The durability of cement bound minestone

The demand for road making materials continues to pressurise the supply of traditional good quality aggregates. Over the years, therefore, consideration has been given to alternative materials including industrial wastes. This thesis is concerned with potential use of Minestone, the by-product of coal mining, for the lower structural layers of pavement construction. Because of their clay like nature, Minestones do not merit consideration for such applications in an unbound state and, therefore, some form of stabilisation is necessary. Previous research has demonstrated that certain cement bound minestones, containing between 5 and 10 per cent cement, satisfy current Department of Transport requirements for use in pavement construction and, furthermore, they are not frost susceptible. However, doubts concerning the durability of cement bound minestones still remain. The thesis includes a review of both the cement and lime stabilisation techniques and also traces the origin and development of the methods used to assess the quality and durability of stabilised materials. An experimental study is described in which cement bound minestone specimens were subjected to a programme of tests which examined compressive strength, resistance to immersion, and resistance to freezing and thawing. The results of the tests were related to the properties of the raw materials. It was discovered that the response to cement stabilisation was governed mainly by the source of the minestone and, to a lesser degree, the cement content. It was also found that resistance in the durability tests was generally improved when the initial moisture content was raised above the optimum value. The result suggest that current methods for assessing cement stabilised materials are not appropriate to cement bound minestones. Alternative methods and criteria, based on volume change and retained strength following immersion and freeze-thaw tests, have been proposed. It is believed that these methods and criteria should also apply to other cement bound materials.

Mouse embryo culture induces changes in postnatal phenotype including raised systolic blood pressure

A key factor in the use of assisted reproductive technologies (ART) for diverse species is the safety of procedures for long-term health. By using a mouse model, we have investigated the effect of in vitro culture and embryo transfer (ET) of superovulated embryos on postnatal growth and physiological activity compared with that of embryos developing in vivo. Embryo culture from two-cell to blastocyst stages in T6 medium either with or without a protein source reduced blastocyst trophectoderm and inner cell mass cell number compared with that of embryos developing in vivo. Embryo culture and ET had minimal effects on postnatal growth when compared with in vivo development with an equivalent litter size. However, embryo culture, and to a lesser extent ET, led to an enhanced systolic blood pressure at 21 weeks compared with in vivo development independent of litter size, maternal origin, or body weight. Moreover, activity of enzymatic regulators of cardiovascular and metabolic physiology, namely, serum angiotensin-converting enzyme and the gluconeogenesis controller, hepatic phosphoeno/pyruvate carboxykinase, were significantly elevated in response to embryo culture and/or ET in female offspring at 27 weeks, independent of maternal factors and postnatal growth. These animal data indicate that postnatal physiological criteria important in cardiovascular and metabolic health may be more sensitive to routine ART procedures than growth. © 2007 by The National Academy of Sciences of the USA.