Metakaolin Influence on Concrete Durability Properties

Mineral admixtures are being used today almost in all concretes partially, to improve workability, engineering properties and also to enhance durability of the concrete. These admixtures are industrial by-products. In the present study, mineral admixture such as metakaolin (MK) is replaced partially in cement to investigate permanence properties of concrete in terms of initial water absorption, final water absorption and confrontation to acid attack. Inorder to identify the durability properties, concrete of M30 grade was prepared. The mineral admixture content was varied from 0% to 30% by volume of cement with 10% gradient. In acid attack, 3% H2SO4 solution is used for curing of specimens and the corresponding weight losses (%) were evaluated for curing periods of 7 days, 14 days and 28 days. Both initial and final water absorptions of the metakaolin-modified concrete have been improved when metakaolin content was increased up to 10% advantageously. And, also weight loss was decreased when metakaolin content varied from 0% to 30%.

Regular finite decomposition complexity

We introduce the notion of regular finite decomposition complexity of a metric family. This generalizes Gromov’s finite asymptotic dimension and is motivated by the concept of finite decomposition complexity (FDC) due to Guentner, Tessera and Yu. Regular finite decomposition complexity implies FDC and has all the permanence properties that are known for FDC, as well as a new one called Finite Quotient Permanence. We show that for a collection containing all metric families with finite asymptotic dimension, all other permanence properties follow from Fibering Permanence.

Tensor products and direct limits of almost Cohen–Macaulay modules

We investigate the almost Cohen–Macaulay property and the Serre-type condition [Formula: see text] for noetherian algebras and modules. More precisely, we find permanence properties of these conditions with respect to tensor products and direct limits.

COARSE COHERENCE OF METRIC SPACES AND GROUPS AND ITS PERMANENCE PROPERTIES

We introduce properties of metric spaces and, specifically, finitely generated groups with word metrics, which we call coarse coherence and coarse regular coherence. They are geometric counterparts of the classical algebraic notion of coherence and the regular coherence property of groups defined and studied by Waldhausen. The new properties can be defined in the general context of coarse metric geometry and are coarse invariants. In particular, they are quasi-isometry invariants of spaces and groups. The new framework allows us to prove structural results by developing permanence properties, including the particularly important fibering permanence property, for coarse regular coherence.

Sequentially split ∗-homomorphisms between C*-algebras

We define and examine sequentially split ∗-homomorphisms between C*-algebras and C*-dynamical systems. For a ∗-homomorphism, the property of being sequentially split can be regarded as an approximate weakening of being a split-injective inclusion of C*-algebras. We show for a sequentially split ∗-homomorphism that a multitude of C*-algebraic approximation properties pass from the target algebra to the domain algebra, including virtually all important approximation properties currently used in the classification theory of C*-algebras. We also discuss various settings in which sequentially split ∗-homomorphisms arise naturally from context. One particular class of examples arises from compact group actions with the Rokhlin property. This allows us to recover and extend the presently known permanence properties of Rokhlin actions with a unified conceptual approach and a simple proof. Moreover, this perspective allows us to obtain new results about such actions, such as a generalization of Izumi’s original [Formula: see text]-theory formula for the fixed point algebra, or duality between the Rokhlin property and approximate representability.

On the category of near-rings

We consider the category of near-rings and study some categorical permanence properties. We investigate the connection between the concepts of monomorphism and, respectively, epimorphism of near-rings and the concepts of injective and, respectively, surjective morphism of near-rings. We also present some interesting properties of epimorphisms in the category of near-rings.