Supersulphated cements are considered to be some of the first alkali-activated cements. Ground granulated blast-furnace slag is activated with a small amount of Portland cement in the presence of gypsum, providing C-S-H gel and ettringite as the main reaction products. These materials exhibit some good properties; the most important of these being good sulphate resistance and also good environmental effects. Standard EN15743+A1 "supersulphated cement" describes the conditions for the composition of this binder. In this paper, the product after desulphurisation (PPR) from the Třebovice heating plant (Ostrava) was used as a source of gypsum. Strength development was recorded up to 91 days for different ratios of compounds. Early strengths are very low and are higher for higher ordinary Portland cement content. At 28 and 91 days of age, the strengths are almost the same for gypsum contents from 10 to 20% and all cement contents (2.5, 3.75, and 5%). These strengths are relatively high—around 50 MPa. Supersulphated cements can be a good choice for the use of waste material—the product after desulphurisation.

The use of additions to replace cement in sprayed concrete applications is crucial in order to obtain matrices with proper mechanical properties and durability. Blast-furnace slag is not commonly employed to produce sprayed concrete because of its low reactivity. In this context, the objective of this study is to evaluate the chemical and mechanical properties of sprayed concrete produced with cement and blast-furnace slag as a partial cement replacement. Hydration kinetics were characterized by isothermal calorimetry, while mechanical properties were evaluated by needle penetration resistance and compressive strength of extracted cores. Results showed that slag was activated by accelerators and the resulting matrix fulfilled the requirements of the strength class J 2 . Therefore, blast-furnace slag may be used in sprayed concrete when the average strength class is specified.

The current exponential growth in cement demand and the gradual reduction in the availability of the supplementary cementitious materials (SCMs) conventionally employed in the cement sector (fly ash, blast furnace slag, etc.) have brought awareness over the need to find alternative sources of pozzolanic materials. Whereas the use of calcined kaolinitic clays (metakaolinite) could represent an excellent substitute for the traditional SCMs, the environmental and economic cost associated with kaolinite extraction thwarts the development of this course of action. Conversely, the clayey wastes obtained in the coal mining industry could represent an inexpensive and environmentally sound raw material for the production of recycled metakaolinite, promoting at the same time a Circular Economy model.

This work describes the physical and durable properties of binary mortars prepared with different substitution levels (20 % and 50 %) of thermally activated coal mining waste (600 ºC/2 hours), placing emphasis on their chloride resistance. The results show that the differences observed in the pore network and in the mineralogical composition of the blended matrices result in a superior resistance to chloride ingress and, therefore, in a decrease in the risk of corrosion of the subsequent structures and an increase in their service life.

This paper presents the results from tests examining the performance of high-strength concrete (HSC) and normal-strength concrete (NSC) columns subjected to blast loading. As part of the study six columns built with varying concrete strengths were tested under simulated blast loads using a shock-tube. In addition to the effect of concrete strength, the effects of longitudinal steel ratio and transverse steel detailing were also investigated. The experimental results demonstrate that the HSC and NSC columns showed similar blast performance in terms of overall displacement response, blast capacity, damage and failure mode. However, when considering the results at equivalent blasts, doubling the concrete strength from 40 MPa to 80 MPa (6 to 12 ksi) resulted in 10%-20% reductions in maximum displacements. On the other hand, increasing the longitudinal steel ratio from ρ = 1.7% to 3.4% was found to increase blast capacity, while also reducing maximum displacements by 40-50%. The results also show that decreasing the tie spacing (from d/2 to d/4, where d is the section depth) improved blast performance by reducing peak displacements by 20-40% at equivalent blasts. The use of seismic ties also prevented bar buckling and reduced the extent of damage at failure. As part of the analytical study the response of the HSC columns was predicted using single-degree-of-freedom (SDOF) analysis. The resistance functions were developed using dynamic material properties, sectional analysis and a lumped inelasticity approach. The SDOF procedure was able to predict the blast response of HSC columns with reasonable accuracy, with an average error of 14%. A numerical parametric study examining the effects of concrete strength, steel ratio and tie spacing in larger-scale columns with 350 mm x 350 mm (14 in. x 14 in.) section was also conducted. The results of the numerical study confirm the conclusions from the experiments but indicate the need for further blast research on the effect of transverse steel detailing in larger-scale HSC columns.

This paper provides an overview of simplified methods for dynamic blast analysis of structural members. The presented approach focuses on the use of a general simplified non-linear single degree of freedom dynamic model commonly used for typical flexural members such as slabs, beams or columns. The presented approach also allows modeling of members retrofitted against blast loading using fiber composites. The fiber composites considered in this paper include conventional Steel Fiber Reinforced Composites (FRC) as well as High Performance Fiber Composites (HPFRC). HPFRC’s include Short Steel Slurry Infiltrated Concrete (SIFCON), Long Continuous Slurry Infiltrated Steel Fibers Mat Concrete (SIMCON), and Fiber Reinforced Polymers (FRP). The model identifies different material parameters that affect the response of the structure. The effect of the material properties on the composite response is discussed within the framework of the existing blast-resistance guidelines and standards. Different retrofit techniques for existing concrete structures using fiber reinforced composites and the effect of varying the composite material properties on the response is presented. Final conclusions and recommendations are provided in terms of composite material’s properties, modeling performance and response. Specific limitations on their use is also discussed.