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International Concrete Abstracts Portal

Showing 1-5 of 706 Abstracts search results

Document: 

SP-350_15

Date: 

November 1, 2021

Author(s):

Wael A. Zatar, M. Ammar Alzarrad, Tu T. Nguyen, and Hai D. Nguyen

Publication:

Symposium Papers

Volume:

350

Abstract:

In this paper, the artificial neural network (ANN) method is utilized to predict ground-penetrating radar reflection amplitudes from four different inputs, namely, temperature, ambient relative humidity, chloride level, and corrosion condition on the surface of the reinforcing bar. A total of 288 ground penetrating radar (GPR) data points were collected from a series of chloride-contaminated concrete slabs under various environmental profiles that were used to train, validate, and test the proposed ANN model. The ANN model performed well in predicting the GPR reflection signals, with the overall coefficient of determination (R2) being 0.9958. The overall mean squared error (MSE) and root mean squared error (RSME) values are 0.015 and 0.122, respectively. These values are very low, which means that the ANN model has an excellent prediction capability. The research results show that the GPR reflection amplitudes are more sensitive to the temperature changes and chloride level parameters than the ambient relative humidity and rust condition on the reinforcing bar surface. Using the ANN method to predict the GPR reflection amplitudes is relatively new for structural concrete applications. This study paves the way for further developments of neural networks in civil and structural engineering.


Document: 

SP-349_51

Date: 

April 22, 2021

Author(s):

Erandi Ariyachandra, Sulapha Peethamparan

Publication:

Symposium Papers

Volume:

349

Abstract:

The utilization of recycled concrete as an adsorbent to sequester NO2 without additives or catalysts is an innovative, cost-effective, and sustainable approach to capture NO2 from targeted industrial facilities. During NO2 sequestration, alkaline products such as calcium hydroxide (CH) in the adhered old mortar of recycled concrete can react with NO2 to form Ca(NO2)2 and Ca(NO3)2. Thus, the use of NO2 sequestered recycled concrete aggregates (NRCA) as a constituent of concrete can be beneficial since Ca(NO2)2 and Ca(NO3)2-based chemical compounds are widely used as multi-functional admixtures for concrete applications. This study investigates the influence of the properties of the parent (demolished) concrete on the mechanical and durability performance of NRCA incorporated ordinary portland cement (OPC) concrete. Two types of recycled concrete aggregate (RCA) were derived from 2 and 20-year old concrete blocks to produce two types of NRCA—2-NRCA (2-year-old NRCA) and 20-NRCA (20-yearold NRCA) by exposing them to a humidified air/NO2 mixture (at RH = 50% and 23±2°C) for two weeks. NRCA was used as a partial replacement for natural fine aggregate in fresh OPC mixtures at 20% and 40% rates by volume. The influence of NRCA on concrete compressive strength, porosity, and long-term chloride diffusion coefficients were assessed. In addition, open-circuit and potentiodynamic polarization tests were conducted to evaluate the resistance to chloride-induced corrosion of steel in concrete. Control test mixtures containing a commercially available Ca(NO2)2 based corrosion inhibitorwere also tested for comparison purposes. Both types of NRCA enhanced the mechanical and durability properties of concrete compared to control mixtures. Test mixtures containing 2-NRCA showed better resistance against chloride-induced corrosion than concrete with 20-NRCA.


Document: 

SP-349_21

Date: 

April 22, 2021

Author(s):

Laura Caneda-Martínez, Moisés Frías, Mª Isabel Sánchez de Rojas, Javier Sánchez, and César Medina

Publication:

Symposium Papers

Volume:

349

Abstract:

The current exponential growth in cement demand and the gradual reduction in the availability of the supplementary cementitious materials (SCMs) conventionally employed in the cement sector (fly ash, blast furnace slag, etc.) have brought awareness over the need to find alternative sources of pozzolanic materials. Whereas the use of calcined kaolinitic clays (metakaolinite) could represent an excellent substitute for the traditional SCMs, the environmental and economic cost associated with kaolinite extraction thwarts the development of this course of action. Conversely, the clayey wastes obtained in the coal mining industry could represent an inexpensive and environmentally sound raw material for the production of recycled metakaolinite, promoting at the same time a Circular Economy model.

This work describes the physical and durable properties of binary mortars prepared with different substitution levels (20 % and 50 %) of thermally activated coal mining waste (600 ºC/2 hours), placing emphasis on their chloride resistance. The results show that the differences observed in the pore network and in the mineralogical composition of the blended matrices result in a superior resistance to chloride ingress and, therefore, in a decrease in the risk of corrosion of the subsequent structures and an increase in their service life.


Document: 

SP-349_45

Date: 

April 22, 2021

Author(s):

Bakhta Boukhatem, Ablam Zidol and Arezki Tagnit-Hamou

Publication:

Symposium Papers

Volume:

349

Abstract:

This study presents an accurate corrosion prediction through an intelligent approach based on deep learning. The deep learning is used to predict the time-to-corrosion induced cover cracking in reinforced concrete elements exposed to chlorides ions. The key parameters taken into consideration include thickness, quality and condition of the concrete cover. The prediction performance of the deep learning model is compared against traditional machine learning approaches using neural network and genetic algorithms. Results show that the proposed approach provides better prediction with higher generalization ability. The efficiency of the method is validated by an accelerated corrosion test conducted on 91 and 182-day moist cured reinforced fly ash concrete samples with different water-to-binder ratios. The results are in agreement with the model predictions. They also show that using the proposed model for numerical investigations is very promising, particularly in extracting the effect of fly ash on reducing the extent of corrosion. Such an intelligent prediction will serve as an important input in order to assist in service life prediction of corroding reinforced concrete structures as well as repair evaluation.


Document: 

SP-345_02

Date: 

February 1, 2021

Author(s):

Jan Bielak, Norbert Will, Josef Hegger, and Sven Bosbach

Publication:

Symposium Papers

Volume:

345

Abstract:

Textile-reinforced concrete (TRC) combines high-performance fabrics made of impregnated carbon yarns with state-of-the-art high strength concrete. Due to the corrosion resistance of non-metallic reinforcement, the application of TRC for external components especially with freeze-thaw and de-icing salt exposure is promising. This allows for reduction of concrete cover, to create slender structural elements and to execute thin slabs without additional waterproofing or protective decking. Different existing theoretical models and experience from various research projects were used in design of several pedestrian- and road bridges in Germany. The pedestrian bridges in Rems Valley and Ottenhöfen use TRC slabs without shear reinforcement as transversal loadbearing component. For the road bridges in Gaggenau, skew slabs made of TRC with shear reinforcement were chosen as principal structural system. Prior and during construction, experimental investigations on shear capacity were performed at the Institute of Structural Concrete (IMB) of RWTH Aachen. A comprehensive characterization of the material properties of the non-metallic reinforcement is a prerequisite for transfer and adaption of existing design rules, e.g. the determination of tensile strength of the bent portion of pre-formed shear reinforcement. This paper highlights the application potential and further challenges for the use of textilereinforced concrete in new engineering constructions.


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