Potential reduction of concrete deterioration through controlled DEF in hydrated concrete

Delayed ettringite formation (DEF) is a chemical reaction with proven damaging effects on hydrated concrete. Ettringite crystals can cause cracks and their widening due to pressure on cracked walls caused by the positive volume difference in the reaction. Concrete may show improvements in strength at early ages but further growth of cracks causes widening and spreading through the concrete structure. In this study, finely dispersed crystallization nuclei achieved by adding air-entraining agent (AEA) and short vibration of specimens is presented as the main prerequisite for reducing DEF-induced deterioration of hydrated concrete. The study presents the method and mechanism for obtaining the required nucleation. Controlling long-term DEF by providing AEA-induced crystallisation nuclei, prevented excessive and rapid initial strength improvements, and resulted in a slight increase of compressive strength of fine grained concrete with only marginally lower density.

The use of drama to teach social skills in a special school setting for students with autism.

For children with autism, social challenges may be both part of the disability and a barrier to accessing education. This paper reports on a project which used drama to address such challenges by drawing on the social skills of non-autistic peers in a special school setting. The paper demonstrates how drama’s flexibility may be harnessed in order to help students support each other’s development of creative and communicative skills. Focusing on two children in particular, specific examples are given to illustrate how they participated in group work, made imaginative contributions to verbal and physical representations, and engaged with abstract ideas. The project’s outcomes suggest, given a concrete structure and an invitation to collaborate, drama can be a powerful learning medium for children with ASD. The conclusion reflects on the diverse meaning of inclusive practice which can be achieved within specialist settings.