Study on Cr(VI) Leaching from Cement and Cement Composites

This paper reports an experimental study on hexavalent chromium leaching from cement samples and cement composites containing silica fume and zeolite additions that were subjected to various leaching agents. The water-soluble Cr(VI) concentrations in cements ranged from 0.2 to 3.2 mg/kg and represented only 1.8% of the total chromium content. The presence of chromium compounds with both chromium oxidation states of III and VI was detected in the cement samples by X-ray photoelectron spectroscopy (XPS). Leaching tests were performed in a Britton-Robinson buffer to simulate natural conditions and showed increased dissolution of Cr(VI) up to 6 mg/kg. The highest amount of leached hexavalent chromium was detected after leaching in HCl. The findings revealed that the leaching of chromium from cements was higher by 55–80% than that from the cement composites. A minimum concentration was observed for all cement samples when studying the relationship between the soluble Cr(VI) and the cement storage time

The study of concrete properties prepared with a proportion of fly ash

The current annual worldwide production of by-products is estimated about 700 million tons of which 70 % is fly ash at least. Large quantities of fly ash are available at low costs around the world and its use in concrete seems to offer the best solution to reduce its consumption. With regard to these facts and Slovak needs, the chemical and mechanical properties of hardened concrete composites with various share of fly ash were studied. Other focus of this study is the investigation of the influence of different chemical admixtures on development of the concrete properties, their environmental and economic impacts

Diastasis of Rectus Abdominis Muscles in Low Back Pain Patients

Background: Abdominal muscles are important spinal stabilizers and its poor coordination, as seen in diastasis of rectus abdominis (DRA), may contribute to chronic low back pain (LBP). However, this has not yet been studied directly. Objectives: To conduct a pilot study to examine the association between DRA and LBP. Methods: Using a digital caliper, standard clinical DRA measurement was performed in 55 participants with and 54 without chronic LBP. Results: Participants were on average 55 years old, 69 (63%) were women. Among the 16 participants with DRA, 11 (69%) had chronic LBP; among the 93 participants without DRA, 44 (47%) had LBP. Among men, 7 of 9 (77%) with DRA had LBP and 14 of 31 (45%) without DRA had LBP. Among women, 4 of 7 (57%) with DRA had LBP and 30 of 62 (48%) without DRA had LBP. BMI was the strongest correlate of DRA and may explain the relation between DRA and chronic LBP. Conclusions: DRA and LBP may be interrelated, especially among men. This may be a function of greater BMI in individuals with chronic LBP. Understanding the association between DRA, LBP, and BMI may have important implications for treatment of LBP and for intervention