Evaluation of consistency properties of freshly mixed concrete by cone penetration test

This study is directed to evaluate the ability of using cone penetration test as a simple method to investigate the consistency level of fresh concrete. A cone of 30° apex angle attached with different load values was used. Eighteen concrete mixes divided into three groups were conducted. Three types of coarse aggregate were tried. Crushed dolomite, round gravel, and crushed basalt all of 20 mm maximum grain size were investigated. For each type of coarse aggregate, six levels of concrete consistency calibrated by standard slump test were tried. For the investigated mixes and at a specified consistency level, the displaced volume values were directly proportional to the applied load. The inclination of this relation is termed as the displaced volume rate (D.V). The results of cone penetration were analyzed and compared to the corresponding slump test values. The displaced volume per unit mass, bearing strength, as well as shear yield strength were the evaluated properties. The results introduce the cone penetration test as a simple instrument that could be adopted either at a laboratory or at site to evaluate fresh concrete workability. Moreover, it is being more sensitive compared to the well known slump test. It can simply and clearly distinguish between stiff mixes as well as floppy ones. Very useful numerical limits for the evaluated properties controlling the workability levels of very low, low, medium, high and very high were proposed

Performance of Portland cement mixes containing silica fume and mixed with lime-water

This study is planned to investigate the properties of Portland cement mixtures containing silica fume and mixed with saturated lime water. The conducted Portland cement mixes included three groups; cement pastes, cement mortars and cement concrete mixes. The main parameters were; type of mixing solution (water or lime-water) as well as the percentage of Portland cement replaced by silica fume. Consistency level, times of initial and final settings, compressive strength development, existence and intensity of CH crystals with age, pozzolanic activity as well as efficiency of the investigated matrices to delay the corrosion of embedded steel bars were the investigated properties. Test results show that using lime-water in mixing enhances consistency degree compared to the corresponding control mixes. Furthermore, it delays both initial and final setting times compared with traditional water due to the common ion effect principles. Moreover, combined use of lime-water and silica fume enhances the pozzolanic reaction that was identified by the strength development at both early and later ages. The existence of CH crystals for higher percentages of silica fume (up to 30%) for further reaction at later ages was observed by XRD results. Moreover, combined use of silica fume and lime-water ensures a high alkaline media around steel bars from the moment of ingredients mixing as long as later ages despite of pozzolanic reaction that was identified from results of chloride attack

Antifungal Thiazolidines: Synthesis and Biological Evaluation of Mycosidine Congeners

Novel derivatives of Mycosidine (3,5-substituted thiazolidine-2,4-diones) are synthesized by Knoevenagel condensation and reactions of thiazolidines with chloroformates or halo-acetic acid esters. Furthermore, 5-Arylidene-2,4-thiazolidinediones and their 2-thioxo analogs containing halogen and hydroxy groups or di(benzyloxy) substituents in 5-benzylidene moiety are tested for antifungal activity in vitro. Some of the synthesized compounds exhibit high antifungal activity, both fungistatic and fungicidal, and lead to morphological changes in the Candida yeast cell wall. Based on the use of limited proteomic screening and toxicity analysis in mutants, we show that Mycosidine activity is associated with glucose transport. This suggests that this first-in-class antifungal drug has a novel mechanism of action that deserves further study. © 2022 by the authors. Licensee MDPI, Basel, Switzerland