Determination of alkali-silica reaction effects of zeolitic tuff addition on the different aggregates

The aim of this study is to determine the alkali-silica reaction (ASR) related characteristics of crushed stones that are produced from rocks of perlite, andesite and limestone when zeolitic tuff (ZT) is used in the mortar mix as cement replacement in different ratios. Accelerated mortar bar experiments in accordance with ASTM C 1260 were carried out on crushed stone aggregate samples to determine the ASR. CEM I 42.5 R type cement was replaced by ZT material in the following ratios: 0, 10, 20, 30 and 40%; in order to investigate the effects of replacement on the ASR pertaining to the aggregate types, 45 mortar bar pieces were produced. The length change values of the samples were measured on the 3, 7, 14, 28, 42, 56 days according to the accelerated mortar bar method. Measured length changes for the control samples on 14th day were found to be 0.570% at the level of potentially harmful for perlite, 0.101% at the level of critic for andesite and 0.061% at the level of harmless for limestone. Length changes at the harmful levels were taken under control for perlite at 30 and 40%, for andesite at 20, 30 and 40% ZT replacement ratios. Length change values of all samples decrease as ZT replacement increases. As a result, ZT replacement is effective to suppress the ASR of reactive aggregates

Cyclic lateral behavior of friction stir spot welds of AA2219 aluminum alloy: impact of inherent flow defects

Structural damage and fatigue life of engineering materials are controlled by inherent defects and the nature, level, and location of applied external loads. This paper studies the effect of cyclic lateral loads on the pinless and conical-pin assisted friction stir spot welds of AA2219 alloy. The results reveal the presence of upward-flow induced hook defect and outstretching-flow induced microscopic toe-notch in the conical pin and pinless welds, respectively. Extruded flash root contributed to the fracture pattern of the conical pin welds while it did not influence the fracture of the pinless weld. Grain refinement, microhardness, and microscopic toe-notch affect the fracture mode of pinless weld whereas complex fracture morphology ensues in conical pin weld. A decrease in the cyclic lateral stress level improves the lateral fatigue lives of both weld categories. Lateral fatigue improvement of welds requires the minimization of inherent nugget defects and extruded flash

On the structure of the particle source in ultrarelativistic nuclear collisions

In previous work some evidences were given for particle source structures. In the present work we use simulation with HIJING code to analyze the possibility to find such structures in Au-Au collisions at RHIC - BNL available energies. We used the program CRAB (Scott Pratt from Michigan State University, USA). For different impact parameters we calculate the correlation function. A few peaks in correlation function are observed. For these peaks we analyzed the correlation function by fitting with some adequate functions. We can conclude that there are conditions that in Au-Au collision at CMS energies between 56 A GeV and 200 A GeV the particle source has internal structure. The correlation function offers information on the space-time characteristics of the particle source, too. (authors