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The main objective of this study was to carry out more detailed research on the effects of the amount of cement paste on the physical and mechanical properties of porous fine aggregate concrete (PFAC). Fine foamed glass aggregate (prepared of local glass breaks) and crushed expanded polystyrene aggregate (prepared of local packing tare of household equipment), ordinary Portland cement (OPC), plasticizing and air entraining admixtures, as well as pozzolanic additive – metakaolin-based waste (local waste in production process of foamed glass aggregate), were used for the preparation of forming mixtures. Fine aggregates were coated by an extremely thin layer of porous cement paste in the samples with the lowest amount of OPC (70 kg/m3), and the aggregates contact with each other mainly at the points (empty spaces between the aggregates are interconnected between each other). There were no empty spaces between the aggregates observed, and porous cement paste seems to be monolithic in the samples with the highest amount of OPC (370 kg/m3). Increased amount of OPC (from 70 to 370 kg/m3) results in denser structure, increased dry density, compressive strength, thermal conductivity coefficient and decreased water absorption of the samples.

One of the methods recently applied for the noticeably improvement of properties of cementitious materials is the use of the single or multi-walled carbon nanotubes (CNTs) as nano-reinforcements in cementitious materials. The positive action of CNTs highly depends not only on its nature, length and amount, but also on previous treatment of CNTs and quality of CNTs dispersion. It is important to obtain the effects of multi-walled CNTs, dispersed only in carboxyl-methyl cellulose – commercially available pellets without the use of any commercially available surfactants or plasticizers. The influence of dispersed CNTs on the rheological properties of fresh cement pastes and physical and mechanical properties of hardened specimens was analyzed in this work. Compared to the dynamic viscosity of pure distilled water smaller amounts of CNTs (0.00005–0.005%) reduce the dynamic viscosity down to the 15% whereas higher amounts of CNTs (0.05–0.5%) increase the dynamic viscosity from 1.3 to 4.7 times. Mechanical tests of hardened for 28 days cement paste specimens showed that smaller amounts of CNTs (0.00005–0.005%) increase the compressive and flexural strengths by 38.07– 42.3% and 40.1– 44.6%, whereas higher amounts of CNTs (0.05–0.5%) increase these strengths just by 21.11–18.82% and 18.33–6.6% respectively.

Expanded polystyrene (EP) is widely used as a packaging material for many types of goods. However, once the material is used, it is disposed of in landfills, where it can remain intact for the lifetime of several generations. Recycling of disposed EP packaging is of high relevance worldwide. The main objective of this study is to make a more detailed research into the effect of EP aggregate waste of different fineness and shape on physical and mechanical properties of porous lightweight aggregates concrete (PLWAC) with EP waste aggregates. Tests were done with Portland cement, EP waste of different fractions, resulted from crushing (EPR) and cutting (EPU), metakaolin, superplasticizer and air entraining admixture. Six batches of PLWAC specimens were formed with different EPR/EPU ratios, ranging from 0.5 to 3.The change in EPR/EPU ratio in PLWAC leads to structural changes and density reduction from 550 to 410 kg/m3 after drying. When EPR/EPU ratio in the PLWAC is increased to 2, the compressive strength of the specimens drops from 2.3 to 1.75 MPa and down to 0.55 MPa, when EPR/EPU ratio is increased to 3.

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It is important to select a certain type and amount of a superplasticizer (SP) for successful cement applications in concrete. The results show that the SPs ((lignosulphonates (LS), polyacrylates (PA) and polycarboxylates (PCE)) especially differ by their electrical conductivity (EC) values (from 2.5 to 4 times) and mostly influence the spreadability, viscosity, temperature and hydration course of the cement paste with an SP. Compared to the pure cement paste's viscosity, all the tested amounts of LS, PA and PCE lower the initial temperature of the cement paste, but only PCE and PA noticeably reduce the viscosity. It can be highlighted that LS, characterised with high EC values causes a rise in the cement paste temperature and a sharp growth in the viscosity. PCE and PA with much lower EC values, reduce the temperature and, correspondingly, the viscosity of the paste. EXO temperature tests revealed that the same amount of SP's (0.2 %) has a different effect on the course of the hydration, the EXO maximum time and the temperatures. Compared to the pure cement paste, LS reduced the EXO maximum time by 17 % and lowered the EXO maximum temperature by 6 °C, whereas PCE and PA extended the EXO maximum time by 11.3 % and 12.2 %, respectively.