Carbonation Depth Research Articles

INVESTIGATED THE CARBONATION BEHAVIOR OF CONCRETE BY ADDED GROUND GRANULATED BLAST FURNACE SLAG (GGBS)

Constructors and researchers have been concerned about carbonation because it has been a concern of the concrete by decreasing the interstitial solution's pH, it may encourage the reinforcement material deposition for reinforced concrete and subsequent corrosion. The use of geopolymeric materials, such as Ground Granulated Blast Furnace Slag (GGBS), is one of the factors that affect carbonation. This study explores the effects of replacement 0, 20, 40, and 60% from cement mass by GGBS on the physical and mechanical properties in particular, the carbonation of concrete. According to the results, it was observed that the higher the percentage of cement replacement with GGBS, the lower the carbonization depth, as the best result was achieved at the replacement ratio of 60%. As for the compressive strength, it increases with an increase in the proportion of cement replacement with GGBS. Moreover, the addition of GGBS reduced the water absorption.

A Carbonation and Chloride Induced Corrosion Model for Hot-dip Galvanised Reinforcement Bar Material in Concrete

This paper focuses on methodological issues relevant to corrosion risk prediction models. A model was developed for the prediction of corrosion rates associated with hot-dip galvanised reinforcement bar material in concrete exposed to carbonation and chlorides in outdoor environment. One-year follow-up experiments, over five years, were conducted at various carbonation depths and chloride contents. The observed dependence of corrosion rate on the depth of carbonation and chloride content is complex indicating that the interaction between the carbonation and chloride influencing the corrosion. A non-linear corrosion model was proposed with statistical analysis to model the relationship between the corrosion rate and the test parameters. The main methodological contributions are (i) the proposed modeling approach able to take into account the uncertain measurement errors including unobserved systematic and random heterogeneity over different measured specimens and correlation for the same specimen across different measuring times, which best suits the measurement data; (ii) the developed model in which an interaction parameter is introduced especially to account for the contribution and the degree of the unobserved carbonation-chloride interaction. The proposed model offers greater flexibility for the modelling of measurement data than traditional models.

Study on Mechanical and Microscopic Properties of Nickel–Copper-Contaminated Soil Solidified by Cement, Fly Ash and Desulfurization Gypsum Under Carbonization Condition

The engineering characteristics of remediated soil are easily affected by CO2 erosion in nature. However, there are limited investigations on the mechanical and microscopic properties of heavy metal-contaminated soil. This study introduces effect of accelerated carbonization on the mechanical and microscopic properties of nickel–copper-contaminated soil, and the soil has been treated with a novel curing agent, formed by mixing cement, fly ash and desulfurization gypsum (CFG). The objective of the study is to ascertain CO2 erosion resistance of nickel–copper-contaminated soil solidified by CFG. Using unconfined compressive strength (UCS) tests, carbonization depth, X-ray diffraction, and scanning electron microscopy, the sample’s characteristics are investigated under different carbonization times and heavy metal ion concentrations. The results demonstrate that the UCS of samples of Ni0Cu0, Ni0.02, and Ni0.4 decrease with the increasing carbonization time, while that of Ni1, Cu1, and Ni1Cu1 increase initially and then decrease; in addition, when the concentration of heavy metals is lower, the effect of carbonization on UCS of samples is more significant. Moreover, the carbonization depth of samples increases with the increasing carbonization time, and the prediction model is given. Furthermore, the microscopic analysis demonstrates that calcium carbonate is the main carbonization product. The decomposition of hydrated calcium silicate gel leads to poor integrity of the structure and more pores produced in samples, which is the main reason for the decrease of the UCS in the process of carbonization. The outcomes of this investigation provide a reference for the durability in practical engineering of heavy metal-contaminated soil solidified by CFG.

Microstructure of Portland cement paste subjected to different CO2 concentrations and further water curing

Understanding the effect of formed calcium carbonate and highly polymerization of silicates on the microstructure of cement paste exposed to early CO2 curing and further hydration process is crucial to comprehend the mechanisms of CO2 curing. In this paper, the cement pastes were further cured in water after CO2 curing under two CO2 concentrations (3% and 20%) and the carbonation depth, compressive strength, composition and morphology of the formed products were characterized. The results showed that calcite was the main product generated in CO2-cured pastes and its content was increased with the increasing CO2 concentration. The formed calcium carbonate provided additional nucleation sites and accelerated the hydration of C3S in further water curing. Furthermore, calcium carbonate was consumed by C3A to form calcium aluminate monocarbonate, which delayed the transformation of ettringite to monosulfate during further water curing. The decarbonation temperature of the formed calcium carbonate was increased with the increase of the CO2 concentration, but it was decreased in further water curing due to participating the further hydration process. The early carbonation curing improved the polymerization of silica gel, which was decreased in the subsequent hydration due to the formation of C-S-H. The CO2-cured sample showed higher early compressive strength and comparable long-term compressive strength compared to the conventional samples due to the lower porosity.

Study on the evolution of oxygenated structures in low-temperature coal tar during the preparation of needle coke by co-carbonization

Low-temperature coal tar is rich in oxygenated compounds which are hard to remove and make a great influence on the quality of needle coke. Low-temperature coal tar (LTCT) and decant oil (DO) were used to co-carbonize to prepare needle coke by liquid phase carbonization, and the evolution of oxygenated structures in LTCT during the preparation of needle coke was investigated. In the early stage of carbonization process, the C–OH/C–O/C–O–C functional groups were mainly transformed into COO– groups. With the deepening of carbonization depth, the COO– functional groups gradually converted into CO functional groups. The enrichment of aromatics and the introduction of high aromaticity material further promoted the conversion of oxygenated structures and the oxygen-containing crosslinking behavior. Excessive aromatic molecules provided active sites and free radicals for polycondensation and dispersed the distribution of oxygenated cross-linked structures in the whole carbonaceous structures, thus resulting into a more ordered lamellar orientation. This study provided theoretical basis for weakening the influence of the oxygenated structures on the quality of needle coke by enhancing aromatic content during co-carbonization.

Neural network model for predicting the carbonation depth of slag concrete

Neural network model for predicting the carbonation depth of slag concrete

Safety inspection system and comprehensive evaluation method for concrete structure of gas pipeline tunnel based on fuzzy mathematics

Regular safety inspections are an important guarantee to ensure the high-quality operation of concrete structures of tunnels. The Chinese West-east Gas Pipeline Project is large in scale and complex in construction environment. These tunnels are equipped with gas pipelines, and the concrete structural defects of the tunnels are continuously exacerbated during the long-term operation. There are few studies on the safety evaluation methods of concrete structures of gas tunnels. Based on the characteristics of the operation of the gas tunnels, this paper proposes the establishment of a structural safety comprehensive inspection system from the following seven aspects, that is, the void between the concrete lining and surrounding rock, the strength of the concrete lining, the thickness of the protective layer of the reinforced concrete lining, the carbonization depth of the concrete lining, the deformation of the tunnel section, the cracks in the concrete lining, and the auxiliary concrete structure of the tunnel. In addition, a corresponding quantitative determination method and safety level classification standard are established. Based on the fuzzy mathematics theory and a structural safety comprehensive inspection system, a five-level safety evaluation method for tunnel concrete structures is proposed. Finally, a comprehensive inspection and evaluation were carried out for a tunnel running across the mountain.

A modified numerical model for predicting carbonation depth of concrete with stress damage

A modified carbonation model centered on humidity-temperature-CO2 coupling was proposed. Its parameters were determined based on a 3-year natural carbonation test. The model was then verified by comparing carbonation results with that of accelerated experiment (2% and 20% CO2) and other publications. The effect of coarse aggregate, crack, and carbonation direction was investigated for undamaged concrete. The influence of stress damage (calculated by ABAQUS) and evaluating method was investigated for stress damaged concrete. The results indicated that the proposed model put more weight on the stress damage. It predicted the service life decreases to 1/3 of undamaged concrete for the example in this article.

Synthesis of rubberized Alkali-activated Concrete: Experimental and numerical evaluation

This paper evaluated feasibility of using the waste rubber tire crumbs (WRTCs) as partial replacement for the natural aggregates in production of alkali-activated rubberized concrete (AARC). Numerical model calculations using the neural network technique were performed to evaluate the overall performance of the proposed rubberized concretes in terms of the compressive strength, splitting tensile strength, flexural strength, water absorption, carbonation depth and impact resistance to dynamic load. The AARC modified with 30% of WRTCs as the natural aggregates replacement showed improved mechanical strength wherein the compressive strength after the curing age of 28 days was 30 MPa, indicating its suitability for diverse construction applications. Inclusion of WRTCs as substitute to the natural aggregates was shown to improve the concrete ductility.

Evaluation Carbonation Service Life of Mortar-Coated Concrete Considering Global Warming

Mortar finishing is frequently used to improve the carbonation service life of structural concrete. Moreover, carbonation is aggravated due to global warmings, such as the increase of CO2 concentration and temperature. This study shows a probability-based approach for evaluating the carbonation service life of coated concrete considering global warming. First, a carbonation model is proposed for assessing the carbonation depth of concrete with mortar finishing. The effect of global warming on carbonation is considered in the carbonation model. Second, a probability-based method is employed to determine the carbonation service life considering the thickness and mixtures of mortar finishing and substrate concrete. Based on the statistical analysis of calculation results, we find that for a concrete structural with 50 years’ service life, 15% service life will be reduced due to global warming.

Durability Performance of SCC and SCGC Containing Recycled Concrete Aggregates: A Comparative Study

This study assesses the behaviour of self-compacting geopolymer concrete (SCGC) with and without recycled concrete aggregates (RCA) by studying the rheological, mechanical and durability properties and comparison with self-compacting concrete (SCC). The idea of using RCA in geopolymer is to attain sustainable development goals, i.e., with less carbon footprint and the use of waste materials such as fly ash and RCA. Two types of concretes were prepared, namely “self-compacting concrete (SCC)” and “self-compacting geopolymer concrete (SCGC)”. Using each concrete type, two design mixes were prepared. The first mix contained 100% natural coarse aggregates (NCA), whereas, in the second mix, 30% NCA were replaced with RCA. The result of rheological properties indicated that the viscosity, passing ability, and segregation results of SCC and SCGC mixes were higher when NCA was partially replaced with RCA. Results of mechanical properties indicated that the increase in the compressive strength of the control mix of SCC (denoted as SCC-0) and SCGC mix (denoted as SCGC-0) at 28 days was 38.3% and 33.1% higher than those containing 30% RCA (denoted as SCC-30 and SCGC-30), respectively. The percentage increase in the compressive strength of SCC-0 and SCC-30 mixes was 20.24% and 13.45% higher compared to SCGC-0 and SCGC-30 mixes. The increase in the split tensile strength of SCC-0 and SCC-30 mixes was 9% and 21.74% higher than SCGC-0 and SCGC-30 mixes. The split tensile strength of control mixes SCC-0 and SCGC-0 is 47.73% and 55% higher than SCC-30 and SCGC-30 at 28 days, respectively. Durability performance of SCC and SCGC mixes was investigated by performing hydraulic permeability, accelerated carbonation, half-cell potential and pull-out tests at 28, 90, 180, 365, and 720 days, and were found inferior for SCGC mixes. The water penetration depth of SCGC-0 and SCGC-30 mixes was 5.71% to 16.1% and 10% to 18.6% higher than SCC-0 and SCC-30 mixes at 28 to 720 days. The carbonation depth in SCGC-0 and SCGC-30 mixes was 8.11% to 20.83% and 7.89% to 13.73% higher than SCC-0 and SCC-30 mixes at 28 to 720 days. The half-cell potential difference results for SCGC-0 and SCGC-30 mixes were 27.5% to 50% and 8.3% to 16.41% higher than SCC-0 and SCC-30 mixes at 28 to 720 days. The pull-out strength of SCC-0 and SCC-30 mixes was 11.36% to 29.5% and 8.3% to 38.97% higher than SCGC-0 and SCGC-30 mixes at 28 to 720 days, respectively. Overall, the mechanical and durability properties of SCC mixes were better than SCGC at the same exposure period.

Prediction of carbonation depth for recycled aggregate concrete using ANN hybridized with swarm intelligence algorithms

This paper investigates the prediction of carbonation depth for recycled aggregate concrete (RAC) with machine learning models. Nine parameters including RAC intrinsic properties and environmental conditions were considered as input variables. A dataset comprising 593 test data was used to train, validate, and test machine learning models. Results show that the Random forest model shows superior performance than the Gaussian progress regression model and standalone artificial neural network (ANN) model. All ANN models hybridized with swarm intelligence algorithms outperform the standalone ANN model, especially for the ANN model hybridized with the whale optimization algorithm. All machine learning models show higher accuracy than the existing code models and statistical models. The variable importance analysis shows that the carbonation resistance for RAC was determined by both internal and external factors. Based on the parametric analysis, the robustness of the proposed machine learning models was further confirmed.

Engineering properties of self-cured normal and high strength concrete produced using polyethylene glycol and porous ceramic waste as coarse aggregate

This study investigates the effect of curing regimes generally used for self-curing concretes (SC) on the engineering properties of normal strength concrete (NSC) and high-strength concrete (HSC). This study also examines the effect of exposing SC concrete to high temperatures up to 800 °C. This study applies five types of curing regimes. The first type is immersing concrete samples in a water tank. The second type is placing concrete samples in the air under lab conditions without curing. The third type is using different polyethylene glycol (PEG) doses by 1%, 2%, 3% and 4% of cement mass. The fourth type is using porous ceramic wastes aggregate (PCWA) as a course aggregate replacement by 10%, 15%, 20% and 25%. The fifth type is combining PEG doses by 1% and 2% with 10% of PCWA. Tests were conducted to investigate the mechanical properties of compressive, splitting, and flexural strength. The durability tests such as water absorption, water sorptivity, water permeability, chloride ion penetrability, carbonation depth and drying shrinkage were investigated. Weight loss and residual compressive strength tests were performed after exposure to high temperatures. The study recommends three self-curing regimes for NSC AND HSC based on a) compressive strength achieved, b) durability and c) mechanical and durability performance of concrete subjected to high temperatures. First: SC regime with a combination of 2% PEG and 10% PCWA achieved the maximum compressive strength of concrete that was reported to be 14.7% and 19.3% higher for NSC and HSC, respectively, compared to water immersion curing technique. Second: SC regime with a dose of 3% PEG (NCP3) achieved the optimum durability properties of NSC and HSC that were studied in this research. Third: SC regime, replacing coarse aggregate by PCWA up to 25%, that reduced the deleterious effects of high temperature on density loss and compressive strength.

Description of the concrete carbonation process with adjusted depth-resolved thermogravimetric analysis

AbstractThe thermal gravimetric analysis (TG) is a common method for the examination of the carbonation progress of cement-based materials. Unfortunately, the thermal properties of some components complicate the evaluation of TG results. Various hydrate phases, such as ettringite (AFt), C–S–H and AFm, decompose almost simultaneously in the temperature range up to 200 °C. Additionally, physically bound water is released in the same temperature range. In the temperature range between 450 °C and 600 °C, the decomposition of calcium hydroxide and amorphous or weakly bound carbonates takes place simultaneously. Carbonates, like calcite, from limestone powder or other additives may be already contained in the noncarbonated sample material. For this research, an attempt was made to minimise the influence of these effects. Therefore, differential curves from DTG results of noncarbonated areas and areas with various states of carbonation of the same sample material were calculated and evaluated. Concretes based on three different types of cement were produced and stored under accelerated carbonation conditions (1% CO2 in air). The required sample material was obtained by cutting slices from various depths of previously CO2-treated specimen and subsequent grinding. During the sample preparation, a special attention was paid that no additional carbonation processes took place. As reference method for the determination of the carbonation depth, the sprayed application of phenolphthalein solution was carried out. Microscopic analysis was examined to confirm the assumptions made previously. Furthermore, the observed effect of encapsulation of calcium hydroxide by carbonates caused by the accelerated carbonation conditions was examined more closely.

Cathodic Protection Range of the Embedded Sacrificial Zinc Anode for RC Member Deteriorated by Carbonation and Mixed Chloride

Much is left unknown about applicable conditions of the method or quantification of the cathodic protection range. In particular, little has been studied about how the range or effect of cathodic protection is influenced by such factors as the thickness of reinforcing bars (rebars) to be protected, combined deterioration by carbonation and mixed chloride, amount of chloride ions and carbonation depth. This study experimentally evaluated the effect of differences in the chloride ion content in concrete, the carbonation depth or the rebar thickness on the cathodic protection range of the embedded sacrificial anode method. The results of the experiment were that the smaller the carbonation depth, the amount of chloride ions or the rebar thickness, the larger the amount of depolarization of the rebars in the concrete to be protected was. That is, for corrosion protection of rebars near patch repair areas embedded with sacrificial anodes, it would be appropriate to make the steel surface area of components smaller and the salt damage environment less corrosive.

Accelerated carbonation of ternary cements containing waste materials

Limestone calcined clay cement has great potential for reducing the environmental footprint associated with cement production. Few studies have explored ternary cement (TC) carbonation or the production of TC-containing waste materials. This study investigates TC carbonation using supercritical carbon dioxide (ScCO2) as an alternative method to accelerate the process. TCs were produced from waste raw materials, including wastes of clay brick (WCB), clay tiles (WCT), marble (WM), and phosphogypsum (PG). The formation of phases before and after ScCO2 attack were analysed using TG/DTG/DTA, XRD-Rietveld, and FTIR. The axial compressive strength, Rockwell surface hardness, and the advance of the carbonation depth were determined for different TC pastes. The results show that the aforementioned wastes can be used as alternatives to natural sources of supplementary cementitious materials (SCMs) to produce TC. Using WCB to replace calcined clay in TC resulted in the highest quantity of carboaluminates among the investigated pastes, in addition to high axial compressive strength and resistance to attack by ScCO2. The properties of the TCs were similar to those reported for limestone calcined clay cement in the literature, presenting less durability than Portland cement (PC) under carbonation by ScCO2 in the applied conditions. The calcined clay/limestone ratio influenced the behaviour of the pastes through changes in the C–H content. Increasing this ratio increased the extent of carbonation of WCT pastes and decreased the extent of carbonation of WCB pastes. The sustainability of TC can be improved via the use of waste materials.

Analysis of different oil well cement slurry formulations exposed to a CO2-rich environment

Portland cement hydrated products exposure to carbon dioxide (CO2) results in physicochemical transformations which are deleterious for the cement matrix. Therefore, cement slurry formulations need to be designed carefully to handle situations where the hardened cement will be exposed to CO2, so optimized formulations need to be considered. The present study investigated different cement slurry formulations and different densities for each formulation, with all samples exposed to CO2 during periods of 30, 60 and 90 days. The densities studied were 15.8 ppg (1890 kg/m³), 16.5 ppg (1980 kg/m³) and 17.0 ppg (2040 kg/m³), for which the study started with a simple composition and other additives were put into the formulations, with the last being the most complex. Static sedimentation analysis, carbonation depth and area calculation were used to investigate the effects of carbonation on the systems, and the results showed that the optimized formulation designs presented the best results on CO2 attack in the highest densities of 16.5 ppg and 17.0 ppg. A proper formulation designed for application in CO2-rich wells is mandatory for the well integrity from the construction phase to abandonment.

Neural Network Method Based on Concrete Carbonation Depth Prediction

Carbonation is a typical disease that affects the long-term durability of concrete. In this paper, neural network toolbox in MATLAB software was employed to analyze sample parameters such as CO2 concentration, compressive strength, age and water-cement ratio in concrete carbonation research, and to predict the depth of carbonation. The results show that under the premise of setting reasonable parameters, the sample training results are satisfactory, the average error is about 7%∼14%, which basically meets the precision requirements of the preliminary identification of concrete carbonation depth.

Fire damaged box girder inspection and assessment and strengthening treatment

Based on a fire accident in a bridge of the Jinan-Qingdao high-speed railway, the preliminary damage assessment of the box girder was conducted through surface inspection, concrete strength testing, concrete carbonation depth testing and reinforcement protective layer thickness testing methods. Then a corresponding numerical model of the fire damaged box girder was created by the Midas software, and the heat transfer analysis and thermal stress analysis were carried out. The results showed that the fire damaged level of the box girder were Grade II (moderate damage). Finally, the corresponding reinforcement measures were recommended.

Assessment of a fire damaged reinforced concrete building

A proper condition assessment of reinforced concrete structure after a fire event involves field and la-boratory work to determine the extent of fire in order to design an appropriate and cost effective repair scheme. The present paper presents a case study where an attempt has been made to carry out a condition assessment of a fire damaged building in a systematic manner. The approach adopted broadly consisted of questioning of on-site per-sonnel, a detailed visual survey, on-site non-destructive / partially-destructive tests, collection of in-situ samples from site along with some laboratory based investigations on samples collected from site. Differential Thermal Analysis (DTA), X-Ray Diffraction (XRD) Analysis and Scanning Electron Microscopy (SEM) Imaging were con-ducted for microstructural characterization and analysis of concrete to correlate, corroborate and validate the results obtained through on-site assessment. Since the building was an old structure, carbonation depth in structural mem-bers was also evaluated. Finally, based on the visual inspections indicating the condition of surface and structural elements such as spalling, exposure and condition of reinforcement, cracks, honeycombing etc. along with Non-Destructive Test / Laboratory test results, the repair methodology of structural members are presented.