Key Engineering Materials Vol. 838

Abstract: This study introduces the experiment based on following parameters: kind of aggregate (natural river gravel and air-cooled blast furnace slag), the aggregate gradation and content of binder. Main properties such as compressive strength, void content and hydraulic conductivity of pervious concrete were investigated in the experiment. The experiment showed satisfactory results in the case of pervious concrete made of natural aggregate. Results of pervious concrete made of air-cooled blast furnace slag aggregates are perspective, however needs for some optimizations. Results confirmed the opposite relationship between compressive strength and void content/hydraulic activity. ACBFS performs worse than NA as for compressive strength, while it performs better in the case of hydraulic conductivity and void content.

Abstract: This article presents the results of research on the use of unstable steel slag with a fraction of 0/8 mm as a 100% substitute for natural aggregate in concrete production. Two types of cements were used for the production of concrete: Portland cement CEM I 42.5N and hybrid cement H-CEMENT. Both of these cements were produced by the company Považská cementárna, a.s., Ladce. The main objective of this study was to assess the suitable type of binder to be combined with unstable steel slag in the production of concrete composite. The prepared concrete was used to test the properties of a fresh concrete mix, i.e. its consistency and bulk density. Hardened concrete was used to test the strength and deformation properties, including cube strength after 3, 7, 14, 21, 28 and 90 days, as well as prism strength after 28 days. The static modulus of elasticity was determined using prisms after 28 days of age of the test specimens. Our attention was also focused on determining the class of leachability of the concretes based on steel slag with CEM I 42.5N and H-CEMENT. The durability of concrete prepared on the basis of steel slag was tested in an environment with increased temperature and pressure. The results of the strength characteristics tests show a difference between the 28-day average cube strength of concrete using CEM I 42.5N and H-CEMENT (34.6 MPa and 29.1 MPa), while after 90 days, the average cube strength value stabilized at about 38 MPa. The average values ​​of the static modulus of elasticity when using CEM I 42.5N and H-CEMENT are almost identical, achieving values ​​of 32.5 GPa and 32.8 GPa, respectively. Concrete based on steel slag with CEM I 42.5N and H-CEMENT can be included in leachability class IIb. The results of the durability test of concrete based on steel slag in an environment with increased temperature and pressure confirmed the use of H-CEMENT hybrid cement from the company Považská cementáren, a.s., Ladce, as a suitable binder. .

Abstract: This article deals with the evaluation of the effects on soil caused by leaching of materials from curbs, which were made using cement kinl dust from the cement plant Horné Srnie. Attention is also paid to a condition of the grass growing near the curbs. These laboratory curbs (bricks) were produced with addition of cement kiln dust and fly ash after denitrification by the SNCR method in alkaline activated materials based on blast furnace slag granules activated by anhydrous disodium metasilicate During the experiment the effects of laboratory curbs on grass growth in testing flower pots were investigated. The aim of the experiment was to obtain a product suitable for curbs with supposed direct contact with the soil. The experiment dealt with the properties of laboratory curbs stored in situ as well as with their influence on the soil and the effect of leached substances on the surrounding grass. The main part of the experiment was conducted in situ.

Abstract: This paper is aimed to investigate the total sand filler replacement by two types of cellulosic fibers (bleached wood pulp - WP and recycled fibers from waste paper - RF) in cement-based mortars. Two different types of cement mortar, one with addition of finely ground limestone and other with powdered granulated slag, were mixed with fibers. The changes in consistency of fresh fiber cement mortars and development of compressive and flexural strength of mortars in dependence on hardening time up to 90 days was studied. The development of compressive and flexural strength with increasing hardening time of cellulose fiber mortars and two binders with different properties confirmed that binder mixtures containing finely ground slag and recycled cellulose fibers achieved higher values of these strength parameters. Also adhesion testing of fiber cement mortars on two substrates (ceramic fitting and aerated concrete block) after 28 days of their application showed better adhesion of cement mortars with finely ground granulated slag on the ceramic fitting surface compared to the mortars containing finely ground limestone. However, any cracks have occurred on both substrates during the maturing of mortars with slag. Based on the above facts, it can be concluded that suitable plaster mixtures for their use in the interior appear the cement recipes with both cellulose fibers (wood pulp and fibers from recycled waste paper) and with finely ground limestone.

Abstract: With the innovations in the field of building materials production, some by-products or wastes are also generated. This is closely related to the need for adequate environmental treatment of these products. One such product is by-pass dust from cement production, which can be characterized as a fine-grained material consisting mainly of Ca, Mg, K, S and Cl oxides. Bypass dust has high alkaline reaction due to its composition; therefore careful research is needed to assess its properties and subsequent practical use in the construction industry. Preliminary results of composites prepared on the basis of bypass dusts and other selected fly ash are discussed. The main aim of the experiments was to verify the possibilities of bypass dust utilization as partial substitution of cement in the preparation of composites. The composites prepared with different water/cement coefficient were tested for compressive strength of 28 days of hardening. It has been shown that a mixture of bypass cement dust and selected ashes can be used as a partial binder substitution up to 33% weight of cement, which can represent considerable benefits for practice. Preliminary investigation at the same conditions revealed that water/cement coefficient will need to be optimized in further research.

Abstract: The article deals with the temperature of the fresh cement pastes (CP) prepared from various type of cement in connection to its consistency. The aim of the experiment was to simulate the real condition at a concrete mixing plant with the comparison of laboratory method of cement testing – test of water need for achieving the normal consistency. In the experiment, cement types CEM I 42.5 R, CEM II/A-LL 42.5 R, CEM II/B-S 42.5 N, CEM III/A 32.5 R and CEM III/A 32.5 N were used. Results from the previous experiment with CEM II/A-S 42.5 R were adopted. Particular water-cement ratios were determined within each of cement type and stayed the same for each of CP temperatures. Increasing of temperature of the CP was achieved by mixing water with various temperatures. Different behavior of consistency change with increasing of temperature within different cement composition was observed. Approach to methods of cement testing at the concrete plant as well as using different cement type in different season of the year in context of durability and sustainability were also discussed.

Abstract: The research was dealing use of ladle slag and its impact on the physical and mechanical parameters of hardened cement composites. The goal was to find a suitable percentage share of ladle slag used as an admixture. The results of compressive strength tests show the possibility of replacement of a significant amount of cements with a specific secondary product. A decrease in compressive strength of about 8% after 28 days has to be taken into account when using Portland cement CEM I 42.5R and a 10% replacement with ladle slag.

Abstract: This article presents the results of a study dealing with the use of a combination of recycled rubber from waste tires as a 100% replacement of aggregate and waste sludge water from a concrete plant as a partial replacement of mixing water in the production of cement composites. The aggregate was replaced with recycled rubber material in two ratios. The first ratio was 50/50 and the other one was a 40/60 ratio of fraction 0/1 mm and fraction 1/3 mm. The mixing water was replaced with waste sludge water from a concrete plant in the amounts of 25% and 50%. The designed cement composite formulas were subjected to the test of their physical and mechanical characteristics in order to determine the properties when using a combination of recycled rubber and waste sludge water from a concrete plant. The tested properties include: consistency of the grain curve, mixing water properties, consistency of cement mortar, strength characteristics (tensile flexural strength and compressive strength). The study presents the results that are fundamentally different from the comparative samples and their use in the building industry but, at the same time, they also open up new possibilities of their use as building material.

Abstract: Concrete has not only fulfilled the load-bearing function, but also its aesthetic function comes to the fore. It is precisely coloured concrete that performs this function best. The second phenomenon of today is "green concrete". In the paper, the properties of coloured concrete are compared with its "greener" alternative - coloured concrete with fly ash as a binder substitution. Experimental samples were measured for compressive strength and water absorption over a period of 7 days to 2 years. The results showed that the combination of coloured pigment and fly ash has an interesting synergistic effect, as evidenced by a 45MPa compressive strength and a 15% decrease of water absorption.