Water Absorption Of Aggregate Research Articles

Effect of Silane Coupling Agent Treatment of Aggregates on Mortar Workability, Strength and Interfacial Microscopic Properties

In this study, 3-aminopropyltriethoxysilane (KH550) and vinyltrimethoxysilane (KH171) were used to modify aggregates and prepare aggregates with different surface wettability. The effect of silane coupling agents on aggregate surface properties was characterized through FT-IR, XPS, contact angles and aggregate water absorption. The influence of the aggregate’s surface wettability on the interface properties was discussed using MIP, SEM, BSE and nanoindentation, and then the influence mechanism of the interface microscopic properties on the macro-properties of mortar was revealed. The results showed that the type of silane has an intense impact on the surface properties of aggregates. KH550-modified aggregates increased the contact angle from 23.6° to 59°, while KH171-modified aggregates increased it from 23.6° to 91.6°. Silane-modified aggregates reduced the surface hydrophilicity, thereby reducing the water absorption and improving the mortar’s workability. However, KH550-modified aggregates exhibited a more effective enhancement of the mortar’s mechanical properties. Specifically, KH550-modified aggregates reduced the aggregate’s surface hydrophilicity, consequently alleviating the interfacial edge effect. This led to a 10% increase in the compressive strength of the mortar, an 11.6% reduction in the porosity, an 8.4% decrease in the interfacial porosity, and a 42.3% increase in the elastic modulus of the ITZ. Meanwhile, the cement matrix obtained a greater amount of water for cement hydration, resulting in an increased degree of hydration and an 18.5% increase in the elastic modulus of the cement matrix. The improvement in the ITZ between the modified aggregates and the cement matrix is considered to be one of the fundamental reasons for the enhancement of the mortar’s performance.

Mechanical behaviour of E-waste aggregate concrete using a novel machine learning algorithm: Multi expression programming (MEP)

Technological advancement encourages the usage of electronic appliances in daily life and makes it possible for users to switch to more advanced devices very easily and at a reasonable cost. As new devices are produced and manufactured at an alarming rate around the world, outdated old devices become e-waste. This research work aims at using a popular machine learning (ML) method known as Multi-expression programming (MEP) to examine the compressive strength (CS) and tensile strength (TS) of E-waste aggregate-based concrete (EWAC). 279 and 105 scientific entries for CS and TS, respectively, were culled from reputable literature. The ten convincing input parameters selected based on multicollinearity analysis (correlation matrix and variance inflation factor) were E-waste coarse aggregate (ECA%), E-waste fine aggregate (EFA%), water-cement ratio (w/c), age of concrete (A in days), fine aggregate water-absorption (WAF%), coarse aggregate water-absorption (WAC%), E-waste aggregate water-absorption (WAE%), E-waste aggregate specific-gravity (SGE), coarse aggregate specific-gravity (SGC), and fine aggregate specific-gravity (SGF). To estimate the functioning of the projected models, root-squared-error (RSE), mean-absolute error (MAE), mean-absolute-percent error (MAPE), Nash-Sutcliffe-efficiency (NSE), root-mean-squared error (RMSE), objective-function (OF), coefficient-of-correlation (R), root-mean-squared-logarithmic error (RMSLE), and performance-index (PI) were used. The R-value for both MEP models exceeds 0.9, showing “excellent” with MAPE values in the testing stage equals to 6.68% and 6.78% for the CS-MEP and TS-MEP models, respectively. While for non-linear regression (NLR) models, the MAPE exceeds 20% and 30%, respectively, making them unsuitable for future prediction. Moreover, the sensitivity analysis carried out to evaluate the MEP equations' consistency with the observed physical phenomena, indicates that for both CS and TS, the w/c, ECA%, and EFA% remain the most sensitive parameters with a sensitivity index greater than 0.60. Due to the accuracy and viability of developed models, they can be used to reduce the time needed for laborious laboratory tests.

Optimization of sodium alginate aided bio-deposition treatment of recycled aggregates and its application in concrete

Bio-deposition treatment based on microbial induced carbonate precipitation is a promising method to enhance the properties of recycled aggregates, because the generated biological precipitates can repair the defects of recycled aggregates. However, the main problem of current bio-deposition treatment is the uneven distribution of the precipitates on aggregates, which greatly diminishes the enhancing efficiency. Therefore, sodium alginate (SA) was innovatively utilized to improve the uniformity of the precipitates on aggregates surface during the bio-deposition treatment in this study. The principle was that SA and the network structure of Ca-alginate were applied to uniformly “fix” the bacteria on the surface of recycled aggregates, which was supposed to promote the uniform in-situ precipitation on the surface of aggregates. The influences of the concentrations of bacteria and deposition solution (containing equimolar urea and Ca-nitrate), on the treatment efficiency were studied. The results indicated that the optimized SA-aided bio-deposition treatment group was under 0.2 wt% SA, 109 CFU/mL of bacterial solution, and 0.5 M of deposition solution, the water absorption of aggregates was reduced by 39.63% on average, the effective mass increase of calcium carbonate was increased by 3.14%, and the crush value decreased by about 13.8%. Using aggregates subjected to the optimized SA-aided bio-deposition treatment to produce concrete, it was found that, comparing with the untreated recycled aggregate concrete, the saturated water absorption of the treated recycled aggregate concrete decreased by about 15.3%. It can be concluded that the optimized SA-aided bio-deposition treatment can improve the strength of aggregates and durability of recycled concrete.

Using sodium alginate aided bio-treatment for improving the uniformity of precipitates on recycled aggregates.

The recycled concrete aggregates have high porosity and water absorption, which hinders their utilization in concrete production. Microbial-induced calcium carbonate precipitation was regarded as a very promising method for strengthening recycled aggregates. However, the uneven distribution of CaCO3 on surface of aggregates encountered in the current bio-deposition treatment weakened the efficiency, especially in the aspect of the decrease of water absorption. Therefore, this study innovatively applied a sodium alginate aided bio-deposition treatment to improve the uniform distribution of biogenic CaCO3. The principle was that sodium alginate was used to uniformly "fix" the bio-agents (urea or bacterial cells) on the surface of recycled aggregates, which was supposed to promote the uniform in-situ precipitation of CaCO3 on the surface of aggregates, and hence effectively blocking surface pores, and reducing the water absorption of the aggregates. Two concentrations of sodium alginate (0.2w% and 0.5w%) and four sodium alginate aided bio-deposition treatments were studied. It was found that CaCO3 (a mass increase of 4.05%) was formed on the aggregates after the suitable sodium alginate aided bio-deposition treatment. The participation of sodium alginate made CaCO3 uniformly deposited on full surface of the aggregates, resulting in a significant decrease (42.10%) of water absorption. The biogenic CaCO3 showed limited mass loss under ultrasonic attack, indicated a strong cohesion and bonding strength with aggregates. The results demonstrated that sodium alginate-aided bio-deposition treatment can enhance the efficiency, which was beneficial to improve the quality of recycled aggregates and their utilization of recycled aggregates in concrete production. KEY POINTS: • The SA-aided bio-treatment promoted the distribution uniformity of CaCO3 on aggregates. • The water absorption of aggregates decreased by 42.10%. • The formed CaCO3 showed excellent cohesion and adhesion.

Use parent concrete strength and equivalent water absorption of recycled concrete aggregates to identify concrete properties

This article focuses to study some properties of recycled aggregate concretes (RAC) according to the equivalent water absorption of aggregates and the parent concrete strength of RCA and thus new relationships were deduced. The results indicated that 1% increase of the equivalent water absorption induced 0.12% increase in superplasticiser dosages. The hyperbolic model seems to be more adequate to estimate compressive strength and shrinkage of RAC when the parent concrete strength and the equivalent water absorption were introduced. According to the obtained results, the parent concrete strength of RCA must not be less than 10 MPa than that of the reference concrete to avoid the drop in compressive strength. For high equivalent water absorption, the ultimate shrinkage became higher and slower.

Effect of Water Absorption and Loss Characteristics of Fine Aggregates on Aggregate-Asphalt Adhesion

This study aims to investigate the effect of aggregate water absorption and loss characteristics on aggregate-asphalt adhesion. Lab tests were designed to analyze the water absorption and loss characteristics of limestone, basalt. and steel slag fine aggregates with different particle sizes under various temperatures and humidity conditions. Meanwhile, the low temperature nitrogen adsorption test, combined with the Brunauer, Emmett and Teller (BET) theory and Barret, Joyner and Halend (BJH) model, were used to calculate the specific surface area and pore size distribution of aggregate. Moreover, the asphalt-aggregate adhesion was evaluated by the net adsorption test. The results indicated that the change trends of water absorption and loss for the aggregates exhibited two stages. In the first stage, the amounts of water absorption and loss of aggregates were large and their change rates were high, while in the second stage, an opposite trend was observed. Humidity had the greatest influence on the water absorption and loss of aggregates, followed by aggregate particle size, contact time, temperature, and aggregate type. The smaller-sized aggregates had greater specific surface area, which led to a higher sensitivity to temperature and humidity changes. In comparison, the 0.3 mm-sized aggregate had a large capillary energy inside the pores, and it was the most sensitive to moisture. The steel slag aggregate had the strongest adhesion with asphalt, followed by the limestone aggregate, and the worst was basalt aggregate.

Determining the continuous water absorption of unbound granular aggregates utilising hydrostatic weighing approach

In most flexible pavement structures, Unbound Granular Materials (UGMs) are exposed to the surrounding environment. Whilst in direct contact with materials, weathering agents can trigger chemical reactions and cause ageing and deterioration of UGMs. In practice, propensity to water absorption can be a principal durability parameter of a road material; however, current testing methodologies fail to suggest a clear understanding of the real-time appetite of aggregate for water. This study devised a Continuous Water Absorption (CWA) testing procedure, based on Archimedes’ principle to gain insight into water-aggregate interactions. The robustness of this method is demonstrated by conducting tests on three replicated samples from two sources of aggregates, Premium and Marginal andesite. Aggregates were tested in various conditions, including three temperatures (5 °C, 20 °C, and 35 °C), and two compositions of the solution (distilled water and tap water). Overall, the CWA results revealed that water absorption of aggregates is highly temperature and solution composition dependent; and the traditional water absorption test methodology generally underestimates the appetite of aggregates to absorb water. In addition, it was proven that the presence of clay minerals in the structure of Marginal aggregates could cause an increase in the propensity of aggregates to absorb water. It is also notable that Premium aggregates indicated higher susceptibility to the testing conditions. In order to reduce the chemical weathering of UGMs, the CWA test results can be used to approximate an effective time to drain water from Unbound Granular Layers (UGLs).

Properties of concretes bearing mixed recycled aggregate with polymer-modified surfaces

The growing socio-economic interest in conserving the environment constitutes a challenge for businesses with a heavy environmental impact. In the construction industry, the efficient use of recycled construction and demolition waste (CDW) as aggregates in structural concrete and the implications of that practice for a sustainable flow of materials are contributing to the establishment of a circular economy. Mixed recycled aggregates (MRA) account for a substantial fraction of the total. The main hurdle to MRA valorisation is its non-uniformity and certain intrinsic properties that have a direct effect on the performance of recycled concretes. In light of those drawbacks, this study assessed a surface treatment consisting in soaking these mixed materials in polymers to improve their physical and mechanical properties with a view to their use, determining the optimal treatment conditions (concentration, soaking time and drying method). The study also addressed the effect of using the treated MRA to replace 100% of the natural gravel (~40% of the total aggregate) on the fresh state consistency and hardened state compressive and tensile strength and water permeability of the new material. The findings showed that the treatment induced a reduction in mixed recycled aggregate water absorption and a rise in its abrasion resistance. Although treating the MRA as described had no significant effect on concrete mechanical properties, it improved durability significantly.

Formulation and Characterization of Light Aggregates from Phosphate Ore Processing Waste from the Hahotoe and Kpogame Mines, Potential Use for Agricultural Applications

This study relates to the development of light aggregates from phosphate sludge, rejects to sieves and clays. Three types of aggregates denoted S9, S10 and S11 have been developed. Samples S9 are composed of clay, screenings and phosphate sludge, samples S10 of clay and screenings and samples S11 of clay and phosphate sludge. The influence of temperature and cooking time on the properties (water absorption, density, porosity, etc.) of the aggregates produced was studied, as well as their mineralogical composition. For this purpose, three different cooking temperatures 900°C, 950°C and 1000°C, and two cooking times 30 and 60 min were considered. This study showed that the water absorption of aggregates cooked for 30 min varies between 12.71% and 14.93% while that of aggregates cooked for 60 min varies between 12.78% and 15.16%. The lowest water absorption is observed at the S10 aggregates sintered at 900°C for 30 min while the highest water absorption is observed at the S9 aggregates sintered at 900°C for 60 min. The dry density of aggregates cooked for 30 min varies between 1.27 and 1.68 g/cm³ while that of aggregates cooked for 60 min varies between 1.75 and 2.13 g/cm³. With the exception of S11 aggregates baked at 950 and 1000°C for 60 min, which have their density greater than 2 g/cm³, all the others can be considered light aggregates. It should also be noted that the aggregates cooked for 30 min have a lower density than the aggregates cooked for 60 min. The porosity of the aggregates cooked for 30 min varies between 16.30 and 20%, on the other hand the aggregates cooked for 60 min varies between 19.06 and 23.64%. X-ray diffraction analysis of the aggregates shows that they are mainly composed of fluoroapatite, quartz, hematite and plagioclases (albite, labradorite, and anorthite). The study also showed that the amount of quartz and fluoroapatite decrease with temperature. On the basis of the physical and mineralogical analysis carried out on the light aggregates, we could find them suitable for agricultural applications, especially their uses as substrates in hydroponics, in greenhouse cultivation in general, and in gardening.

Recent advances in artificial aggregate production

Artificial aggregates (AAs) are man-made construction material, and the properties greatly depend on its manufacturing process (e.g. granulation and hardening) and the raw materials (usually different source of wastes) used. This paper reviews the granulation process and suitable raw materials for each hardening method. Hardening methods including sintering, cold-bonding, accelerated carbonation and alkaline activation can significantly impact the final properties of the produced AAs. In general, finer material fractions are required for granulation to increase the pelletization efficiency and strength of AAs. Among the hardening methods, sintering usually gives a better physical and mechanical properties of AAs with a condition that SiO 2 /∑flux ratio of raw materials used should exceed 2, and (SiO 2 +Al 2 O 3 )/∑flux ratio of between 3.5 and 10. The cold-bonded method requires hydraulic raw materials and is restricted by a longer curing time, but this can be solved by introducing autoclaving or alkaline activation approaches to accelerate the strength gain. Post curing of AAs under a strongly alkaline solution can also effectively reduce the water absorption of aggregate by nearly 90%. The accelerated carbonation technique seems to be a green and more sustainable hardening method, as it can turn less valuable waste into strength bearing calcite and permanently store the waste CO 2 through mineral carbonation. In terms of leachability, sintering can stabilize most heavy metals, while other hardening methods such as cold bonding and carbonation are only effective for stabilizing certain heavy metals. • Recent advances in manufacturing technology of artificial aggregate were reviewed. • Sintered aggregates usually show low density and good physical properties. • Accelerated carbonation is a green and carbon negative approach with excellent CO 2 uptake. • Most artificial aggregates are classified as lightweight aggregate and their strength is below 10 MPa. • Sintering technology is the most effective method to limit the leaching of heavy metals.

Influence of Critical Parameters of Mix Proportions on Properties of MK-Based Geopolymer Concrete

Conventional Portland cement concrete has been extensively used in the past century due to its superior performance compared to other building materials. Recognizing the environmental impact of cement composites and global pressure toward implementation of sustainable construction materials, geopolymer concrete has been introduced as a potential alternative to conventional cement concrete. This study investigates the properties of metakaolin-based geopolymer concrete by employing various mix design parameters based on locally sourced materials. The test results reported herein comprised 16 mixes divided into three groups to understand the influence of various parameters on the workability and compressive strength of the concrete and hence optimizing the mix proportions. The outcome of this research provided insights into the curing conditions, curing age, sodium hydroxide molarity, sodium silicate content, molar ratios of the mix, and aggregate water absorption effect on the geopolymer concrete behavior. A model is proposed for deciding the water to solids ratio based on the total aggregate percentage for workable geopolymer mixes. In order to produce MK-based geopolymer concrete for structural applications, thresholds are proposed for the three molar ratios, namely sodium oxide to silicon oxide, sodium oxide to aluminum oxide, and water to sodium oxide ratios.

Preparation of glass shell fly ash-clay based lightweight aggregate with low water absorption by using sodium carbonate solution as binder

Fly ash-clay based lightweight aggregates with low density and low water absorption were prepared using sodium carbonate solution as binder and coke particles as pore-forming agent. The addition of 60 wt% coke particles to the initial formula of only fly ash and clay could form the porous structure and effectively lower the apparent density. The apparent density, water absorption and strength of the aggregates at different conditions including mass concentration and sintering temperature were tested. It was found that the mass concentration 10 wt% of the sodium carbonate solution was the best concentration to form the completely glassy shell at 1220 °C. And the glassy shell could significantly lower the water absorption from 22.97% to 8.84%. Then the glassy shell aggregates with low density (1.22 g/cm3 apparent density), 8.84% water absorption and particle strength (4.25 MPa) were obtained. All the properties meet the national standards of GB/T 17431. Therefore, using sodium carbonate solution to replace water as the binder by spraying in the forming process is a simple and applicable way to lower the water absorption of aggregates in the industrial production of lightweight aggregates. At the same time, the production of aggregates using solid waste fly ash as a raw material can effectively reduce production costs.

Compressive Strength and Workability of Cement Mortar Containing Recycled Asphalt Pavement

This article presents the compressive strength and workability of cement mortar (CM) containing recycled asphalt pavement (RAP) as fine aggregate replacement. The effect of the RAP replacement, water to cement ratio, curing time, and aggregate water absorption on compressive strength and flow workability are reported. The results show that the mixing water and mixing time play a significant role in the compressive strength and unit weight of CM containing RAP. The RAP has a higher water absorption and slower rate of water absorption than those of sand. The flow workability of CM increases with RAP replacement due to the unabsorbed water at the initial mixing stage. The main negative factors that affected the compressive strength of CM containing RAP as a fine aggregate replacement are revealed. The unabsorbed water at the initial state of mixing before hardening causes increased flow workability and decreased compressive strength. The findings from this research will promote the mix design approach of CM containing RAP as a fine aggregate replacement, for moving toward increased applications of recycled materials in a sustainable manner in civil engineering construction.

Mechanical properties of concrete with coarse spontaneous combustion gangue aggregate (SCGA): Experimental investigation and prediction methodology

Spontaneous combustion gangue aggregates (SCGAs) have inferior qualities compared with natural aggregates (NAs). The aim of this study is to investigate the effects of the replacement (rSCGA) ratio and particle size distribution of coarse SCGAs on the mechanical properties of concrete, as well as to propose prediction methods for coarse SCGA concrete. Slump values were obtained to evaluate the effect of coarse SCGAs on the workability of fresh concrete; the compressive strength, tensile splitting strength, and elastic modulus on different days were measured to investigate the effect of coarse SCGAs on the mechanical properties of hardened concrete. Scanning electron microscopy analysis was conducted to reveal the mechanical mechanisms of coarse SCGA concrete. The results indicated that coarse SCGAs significantly affected the mechanical properties of concrete, and for an SCGA replacement ratio of 100%, reductions of 19.4%, 36.1%, and 32.2% were obtained in the compressive strength, tensile splitting strength, and elastic modulus, respectively; while the effect of particle size distribution of coarse SCGAs on the concrete properties was limited. The mechanical properties of coarse SCGA concrete at different rSCGA ratios can be reasonably estimated using the weighted density and weighted water absorption of aggregates used in the concrete mixtures.

Physical and mechanical properties of river stone as coarse aggregate for concrete production

In this research, the physical and mechanical properties of river stone as coarse aggregate for concrete production was investigated. This will provide alternative construction materials to the society especially in areas where there is unavailability of good crushed aggregates. Physical and mechanical tests was conducted on samples of river stone which included; specific gravity of aggregates, bulk density of aggregates, water absorption of aggregates, crushing value of aggregates and grading of aggregates. Results obtained show that the specific gravity value for the sampled river stone is 2.6. The loose bulk density of the river stone is 1474kg/m 3 . Water absorptions test conducted on the aggregates gave a value of 0.9%. Crushing value of the river stone aggregates was obtained as 34.5. It is recommended that the inclusion of river stone as coarse aggregates in normal weight concrete production be encouraged especially in areas where quality coarse aggregates for normal weight concrete production is scarce and expensive. Keywords: River Stone, Specific Gravity, Bulk Density, Coarse Aggregates

Experimental Observation on Variation of Rheological Properties during Concrete Pumping

Workability of concrete varies during pumping. Even though concrete satisfies the required workability before pumping, it often does not satisfy the required standard after pumping. Moreover, serious problem could happen such as segregation and blockage. In this study, the rheological properties of concrete change during pumping from the pressure distribution over the pipe length was investigated. The rheological properties and the pressures measured from seven different real-scale pumping tests with 116 m to 1000 m long pipelines and 24 MPa to 100 MPa concrete were analyzed. As a result, it was found that the rheological properties vary gradually along the pipeline, and could abruptly change inside the pump. The variation of rheological properties during pumping seems to be attributed in part to the increase of water absorption in aggregates under high pressure and the additional mixing effect, namely, intensive shearing under high pressure inside pump.

Attribution of molasses dosage on fresh and hardened performance of recycled aggregate concrete

Molasses is a by-product of sugar production; which not only improves concrete fluidity but also prevents early hardening of cement paste. Moreover, the usage of recycled aggregates in concrete is not a novel practice; however, the key issue observed in its utilization is the high water absorption of aggregates leading to low workability and ultimately poor mechanical strength. This paper investigates the possibility of using cane molasses as a water-reducing admixture in recycled aggregate concrete. The addition of molasses along with recycled aggregate in concrete has the potential of mitigating the negative effects observed with the use of recycled aggregate only. Hence, various dosages of cane molasses (0.25–0.75% by weight of cement) were utilized in this study to investigate the fresh properties of cement pastes and recycled aggregate concrete. Key properties of hardened concrete, such as compressive strength, splitting tensile strength and shear strength were assessed up to 365 days. X-ray diffraction analysis was also performed at all ages of testing. With the addition of molasses reduction in water demand for normal consistency, whereas increase in setting times and workability was observed. By experiments and analytical discussions, improvement in mechanical performance of recycled aggregate concrete was also revealed with the addition of molasses up to 0.25%. The obtained results disclosed that the use of molasses in concrete with recycled aggregates is encouraging, provided that the dosage limitations are taken into account.

Effect of recycled coarse aggregates enhanced by CO2 on the mechanical properties of recycled aggregate concrete

It is environmentally friendly to crush waste concrete as recycled aggregate for cyclic utilization, and it also can solve the shortage of natural aggregate. However, the performance of the recycled aggregate concrete was poor caused by the surface adhesion of old cement mortar on the aggregate and the micro crack properly generated during the crushing process. The pressure pretreatment on recycled coarse aggregate by CO2 was used to improve its basic performances. The variables carbonization time (0h, 6h, 12h, 24h, 48h, 72h) and CO2 carbide gas pressure (0.1MPa, 0.4MPa, 0.8MPa) were studied, and the basic properties of recycled coarse aggregate before and after carbonization were compared and analysed, and the degree of improvement on recycled aggregate concrete were also investigated to determine the optimal scheme for carbonation, which was in the container with 0.4MPa pressure for 24h. Based on the optimum carbonation scheme, the influence of recycled coarse aggregate on mechanical properties of recycled aggregate concrete was studied with the substitution rate of recycled coarse aggregate (30%, 50%, 70% and 100%) before and after carbonization respectively. The results showed that the CO2 reinforced recycled coarse aggregate water absorption rate and crushing index was decreased, apparent density was increased. At the same substitution rate, the compressive strength and elastic modulus of carbonized recycled aggregate concrete was higher than that of non-carbonized recycled aggregate concrete.

A new methodology for determining water absorption of lightweight, normal-weight and heavyweight aggregates in a viscous medium

Water absorption in aggregates has important effects on the properties of concretes especially in lightweight aggregate concretes (LWAC). It is assumed that during the production of LWAC the lightweight aggregate (LWA) absorption is equivalent to a certain percentage of the absorption determined in an aqueous medium. A new procedure for determining the absorption by aggregates in concrete (viscous medium) is proposed. This methodology makes possible to determine the water absorption in a viscous medium and it allows specifying accurately the amount of mixing water to produce concretes.

Prediction model of carbonation depth for recycled aggregate concrete

The prediction of carbonation depth for recycled aggregate concrete (RAC) is investigated in this paper. The existing prediction models were evaluated, and it showed that the coefficient of variation (COV) of model error for the existing models is high. By introducing the weighed water absorption of aggregates, the COV of model error can be effectively decreased. Compared with the existing models, the proposed model can predict more accurate carbonation depths. For RAC specimens, compared with the fib model and Xiao and Lei's model-a, the COV of model error of the proposed model is 0.36 which is decreased by 33.3%, and when compared with Xiao and Lei's model-b and Silva et al.’s model, the corresponding decreases are 55.2% and 16.2%. Finally, the proposed model is validated by a 10-year-old carbonation experiment, which indicates that the proposed model is reasonable and can be applied to predict the carbonation depth of RAC.