Effect of retardant admixtures type and their using method on the behavior of concrete

2021 ◽  
Vol 12 (3) ◽  
pp. 104
Author(s):  
Tamer Ibrahim Ahmed ◽  
Mohamed Roshdy Afify
Keyword(s):  
Compressive Strength ◽  
Fresh Concrete ◽  
Setting Time ◽  
Casting Process ◽  
Additional Dose ◽  
Construction Sites ◽  
Effective Option ◽  
Initial Setting ◽  
Crisis Conditions ◽  
Ready Mix Concrete

Construction sites may be exposed to crisis conditions during the casting process, resulting in delays of several hours and causing destruction of ready-mix concrete. This study suggests an experimental analysis of the possibility of using a specific additional dose of retardant admixtures, which may be used to ready-mix concrete before the initial setting of the concrete occurs. The effect of this additional dose on concrete characteristics in terms of workability, setting time, and compressive strength is also being studied. To conduct this investigation, three types of retardant admixtures from three branded companies were used. In addition, a penetration resistance experiment was conducted on the concrete to determine its setting time. The setting time of concrete was measured at different period intervals depending on when the additional dose of the retardant admixtures was added from the start of the concrete mixing. The results showed that concrete maintained proper workability for a period of more than 5 hours after using the additional dose of retarding admixtures. The additional dose of retarding admixtures not only delayed the concrete setting but also improved the compressive strength of the concrete. This implies that the use of an additional dose of retardant admixtures specifically tailored for ready-mix concrete is an effective option to avoid the return of ready-mixed fresh concrete.

Preliminary Study on Reaction of Fresh Concrete with Carbon Dioxide

2018 ◽  
Vol 382 ◽  
pp. 230-234
Author(s):  
Ming Ju Lee ◽  
Ming Gin Lee ◽  
Yung Chih Wang ◽  
Yu Min Su ◽  
Jia Lun Deng
Keyword(s):  
Carbon Dioxide ◽  
Compressive Strength ◽  
Fresh Concrete ◽  
Setting Time ◽  
Cement Matrix ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Initial Setting Time ◽  
Initial Setting ◽  
Short Time

In order to let fresh concrete react with carbon dioxide sufficiently, the carbon dioxide was added to mixing concrete. The study used three water cement ratio (0.55, 0.65, 0.75), three CO2 pressures (0.2, 0.4, 0.6 MPa), and two CO2 concentration (50% and 100%) to make concrete samples, and observed the effect of carbon dioxide adsorption in the above parameters. Finally, the compressive strength and carbonation degree of concretes were tested after three curing time (7, 14 and 28 days). The research showed that concrete could be more efficient to absorb carbon dioxide by using this pressure method. The results found that the mixing concrete react with carbon dioxide in a short time, and shorten the initial setting time of concrete. But this method would greatly reduce the workability of concrete after mixing with carbon dioxide and it might be enhanced by water or superplasticizer. The bond of cement matrix might cut down after reacting with carbon dioxide. Based on the above, the compressive strength of concrete which was mixed with carbon dioxide would be impaired. The proposed CO2-mixing method has the capacity to uptake 9.5% carbon dioxide based on water cement ratio and CO2 pressure.

scholarly journals Effect of Calcium Nitrate on the Properties of Portland–Limestone Cement-Based Concrete Cured at Low Temperature

Materials ◽  
2021 ◽  
Vol 14 (7) ◽  
pp. 1611
Author(s):  
Gintautas Skripkiūnas ◽  
Asta Kičaitė ◽  
Harald Justnes ◽  
Ina Pundienė
Keyword(s):  
Compressive Strength ◽  
Cement Paste ◽  
Setting Time ◽  
Calcium Nitrate ◽  
Curing Temperature ◽  
Hardened Concrete ◽  
Cement Pastes ◽  
Initial Setting Time ◽  
Initial Setting ◽  
Early Strength

The effect of calcium nitrate (CN) dosages from 0 to 3% (of cement mass) on the properties of fresh cement paste rheology and hardening processes and on the strength of hardened concrete with two types of limestone-blended composite cements (CEM II A-LL 42.5 R and 42.5 N) at different initial (two-day) curing temperatures (−10 °C to +20 °C) is presented. The rheology results showed that a CN dosage up to 1.5% works as a plasticizing admixture, while higher amounts demonstrate the effect of increasing viscosity. At higher CN content, the viscosity growth in normal early strength (N type) cement pastes is much slower than in high early strength (R type) cement pastes. For both cement-type pastes, shortening the initial and final setting times is more effective when using 3% at +5 °C and 0 °C. At these temperatures, the use of 3% CN reduces the initial setting time for high early strength paste by 7.4 and 5.4 times and for normal early strength cement paste by 3.5 and 3.4 times when compared to a CN-free cement paste. The most efficient use of CN is achieved at −5 °C for compressive strength enlargement; a 1% CN dosage ensures the compressive strength of samples at a −5 °C initial curing temperature, with high early strength cement exceeding 3.5 MPa but being less than the required 3.5 MPa in samples with normal early strength cement.

scholarly journals Aplikasi Response Surface Methodology pada Optimasi Penambahan Blast Furnace Slag Terhadap Waktu Pengikatan dan Kuat Tekan Semen

2020 ◽  
Vol 4 (1) ◽  
pp. 61
Author(s):  
Hardjono Hardjono ◽  
Cucuk Evi Lusiani ◽  
Agung Ari Wibowo ◽  
Mochammad Agung Indra Iswara
Keyword(s):  
Compressive Strength ◽  
Response Surface Methodology ◽  
Blast Furnace ◽  
Response Surface ◽  
Blast Furnace Slag ◽  
Setting Time ◽  
Initial Setting Time ◽  
Initial Setting ◽  
Central Composite ◽  
Furnace Slag

Produksi semen setengah jadi (clinker) membutuhkan energi yang tinggi sehingga menggunakan batu bara dalam jumlah besar. Hal ini menyebabkan biaya produksi dari pabrik semen juga tinggi. Kebutuhan energi yang besar untuk menghasilkan clinker tersebut dapat dikurangi dengan menambahan blast furnace slag sebagai campuran pembuatan semen. Campuran clinker dapat menghasilkan produk semen yang memiliki waktu pengikatan dan kuat tekan sesuai SNI. Pengaruh penambahan blast furnace slag sebagai campuran clinker terhadap waktu pengikatan dan kuat tekan semen dapat dioptimalkan dengan response surface methodology (RSM) menggunakan Central Composite Design (CCD). Optimasi dengan menggunakan RSM bertujuan untuk mengetahui kondisi optimum pada penambahan blast furnace slag dan clinker terhadap variabel respon berupa waktu pengikatan awal, waktu pengikatan akhir, dan kuat tekan. Hasil uji ANOVA dan analisis response surface menunjukkan bahwa penambahan blast furnace slag sebagai campuran dalam pembuatan semen memberikan pengaruh yang signifikan terhadap waktu pengikatan awal, waktu pengikatan akhir, dan kuat tekan. Penambahan 5% blast furnace slag dengan 92,5% clinker pada campuran clinker dan gypsum merupakan kondisi optimum yang memberikan pengaruh signifikan terhadap variabel respon.The production of clinker consumes high energy and causes high production cost of cement industry. It can be reduced by adding blast furnace slag as a mixture in cement production. The blast furnace slag - clinker mixture can produce cement with setting time and compressive strength according to SNI. The effect of the addition of blast furnace slag as a clinker mixture to the setting time and compressive strength of cement can be optimized by response surface methodology (RSM) using Central Composite Design (CCD). Optimization by using RSM aims to determine the optimum condition of the blast furnace slag – clinker mixture to the initial setting time, final setting time, and compressive strength. ANOVA test results and response surface analysis show that the addition of blast furnace slag into the cement mixture has a significant influence on the initial setting time, final setting time, and compressive strength. The addition of  5% blast furnace slag with  92.5% clinker in the mixture of clinker and gypsum is the optimum condition which gives a significant effect on the response variable.

scholarly journals Analysis of the Influence of Crystalline Admixtures at Early Age Performance of Cement-Based Mortar by Electrical Resistance Monitoring

Materials ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 5705
Author(s):  
Rubén Beltrán Cobos ◽  
Fabiano Tavares Pinto ◽  
Mercedes Sánchez Moreno
Keyword(s):  
Compressive Strength ◽  
Thermogravimetric Analysis ◽  
Remote Monitoring ◽  
Electrical Resistance ◽  
Setting Time ◽  
Early Age ◽  
Resistance Monitoring ◽  
Initial Setting Time ◽  
Characterization Techniques ◽  
Initial Setting

Crystalline admixtures are employed for waterproofing concrete. This type of admixtures can affect the early age performance of cement-based mixes. The electrical resistance properties of cement have been related to the initial setting time and to the hydration development. This paper proposes a system for remote monitoring of the initial setting time and the first days of the hardening of cement-based mortars to evaluate the effect of the incorporation of crystalline admixtures. The electrical resistance results have been confirmed by other characterization techniques such as thermogravimetric analysis and compressive strength measurements. From the electrical resistance monitoring it has been observed that the incorporation of crystalline admixtures causes a delay in the initial setting time and hydration processes. The measurements also allow to evaluate the influence of the amount of admixture used; thus, being very useful as a tool to define the optimum admixture dosage to be used.

Use of Cement Hydration Stabilizer Admixture at Ready Mix Concrete to Avoid Material Waste

2013 ◽  
Vol 818 ◽  
pp. 24-29 ◽  
Author(s):  
Assed Naked Haddad ◽  
Bruno Grifo Ferreira Rossi Cortes ◽  
Ana Catarina Jorge Evangelista
Keyword(s):  
Construction Industry ◽  
Fresh Concrete ◽  
Setting Time ◽  
Environmental Benefits ◽  
Raw Material ◽  
Experimental Program ◽  
Construction Sector ◽  
Source Materials ◽  
Specific Part ◽  
Ready Mix Concrete

Concrete from ready mix plant is the main raw material consumed in construction industry. A significant waste quantity is generated with fresh concrete returned to the production center due to their inadequate allocation or demand preview. To minimize the amount of this material wasted, misused, discarded, could be used the Hydration Stabilizer Admixture (HSA). This product enables stabilization of the concrete setting time until 72 h. Waste generated by the building industry is becoming increasingly focused on discussions and studies, due to great importance that this topic is achieving. Generation of this waste in the construction sector and the large representation of this sector in society is one of the main problems encountered in the reuse of waste from construction. Its characteristic, heterogeneous and unknown, however, a specific part of that waste generated in the central metering concrete, has a high potential for reuse, mainly because they come from a production highly controlled, where the source materials and the final product are physically and chemically known. This work aims to study the environmental benefits and technical feasibility of stabilizing additive hydration as a solution for the reuse of residual concrete from central metering, always under a sustainable vision of the entire process through an experimental program. This work presents results of setting time, slump test, incorporated air, compressive strength at 3days, 7days, 14days, 28days and 45 days and elastic modulus ate 28 days. The reference concrete was compared with concrete stabilized mixtures (0.15%, 0.30%, 0.45% content of HSA), both presenting the same constituent materials. The results indicate the feasibility to the use of the HSA despite the reduction of the mechanical properties of the concrete.

scholarly journals Effects of Seawater on Setting Time and Compressive Strength of Concretes with Different Richness

2021 ◽  
Vol 7 (5) ◽  
pp. 857-865
Author(s):  
Ahmed I. Ghazal ◽  
Mohammed Y. El-Sheikh ◽  
Ahmed H. Abd El-Rahim
Keyword(s):  
Compressive Strength ◽  
Beneficial Effect ◽  
Fresh Water ◽  
Cement Paste ◽  
Detrimental Effect ◽  
Tap Water ◽  
Concrete Strength ◽  
Setting Time ◽  
Strength Tests ◽  
Initial Setting

Water is one of the main constituents of concrete. Although many types of water exist, fresh water is the mostly used in concrete industry. Fresh water is expected to be in a great shortage by 2050 according to UN world water development report. Incorporating seawater in concrete mixture can help in the expected problem of scarcity of fresh water. Also, in many cases seawater may be the only available water especially in coastal regions. Many reports mention various possibilities of using seawater in concrete without detrimental effect on concrete properties. In this study another beneficial effect of seawater over tap water was concluded. Setting tests of cement paste mixed with seawater was determined using Vicat apparatus and compared to tap water. Compressive strength tests at the age of 28 days of Portland cement concretes with varied quantity of cement i.e. 300, 350, 400, 450, and 500 kg, and mixed with seawater was also performed and compared to tap water. The results show that seawater affects standard consistency of cement paste and two percent increase was required in order to attain the same consistency as tap water. It shows also seawater slightly accelerates initial setting of cement but the effect is not so pronounced so as to cause a trouble in concrete and final setting time almost remains unaltered. Compressive strength tests show an increase in concrete strength mixed with seawater for all tested mixtures and depending on quantity of cement. It also shows a beneficial effect of seawater on compressive strength of rich concrete with quantity of cement 450 and 500 kg over tap water. Doi: 10.28991/cej-2021-03091695 Full Text: PDF

Study of Calcium Acrylate on Compressive Strength and Hydration Process of Cement

2013 ◽  
Vol 816-817 ◽  
pp. 161-165
Author(s):  
Fu Lan Wang ◽  
Qi Wang ◽  
Peng Song ◽  
Zhong Xi Yang ◽  
Lei Tian
Keyword(s):  
Hydrogen Peroxide ◽  
Compressive Strength ◽  
Induction Period ◽  
Setting Time ◽  
Comprehensive Analysis ◽  
Hydration Process ◽  
Cross Linking ◽  
Initial Setting Time ◽  
Initial Setting ◽  
Speed Up

In this paper, the hydration process and strength of calcium acrylate (CA) modified cement under the effects of different additives, such as, initiator-hydrogen peroxide, accelerator-triethanolamine, and cross-linking agent-butyl acrylate, were studied. Through comprehensive analysis, the optimal content of additives of initiator, cross-linking agent, and accelerator is ascertained 3%, 10% and 3%, respectively. On the condition of optimal content of additives and CA, it can be obtained that CA can increase the exothermic rate of cement within one hour and accelerate the exothermic rate in the induction period, shorten the time of the induction period, and speed up the initial setting time of cement. Besides, CA can inhibit the transformation of AFm from AFt, improve the dispersion of cement paste, make later hydration more fully, and promote later strength.

scholarly journals Preparation and Performance of a New-Type Alkali-Free Liquid Accelerator for Shotcrete

2017 ◽  
Vol 2017 ◽  
pp. 1-9
Author(s):  
Yanping Sheng ◽  
Bin Xue ◽  
Haibin Li ◽  
Yunyan Qiao ◽  
Huaxin Chen ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Cement Paste ◽  
Cement Mortar ◽  
Retention Rate ◽  
Setting Time ◽  
Test Results ◽  
Initial Setting Time ◽  
Initial Setting ◽  
New Type ◽  
And Performance

A new type of alkali-free liquid accelerator for shotcrete was prepared. Specifically, the setting time and strength and shrinkage performance of two kinds of Portland cement with the accelerator were fully investigated. Moreover, the accelerating mechanism of alkali-free liquid accelerator and the hydration process of the shotcrete with accelerator were explored. Results show that alkali-free liquid accelerator significantly shortened the setting time of cement paste, where the initial setting time of cement paste with 8 wt% of the accelerator was about 3 min and the final setting time was about 7 min. Compressive strength at 1 day of cement mortar with the accelerator could reach 23.4 MPa, which increased by 36.2% compared to the strength of cement mortar without the accelerator, and the retention rate of 28-day compressive strength reached 110%. In addition, the accelerator still shows a good accelerating effect under low temperature conditions. However, the shrinkage rate of the concrete increased with the amount of the accelerator. 5~8% content of accelerator is recommended for shotcrete in practice. XRD and SEM test results showed that the alkali-free liquid accelerator promoted the formation of ettringite crystals due to the increase of Al3+ and SO42- concentration.

scholarly journals Compressive Strength and Setting Time of MTA and Portland Cement Associated with Different Radiopacifying Agents

2012 ◽  
Vol 2012 ◽  
pp. 1-4 ◽  
Author(s):  
Mario Tanomaru-Filho ◽  
Vanessa Morales ◽  
Guilherme F. da Silva ◽  
Roberta Bosso ◽  
José M. S. N. Reis ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Portland Cement ◽  
Zirconium Oxide ◽  
Setting Time ◽  
Strontium Carbonate ◽  
Strength Test ◽  
Initial Setting Time ◽  
Final Setting Time ◽  
Compressive Strength Test ◽  
Initial Setting

Objective. The aim of this study was to evaluate the compressive strength and setting time of MTA and Portland cement (PC) associated with bismuth oxide (BO), zirconium oxide (ZO), calcium tungstate (CT), and strontium carbonate (SC). Methods. For the compressive strength test, specimens were evaluated in an EMIC DL 2000 apparatus at 0.5 mm/min speed. For evaluation of setting time, each material was analyzed using Gilmore-type needles. The statistical analysis was performed with ANOVA and the Tukey tests, at 5% significance. Results. After 24 hours, the highest values were found for PC and PC + ZO. At 21 days, PC + BO showed the lowest compressive strength among all the groups. The initial setting time was greater for PC. The final setting time was greater for PC and PC + CT, and MTA had the lowest among the evaluated materials (P<0.05). Conclusion. The results showed that all radiopacifying agents tested may potentially be used in association with PC to replace BO.

scholarly journals Evaluation of the superplasticizer effect on the workability and strength of concrete

2020 ◽  
Vol 9 (1) ◽  
pp. 198
Author(s):  
Salahaldein Alsadey ◽  
Saieed Mohamed
Keyword(s):  
Compressive Strength ◽  
Adverse Effects ◽  
Water Demand ◽  
Fresh Concrete ◽  
Setting Time ◽  
Cement Ratio ◽  
Optimum Dosage ◽  
Effects Of Temperature ◽  
Hot Weather ◽  
Sive Strength

The adverse effects of temperature on the properties of fresh concrete include increased water demand, shorter setting time and increased slump loss. Superplasticizer (SP) is important for enhancing the workability and setting time of concrete in hot weather. Hence, an experi-mental investigation was conducted to determine the optimum dosage of an admixture and to study the effect of over dosing this admixture. Concrete mixes with SP dosages of 0.8%, 1% and 1.2% by weight of cement were prepared along with a control mix (water/cement ratio of 0.55). After casting, the concrete samples underwent normal curing. Among the properties of fresh concrete determined were compressive strength as well as workability. The over dosage of SP appeared to degrade the properties of concrete with an indication of lower compres-sive strength. However, if the dosage levels are lower than the optimum dosage, raising the admixture dosage might help enhance the con-crete characteristics. 

Sign in / Sign up

Export Citation Format

Share Document