Slag cement as a potential replacement for ordinary portland cement (OPC) could solve the global CO₂ emission problem from cement productions. However, such slag-based binders provide poor workability and require activation by alkali solutions. Unfortunately, so far no sufficiently performing superplasticizer has been identified for these alkali-activated slag (AAS) systems. In this study, a series of α-methallyl-ω-hydroxy poly (ethylene glycol) ether (HPEG)-based polycarboxylate polymers possessing different anionic charge density or side chain lengths was synthesized. Then, the solubility and dispersing performance of these polymers were tested in both sodium hydroxide (NaOH) and sodium carbonate (Na₂CO₃) activated slag systems. Specific HPEG-based PCE polymers with higher anionicity, shorter side chain length, and higher Mw were identified which provide outstanding dispersing performance in a NaOH activated slag system while none of polymers were able to increase fluidity in a Na₂CO₃ activated slag system. The possible reasons for such poor results in a Na₂CO₃ system are the solubility issue and the almost complete removal of calcium cations from the pore solution stemming from precipitation by the carbonate ions.

The rheology of alkali-activated materials is a very complex issue that is strongly influenced, among others, by the chemical nature of the alkaline activator. The most widely used are sodium and potassium compounds, but it is well-known that Na+ and K+ have different impacts on rheology, causing different behaviors of fresh mixtures. Therefore, in this study, the rheological parameters of NaOH and KOH activated slag were investigated, especially with respect to various hydroxide concentrations that ranged from 0 to 40% for both hydroxides. The pastes were tested in terms of flow table test and using a rotational rheometer equipped with a vane in cup geometry in both rotation and oscillation mode. Increasing concentrations of both hydroxides up to 20-25% resulted in a similar evolution of rheological properties in terms of increased flowability, but differed greatly for higher concentrations, as the beneficial effect of KOH was observed throughout the concentration range, while high concentrations of NaOH resulted in a dramatic increase in all rheological parameters, such as yield stress, consistency index, viscoelastic moduli or stresses corresponding to the limit of the viscoelastic region and flow point. The paper shows the potential of oscillatory tests to study the structural breakdown of inorganic binders.

Pavement subgrade is an in-situ material upon which the pavement structure is constructed. A soil with a high plasticity index will experience high shrinkage and swell depending upon its moisture content with detrimental impacts on its supported pavement structure. Removing and replacing the weak soil with better-quality soil is an alternative to stabilization of poor subgrade soil and may be a very expensive solution, typically for large road networks. Secondly, stabilization of weak soil -subgrade using conventional cement may not be sustainable due to its high CO₂ footprint. The feasibility of this non-conventional method using blended geopolymer binder for stabilization of weak subgrade soil was investigated compared to the conventional cement stabilization method. Laboratory testing of design mixes included unconfined compression test, maximum dry density, CBR and shrink & swell testing determining its feasibility and optimum extent. This research paper will present the findings on the effectiveness of blended geopolymer (fly ash and slag) as an alternative to conventional cement-based soil stabilizers for weak subgrade and its sustainability potential.

The present paper shows the study of a mixture design of the concrete used in the reinforced foundations of the bridge on the Straits of Messina in Italy. A cube compressive characteristic strength of 35 MPa (5,075 psi) is required for the foundation concrete. Due to the peculiar shape of the concrete foundations (completely embedded in the excavated ground), the damages caused by the thermal stress, the steel corrosion, and the alkali-silica reaction cannot be monitored and repaired. Therefore, a concrete structure must be designed without any damage for at least 200 years due to the very important role of this structure from a social point of view. In order to guarantee this long-term durability, there are two problems to be faced and solved: 1) the heat of cement hydration could cause cracks inside the foundation due to thermal gradients between the hotter nucleus of the massive structure and the colder peripheral areas; 2) the corrosion of the metallic reinforcements caused by the reaction between the metallic iron and the oxygen (O₂) present in the air to an extent of about 20%; 3) the alkali-silica reaction causing a local disruption in the concrete. All these problems can be solved using a blast-furnace slag cement such as CEM III B 32.5 R characterized by a very small heat of hydration and adopting a ground coarse aggregate with a maximum size as large as 32 mm (1.28 in): the choice of this aggregate produces a reduction in the amount of mixing water and then of the cement content and reduces the volume of the entrapped air at about 1.3% by concrete volume. This amount of O₂ would cause the corrosion of a negligible amount of iron corresponding to only 10 to 13 g (0.4 to 0.5 oz) of steel in 1 m³ (1.31 yd³) of concrete of each foundation. In order to prevent any ingress of air from the environment, the top of the foundation should be protected by self-compacting, self-compressing, and self-curing concrete.

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.