Papers by Keyword: Carbonation Depth

Abstract: During the research study focused on 100-year-old concrete bridges, a couple of them were found with a very low carbonation depth under an ordinary cement-based protective render coat (PRC). Phenolphthalein test showed at this place carbonation depth up to 2 mm. Bridge concrete was carbonated up to 80 mm, when a PRC spalled up. Close correlation between the surface permeability of a PRC estimated by the Torrent method and the carbonation depth of the base concrete beneath it, was observed. Most of the PRCs appeared to be almost impermeable showing the coefficient of permeability below 0.01 × 10^-16 m². The field experiments were replaced by those of laboratory-made aiming to a PRC development from currently available materials. For this purpose, material composition and rheological optimization of the PRCs were suggested and relevant tests performed. The PRCs applied to a surface of concrete panel were tested for permeability (Torrent method), adhesion (target) and crack propagation. The resistance to carbonation of the plain concrete C8/10 strength class according to EN 206 + A2 and those of PRC-protected were verified by an accelerated carbonation in 20 °C/60 % R.H./20 % vol. CO₂-exposure. By contrast, dry-air cure served as a reference cure. This article is mainly focused on the laboratory tests evaluation and explanation of the observed low carbonation of the base concrete covered by a PRC.

Abstract: Scrap tyres disposal revival the environmental concern except if recycled in an eco-friendly way. The inclusion of waste tyre crumb rubber (WTCRs) as a partial replacement of natural aggregate can be possible solutions for those concern. Thus, this study investigates the effect of using WTCRs at various contents (5, 10, 20 and 30% of volume) as a replacement agent of fine or/and coarse aggregate on water absorption, carbonation depth and chloride ion penetration rubberised concrete prepared with 20% ground blast furnace slag (GBFS) as Portland cement (OPC) replacement. Twelve batches are prepared by mixing the industrial wastes of GBFS and WTCRs. The results shown that modified rubberised containing 5% WRTCs as a substitute to natural aggregate, provided high durable performance such as lower water absorption, carbonation depth and chloride ion penetration compared to control specimen of traditional concrete. However, the rubberised concrete durability performance slightly trends to decrease with increasing WRTCs content from 5% to 30%, these proposed mix designs have a high potential for a wide variety of concrete industrial applications, especially in acid and sulphate risk.

Abstract: Four different material of activated carbon, i.e., coconut shell, fruit shell, wood and coal, were used to be mixed with concrete, the radon exhalation rates of concrete then was measured. At the same time, the pore distribution of activated carbon and some performances of concrete were tested. The results show that coconut shell carbon has the best effect for reduction radon exhalation rates of concrete, fruit shell carbon comes second. The adsorption mechanisms of activated carbon towards the radon gas in the solid and in the air are similar. Activated carbon have less effect on the strength of concrete, however, they have greater influence on the constructability and durability.

Abstract: Fly ash, silica fume and ground steel slag are chosen to make up composite mineral admixtures. Through the orthogonal test, carbonization resistance property of High Performance Concrete (HPC) mixed with composite mineral admixtures is studied. Test results show that the carbonization resistance property of HPC can be improved with defined amount of composite mineral admixture mixed, in addition, the effect of ternary composite admixture of ground steel slag, fly ash and silica fume is more obvious than that of binary composite admixture.

Abstract: This study presents an investigation into durability performance of concrete with various combinations of circulating fluidized bed combustion (CFBC) fly ash and coal-fired fly ash. All cylindrical specimens with the same binder content of 420 kg/m³ and water/binder ratio of 0.5 were cast and cured in the saturated limewater. Permeability test, sulfate attack resistance test, rapid chloride ion penetration test (RCPT) and carbonization test were performed. Test results demonstrate that the adding of CFBC fly ash and coal-fired fly ash would reduce the water permeability and chloride ions penetration, and increase the sulfate attack resistance, but an increase in carbonization depth. The carbonization depth increases with an increasing contents of CFBC fly ash and coal-fired fly ash. There exists a negative relationship between compressive strength and carbonization rate. Based on the test results, CFBC fly ash and coal-fired fly ash can be considered as cement replacement materials and employed in concrete.

Abstract: This study investigates carbonation properties of concrete mixed with alkaline potential water (APW). A miniature electrolyzer made up of diaphragm electrolytic cells was made to produce APW. Results show that APW concrete gains greatly in carbonation property - carbonation depth deepened by 21% in the 28day fast carbonation test. A new mold is developed to make concrete samples with spherical concaves which promised a smooth test surface to the sample, realizing the lossless test of concrete carbonation. A long term carbonation test (90 days) of concrete mixed with ARPW is carried out. Applying grey system theory, the time dependence rule, which decides the dynastic model of carbonation formula is studied, offering a more scientific basis for estimating the structural durability of concrete.

Abstract: The shajiang river bridge on the appearance test, concrete rebound detection, concrete cover depth detection, concrete carbonation depth detection, concrete chlorine ion content detection, and the detection results in statistics and analysis. Based on the bridge of the service the atmospheric environment parameters and testing data, the paper calculates and analyzes the main stress components the carbonation bridge reliability index and remaining life of carbide, assessing the bridge for the service life and reinforcement maintenance and offer the scientific basis.

Abstract: To study the impact of mineral admixtures and water-binder ratio on carbonization resistance of high performance manufactured sand concrete, high performance concrete of single mixed flyash, admixing silica fume and no admixture were compounded, carbonation depth of 3d, 7d, 14d and 28d was recorded by the way of indoor test. The test results show that with the decrease of water-binder ratio, carbonation resistance of high performance manufactured sand concrete increase, and when the concrete compressive strength is over 55Mpa, carbonation resistance is good, and when water-binder ratio is lower than 0.38, the impact of mineral admixtures on the carbonation resistance can be neglected.

Abstract: Though the introduction of light rail transit status and the reinforcement of prestressed track beams, this paper explored the carbonation mechanism of prestressed track beams, and analysised the main influencing factors of prestressed track beams. Based on concrete carbonation depth forecasting model, this paper analysised the carbonation law of of prestressed track beams in Chongqing, and proposed the durability design measures to prestressed track beams.

Abstract: It investigated the influence of superplasticizer on anti-carbonation property of different strength grade concrete with seven kinds of polycarboxylate superplasticizer. The results indicated that concrete carbonation property would be more impacted by superplasticizer for low-strength concrete. With the growth of the concrete strength, the impact gradually decreased. The anti-carbonation property of concrete could be improved by using an appropriate amount of compound mineral admixtures or lowing water-binder ratio.