Fundamental Properties of Industrial Hybrid Cement Important for Application in Concrete

Hybrid cement (H-Cement/HC) takes advantages of the material properties of cement and alkali-activated cement with the resulting benefit on utility properties so that hybrid cement can replace in large quantities ordinary Portland cement (PC) as follows: H-Cement is used by the same way as traditional cements; H-Cement is suitable for use in ready-mixed concrete up to C30/37 strength class; H-Cement has shrinkage-reducing and alkali-aggregate-mitigating property; H-Cement shows the same sulphate resistance with sulphate-resistant Portland cement with C3A = 0; H-Cement is a suitable binder for use in concrete containing the swelling steel slag aggregate as a full replacement of natural aggregate. This low-energy, low-cost and environmentally friendly hybrid cement belongs to the group of advanced cements, in which parameters predetermine it to overcome PC serviceability in certain applications. The objective of this chapter is to characterize fundamental properties and some durability aspects of H-Cement in concrete

Mobility of Trace Elements in Pore Solutions of Portland Cement Pastes Exposed to Leaching

Two Portland cement pastes, CEM I 42.5R and CEM III/A 52.5N were exposed to leaching by soft water throughout a one–year hydration period. Mobility of trace elements was investigated by determination of their pore solution concentration in the course of time. Eleven trace elements were included in this research: antimony, arsenic, cadmium, chromium, cobalt, copper, mercury, nickel, lead, vanadium and zinc. The possible usage of the pore solution trace elements concentration in monitoring of deleterious leaching reactions and prediction of environmental risk was investigated. This work is licensed under a Creative Commons Attribution 4.0 International License

Research focused on low carbonation of concrete under old cement-based render

In-situ research and laboratory study of the concrete of old bridges shows that despite the low strength classes of concrete and the long time of exposure to CO2, it is possible to moderate the depth of their carbonation. Many old bridges were found during the in-situ survey in Slovakia, which showed negligible carbonation under an old cement render (PRC) even after more than 100 years of direct exposure to CO2. At the same time, it was found that if this protective layer was significantly damaged or missing in some places, the depth of carbonation of the same concrete reached considerable depths, locally 70-80 mm. The article presents and summarizes the findings from in-situ and laboratory research with a possible explanation of this phenomenon

LONG – TERM PROPERTIES OF CEMENT COMPOSITES WITH VARIOUS METAKAOLINITE CONTENT

The optimal temperature transformation of kaolin sand to metakaolin sand (MKS) resulting in complete conversion of kaolinite to pozzolanic active metakaolinite (MK) is 650°C in the time of 1 hour. To obtain information on mechanism of pozzolanic reaction in studied binary system, the cement pastes with two MKS at substitution level of Ordinary Portland cement (OPC) with MKS by 10, 20 and 40 wt. % corresponding to 3.6 - 16.0 % MK content in pastes, were tested. Pozzolanic reaction of MK with hydrating OPC was clearly confirmed mainly by XRD and thermal analyses. This process accompanied with gradual reduction of Ca(OH)2 content was the most intense in pastes with the highest MK contents (14.4 and 16.0 %). The decrease of micropore and total pore volume until MK content in paste of 7.2 % is measure of pore structure improvement specified as pore structure refinement. Until MK content of 8.0 % in paste, micropores portion with pore radius less than 10 nm rises and pore radius in the range between 10 and 100 nm declines. Resulted compressive strengths of related cement pastes with various MK content were comparable with strengths of pastes without MK. The obtained results confirmed that MKS can be used as promising additive in OPC to form prospective blended cements

The Resistance of New Kind of High-Strength Cement after 5 Years Exposure to Sulfate Solution

This article deals with the determination of technically important properties, the recognition of microstructure and pore structure, and the mortar resistance of a new cement kind NONRIVAL CEM I 52.5 N containing 7.94% wt. of C3A to 5% sodium sulfate solution. Both reference types of cement were industrially manufactured: 1) ordinary Portland cement CEM I 42.5 R and 2) Portland cement CEM I 42.5 R – SR 0, declared as sulfate resistant because of C3A = 0%. The research was carried out at standardized mortars. The used sodium sulfate solution, which contained 33802.8 mg of aggressive SO42− per liter, exceeded approximately 5 to 10 times the concentration of the third degree of aggressiveness of the XA chemical environment according to STN EN 206 + A1. The reference medium was drinking water. The 5-year results of non-destructive and destructive physical-mechanical tests as well as the formed microstructure and pore structure in both liquid media were evaluated. The cause of the NONRIVAL CEM I 52.5 N sulfate resistance was explained, despite the manufacturer’s declared C3A content of up to 8% by weight. Sulfate resistance of NONRIVAL CEM I 52.5 N is found comparable to that of sulfate resistant CEM I 42.5 R – SR 0

Low carbonation of concrete found on 100-year-old bridges

This work investigates an unexpectedly low carbonation depth found in two bridges. A protection against carbonation is ensured by approximately 2–3 mm thick dense plaster coat covering the outer surface of concrete. The plaster coat consists prevailingly of compact carbonate micro particles, showing no open pores and such a density, which gives this extremely thin layer non-permeability property for carbon oxide penetration over time. Keywords: Old bridge, Concrete, Carbonation, Plaster coat, Permeability, Durabilit

Design of Concrete Made with Recycled Brick Waste and Its Environmental Performance

In addition to the known uses of natural clays, less publication attention has been paid to clays returned to the production process. Industrially recovered natural clays such as bricks, tiles, sanitary ceramics, ceramic roofing tiles, etc., are applicable in building materials based on concrete as an artificial recycled aggregate or as a pozzolanic type II addition. In this way, the building products with higher added value are obtained from the originally landfilled waste. This paper details the research process of introducing concrete with recycled brick waste (RBW) up to the application output. The emphasis is placed on using a RBW brash as a partial replacement for natural aggregates and evaluating an RBW powder as a type II addition for use in concrete. A set of the results for an RBW is reported by the following: (a) an artificial RBW fine aggregate meets the required standardized parameters for use in industrially made concrete, (b) a RBW powder is suitable for use in concrete as industrially made type II addition TERRAMENT showing the same pozzolanic reactivity as a well-known and broadly used pozzolan-fly ash, and (c) such an RBW as aggregate and as powder are, therefore, suitable for the production of industrially made TRITECH Eco-designed ready-mixed concrete