Application of response surface methodology for chloride transport properties in nano metaclayed-UHPC

The major concern on the deterioration of reinforced concrete structure is due to the corrosion of steel reinforcement from the aggressive environment such as chloride penetration. Ultra-high performance concrete (UHPC) is an advanced concrete material having ultra-high strength with excellent durability properties. Inclusion of nano metaclay in UHPC is expected to overcome the chloride transport properties in UHPC by providing nano filler effect. Two (2) assessments were conducted which are chloride content and chloride depth were examined. All the concrete specimens were immersed in 3% NaCl solution up to 365 days and the tests conducted were performed at 3, 7, 28, 56, 91, 182 and 365 days. Response surface method (RSM) was performed to evaluate the interaction and relationship between operating variables (compressive strength and nano metaclay content). Based on RSM analysis, inclusion of nano metaclay in UHPC have good relationship towards the chloride resistance characteristics and adequate durability performance in terms of chloride penetration resistance. The results exhibited that inclusion of 1% nano metaclay significantly and positively affect in term of chloride penetration resistance

Improved cluster partition in principal component analysis guided clustering

Principal component analysis (PCA) guided clustering approach is widely used in high dimensional data to improve the efficiency of K- means cluster solutions. Typically, Pearson correlation is used in PCA to provide an eigen-analysis to obtain the associated components that account for most of the variations in the data. However, PCA based Pearson correlation can be sensitive on non-Gaussian distributed data, which involve skewed observations such as outlying values. Thus, applying PCA based Pearson correlation on such data could affect cluster partitions and generate extremely imbalanced clusters in a high dimensional space. In this study, Tukey's biweight correlation based on M-estimate approach in PCA is used as an alternative to Pearson correlation. This approach is more resistant to outlying values as it examines each observation and down weight those that lie far from the center of the data. In particular two major features are highlighted: (1) fewer components are retained and imbalanced clusters at the recommended cumulative percentage of variation threshold is avoided; (2) the cluster quality with respect to external, internal and relative criteria as shown in Rand, Silhouette and Davies-Bouldin indices, outperform that of the clusters from PCA based Pearson correlation

Concrete-Filled Prefabricated Cementitious Composite Tube (CFPCCT) under Axial Compression: Effect of Tube Wall Thickness

Research on different prefabricated cementitious composites for constructing composite concrete columns is comparatively more limited than that of concrete filled steel tube columns. The main objective of this study was to observe the axial compressive behavior of concrete-filled prefabricated cementitious composite tube (CFPCCT) specimens. In the CFPCCT composite column, the spiral steel bar is arranged as a hoop reinforcement in the cementitious tube before its prefabrication. Following this, the concrete is poured into the prefabricated cementitious composite tube. The tube is able to provide lateral confinement and can carry the axial load, which is attributed to the strength of CFPCCT composite column. The effect of tube wall thickness on the behavior of CFPCCT is studied in this research. A total of eight short-scale CFPCCT composite columns, with three different tube wall thicknesses (25 mm, 30 mm and 35 mm), are tested under axial compressive load. The cementitious composite tube-confined specimens showed a 24.7% increment in load-carrying capacity compared to unconfined specimens. Increasing the wall-thickness had a positive impact on the strength and ductility properties of the composite column. However, poor failure behavior was observed for thicker tube wall. Therefore, concrete-filled cementitious composite tube columns can be considered as an alternative and effective way to construct prefabricated concrete columns

Exploratory Study of Rubber Seed Shell as Partial Coarse Aggregate Replacement in Concrete

Malaysia being a major rubber trees growing country has been generating a large amount of rubber seed shell which regarded as waste. At the same time, the growing construction industry which boosts the concrete production trade has results in higher consumption of natural coarse aggregate which open the door for depletion of this material in future. This study focuses on investigating the possibility of integrating crushed rubber seed shell as partial coarse aggregate replacement material in concrete making. Total of five mixes consisting various content of crushed rubber seed shell as partial coarse aggregate replacement ranging from 0, 5, 10, 15 and 20%, respectively were prepared in form of cubes. All the specimens were water cured before tested at 7 and 28 days. The workability test, compressive strength test and flexural strength test of the mixes was conducted in accordance to MS26 Part 1: Section 2, BSEN 12390 and ASTM 293-79 respectively. Generally, workability, compressive strength and flexural strength decrease with the increase in the crushed rubber seed shell replacement level. However, mix consisting around 10% of crushed rubber seed shell is suitable for the application in concrete work