Borders and Boundaries in Markets: A Sociocognitive Approach for Market Definition and Implications for Antitrust

Categorical distinctions are foundational to firm competition and regulation. Yet, market categories are notoriously difficult to define. The question of how to delineate markets is well-worn in the antitrust literature but is now the focus of a growing sociocognitive literature in strategy and organizational sociology.1 Historically, there has been little cross-pollination between these research areas. More integration, however, may be increasingly important in modern markets, where change is rapid, new technologies are key differentiators in many traditional industries, and platform competition is on the rise. In this paper, I introduce recent theoretical and empirical advances in sociocognitive research on categories in markets. I describe a theoretical model that incorporates the probabilistic nature of how people categorize, ambiguity in category boundaries, and that multiple audiences are relevant in most markets. Empirically, researchers employ a range of approaches to represent these aspects of market definition, from qualitative studies, to surveys, to computational approaches that leverage recent advances in machine learning applied to large corpora of text. I discuss key implications from this theoretical model and how they might inform market definition in antitrust

Rheological behavior of fresh inorganic polymer paste: Polymer bridging effect of the alkali silicate solution

Inorganic polymers (IP), produced by alkali activation of a glassy precursor, have been mainly investigated on their microstructure and mechanical strength properties. However, it is important to understand how the IP flow behaves under shear conditions, in particular when pumping is required. The activating solution is one of the main parameters influencing rheology. Therefore, the physical effect of the silicate structure on the rheology was investigated by varying the SiO2/Na2O molar ratio from 1.4 to 2.0 in the activator. The elastic and rheological properties of the IP were measured with a rheometer. In order to investigate the activator silicate structure and IP polymerisation development, Fourier Transform Infrared Spectroscopy (FTIR) and Nuclear Magnetic Resonance Spectroscopy (NMR) were performed. A decrease in elasticity was monitored for IP with a low SiO2/Na2O ratio as a result of the dissolved species, which can be correlated to NMR. The FTIR spectra implied that an activating solution with a higher SiO2/Na2O ratio resulted in the formation of a 3D silicate network with Q3 and Q4 crosslinks. The presence of a network modifier in the activating solution, such as Na, resulted in more Q1 and Q2 crosslinks. A higher stress, at a shear rate of 0.1 s-1; was observed in IP which consisted of a 3D silicate network as a result of the polymer bridging effect between the particles. A stronger shear thinning was observed in an IP with a higher SiO2/Na2O ratio, due to the steric hindrance from the entangled silicates. The rheological data of the IP can be fitted with the Herschel-Bulkley model

Influence of the type of alkaline activator on the reactions and mechanical properties of autoclaved bauxite residue-based monoliths

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Mixture optimization of an alkali-activated steel slag to maximize binder strength using optimal design of experiments

The diversity of precursors suitable for alkali activation demands a flexible methodology to study the properties of alkali-activated binders. Optimal design of experiments (ODOE) [1] allows a systematic and efficient exploration of effects and interactions among mix components and processing conditions, a situation commonly found during proportioning studies. Moreover, the ODOE algorithms provide sets of experiments of an optimized size that consider all the factors studied at the same time, a key feature to detect absolute maximums (or minimums) of a response. In this case, the strength-optimized proportioning for basic-oxygen-furnace (BOF) slag specimens activated with NaOH solutions was determined. The impact of solution molarity ranging from 0M (only water) to 0.5M and the additions of gypsum (2 to 6 wt%), Portland cement (0 to 10 wt%) and 0.2 wt% of a commercial plasticizer (polycarboxylate-based dispersant) were mapped. Proportions tested were selected running ODOE software using an I-optimality criteria algorithm, which minimizes the average variance of model prediction. A response surface model (RSM) for 28-day strength was defined. Paste and mortar specimens were produced with the predicted proportioning of highest strength and its binding matrix was characterized and compared with low-strength samples using X-ray diffraction (XRD), secondary electron microscopy (SEM) and infrared spectrometry (FTIR). The results obtained confirm that the methodology generates a model able to predict mechanical response, detecting general trends, high impact factors and interactions. More important, the optimal experimental design can be used to effectively study changes in the binding matrices and link them to the binder’s mechanical performance. Please click Additional Files below to see the full abstract

HYDRAULIC AND LEACHING BEHAVIOUR OF BELITE CEMENTS PRODUCED WITH ELECTRIC ARC FURNACE STEEL SLAG AS RAW MATERIAL

Three belite-rich cements consisting of a clinker made with 0 (BC), 5 (BC5) and 10 wt. % (BC10) electric arc furnace steel slag (EAFS) as raw material, were studied for their hydraulic and leaching behaviour. Hydration behaviour was studied by FTIR, TG/DTG and SEM analyses. The cements with EAFS resulted in a higher C2S/C3S and C4AF/C3A ratio compared to the reference body. As a result, the rate of hydration was low at early days whereas the structure was porous with scattered AFm and C–S–H crystals. At 28 days, a comparable dense microstructure consisting largely of C–S–H is observed in all mortars. Leaching was studied for V and Cr by means of tank test according to standard NEN 7345. The results showed V release below 2 μg/l. Chromium release calculated per 24 h was 1.4 μg/l in BC5 and 2.4 μg/l in BC10, which is much lower than the parametric value of 50 μg/l specified by the European Directive for drinking water (98/83/EC)

Inorganic polymer cement from Fe-Silicate glasses: Varying the activating solution to glass ratio

Large volumes of Fe-silicate glasses - slags - are produced as residues of metal production and waste treatment processes. It would be interesting if these materials could become an alternative group of precursors for the synthesis of inorganic polymer (IP) cements. This paper investigates the polymerisation of Fe-silicate glasses of composition (in wt%) SiO2: 40; FeO: 30; CaO: 15; Al2O3: 8 and an activating solution of composition (in wt%) Na2O: 15; SiO2: 13; H2O: 72. The mass ratio of the activating solution to the glass (L/S) was varied from 0.3 to 1.0 and the effect on the IP chemistry, microstructure and properties was investigated. Despite the high Fe and low Al contents of the glass, an IP cement could be synthesised, resistant to water dissolution and delivering mortars of compressive strength >52 MPa after 28 days curing at room temperature when using a L/S ratio of 0.45. Lowering the ratio from 1.00 to 0.45 results in a significant improvement in compressive strength, a lower porosity and when immersed in water, Na dissolution is decreased and water pH is lower. Microstructural investigation indicates that when the amount of activating solution is decreased, the degree of glass dissolution is lower resulting in less IP formation and a more homogeneous IP chemistry. Compared to higher L/S ratios, the IP mortar has a more densely packed microstructure of partially dissolved glass and sand aggregates bound by the IP matrix. At lower L/S ratios, the formation of micro scale shrinkage cracks in the IP matrix is strongly reduced, while at higher L/S ratios, shrinkage cracking is more pronounced and individual micro-cracks connect to form more pronounced large scale cracks. At a L/S ratio of 0.45, the IP cement is composed of 90 wt% Fe-silicate glass and only 10 wt% Na-silicate (% of powder mix) and it is indicated that this percentage can still be reduced. As 90 wt% of this IP cement is composed of a waste material and as curing is performed at ambient temperatures, its production is expected to have important ecological and economic benefits.status: publishe

INCREASING THE DIMENSIONAL STABILITY OF CAO-FEOX-AL2O3-SIO2 ALKALI-ACTIVATED MATERIALS: ON THE SWELLING POTENTIAL OF CALCIUM OXIDE-RICH ADMIXTURES

Advanced thermochemical conversion processes are emerging technologies for materials\u2019 recovery and energetic conversion of wastes. During these processes, a (semi-)vitreous material is also produced, and as these technologies get closer to maturity and full-scale implementation, significant volumes of these secondary outputs are expected to be generated. The production of building materials through the alkali activation of such residues is often identified as a possible large-scale valorization route, but the high susceptibility of alkali-activated materials (AAM) to shrinkage limits their attractiveness to the construction sector. Aiming to mitigate such a phenomenon, an experimental study was conducted investigating the effect of calcium oxide-rich admixtures on the dimensional stability of CaO-FeOx-Al2O3-SiO2 AAMs. This work describes the impacts of such admixtures on autogenous and drying shrinkage, porosity, microstructure, and mineralogy on AAMs. Drying shrinkage was identified as the governing mechanism affecting AAM volumetric stability, whereas autogenous shrinkage was less significant. The reference pastes presented the highest drying shrinkage, while increasing the dosage of shrinkage reducing agent (SRA) was found to reduce drying shrinkage up to 63%. The reduction of drying shrinkage was proportional to SRA content; however, elevated dosages of such admixture were found to be detrimental for AAM microstructure. On the other hand, small dosages of calcium oxide-rich admixtures did not induce significant changes in the samples\u2019 mineralogical evolution but promoted the formation of denser and less fractured microstructures. The results presented here show that calcium oxide-rich admixtures can be used to increase AAM\u2019s volumetric stability and an optimal dosage is prescribed