مدل سازی ستون های بتنی ژئوپلیمر مسلح
Abstract
1- Introduction
2- Experimental setup
3- Analytical model
4- Comparisons and discussions
5- Conclusions
References
Abstract
Glass fibre-reinforced polymer (GFRP) bar and stirrup reinforced geopolymer concrete (GPC) is increasingly recognised as a potential replacement to the conventional steel-reinforced ordinary Portland cement (OPC) concrete due to its superior durability. This paper proposed an analytical model to predict the load-displacement relationship of the concentrically and eccentrically loaded GFRP-GPC columns. The cross-section was divided into a number of strips and a strain gradient was assigned to determine the stresses in the cover, core and reinforcement. The theoretical predictions were then validated using experimental results from previous studies on the behaviour of GFRP-GPC, GFRP-OPC concrete and steel-GFRP concrete systems. It was found that the predicted peaks load, displacements at peak load and ductility indices were generally in close agreement with the experimental results of the GFRP-GPC columns. However, the model had a tendency to over-predict the stiffness of GFRP-OPC concrete and steel-OPC concrete columns in the elastic range. Overall, the proposed analytical model is suitable for GFRP-GPC systems and could facilitate the widespread use of this composite material.
Introduction
Corrosion causes millions of dollars of damage in steel reinforced concrete structures every year. The service life of such structure is critically affected without adequate corrosion protection, especially in harsh environments such as the coastal zones in Australia. Therefore, alternative construction materials were investigated to reduce the cost and maintenance of the structure. Geopolymer concrete (GPC) was considered to have better chloride and sulphate resistance than the Ordinary Portland Cement (OPC) concrete [1,2]. The GPC relies on the formation of an amorphous polymeric Si-O-Al framework instead of the calcium-silicate-hydrates (C-S-H) and calcium hydroxides (CeH) found in OPC matrix. The lack of CeH is advantageous as it actively reacts with the chlorides and sulphates, which in turn reduces the alkalinity in the matrix. The improved chemical stability means that the GPC will continuously provide protection to the embedded reinforcement, extending the service life of the structure. Due to the difference in microstructure, GPC has a lower elastic modulus than OPC concrete [3]. Glass Fibre-Reinforced Polymer (GFRP) is also gaining popularity due to its excellent corrosion resistance and high tensile strength. Unlike steel, the GFRP bars do not yield and could be assumed to possess a linear elastic behaviour until failure [4].