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 of Concrete with Nano Cement

2021 ◽  
Author(s):  
Jemimah Carmichael Milton ◽  
Prince Arulraj Gnanaraj
Keyword(s):  
Compressive Strength ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Cement Paste ◽  
Cement Mortar ◽  
Setting Time ◽  
Replacement Level ◽  
Initial Setting Time ◽  
Initial Setting

Nano technology plays a very vital role in all the areas of research. The incorporation of nano materials in concrete offers many advantages and improves the workability, the strength and durability properties of concrete. In this study an attempt has been made to carry out an experimental investigation on concrete in which cement was replaced with nano sized cement. Ordinary Portland cement of 53 grade was ground in a ball grinding mill to produce nano cement. The characterization of nano cement was studied using Scanning Electron Microscope (SEM), Brunauer Emmett–Teller (BET), Energy Dispersive X ray microanalysis (EDAX) and Fourier Transform Infrared Spectroscopy (FTIR). From the characterization studies, it was confirmed that particles were converted to nano size, the specific surface area increased and the chemical composition remained almost the same. The properties of cement paste with and without nano cement were found. For the experimental study, cement was replaced with 10%, 20%, 30%, 40% and 50% of nano cement. Cement mortar of ratio 1:3 and concrete of grades M20, M30, M40 and M50 were used. Compressive strength of cement mortar and concrete with different percentages of nano cement was found. The cement mortar was also subjected to micro structural study. It was found that the strength increased even up to the replacement level of 50%. Further increase in the replacement is not possible since the addition of nano cement reduces the initial and final setting time of cement paste. At 50% replacement level, the initial setting time got reduced to 30 minutes which the least permitted value as per IS 12269: 2013. The increase in strength was due to the fact that nano cement acts not only as a filler material but also the reactivity increased due to the higher specific surface area. The SEM image shows the formation of additional C-S-H gel. The percentage increase in compressive strength was found to increase up to 32%. The workability of concrete with nano cement was found to be significantly more than that of the normal cement concrete.

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 Development of a New Type of Alkali-Free Liquid Accelerator for Wet Shotcrete in Coal Mine and Its Engineering Application

2015 ◽  
Vol 2015 ◽  
pp. 1-14 ◽  
Author(s):  
Gang Zhou ◽  
Weimin Cheng ◽  
Sen Cao
Keyword(s):  
Compressive Strength ◽  
Raw Materials ◽  
Setting Time ◽  
Engineering Application ◽  
First Grade ◽  
Dust Concentration ◽  
National Standard ◽  
Initial Setting Time ◽  
Initial Setting ◽  
New Type

In order to address issues such as large rebound rate, high dust concentration, and low compressive strength of shotcrete when adding liquid accelerator during wet spraying, the factors influencing the efficiency of liquid accelerator were experimentally analyzed. The single-admixture, combination, and orthogonal tests were conducted on the five fundamental raw materials required to develop the new liquid accelerator. The WT-1 type liquid accelerator, which had better adaptability to different kinds of cement, was developed with the mass concentration ratio of 55% aluminum sulfate octadecahydrate, 4% sodium fluoride, 2.5% triethanolamine, 0.5% polyacrylamide, 5% bentonite, and 33% water. Experimental investigation showed that the initial setting time of the reference cement with 6% mass content of this liquid accelerator was 2 minutes and 15 seconds, and the final setting time was 7 minutes and 5 seconds. The compressive strength after 1 day of curing was 13.6 MPa and the strength ratio after 28 days of curing was 94.8%, which met the first grade product requirements of the China National Standard. Compared with the conventional type liquid accelerator, the proposed type WT-1 accelerator is capable of effectively reducing the rebound rate and dust concentration while significantly increasing the compressive strength of the shotcrete.

Study on the Early Hydration of Cement Paste Containing Sodium Chloride

2014 ◽  
Vol 621 ◽  
pp. 35-38 ◽  
Author(s):  
Rahimah Embong ◽  
Andri Kusbiantoro
Keyword(s):  
Compressive Strength ◽  
Sodium Chloride ◽  
Cement Paste ◽  
Setting Time ◽  
Chloride Ion ◽  
Strength Development ◽  
Early Hydration ◽  
Initial Setting Time ◽  
Additive Component ◽  
Initial Setting

This paper studies the effect of sodium chloride as the additive component in cement paste. Sodium chloride was included at 0.5%, 1%, 1.5%, and 2% by weight of cement content. Analysis on the performance of this reagent was conducted via setting time, compressive strength, and porosity test. Based on the setting time analysis, the inclusion of sodium chloride can extend the initial setting time of cement paste up to 24.91% longer than control specimen. Obstruction on the formation of calcium silicate hydrate gel by sodium and chloride ion was one of the possible causes to this phenomenon. Acceleration on the compressive strength development by sodium chloride was also detected. It appears that sodium chloride was able to de-flocculate the coagulated cement particles and reduced the viscosities of cement slurries; hence resulted in faster early hydration process.

scholarly journals Pengaruh Bahan Tambah Gula Pasir Terhadap Waktu Pengikatan dan Kuat Tekan

2020 ◽  
Vol 6 (1) ◽  
pp. 1
Author(s):  
Retno Trimurtiningrum ◽  
Bantot Sutriono ◽  
Billy Arrowrichta ◽  
Hiasintus Bertus Watu ◽  
Misrawi Misrawi
Keyword(s):  
Compressive Strength ◽  
Setting Time ◽  
Test Results ◽  
Construction Process ◽  
Initial Setting Time ◽  
Chemical Admixtures ◽  
Chemical Admixture ◽  
Compressive Strength Test ◽  
Initial Setting ◽  
Project Location

ABSTRAKDalam pelaksanaan pembangunan konstruksi beton, seringkali ditemui beberapa kendala, seperti lokasi batching plan yang berbeda dengan lokasi proyek serta tingginya temperatur saat pengecoran, sehingga dapat mempercepat waktu pengikatan beton. Untuk mencegah waktu pengikatan lebih awal, diperlukan bahan tambah kimia yang dapat memperlambat waktu pengikatan yaitu retarder. Akan tetapi, bahan tambah kimia mempunyai harga yang relatif tinggi. Oleh karena itu, pada penelitian ini digunakan gula sebagai bahan tambah alternatif, karena gula merupakan salah satu penyusun dalam komposisi retarder serta mempunyai harga yang cukup ekonomis. Persentase gula pasir yang digunakan bervariasi, yaitu 0% (sebagai benda uji kontrol); 0,03%; 0,05% dan 0,1%. Hasil pengujian menunjukkan waktu pengikatan terlama diperoleh campuran dengan persentase gula sebanyak 0,1% dengan waktu ikat awal 157 menit dan waktu ikat akhir 258 menit, sedangkan hasil pengujian kuat tekan maksimum sebesar 225,38 kg/cm2 diperoleh campuran dengan persentase gula sebanyak 0,05%.Kata kunci: waktu pengikatan, gula, kuat tekan, retarderABSTRACTIn concrete construction process, several obstacles are often to be encountered such as the location of the batching plan that is different from the project location, as well as the high temperature while casting causes the acceleration of concrete setting time. To prevent earlier setting time, chemical admixture which can slow down the setting time is needed, namely retarders. However, chemical admixtures have relatively high prices. Therefore, in this study, sugar was used as an alternative ingredient, because sugar is one of the retarder’s composition and has relatively economical price. The percentages of sugar were varied, which are 0% (as a control specimen); 0.03%; 0.05% and 0.1%. The test results showed that the longest setting time is obtained by mixture with 0.1% of sugar, with the initial setting time 157 minutes and the final setting time 258 minutes, while the maximum compressive strength test results are 225,38 kg/cm2 obtained by a mixture with 0,05% of sugar.Keywords: setting time, sugar, compressive strength, retarder

The Influence of Alcohol Amine Admixtures on the Macroscopic Properties of Portland Cement Paste

2014 ◽  
Vol 525 ◽  
pp. 573-579
Author(s):  
Tian Yong Huang ◽  
Dong Min Wang ◽  
Ze Liu
Keyword(s):  
Compressive Strength ◽  
Flexural Strength ◽  
Portland Cement ◽  
Cement Paste ◽  
Setting Time ◽  
Initial Setting Time ◽  
Final Setting Time ◽  
Cement Mortars ◽  
Macroscopic Properties ◽  
Initial Setting

It is studied the influence of triethanolamine (TEA), diethylenetriamine (DEA), Triisopropanolamine (TIPA), aminoethyl ethanolamine (AE), and polyvinyl alcohol ammonium phosphate (PAAP) at different dosages on the properties of fresh and hardened cement pastes and mortars prepared by Portland cement, including standard consistency water, setting time, the cement paste fluidity, and compressive and flexural strength. It is showed that the high polarity alcohol amine molecules exhibit strong chemical interactions with cement matrix, which are reflected in modified macroscopic properties of the cement system. All alcohol amine admixtures increased the standard consistency water and decreased cement paste fluidity of Portland cement. TEA significantly shortened the initial setting time and final setting time of Portland cement. On the other hand, TIPA, DEA, AE and PAAP extended the initial setting time of cement but shortened the cement final setting time. All alcohol amine admixtures except TIPA at 0.2 and 0.5 dosage increased the compressive and flexural strength of the Portland cement mortars at 3 days. Especially when the dosage of PAAP is 1, the compressive strength of the Portland cement mortars at 3 days is increased 10.5MPa. All alcohol amine admixtures except AE at 0.2 and 0.5 dosage increase the compressive and flexural strength of the Portland cement mortars at 28 days, Especially when the dosage of TIPA is 1, the compressive strength of the Portland cement mortars at 28 days is increased 8.8MPa.

scholarly journals Influence of α-Calcium Sulfate Hemihydrate on Setting, Compressive Strength, and Shrinkage Strain of Cement Mortar

Materials ◽  
2019 ◽  
Vol 12 (1) ◽  
pp. 163 ◽  
Author(s):  
Bokyeong Lee ◽  
Gyuyong Kim ◽  
Jeongsoo Nam ◽  
Kyehyouk Lee ◽  
Gyeongtae Kim ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Calcium Sulfate ◽  
Cement Mortar ◽  
Setting Time ◽  
Shrinkage Strain ◽  
Replacement Ratio ◽  
Initial Setting Time ◽  
Initial Setting ◽  
Furnace Slag ◽  
Calcium Sulfate Hemihydrate

This study focused on the quick initial setting time and the expansion strain that occurs during the early aging of α-calcium sulfate hemihydrate (αHH) and examined the setting, compressive strength, and shrinkage strain of αHH-replaced cement mortar. The results show that the initial setting time significantly decreased with an increase in the αHH replacement ratio. Drastic occurrence of ettringite was observed early in the aging of cement mortar when αHH was substituted into the cement; however, the ettringite was not converted to monosulfate with increasing age and thus was not favorable for the development of the compressive strength. When αHH was substituted into cement, using Portland blast-furnace slag cement (PSC) was more advantageous than using ordinary Portland cement (OPC) for the development of the compressive strength. Meanwhile, the expansion of early age αHH can decrease the shrinkage strain of cement mortar. The generation of ettringite is more effective when αHH is substituted into PSC than into OPC and is thus more effective in suppressing the shrinkage strain.

scholarly journals The Effect of Superabsorbent Polymer and Nano-Silica on the Properties of Blended Cement

Crystals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1394
Author(s):  
Renuka Senthil Muthalvan ◽  
Suraj Ravikumar ◽  
Siva Avudaiappan ◽  
Mugahed Amran ◽  
Radhamanohar Aepuru ◽  
...  
Keyword(s):  
Cement Paste ◽  
Cement Mortar ◽  
Setting Time ◽  
Blended Cement ◽  
Experimental Investigations ◽  
Superabsorbent Polymer ◽  
Test Results ◽  
Nano Silica ◽  
Initial Setting Time ◽  
Blended Cement Paste

Incorporating superabsorbent polymer (SAP), which has the abilities of absorption and desorption in cement mortar, can achieve the effect of internal curing. It is expected that the incorporation of nano-silica will improve the workability and strength in cement mortar/concrete. Hence, this study aims to examine the effect of SAP and nano-silica on the properties of blended cement paste. The experimental investigations via several tests such as consistency, setting time, compressive strength, UPV, and acid test were performed. Based on energy-dispersive X-ray analysis (EDX) test and scanning electron microscopy (SEM) test results, the morphology of hydration products and mineral compositions of cement paste were further analysed, and the mechanism of SAP with 0.2% and 0.3% and NS with lower percentages ranging from 0.5% to 2% on the performance of cement paste was studied. The results exhibited that incorporating SAP in various percentages from 0.5% to 2% prolonged the initial setting time, reduced the fluidity, and increased the water content and formation of pores. In addition, various percentages ranging from 0.5% to 2% of NS were added; thereby, an increase in the hydration process and refining the microstructure was found. The microscopic test results showed that the blended cement paste can effectively improve the denser microstructure and refine the pore structure.

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.

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