Effect of concrete carbonation on natural frequency of reinforced concrete beams

Abstract

We carried out an experimental investigation to study the influence of concrete carbonation on the natural frequency of simply supported reinforced concrete beams. A total of 10 reinforced concrete test beams and 12 concrete-carbonation test specimens were subjected to different accelerated carbonation stages for 0, 7, 14, 21, and 28 days. Modal tests were performed on reinforced concrete test beams after the accelerated carbonation stages. In order to reduce the effect of other factors on the modal tests, constant temperature, relative humidity, and boundary conditions of the test beams were maintained in the experimental process. The experimental results show a trend of the natural frequencies of reinforced concrete test beams to decrease with the increase in concrete-carbonation depths. With statistical analyses of experimental data, this study established the relationship between concrete-carbonation depths and natural frequencies. Fitting lines for the drop in natural frequencies and carbonation depths are obtained for the first four modal frequencies. Based on the analysis of the physicochemical processes of concrete carbonation, the main reason behind the drop in natural frequencies is the increase in mass after concrete carbonation. The percentage composition of increase in mass after complete carbonation is obtained based on the analysis of the physicochemical process. This analysis demonstrates part of the reason for the drop in natural frequencies and proves that the experimental results are reliable and credible. This study provides further insight into the use of modal parameters to assess damage in concrete structures in structural health monitoring.

An Investigation of the Ground Walnut Shells’ Addition Effect on the Properties of the Fly Ash-Based Geopolymer

“…The main factors affecting the rate and intensity of carbonation are humidity, and ambient carbon dioxide concentration-carbonation occurs most intensively when the surface of capillaries is covered with a thin film of water, which allows for rapid diffusion of carbon dioxide, which dissolves and reacts with calcium ions [ 49 ]. Moreover, high porosity [ 50 , 51 ], low density of the concrete mixture, and the method of concrete care [ 52 , 53 ] are mentioned as additional factors promoting carbonation in the literature. An analogous mechanism is encountered in the case of geopolymers; however, because of their chemical composition, the appearance of sodium carbonate heptahydrate on their surface may occur [ 54 ].…”

Experimental Study on the Relationship between the Natural Frequency and the Corrosion in Reinforced Concrete Beams

“…e impulse method was used to test natural frequency. e details of the dynamic test method are described in the previous related research [21].…”

“…Nandan and Singh [20] examined variations in the modal frequencies of concrete box girder and T-beam bridge structures caused by ambient temperature, solar irradiance, and wind speed, utilizing the environmental data recorded at a site in North Carolina, USA. Zhang and Sun [21] investigated the effect of concrete carbonation on the natural frequency of RC beams in an acceleration carbonation experiment. Many researchers have started to pay attention to research the effect of corrosion on natural frequency [22].…”

Local damage identification method using finite element model updating based on a new wavelet damage function

“…Two special stainless steel supports, one hinged and one sliding, are designed to ensure time-invariant boundary conditions. This beam belongs to one of the specimens in a carbonation test and more details can refer to Zhang and Sun (2016). The beam should remain undamaged before accelerated carbonation, so the local damage is simulated by loading an 8.56-kg concrete block, because mass increase can also change the modal parameters without introducing any real damage to the beam.…”