Cement

About: Cement is a research topic. Over the lifetime, 68440 publications have been published within this topic receiving 829356 citations.

Influence of elevated temperatures on the mechanical properties of blended cement concretes prepared with limestone and siliceous aggregates

Abstract: The investigation performed was aimed at showing the influence of high temperatures on the mechanical properties and properties that affect the measurement by non-destructive methods (rebound hammer and pulse velocity) of concrete containing various levels (10% and 30%) of pozzolanic materials. Three types of Pozzolans, one natural pozzolan and two lignite fly ashes (one of low and the other of high lime content) were used for cement replacement. Two series of mixtures were prepared using limestone and siliceous aggregates. The W =b and the cementitius material content were maintained constant for all the mixtures. Concrete specimens were tested at 100, 300, 600 and 750 � C for 2 h without any imposed load, and under the same heating regime. At the age of 3 years, tests of compressive strength, modulus of elasticity, rebound hummer and pulse velocity were come out. Results indicate that the residual properties of concrete strongly depend on the aggregates’ and the binder type. Relationships between strength of concrete as well as rebound and pulse velocity versus heating temperatures are established. The above results are evaluated to establish a direct relationship between non-destructive measurements and compressive strength of concrete exposed to fire. � 2004 Published by Elsevier Ltd.

Trabecular bone response to injectable calcium phosphate (Ca-P) cement.

Abstract: The aim of this study was to investigate the physicochemical, biological, and handling properties of a new developed calcium phosphate (Ca-P) cement when implanted in trabecular bone. Ca-P cement consisting of a powder and a liquid phase was implanted as a paste into femoral trabecular bone of goats for 3 days and 2, 8, 16, and 24 weeks. The cement was tested using three clinically relevant liquid-to-powder ratios. Polymethylmethacrylate bone cement, routinely used in orthopedics, was used as a control. The Ca-P cement was easy to handle and was fast setting with good cohesion when in contact with body fluids. X-ray diffraction at the different implantation periods showed that the cement had set as an apatite and remained stable over time. Histological evaluation after 2 weeks, performed on 10 microm un-decalcified sections, showed abundant bone apposition on the cement surface without any inflammatory reaction or fibrous encapsulation. At later time points, the Ca-P cement implants were totally covered by a thin layer of bone. Osteoclast-like cells, as present at the interface, had resorbed parts of the cement mass. At locations where Ca-P cement was resorbed, new bone was formed without loss of integrity between the bone bed and the cement. This demonstrated the osteotransductive property of the cement, i.e., resorption of the material by osteoclast-like cells, directly followed by the formation of new bone. Histological and histomorphometrical evaluation did not show any significant differences between the Ca-P cement implanted at the three different liquid/powder ratios. The results indicate that the investigated Ca-P cement is biocompatible, osteoconductive, as well as osteotransductive and is a candidate material for use as a bone substitute.