Prediction of the Carbonation Depth of Concrete with a Mortar Finish

2008 ◽  
Vol 385-387 ◽  
pp. 633-636 ◽  
Author(s):  
Han Seung Lee ◽  
Xiao Yong Wang
Keyword(s):  
Portland Cement ◽  
Numerical Procedure ◽  
Pozzolanic Reaction ◽  
Surface Coatings ◽  
Reinforced Concrete Structures ◽  
Hydration Products ◽  
Application Time ◽  
Carbonation Depth ◽  
Hydration Model ◽  
Corrosion Of Steel

It is well known that carbonation will result corrosion of steel reinforcement in reinforced concrete structures. To reduce the rate of carbonation, the surface coatings, such as mortar finish, has been used widely to concrete. This paper presents a numerical procedure about carbonation of the coating-concrete system. This numerical procedure starts with a multi-component hydration model. By hydration model which considers both and Portland cement and pozzolanic reaction, the amount of hydration products which are susceptible to carbonate as well as porosity is obtained as function of age. Furthermore, the diffusivity of CO2 is determined and carbonation depth of concrete is predicted. Parameter studies are performed to show the influence of composition and application time of mortar finish on carbonation depth of substrate concrete.

Modeling of hydration reactions to predict the properties of slag blended concrete

2014 ◽  
Vol 41 (5) ◽  
pp. 421-431
Author(s):  
Xiao-Yong Wang ◽  
Ki-Bong Park
Keyword(s):  
Portland Cement ◽  
Cement Hydration ◽  
Blended Cement ◽  
Numerical Procedure ◽  
Reaction Model ◽  
Heat Evolution ◽  
Mineral Admixture ◽  
Temperature History ◽  
Granulated Blast Furnace Slag ◽  
Hydration Model

The granulated blast furnace slag is commonly blended with Portland cement or clinker to produce slag blended cement after being ground to the fineness comparable to Portland cement. Hydration of slag-blended cement is much more complex than that of ordinary Portland cement because of the mutual interactions between the cement hydration and the slag reaction. In this paper, by considering the production of calcium hydroxide in cement hydration and its consumption in the reaction of slag, a numerical procedure is proposed to simulate the hydration of concrete containing slag. The numerical procedure includes two sub components, a cement hydration model and a slag reaction model. The heat evolution rate of slag concrete is determined from the contributions of the cement hydration and the slag reaction. Furthermore, the temperature history in hardening blended concrete is evaluated by combining the proposed numerical procedure with a finite element method. The proposed model is verified through experimental data on concrete with different water–cement ratios and mineral admixture substitution ratios.

Chloride Ion Diffusion of Phosphoaluminate Cement Concrete

2009 ◽  
Vol 79-82 ◽  
pp. 99-102 ◽  
Author(s):  
Zhu Ding ◽  
Feng Xing ◽  
Ming Zhang ◽  
Peng Liu
Keyword(s):  
Portland Cement ◽  
Chloride Ion ◽  
Chloride Ions ◽  
Hydration Products ◽  
Portland Cement Concrete ◽  
Ion Diffusion ◽  
Cement Concrete ◽  
Dense Microstructure ◽  
Corrosion Of Steel ◽  
Chloride Ion Diffusion

Penetration and diffusion of chloride ions in concrete can lead to the corrosion of steel bar and shorten the service life of concrete structures. Phosphoaluminate cement (PAC) is a new cementitious material which has many special properties compared to Portland cement (PC). In the study, chloride ion diffusion in PAC concrete was tested with RCM method. The phase composition and morphology of hydration products, pore volume of hardened paste cured for 28d were analyzed with X-ray diffraction (XRD) and mercury intrusion porosimetry (MIP). The results show that chloride ion diffusion coefficient of PAC concrete is much lower than that of Portland cement concrete under the same test conditions. The hydration products of PAC are main micro-crystalline phase and gel of phosphate and/or phophoaluminate, which formed a dense microstructure. There is no calcium hydroxide produced in the PAC hydration system. In hardened PAC paste, chloride ions might replace the atom group [OH] - and [PO4]3- of hydrates and become stable compounds. The resistance to chloride ion diffusion of PAC concrete will increase with the hydration age, because its microstructure becomes denser with the hydration age increasing.

scholarly journals Structural and microscopy characterization of an alternative low-energy binder containing Ca(OH)2 as an alkaline activator

2021 ◽  
Vol 3 (6 (111)) ◽  
pp. 71-79
Author(s):  
Aditianto Ramelan ◽  
Adhi Setyo Nugroho ◽  
Teti Indriati ◽  
Riska Rachmantyo
Keyword(s):  
Portland Cement ◽  
Water Immersion ◽  
Pozzolanic Reaction ◽  
Low Energy ◽  
Hydration Products ◽  
Amorphous Phases ◽  
Average Maximum ◽  
Hydrated Products ◽  
Pozzolanic Materials

The development of potential alternative binders to Portland cement is still becoming a global challenge in housing and infrastructure aspects. That is because cement and concrete become the major materials needed in building constructions. The Ordinary Portland cement can form a solid and hard mass when mixed with water with a certain ratio. This is due to the formation of ettringite and calcium silicate hydrate (CSH) phases that contribute to the strength of the hydrated products about 33–53 MPa. However, the manufacturing temperature of Portland cement can reach up to 1,500 °C in producing clinker. In order to lower the energy consumption and production cost, scientists were trying to utilize pozzolanic materials. The research of pozzolanic materials as alkali-activated cement, such as soil cement or geopolymer cement, is also still conducted. Hence, a better understanding of pozzolanic reaction and its hydration products is needed. In this work, the hydration products of low-energy binders composed of Ca(OH)2-SiO2 and Ca(OH)2-metakaolin-gypsum mixtures were studied. The hydrated products of 41 wt. % Ca(OH)2 – 41 wt. % metakaolin – 18 wt. % gypsum mixtures followed by water immersion curing at 50 °C for 28 days undergone a pozzolanic reaction. XRD characterization showed that the hydrated product is mainly composed of ettringite (60.0 %) and crystalline-CSH (23.4 %). The diffractograms obtained have shown a specific hump indicating the presence of amorphous phases besides the crystalline. To confirm the presence of the non-crystalline or amorphous phases of the hydrated products, a polarizing optical microscope (OM) using a crossed Nicols method was used. The characterization of the phases is the novelty of the present research. The ettringite, crystalline CSH and the amorphous phases act as a strong binder that consequently contribute to its average maximum compressive strength of 22.17 MPa.

scholarly journals Performance of GGBS Cement Concrete under Natural Carbonation and Accelerated Carbonation Exposure

2021 ◽  
Vol 2021 ◽  
pp. 1-16
Author(s):  
Jun Zhao ◽  
Eskinder Desta Shumuye ◽  
Zike Wang ◽  
Gashaw Assefa Bezabih
Keyword(s):  
Reinforced Concrete ◽  
Portland Cement ◽  
Co2 Concentration ◽  
Reinforced Concrete Structures ◽  
Accelerated Carbonation ◽  
Cement Concrete ◽  
Carbonation Depth ◽  
Carbonation Resistance ◽  
Natural Carbonation ◽  
Exposure Conditions

One of the primary problems related to reinforced concrete structures is carbonation of concrete. In many cases, depth of carbonation on reinforced concrete structures is used to evaluate concrete service life. Factors that can substantially affect carbonation resistance of concrete are temperature, relative humidity, cement composition, concentration of external aggressive agents, quality of concrete, and depth of concrete cover. This paper investigates the effect of varying the proportions of blended Portland cement (ordinary Portland cement (OPC) and ground granulated blast-furnace slag (GGBS)) on mechanical and microstructural properties of concrete exposed to two different CO2 exposure conditions. Concrete cubes cast with OPC, and various percentages of GGBS (0%, 30%, 50%, and 70%) were subjected to natural (indoor) and accelerated carbonation exposure. The aim of this paper is to present the research findings and authenticate the literature results of carbonation by using GGBS cement in partial replacement of OPC. The concretes with OPC are compared to concretes with various percentages of GGBS, to assess the carbonation depth as well as rate of carbonation of GGBS-based concretes, under both accelerated carbonation and natural carbonation exposure conditions. Even though GGBS cement increases the carbonation depth, the results are not the same with different GGBS replacement percentages. A correlation is made between concrete samples exposed to 15 ± 2% carbon dioxide (CO2) concentration and those exposed to natural CO2 concentration. The results reveal that the products formed by carbonation are similar under both exposure conditions. The experimental tests also revealed that GGBS cement concrete has a lower carbonation resistance than OPC concrete, due to the consumption of portlandite by the pozzolanic reaction. The combination of 70% OPC and 30% GGBS behaved well enough with respect to accelerated carbonation exposure, the depth of carbonation being roughly equivalent to that of control group (100% OPC). The results also show that rate of carbonation becomes more sensitive as the percentage of GGBS replacement increases (binder ratio), rather than duration of curing. Concretes exposed to natural carbonation (indoor) achieved lower carbonation rates than those exposed to accelerated carbonation.

Numerical Simulation of Heat Evolution of Eco-Friendly Blended Portland Cements Using a Multi-Component Hydration Model

2008 ◽  
Vol 569 ◽  
pp. 257-260 ◽  
Author(s):  
Xiao Yong Wang ◽  
Han Seung Lee ◽  
Ki Bong Park
Keyword(s):  
Portland Cement ◽  
Pozzolanic Reaction ◽  
Heat Evolution ◽  
Curing Temperature ◽  
Evolution Process ◽  
Waste Materials ◽  
Portland Cements ◽  
Influence Of Water ◽  
Mineral Components ◽  
Hydration Model

With the development of concrete industry, the necessity for utilizing waste materials and decreasing overall energy consumption is becoming increasingly obvious. Fly ash and granulated blast-furnace slag, which are used as blends of Portland cement, are waste materials produced in electric and energy industry, and concretes made with them can have properties similar to ones made with pure Portland cement at lower cost per unit volume. By using blended Portland cement, both ecology benefit and economic benefit can be achieved. Due to the pozzolanic reaction between calcium hydroxide and blended components, compared with ordinary Portland cement, hydration process of blended Portland cement is more complex. In this paper, based on a multi-component hydration model, a numerical model which can simulate heat evolution process of blended Portland cements is built. The influence of water to cement ratio, curing temperature, particle size distribution of cement paste and blended Portland material, and cement mineral components on heat evolution process is considered. The prediction result agrees well with experiment result.

Mechanism of Cement Paste with Different Particle Sizes of Bottom Ash as Partial Replacement in Portland Cement

2017 ◽  
Vol 68 (10) ◽  
pp. 2367-2372 ◽  
Author(s):  
Ng Hooi Jun ◽  
Mirabela Georgiana Minciuna ◽  
Mohd Mustafa Al Bakri Abdullah ◽  
Tan Soo Jin ◽  
Andrei Victor Sandu ◽  
...  
Keyword(s):  
Portland Cement ◽  
Construction Material ◽  
Bottom Ash ◽  
High Volume ◽  
Cement Composite ◽  
Pozzolanic Reaction ◽  
High Specific Surface Area ◽  
Partial Replacement ◽  
Natural Aggregates ◽  
Pozzolanic Properties

Manufacturing of Portland cement consists of high volume of natural aggregates which depleted rapidly in today construction field. New substitutable material such as bottom ash replace and target for comparable properties with hydraulic or pozzolanic properties as Portland cement. This study investigates the replacement of different sizes of bottom ash into Portland cement by reducing the content of Portland cement and examined the mechanism between bottom ash (BA) and Portland cement. A cement composite developed by 10% replacement with 1, 7, 14, and 28 days of curing and exhibited excellent mechanical strength on day 28 (34.23 MPa) with 63 mm BA. The porous structure of BA results in lower density as the fineness particles size contains high specific surface area and consume high quantity of water. The morphology, mineralogical, and ternary phase analysis showed that pozzolanic reaction of bottom ash does not alter but complements and integrates the cement hydration process which facilitate effectively the potential of bottom ash to act as construction material.

scholarly journals Enhancing carbonation and chloride resistance of autoclaved concrete by incorporating nano-CaCO3

2020 ◽  
Vol 9 (1) ◽  
pp. 998-1008
Author(s):  
Guo Li ◽  
Zheng Zhuang ◽  
Yajun Lv ◽  
Kejin Wang ◽  
David Hui
Keyword(s):  
Cement Hydration ◽  
Mercury Intrusion Porosimetry ◽  
Hardened Concrete ◽  
Optimal Dosage ◽  
Hydration Products ◽  
X Ray Diffraction ◽  
Carbonation Depth ◽  
X Ray ◽  
Chloride Resistance

AbstractThree nano-CaCO3 (NC) replacement levels of 1, 2, and 3% (by weight of cement) were utilized in autoclaved concrete. The accelerated carbonation depth and Coulomb electric fluxes of the hardened concrete were tested periodically at the ages of 28, 90, 180, and 300 days. In addition, X-ray diffraction, thermogravimetry, and mercury intrusion porosimetry were also performed to study changes in the hydration products of cement and microscopic pore structure of concrete under autoclave curing. Results indicated that a suitable level of NC replacement exerts filling and accelerating effects, promotes the generation of cement hydration products, reduces porosity, and refines the micropores of autoclaved concrete. These effects substantially enhanced the carbonation and chloride resistance of the autoclaved concrete and endowed the material with resistances approaching or exceeding that of standard cured concrete. Among the three NC replacement ratios, the 3% NC replacement was the optimal dosage for improving the long-term carbonation and chloride resistance of concrete.

Effect of W/B ratios on pozzolanic reaction of biomass ashes in Portland cement matrix

2012 ◽  
Vol 34 (1) ◽  
pp. 94-100 ◽  
Author(s):  
V. Sata ◽  
J. Tangpagasit ◽  
C. Jaturapitakkul ◽  
P. Chindaprasirt
Keyword(s):  
Portland Cement ◽  
Pozzolanic Reaction ◽  
Cement Matrix ◽  
Biomass Ashes

Research Progress on the Hydration of Portland Cement with Calcined Clay and Limestone

2021 ◽  
Vol 1036 ◽  
pp. 240-246
Author(s):  
Jin Tang ◽  
Su Hua Ma ◽  
Wei Feng Li ◽  
Hui Yang ◽  
Xiao Dong Shen
Keyword(s):  
Mechanical Properties ◽  
Portland Cement ◽  
Cementitious Materials ◽  
Supplementary Cementitious Materials ◽  
Research Progress ◽  
Hydration Reaction ◽  
Hydration Products ◽  
Early Hydration ◽  
Calcined Clay ◽  
Dense Microstructure

The use of calcined clay and limestone as supplementary cementitious materials, can have a certain influence on the hydration of Portland cement. This paper reviewed the influence of limestone and calcined clay and the mixture of limestone and calcined clay on the hydration of cement. Both limestone and calcined clay accelerate the hydration reaction in the early hydration age and enhance the properties of cement. Limestone reacts with C3A to form carboaluminate, which indirectly stabilized the presence of ettringite, while calcined clay consumed portlandite to form C-(A)-S-H gel, additional hydration products promote the densification of pore structure and increase the mechanical properties. The synergistic effect of calcined clay and limestone stabilize the existence of ettringite and stimulate the further formation of carboaluminate, as well as the C-(A)-S-H gel, contributed to a dense microstructure.

Low Cement/High Fly Ash Concretes: Their Properties and Response to Chemical Admixtures

1987 ◽  
Vol 113 ◽  
Author(s):  
V. H. Dodson
Keyword(s):  
Fly Ash ◽  
Portland Cement ◽  
Calcium Hydroxide ◽  
Pozzolanic Reaction ◽  
Portland Cement Concrete ◽  
Cement Concrete ◽  
Fly Ashes ◽  
Chemical Admixtures ◽  
Reaction With Water

ABSTRACTIn practice, the amount of fly ash added to portland cement concrete varies depending upon the desired end properties of the concrete. Generally, when a given portland cement concrete is redesigned to include fly ash, between 10 and 50% of the cement is replaced by a volume of fly ash equal to that of the cement. Sometimes as much as twice the volume of the cement replaced, although 45.4 kg (100 lbs) of cement will only produce enough calcium hydroxide during its reaction with water to react with about 9 kg (20 lbs) of a typical fly ash. The combination of large amounts of certain fly ashes with small amounts of portland cement in concrete has been found to produce surprisingly high compressive strengths, which cannot be accounted for by the conventional “pozzolanic reaction”. Ratios of cement to fly ash as high as 1:15 by weight can produce compressive strengths of 20.7 MPa (3,000 psi) at I day and over 41.4 MPa (6,000 psi) at 28 days. Methods of identifying these “hyperactive” fly ashes along with some of the startling results, with and without chemical admixtures are described.

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