Apparent Activation Energy of Concrete in Early Age Determined by Adiabatic Test

The apparent activation energy of concrete in early age was determined by adiabatic temperature rise test with different initial temperatures. The influence of mineral admixtures such as fly ash, slag and silica fume on the apparent activation energy of concrete was investigated. The equivalent age that expresses the maturity of concrete was calculated to evaluate the cracking risk of concrete in structures. The results reveal that a substitution of 20% fly ash for Portland cement obviously decreases the apparent activation energy of concrete, however, a substitution of 10% silica fume for Portland cement increases the apparent activation. Finite element method analysis of a simulating concrete wall shows that the concrete containing 20% fly ash has the lowest cracking risk.

Mesocosmic study on autogenous shrinkage of concrete with consideration of effects of temperature and humidity

A study on the autogenous shrinkage （AS） of concrete from a mesocosmic perspective was carried out using numerical simulation technology. The temperature history and the autogenous relative humidity （ARH）, two factors that have been shown to have occasional influence on this process in previous studies, were introduced into this study. According to these concepts, a program for simulation of the temperature field, humidity field, and stress field based on the equivalent age method and a fully automatic aggregate modeling tool were used. With the help of these programs, the study of a small concrete specimen provided some useful conclusions： the aggregate and the matrix show distinct distribution properties in the temperature field, humidity field, and stress field; the aggregate-matrix interface has a high possibility of becoming the location of the initial cracking caused by AS of concrete; the distribution of random aggregates is extremely important for mesoscopical analysis; and the temperature history is the main factor affecting the AS of concrete. On the whole, inherent mechanisms and cracking mechanisms of AS of concrete can be explained more reasonably and realistically only by considering the different characteristics of material phases and the effects of temperature and humidity.

The Gross Motor Development Level of Children Aged 9 Years

The purpose of the study is to investigate the age group of children aged 9 years old who have experienced delays in gross motor development. Instrument used in this study is TGMD （test gross motor development）-2, Ulrich, which was adopted at the international level. Gross motor development data were obtained by video recording （Sony DRC-SR42 with a 40x optical zoom capability, and software Ultimate Studio 14） on locomotors and manipulative skills. A total n = 64 persons, children of 9 years （9.30± 0.43） at Mutiara Perdana Primary School, Bayan Lepas, Penang were involved as the subjects. The result of the study found that children aged 9 years old experienced delays in age equivalent locomotor score （4.61 ± 0.69）, age equivalent manipulative score （5.52 ±0.62） and gross motor development quotient （7.26 ± 2.14）.