h i g h l i g h t sPhysical properties of PVA. Application of PVA in cement-based composite materials. Effects of PVA on the engineering properties of cement-based composite materials. Effects of PVA on the microstructure behavior of cement-based composite materials. a r t i c l e i n f o t r a c tPolyvinyl alcohol (PVA) was created about 90 years ago as the first synthetic colloid and it has been used for various applications since then. One of the significant applications of PVA is in the building industry. It was found that PVA can be used as a modifier, aggregate surface pre-treatment agent and fiber reinforcement in cement-based composite materials. This paper provides a review on the physical properties of PVA and discusses on the effects of PVA towards the engineering properties of cement-based composite materials. The effects of PVA on the changes in the fracture surface, structure of the interfacial transition zone (ITZ) and composition in ITZ of cement-based composite materials are also presented. In addition, the needs in research for future development of PVA in the building industry are also addressed.

In Part I of this paper, a simple "pseudo-section analysis" method which accounts for second-order effects in a simply supported, externally prestressed beam subjected to two symmetrically applied concentrated loads was developed. In this paper, an experimental investigation of the flexural behaviour is reported. A total of nine simply supported prototype beams were tested to evaluate the effect of span-to-depth ratio and second-order effects. It was found that span-to-depth ratio has no significant effect on the flexural behaviour of the beams. For beams with spanto-depth ratio of up to 22.5, a single deviator provided at midspan section is effective in minimising second-order effects, that is, maintaining higher load-carrying capacity and ensuring ductility at the ultimate limit state for the beams. However, second-order effects prevailed in a longer beam with larger span-to-depth ratio of 30.0 despite the provision of a single deviator at midspan. This type of long beams would require at least two deviators placed at one-third span sections, hence reducing the deviator spacing in order to minimise second-order effects so that the beams would achieve the desired flexural performance with regard to beam strength and ductility. Theoretical predictions of the load-deformation responses using the proposed analytical model were found to agree well with the test results in this study and experimental data of other investigations.

Two features that distinguish an externally prestressed beam from an otherwise internally bonded, prestressed beam are: (i) the tendon stress depends on the overall deformation of the beam; and (ii) the tendons are free to move relative to the section depth, resulting in eccentricity variations defined as second-order effects. This paper presents a simple "pseudo-section analysis" method which accounts for second-order effects in simply supported, externally prestressed beams subjected to two symmetrically applied concentrated loads. The proposed method predicts the load-deflection curve and provides explicit expressions for the tendon stress, which can be used to evaluate the moment capacity of the beam by section analysis based on the bond reduction coefficient in strain compatibility.

A new approach that adopts the use of fuzzy adaptive resonance theory (ART) neural network in estimating high-performance concrete (HPC) mix proportion from experimental data is devised. The proposed model receives a set of desired concrete performances, searches for a set of mix proportions that is near to the desired concrete performances, classifies the mix proportions into clusters, measures the similarity between performances of deduced clusters with desired performances, and deduces a mix proportion. The proposed model was used to estimate the mix proportions of five batches of concrete based on the performance criteria of 7th and 28th day compressive strengths. The generated mix proportions were used in an experimental work and the errors were within 13% for 7th compressive strength; and 7% for the 28th day compressive strength, signifying the reliability of the fuzzy ART-based model in estimating the mix proportion of HPC. This article contributes to an alternative method of mix proportion estimation of HPC by avoiding the use of complicated function approximation techniques. NOTATIONSThe following symbols are used in this article: FDesired concrete performances ε Tolerance range q m

No abstract