed on the dynamic shear modulus, dynamic damping ratio, small-strain shear modulus, and small-strain damping ratio, as well as shear modulus degradation G(γ)/G_max, the damping ratio increase D(γ)/D_min, and the threshold shear strain amplitudes γ_tl and γ_tv. Artificially prepared fRCAs with varying fine fraction contents (0% ≤ FF ≤ 30%, within increments of 5%) have been tested at different pressures (p′ = 90, 180, and 270 kPa) and relative densities of D_r > 65%. This study also examined the effect of two tamping-based sample preparation methods, i.e., dry and wet tamping. The results presented herein indicate that the analyzed anthropogenic material, although derived from concrete and produced by human activities, behaves very similarly to natural aggregate when subjected to dynamic loading. The introduction of a fine fraction content to fRCA leads to changes in the dynamic properties of the tested mixture. Concrete material with lower stiffness but, at the same time, with stronger damping properties can be obtained. A fine fraction content of at least 30% is sufficient to cause a significant loss of stiffness and, at the same time, a significant increase in the damping properties of the mixture. This study can serve as a reference for designing fRCA mixtures in engineering applications.

It is proven that human construction activities affect the environment negatively. The threat of global ecological disaster is one of the most important factors, appearing due to unbalanced human activities and insufficient use of natural resources. In Lithuania there are building materials (bricks, concrete, reinforced concrete and other materials) used for construction of buildings that require a lot of energy. Prices of energy grew up several times in recent years, so the prices of construction materials significantly increased. It is suggested to use more local building materials produced with low energy consumption. The usage of local, renewable raw building materials can reduce CO2 emissions, ambient air pollution. The use of straw bales as construction material has many advantages. Pressed straw can be used as a natural heat insulating material in the construction of buildings in Lithuania, as it does not contradict the essential requirements of the construction of buildings specified in the Law on Construction and other normative documents. The aim of this study is to evaluate the temperature distribution of the wall of a built building made of straw bales during the cold period of the year. Temperature data loggers with thermocouple sensors were used to record the outdoor air, indoor and wall temperatures. Measurements of the temperature of the wall frame of the building filled with straw showed that the temperature field of the wall is in a constant dynamic state. It was found that the temperature of the individual layers of the walls of the building filled with straw varies tendentiously depending on the outdoor air temperature.

Concrete is one of the most popular construction materials in the world. The concrete properties depend from many factors. One of them is aggregates quality, which can be defined as an impurity level. The most unwanted materials in fine aggregates are clay and soil particles. These particles can impure aggregates due to irregular sands in quarry and during the digging process. In the present paper were estimated how impurity impact the properties of concrete. During the research the aggregates were impured with clay and soil particles. The change of fresh concrete workability, hardened concrete density, compression strength, water absorbability and frost resistance were evaluated. The results show that aggregates impurity with clay and especially with organic materials (soil) is very dangerous. The concrete workability, frost resistance is decreasing. The clay and soil have a different effect on hardened concrete density and compression strength. Soil decreased both parameters while well mixed clay increased these characteristics. However, generalizing all results, can be stated, that keeping the same level of concrete workability it is necessary to raise water and cement ratio and it will give strength loss effect.

Many abandoned (term "hostless" by 2010) hydraulic structures have been exploited for over 30 years, so due to the aging of materials, the probability of failures and accidents increases. Due to the insufficient exploitation in several dams the breakdowns occurred, some ponds in damaged dams have been emptied. It is known that no comprehensive research on technical state evaluation of abandoned hydraulic structures in Lithuania has been carried out. It becomes clear that practical, scientifically based algorithms for the technical state evaluation of abandoned hydraulic structures are needed in order to assess the impact of environmental factors on the technical state, safety, reliability and durability of structures. This paper focuses on the presentation of investigation results of technical state evaluation of 4 abandoned hydroschemes in Raseiniai distr. Due to the noticed significant defects and deteriorations all 4 hydroschemes are in critical state, the pond in Gyliai IV is emptied, the demolition of reinforced concrete structures should be applied in this object.