This paper describes a study of the effect of partial replacement of ordinary Portland cement (OPC) by various mineral additives in the screed mixtures. Ceramic powder, blast furnace slag and fly ash were gradually employed in increments of 12.5 wt.% up to 50 wt.% to replace OPC. The mixtures were designed to a constant consistency. The influence of mineral additives was evaluated in terms of the air content in the fresh mixtures, the compressive strength, the flexural strength and the freeze-thaw resistance and using non-destructive measurements after 28 and 90 days. The accompanied paste sampleswere analysed using thermogravimetry to monitor the hydration process by means of total bound water content. The decrease in the mechanical properties and the frost resistance of the mixtures with the mineral additives were recorded, because of the necessity for a larger addition of water. According to the valid standards for concrete screed related to the frost resistance, it could be concluded that maximal suitable cement replacement contents are 12.5, 37.5 and 50 wt.% for ceramic powder, fly ash and blast furnace slag, respectively. The freeze-thaw resistance of the studied materials was found to be strongly related to the content of CSH and CAH hydrates.

The environmental awareness and potential cost reduction have promoted the recycling of materials in civil engineering. This paper is dealing with the recycling and secondary use of old concrete railway sleepers for reconstruction of old railway lines. In particular, it is focused on the investigation of material properties of a binder prepared from finely crushed old concrete sleepers. This material could be used for strengthening of subsoil and embankments supporting the railway structures. The study shows that the compressive and bending strength of the investigated material is sufficient for this purpose and that the strength can be further increased by suitable curing conditions. These findings could contribute to the utilization of old concrete sleepers during railway reconstructions and safe money spent for the purchase of new materials and disposal of old sleepers.

Using of a larger amount of fly ash in cement and concrete is in practice very actual topic. The reason is the positive economic and environmental impact. If added to the concrete larger amount of fly ash, it affects the final properties of the mixture. This paper deals with cement screed with different content of fly ash (0, 12.5, 25, 37.5 and 50%). On these mixtures was verified consistence of fresh mixtures and mechanical tests were carried out - the compressive strength and tensile strength.

Using of fly ash in concrete screed is becoming a common practice. This situation entails both environmentally and economically positive effect. The problem may occur with the durability and life of such materials. Therefore, it is important to correctly grasp these materials and final properties sufficiently verify. One of these properties is frost resistance. This paper presents the results of measurements on the frost resistance of concrete screed with the substitution fly ash 0-50% by weight of clinker. Specimens were subjected to destructive and non-destructive test of frost resistance after 28 days of ripening and the results were evaluated.

The different properties of building materials are often caused by their varying humidity respectively water saturation levels. The cement paste is a porous material. The cement paste mixed with fly ash is highly porous material whose properties depend on the amount of pores in the material and the state of saturation. Basic material properties like strength, Modulus of elasticity, volume weight are compared in article for cement paste with fly ash for two states, saturated and dried materials. The ratio of cement and bulk ash was 1:1. Article presents results of experiments in age of 1 month after production.