Nondestructive Evaluation: Structural Performance of Masonry
Masonry is one of the world’s most durable construction materials. Masonry structures can remain in service for hundreds or even thousands of years. Masonry structures often outlive their designers, their original design documents, and their original functions. When historic masonry structures are evaluated for preservation, adaptive use, or additions, there are numerous questions that may arise about the construction and the condition of the brick, stone, concrete block, and mortar. One of the first questions typically asked by the design or investigation team is “How is it performing?” It is important to understand observed distress, such as cracks, corrosion, and surface erosion. Often the cause and/or extent of distress can play a major role in rehabilitation work and in determining what other types of nondestructive evaluation are required. Another common question about masonry is “How strong is it?” In order to conduct a structural evaluation, an engineer must have at least some information about the strength of the masonry. A related question often asked next is “How was it constructed?” Masonry characteristics such as ties, voids, headers, and embedded items are often hidden from view, but these items are critical to understanding how the assembly will perform. Finally, in some cases it is important to ask “What is it doing right now?” It can be vital to understand what types of loads and stresses the masonry is currently experiencing, especially in order predict future performance under new or different loads. Other questions regarding moisture permeability, acoustic properties, or thermal behavior of masonry may also arise. This Practice Point focuses on these fundamental questions by providing a summary of current nondestructive-evaluation tools available for the assessment of historic masonry. While case studies and descriptions of specific nondestructive test methods are fairly common, this article provides an overview of numerous techniques, both listing the technologies available and helping in the selection of an appropriate method. A wide range of evaluation methods are available for use, and many claims are made regarding the accuracy of Practice Points NUMBER 09
The pointing hardness tester — an instrument to meet a need
The quality of the pointing in recent brickwork is, at least in The Netherlands, often unsatisfactory. In the author's view an important cause may be that architects seem to be only interested in the aesthetic aspects of the pointing. Another significant reason may be, however, that until recently there was no effective method of measuring the quality of the work done. TNO Building and Construction Research (TNO-IBBC up to 1991) modified the Schmidt pendulum hammer P for plaster and aerated concrete. It can now be used by anyone in the building trade to measure the hardness of pointing in masonry— simply, quickly and reproducibly. The results are so good that the new measuring methodology deserves to be standardized. In anticipation of this a provisional classification is proposed based on several years' experience. The results of both laboratory investigation and practical work are presented.ResumeLa qualité du jointoiement dans les travaux en brique récents est souvents médiocre, tout au moins aux Pays-Bas. De l'avis de l'auteur, ceci séxplique par le point de vue uniquement esthétique de l'architecte. Cependant, ceci peut aussi être imputable à une cause sérieuse, l'absence jusqu'à une data récente de méthode de mesure eficace de la qualité du travail exécuté. L'Institut TNO pour la recherche dans le bâtiment et la construction (TNO-IBBC jusqu'en 1991) a modifié le scléromètre de Schmidt pour le plâtre et le béton cellulaire. Celui-ci peut maintenant être utilisé par quiconque dans la profession pour mesurer la dureté du jointoiement dans la maçonnerie, d'une façon simple, rapide et reproductible. Les résultats sont tellement satisfaisants que la nouvelle méthodologie de mesure mérite d'être normalisée. D'ici là, on propose une classification provisoire qui s'appuie sur plusieurs années d'expérience. On présente les résultants des études menées en laboratoire et du travail pratique.
Novel polymeric hydrogel composites: Synthesis, physicochemical, mechanical and biocompatible properties
In this research study, novel hydrogel composite films were constructed using different ratios of poly (vinyl alcohol) (PVA)/kappa-carrageenan (KC) (PVA90/KC10%, PVA80/KC20%, PVA70/KC30%, PVA60/KC40%) crosslinked with glutaraldehyde (0.025%) and investigated their physicochemical characteristics such as mechanical, thermal, morphological, swelling behaviour, and cell viability. SEM and FTIR revealed that surface morphology changed to heterogeneous and the presence of molecular interaction among the polymers. PVA90KC10 and PVA60KC40 exhibited smaller and larger pores on surface respectively. The change in the proportion of PVA and KC also triggered the tensile strength (Ts) of the film and the highest Ts observed were 21.60 MPa for PVA60KC40. Moreover, the thermal analysis showed three-phase degradation, and an increase in KC40 concentration results inversely proportional to a decrease in the rate of thermal degradation. Further, swelling and in-vitro biodegradation study confirmed the enhanced perseverance of water uptake for PVA60KC40 (286%) due to pores structure of the hydrogel film and PVA and KC alone degraded faster as compare to other films results suggested higher concentration of PVA90KC10 showed lower degradation rate and highest for PVA60KC40 about 6% and 22% respectively. Further, the cell viability was studied with MTT assay method by using NIH3T3 and HEK-293 cells for biocompatibility study revealed NIH3T3 cells were more biocompatible than HEK-293 and cell viability percent for PVA60KC40 showed the highest cell attachment about 99%. Overall corroborating data obtained from the study attested to the average swelling, appreciable mechanical characters, good interaction between molecules, and cell viability of the constructed PVA/KC hydrogel film, these all characters pave to be used as a potential template for biomedical applications such as tissue engineering and drug delivery.