The increasing focus on global climate change, the public and consumer preferences for “green” products and the associated markets in carbon credits have promoted the use of alternate cements in place of pure Portland cement binders. Using alkali activation method, waste materials such as fly ash and slag can be modified to replace ordinary Portland cement. In the present study, a combination of sodium hydroxide pellets and sodium silicate solution is used for the alkali activation of fly ash to prepare geopolymer cement. In the same way, a mixture of KOH (pellets) and K-silicate solution has been used with fly ash and slag (used in British Columbia, Canada) for comparison. Ambient temperature curing has been considered in addition to oven curing. Compressive strength tests indicate that both duration and intensity of the temperature affect the properties of the geopolymer. Higher intensity of the temperature accelerates the polymerization process much faster and gives higher compressive strength for the same duration of curing. On the other hand, longer duration of curing leads to improved hardened properties compared to shorter span at the same intensity. This paper presents data for curing done at ambient temperatures and the effectiveness of using potassium- and sodium-based solutions for geopolymer cement. Further recommendations for future work are also included.
The safety and serviceability of civil infrastructures have to be ensured either as part of a periodic inspection program or immediately following a given hazardous event. The use of digital imaging techniques to identify the deformed or deteriorated surfaces of structures is a substantial area of research and aims to investigate a number of unknown parameters, including damage quantification and condition rating. This manuscript illustrates the integration of previously developed fuzzy logic-based decision-making tools with the currently developed image processing algorithm to quantify the damage for the condition rating of civil infrastructures. The proposed integrated framework exploits visual specifics of different elements of the infrastructure to perform automated evaluation of structural anomalies such as cracks and surface degradation. Two different image segmentation tools, (1) bottom hat transform and (2) hue, saturation, color (HSV) thresholding, are applied to identify the surface defects. The developed image processing software is used with the fuzzy set framework proposed in the previous research to gauge the damage indices due to various deterioration types like corrosion, alkali aggregate reaction, freeze-thaw attack, sulfate attack, acid attack or loading, fatigue, shrinkage, and honeycombing. Case studies of a long-span bridge and a warehouse building are illustrated for concept validation. The refined comprehensive method is presented as a graphical user interface (GUI) to facilitate the real-time condition assessment of civil infrastructures.
This research presents the use of a total of five Non-Destructive Testing Techniques (NDTs) and their combination to detect and quantify subsurface simulated defects in Reinforced Concrete slabs. The NDT techniques were applied on a total of nine 1800 mm × 460 mm reinforced concrete slabs with varying thicknesses of 100 mm, 150 mm and 200 mm. Contour data maps from each technique were prepared. This Data article presents the Non-Destructive Testing Techniques’ specifications, experimental set-up and converted 2-Dimensional NDT data maps for reinforced concrete slabs with simulated damage. The experimental research shows that combining multiple techniques together in evaluating the defects give significantly lower error and higher accuracy compared to that from a standalone test. For more details on the accuracy model of the NDTs, refer to the full length article entitled “Sub-surface simulated damage detection using Non-Destructive Testing Techniques in reinforced-concrete slabs” https://doi.org/10.1016/j.conbuildmat.2019.04.223 Rathod et al., 2019.
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