scholarly journals Improvement in Carbonation Resistance of Portland Cement Mortar Incorporating γ-Dicalcium Silicate

2019 ◽  
Vol 2019 ◽  
pp. 1-10 ◽  
Author(s):  
Zhengxin Chen ◽  
Yunsu Lee ◽  
Hyeongkyu Cho ◽  
Hanseung Lee ◽  
Seungmin Lim
Keyword(s):  
Portland Cement ◽  
Ordinary Portland Cement ◽  
Cement Mortar ◽  
Dilution Effect ◽  
Dicalcium Silicate ◽  
Accelerated Carbonation ◽  
Replacement Rate ◽  
Carbonation Depth ◽  
Carbonation Resistance ◽  
Water Curing

In this study, γ-dicalcium silicate (γ-C2S) was incorporated into ordinary Portland cement (OPC) to sequester CO2 to enhance the carbonation resistance of cement-based composite materials. γ-C2S can react with CO2 rapidly to form vaterite and high dense SiO2 gel which could block the pores off and then inhibit further diffusion of CO2 into the system. Cement mortar specimens containing 0%, 5%, 10%, 20%, and 40% γ-C2S as cement replacement were prepared. After water curing for 28 days followed by curing in an environmental chamber for 28 days, the specimens were then exposed to an accelerated carbonation with 5% CO2 concentration for 28 days. The carbonation depth of the cement mortar with a low replacement rate (5% and 10%) was lower than that of the OPC mortar at all ages due to the sequestration of CO2 by γ-C2S. However, the cement mortar with a high replacement rate (20% and 40%) showed less carbonation resistance due to the dilution effect of γ-C2S replacement and increase in initial porosity caused by nonhydraulic characteristic of γ-C2S.

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.

Ultrafine Grinding of Limestone with Sodium Polyacrylates as Additives in Ordinary Portland Cement Mortar

2014 ◽  
Vol 37 (5) ◽  
pp. 787-794 ◽  
Author(s):  
Katja Ohenoja ◽  
Sandra Breitung-Faes ◽  
Päivö Kinnunen ◽  
Mirja Illikainen ◽  
Juha Saari ◽  
...  
Keyword(s):  
Portland Cement ◽  
Ordinary Portland Cement ◽  
Cement Mortar ◽  
Ultrafine Grinding

Influence the Carbonation Resistance and Mechanical Properties of Shotcrete by Accelerated Carbonation Test

2014 ◽  
Vol 1065-1069 ◽  
pp. 1985-1989
Author(s):  
Jia Bin Wang ◽  
Di Tao Niu ◽  
Rui Ma ◽  
Ze Long Mi
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Compressive Strength ◽  
Steel Fiber ◽  
Splitting Tensile Strength ◽  
Construction Technology ◽  
Accelerated Carbonation ◽  
Carbonation Depth ◽  
Normal Concrete ◽  
Carbonation Resistance

In order to investigate the carbonation resistance of shotcrete and the mechanical properties after carbonation, the accelerated carbonation test was carried out. The results indicate that the carbonation resistance of shotcrete is superior to that of normal concrete. With the increasing of carbonation depth, compressive strength and splitting tensile strength of shotcrete grew rapidly. The admixing of steel fiber can further improve the carbonation resistance, reduce the carbonation rate, and increase the splitting tensile strength of shotcrete greatly. Besides, based on analyzing the effects of construction technology and steel fiber of concrete for the carbonation resistance, a carbonation depth model for shotcrete was established. Key words: shotcrete; carbonation; steel fiber; mechanical properties

Using of Furfural to Modify the Ordinary Portland Cement

2011 ◽  
Vol 147 ◽  
pp. 3-8
Author(s):  
Haleem K. Hussain ◽  
Liu Gui Wei ◽  
Hameed A. Hamdi ◽  
Dawood S. Abed
Keyword(s):  
Portland Cement ◽  
Cement Paste ◽  
Ordinary Portland Cement ◽  
Fresh Concrete ◽  
Critical Value ◽  
Flow Test ◽  
Super Plasticizer ◽  
Curing Methods ◽  
Water Curing ◽  
Better Than

This study reported the results of adding furfural on mechanical properties of Ordinary Iraqi cement. Furfural was used at four different ratios (1%, 2%, 3%, and 5 %) by weight to the mix of Iraqi Portland cement (Um- Quasar factory cement). The effect on the plasticizing and fluidity by table flow test for cement paste and slump test of fresh concrete were studied. The obtained results showed that added furfural is acting as super plasticizer. Effective relation was found between fluidity and ratio of added through effecting time of flow where the most effect additive ratio was found to be 3% .The radius of cement paste circle is linearly dependence which is a indicate of high workability. Obtained results explained in term of electrical charges on cement particles. Also found that adding furfural increasing the dispersion work between cement paste particles and preventing coarse agglomerated. The using of furfural with concrete indicates two kinds of concrete behavior. These behaviors were strongly dependence on furfural ratio .The critical value of added furfural was 1% and after which a plasticizing effect obtained. Splitting and flexural tensile test were conducted. Three types of curing methods include dry, moisture and water curing. The obtained results showed that the moisture curing was better than other curing methods due to good results obtained with splitting tensile (6.18 N/mm2) for 5% ratio and water curing is preferred for flexural tensile (7.05 N/mm2 at 2% wt% of furfural ). Finally, we compared our results with AL-Abraaj Kuwait cement and we found that the Iraqi cement (Um Quasar factory cement) was better.

Effect of Delaying Addition of Heat Stimulated Superplasticizer on Fresh Properties of Mortar

2017 ◽  
Vol 890 ◽  
pp. 396-400 ◽  
Author(s):  
Zabihollah Tahery ◽  
Faraidoon Rahmanzai ◽  
Shigeyuki Date
Keyword(s):  
Portland Cement ◽  
Ordinary Portland Cement ◽  
Cement Mortar ◽  
Polycarboxylic Acid ◽  
Fresh Properties ◽  
External Temperature ◽  
Factors Affecting ◽  
Air Content ◽  
Heat Stimulation ◽  
Stimulation Of

To assure the quality and required workability of mortar or concrete, various types of superplasticizers are used. There are many factors affecting the performance of superplasticizers explicitly, type and dosage of the superplasticizers, type of cement, temperature and mixing procedure, as well as the addition times of the superplasticizers. Some researchers investigated the effect of delaying the addition time of superplasticizer to mortar or concrete, but there is not enough data about the effect of external temperature on performance of superplasticizers and consequent influences on fresh properties of mortar or concrete. In this research the effect of delaying the addition time of superplasticizers and influence of external temperature, namely, heat stimulation of superplasticizers, on fluidity, fresh density and air content of fresh cement mortar was investigated. Two types of Precast and Ready-Mix of Polycarboxylic acid-based ether superplasticizers with Ordinary Portland Cement was used. Delaying the addition time of superplasticizers enhanced the fluidity, slightly decreased the fresh density and increased the air content of mortar in comparison with simultaneous addition time with both heated and non-heated Superplasticizers.

Variation of Carbonation Coefficient of Pumping Concrete with Moist-Curing Time at early Ages and Fly-Ash Content

2011 ◽  
Vol 287-290 ◽  
pp. 899-905
Author(s):  
Qing Ye ◽  
Zhi Wei Song ◽  
Guo Rong Yu
Keyword(s):  
Fly Ash ◽  
Concrete Cover ◽  
Ash Content ◽  
Curing Time ◽  
Accelerated Carbonation ◽  
Carbonation Depth ◽  
Carbonation Resistance

Based on accelerated carbonation test, the variation of carbonation resistance of pumping concrete (C40 grade) with moist-curing time at early ages and fly-ash content was studied. Results indicate that the carbonation coefficient and the accelerated carbonation depth of the concrete increased obviously with a reduction in the moist-curing time at early ages and with an increase in the fly-ash content. For example, in conditions of curing schedules with 28, 7, 3, 2 and 1 d moist-curing at 20 0C with above 95% RH at early ages and then 0, 21, 25, 26 and 27 d air curing at 20 0C with 60% RH, respectively, carbonation coefficients of the concrete incorporated with 30% fly-ash were 2.04, 2.49, 3.16, 3.86 and 5.42 mm/a0.5 respectively, and thus it can be seen that the calculated times when concrete cover (25 mm) was completely carbonated naturally in now atmosphere (0.04% CO2) were 164, 104, 66, 44 and 21 years respectively. The results suggest that for the carbonation resistance of the C40 concrete incorporated with up to 30% fly-ash, the moist-curing time of 7 days at early ages should be necessary.

scholarly journals Physicochemical Properties of Hydrated Portland Cement Blended with Rice Husk Ash

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Joseph Mwiti Marangu ◽  
Cyprian Muturia M’thiruaine ◽  
Mark Bediako
Keyword(s):  
Compressive Strength ◽  
Portland Cement ◽  
Rice Husk ◽  
Elevated Temperatures ◽  
Rice Husk Ash ◽  
Blended Cement ◽  
Strength Development ◽  
Carbonation Depth ◽  
Blended Cements ◽  
Carbonation Resistance

In the presence of significant quantities of carbon dioxide (CO2) and elevated temperatures in the atmosphere due to climate change, cement-based materials are susceptible to carbonation. Blended cements are more prone to carbonation attack than Portland cement. There is a need to evaluate the carbonation resistance of blended cements in a carbonation-prone environment. This paper presents experimental findings obtained from an evaluation of carbonation resistance tests on Rice Husk Ash- (RHA-) blended cement. The blended cement was made by intergrinding of Portland Cement (PC) and RHA to make the test cement (PC-RHA). The RHA dosage in the PC-RHA was varied from 0 to 30% by mass of PC. Pozzolanicity, standard consistency, and setting time tests were conducted on PC-RHA. Mortar prisms measuring 160 mm × 40 mm x 40 mm were separately cast at a water/cement ratio ( w / c ) of 0.50 and 0.60 and cured in water for 2, 7, 14, 28, and 90 days. Compressive strength tests were conducted on the mortar prisms at each of the testing ages. The prepared mortars were also subjected to accelerated carbonation tests in two Relative Humidity (RH) curing regimes, one maintained at an RH greater than 90% and the other between 50–60%. Carbonation resistance of the mixtures was evaluated in terms of the changes in carbonation depth using a phenolphthalein test at the age of 7, 14, 28, and 56 days of curing in a continuous flow of CO2. Compressive strength measurements were also taken during each of the carbonation testing ages. For comparison, similar tests were conducted using commercial PC. The results showed that PC-RHA was pozzolanic while PC was nonpozzolanic. Higher water demand and longer setting times were observed in PC-RHA than in PC. Moreover, there was increased strength development in water-cured samples with increased curing duration. Carbonation results indicated that there was a marked increase in carbonation depth with increased dosage of RHA in PC-RHA binders, increased duration of exposure to CO2, and decreased RH (RH between 50–60%). PC-RHA binders exhibited lower carbonation resistance than PC. In conclusion, for mortars at any w / c ratio, carbonation resistance decreased with increase in RHA dosage and increased w / c ratio.

Experimental Study on Improving Concrete Carbonation Resistance with Silane Impregnation

2013 ◽  
Vol 357-360 ◽  
pp. 805-808
Author(s):  
Zhi De Huang ◽  
Su Fen Dong
Keyword(s):  
Experimental Study ◽  
Cement Mortar ◽  
Hydration Product ◽  
Resistance Mechanisms ◽  
Absorption Test ◽  
Carbonation Depth ◽  
Mixture Ratio ◽  
Concrete Carbonation ◽  
Carbonation Resistance ◽  
Water Absorption Test

Silane impregnation effects on concrete carbonization resistance are systemic researched, through determining blank and silane impregnation specimens carbonation depth, forming 6 mixture ratio cement mortar, treating with silane impregnation and then curing to 30d, 60d, 90d and 180d age naturally. Through XRD microscopic and water absorption test, the improving carbonization resistance mechanisms are analyzed from two aspects including cementations material hydration product concrete pore humidity.

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