Behavior of Cement Pastes and Mortar Containing Phosphogypsum

The aim of this study is to investigate the effects of phosphogypsum on the properties of both cement pastes and mortars. Normal Portland cement CEM Ι 32,5N, Limestone Blended cement CEM ΙΙ B-L32,5N, and Slag cement CEM ΙΙ A-S32,5N were used. These cements were partially substituted by 0,2,4,6,8,10,and 15% of phosphogypsum. The test program was divided to two stages. In the first stage, tests were conducted according to BSEN 196, namely setting times (initial and final), soundness, and compressive strength (at ages 7 and 28 days). In the second stage, X-ray diffraction (XRD), and scanning electron microscope (SEM) were conducted on selected mixes from first stage. The results show that the three types of cements with the various replacement percentages of phosphogypsum met the limit of initial setting time, as well as, provided soundness of 2 mm. Also, in terms of compressive strength, it was proven, that it is possible to partially replace the three tested types of cements by phosphogypsum by up to 8%and 15% with regard to cement/sand ratio of (1:3) and (1:2) respectively.

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

Materials ◽

10.3390/ma14071611 ◽

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.

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Effect of Naphthalene-Based Superplasticizer and Polycarboxylic Acid Superplasticizer on the Properties of Sulfoaluminate Cement

Materials ◽

10.3390/ma14030662 ◽

2021 ◽

Vol 14 (3) ◽

pp. 662

Author(s):

Yonghua Wu ◽

Qiqi Li ◽

Guoxin Li ◽

Shiying Tang ◽

Mengdie Niu ◽

...

Keyword(s):

Compressive Strength ◽

Setting Time ◽

Hydration Products ◽

Polycarboxylic Acid ◽

X Ray Diffraction ◽

Calcium Sulfoaluminate Cement ◽

X Ray ◽

Initial Setting Time ◽

Calcium Sulfoaluminate ◽

Initial Setting

In order to study what the effect of superplasticizers on the setting time, fluidity and compressive strength of calcium sulfoaluminate cement (CSA) a naphthalene-based superplasticizer (BNS) and a polycarboxylic acid superplasticizer (PC) were selected to interact with CSA pastes and ye’elimite, respectively. X-ray diffraction (XRD), thermogravimetric (TG) analysis and scanning electron microscopy (SEM) analytical methods were used to investigate the class, amount and microstructure of the CSA pastes and ye’elimite pastes hydration products under the effect of the superplasticizers. The results showed that the addition of BNS can promote ettringite generation and thus improve the early compressive strength. As the addition of BNS increased from 0.8 wt% to 2.0 wt%, the initial setting time was prolonged 10 min, the final setting time was prolonged 7 min, the 5 min fluidity was improved from no fluidity to 220 mm. However, as the addition of PC increased from 0.08 wt% to 0.20 wt%, the setting time of the PC just changed within 3 min; the 5 min fluidity increased from 110 mm to 195 mm and no 15 min fluidity at all was observed. AS seen by SEM, it can be stated that generated ettringite under the addition of PC was layered and lacking bonding, and its morphology changed from rod-like to flake-like, leading to a decrease in early compressive strength.

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Influence of Ultrafine Natural Steatite Powder on Setting Time and Strength Development of Cement

Advances in Materials Science and Engineering ◽

10.1155/2014/532746 ◽

2014 ◽

Vol 2014 ◽

pp. 1-6 ◽

Cited By ~ 9

Author(s):

K. Sudalaimani ◽

M. Shanmugasundaram

Keyword(s):

Compressive Strength ◽

Setting Time ◽

Element Distribution ◽

Strength Development ◽

X Ray Diffraction ◽

Dormant Period ◽

Initial Setting Time ◽

Final Setting Time ◽

Initial Setting ◽

Cement Binder

This paper deals with the setting time and pozzolanic activity of cement when ultra fine natural steatite powder (UFNSP) is used as replacement for cement. Initial setting time, final setting time, and mortar cube strength were studied, due to the replacement of ultra fine natural steatite powder with cement at 5%, 10%, 15%, 20%, and 25% by mass of cement. The setting time of fresh cement-binder paste and compressive strength of mortar cubes are observed. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were applied to investigate the microstructural behaviour and chemical element distribution inside cement-binder matrix. Results indicate that the length of dormant period is shortened. The replacement of ultra fine natural steatite powder with cement reduces initial setting time, and final setting time and increases mortar cube compressive strength.

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Investigation on the Compressive Strength and Time of Setting of Low-Calcium Fly Ash Geopolymer Paste Using Response Surface Methodology

Polymers ◽

10.3390/polym13203461 ◽

2021 ◽

Vol 13 (20) ◽

pp. 3461

Author(s):

Pauline Rose J. Quiatchon ◽

Ithan Jessemar Rebato Dollente ◽

Anabel Balderama Abulencia ◽

Roneh Glenn De Guzman Libre ◽

Ma. Beatrice Diño Villoria ◽

...

Keyword(s):

Compressive Strength ◽

Fly Ash ◽

Unconfined Compressive Strength ◽

Setting Time ◽

Initial Setting Time ◽

Alkali Activator ◽

Setting Times ◽

Confirmatory Tests ◽

Initial Setting

Approximately 2.78 Mt of coal fly ash is produced in the Philippines, with a low utilization rate. Using fly ash-based geopolymer for construction will lessen the load sent to landfills and will result in lower GHG emissions compared to OPC. It is necessary to characterize the fly ash and optimize the geopolymer components to determine if it can replace OPC for in situ applications. The activator-to-precursor ratio, the water-to-solids ratio, and the sodium hydroxide-to-sodium silicate ratio were optimized using a randomized I-optimal design from the experimental results of 21 runs with five replicates, for a total of 105 specimens of 50 mm × 50 mm × 50 mm paste cubes. The engineering properties chosen as the optimization responses were the unconfined compressive strength (UCS), the initial setting time, and the final setting time. The samples were also ambient-cured with the outdoor temperature ranging from 30 °C to 35 °C and relative humidity of 50% ± 10% to simulate the on-site environment. Runs with high unconfined compressive strength (UCS) and short setting times were observed to have a low water-to-solids (W/S) ratio. All runs with a UCS greater than 20 MPa had a W/S ratio of 0.2, and the runs with the lowest UCS had a W/S of 0.4. The initial setting time for design mixes with a W/S ratio of 0.2 ranged from 8 to 105 min. Meanwhile, five out of seven design mixes with a W/S ratio of 0.4 took longer than 1440 min to set. Specimens with an alkali activator ratio (NaOH/WG) of 0.5 (1:2) and 0.4 (1:2.5) also had significantly lower setting times than those with an alkali activator ratio of 1. The RSM model was verified through confirmatory tests. The results of the confirmatory tests are agreeable, with deviations from the expected UCS ranging from 0 to 38.12%. The generated model is a reliable reference to estimate the UCS and setting time of low-calcium FA geopolymer paste for in situ applications.

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Investigation of Portland cement composites containing high amounts of different kinds of fly ashes

The proceedings of the 13th international conference "Modern Building Materials, Structures and Techniques" (MBMST 2019) ◽

10.3846/mbmst.2019.113 ◽

2019 ◽

Author(s):

Iwona Wilińska ◽

Barbara Pacewska ◽

Wojciech Kubissa

Keyword(s):

Compressive Strength ◽

Fly Ash ◽

Setting Time ◽

Cement Composite ◽

Fly Ashes ◽

Cement Pastes ◽

Initial Setting Time ◽

Initial Setting ◽

Lower Heat ◽

The Impact

Utilization of fluidized fly ash in cement composite is problematic, e.g. because of its changeable chemical composition and increased water demand of the mixture. However, this kind of by-product shows some self-cementing properties, which may be beneficial for low-cement mixtures. The article compares the impact of various kinds of fly ashes, i.e. fluidized fly ash and conventional one, and their mixtures on hydration of fly ash–cement compositions in relation to properties of final material. The amount of fly ash in the binder was 50 wt%. Calorimetry, thermal analysis (TG/DTG) and infrared spectroscopy were used. Compressive strength and water absorption of hardened composites were also registered. It was found that both fly ashes exhibit delay effect in fly ash-cement pastes which causes extension of initial setting time and lower heat released compared to the reference without fly ash. At later hydration days, fluidized fly ash develops higher pozzolanic activity than conventional one. Compositions with fluidized fly ash show better compressive strength compared to those containing conventional one. Mixing of different materials of high and low activity (fluidized and conventional fly ash in this case) seems to be a good way for creation of new cement replacement material.

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Performance of High-Efficiency Liquid Cement Setting Accelerator with Alkali-Free and its Acceleration Mechanism

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.377.69 ◽

2013 ◽

Vol 377 ◽

pp. 69-73

Author(s):

Yan Wang ◽

Jun Wang ◽

Shu Heng Qiu ◽

Fei Gao ◽

Rui Gu

Keyword(s):

Compressive Strength ◽

High Efficiency ◽

Bending Strength ◽

Setting Time ◽

X Ray Diffraction ◽

Initial Setting Time ◽

Acceleration Mechanism ◽

Initial Setting ◽

Strength Retention ◽

Cement Setting

A kind of non-alkali high efficiency liquid cement setting accelerator named ZJ-NSA was developed by regulating the chemical composition of polymerized aluminum sulfate in this paper. The results show that the initial setting time and the final setting time are sharply shortened to 2 minutes 48 seconds and 4 minutes 37 seconds respectively, and the 1 d-aged compressive strength reach to 8.6MPa when it is mixed into P.O42.5 Portland cement with 5% addition; meanwhile, its compressive strength and bending strength retention at the age of 1d and 28d reach to 79.63%, 81.89% and 78.13%, 97.89% respectively. Phase characteristics on the hydrated cement specimens by means of x-ray diffraction (XRD) and differential scanning calorimeter (DSC) were analyzed and the acceleration mechanism was discussed.

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Development of Injectable Calcium Phosphate Cement Adding with ZrO2

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.361-363.347 ◽

2007 ◽

Vol 361-363 ◽

pp. 347-350

Author(s):

J.Y. Gong ◽

Shu Xin Qu ◽

Q. Cui ◽

Jie Weng

Keyword(s):

Compressive Strength ◽

Calcium Phosphate ◽

Setting Time ◽

X Ray Diffraction ◽

Liquid Component ◽

X Ray ◽

Initial Setting Time ◽

Mass Fractions ◽

Initial Setting ◽

Diffraction Peaks

In the present study, ZrO2 was added into the injectable calcium phosphate cements (CPCs) to improve their mechanical strength. Different mass fractions of ZrO2 (5 %, 10 %, 15 %, 20%) were mixed with the powder components consisted of tricalcium phosphate (α-TCP) and hydroxyapatite (HA). Then formed the paste via adding the liquid component consisted of citric acid. The compressive strength, the injectability, the initial setting time and finial time of CPC were measured, respectively. X-ray diffraction (XRD) was employed to analyse the phase of as-prepared CPC. Scanning Electron Microscope (SEM) and Energy dispersive spertrum (EDS) were used to observe the morphology and indicate the element components of CPC. The compressive strength of ZrO2-CPC was higher than that of CPC without added ZrO2. The compressive strength got the maximal when the mass fraction of ZrO2 was 15%. It had no effect on the injectability with adding ZrO2, which were 89 % to 92 %. It had a slight down-regulation of the initial and final setting time with adding ZrO2. SEM showed that there was amounts needle-like substance in CPC, which might be related to the improvement of compressive strength of CPC. XRD showed that there were HA, a few of α-TCP and ZrO2 diffraction peaks in CPCs. The present results indicate that it is feasible to improve the compressive strength of injectable CPC via adding ZrO2.

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

Jurnal Teknik Kimia dan Lingkungan ◽

10.33795/jtkl.v4i1.150 ◽

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.

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

Materials ◽

10.3390/ma14195705 ◽

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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