Bonding Calcium Chloride and Calcium Nitrate into Stable Hydration Portland Cement Products: Stability Conditions of Calcium Hydrochloraluminates and Calcium Hydronitroaluminates

2018 ◽  
Vol 36 ◽  
pp. 69-73 ◽  
Author(s):  
Andrii A. Plugin ◽  
Raisa F. Runova
Keyword(s):  
Portland Cement ◽  
Calcium Chloride ◽  
Thermodynamic Analysis ◽  
Calcium Nitrate ◽  
Cement Matrix ◽  
Stability Conditions ◽  
Decomposition Reactions ◽  
Tricalcium Aluminate

A thermodynamic analysis of the reactions of calcium chloride and calcium nitrate with tricalcium aluminate when used as a hardening accelerator for portland cement, as well as decomposition reactions of calcium hydrochloraluminate (CHChA) and calcium hydronitroalyuminate (CHNA) formed during the hardening was performed. The conditions of stable existence of CHChA and CHNA in the cement matrix were established.

scholarly journals Effect of a Nitrite/Nitrate-Based Accelerator on the Strength Development and Hydrate Formation in Cold-Weather Cementitious Materials

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 1006
Author(s):  
Akira Yoneyama ◽  
Heesup Choi ◽  
Masumi Inoue ◽  
Jihoon Kim ◽  
Myungkwan Lim ◽  
...  
Keyword(s):  
Calcium Nitrate ◽  
Hydrate Formation ◽  
Frost Damage ◽  
Cementitious Materials ◽  
Heat Of Hydration ◽  
Cold Weather ◽  
Strength Development ◽  
Hardened Cement ◽  
Tricalcium Aluminate ◽  
Nitrite Nitrate

Recently, there has been increased use of calcium-nitrite and calcium-nitrate as the main components of chloride- and alkali-free anti-freezing agents to promote concrete hydration in cold weather concreting. As the amount of nitrite/nitrate-based accelerators increases, the hydration of tricalcium aluminate (C3A phase) and tricalcium silicate (C3S phase) in cement is accelerated, thereby improving the early strength of cement and effectively preventing initial frost damage. Nitrite/nitrate-based accelerators are used in larger amounts than usual in low temperature areas below −10 °C. However, the correlation between the hydration process and strength development in concrete containing considerable nitrite/nitrate-based accelerators remains to be clearly identified. In this study, the hydrate composition (via X-ray diffraction and nuclear magnetic resonance), pore structures (via mercury intrusion porosimetry), and crystal form (via scanning electron microscopy) were determined, and investigations were performed to elucidate the effect of nitrite/nitrate-based accelerators on the initial strength development and hydrate formation of cement. Nitrite/nitrate-AFm (aluminate-ferret-monosulfate; AFm) was produced in addition to ettringite at the initial stage of hydration of cement by adding a nitrite/nitrate-based accelerator. The amount of the hydrates was attributed to an increase in the absolute amounts of NO2− and NO3− ions reacting with Al2O3 in the tricalcium aluminate (C3A phase). Further, by effectively filling the pores, it greatly contributed to the enhancement of the strength of the hardened cement product, and the degree of the contribution tended to increase with the amount of addition. On the other hand, in addition to the occurrence of cracks due to the release of a large amount of heat of hydration, the amount of expansion and contraction may increase, and it is considered necessary to adjust the amount used for each concrete work.

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

scholarly journals Mineralogical stabilization of Ternesite in Belite Sulfo-Aluminate Clinker elaborated from limestone, shale and phosphogypsum

2018 ◽  
Vol 149 ◽  
pp. 01073
Author(s):  
K. Ben Addi ◽  
A. Diouri ◽  
N. Khachani ◽  
A. Boukhari
Keyword(s):  
Infrared Spectroscopy ◽  
Phosphoric Acid ◽  
Portland Cement ◽  
Stability Conditions ◽  
X Ray Diffraction ◽  
X Ray ◽  
The Stability

This paper investigates the mineralogical evolution of sulfoaluminate clinker elaborated from moroccan prime materials limestone, shale and phosphogypsum as a byproduct from phosphoric acid factories. The advantage of the production of this type of clinker is related to the low clinkerisation temperature which is known around 1250°C, and to less consumption quantity of limestone thus enabling less CO2 emissions during the decarbonation process compared to that of Portland cement. In this study we determine the stability conditions of belite sulfoaluminate clinker containing belite (C2S) ye’elimite (C4A3$) and ternesite (C5S2$). The hydration compounds of this clinker are also investigated. The monitoring of the synthesized and hydrated phases is performed by X-Ray Diffraction and Infrared spectroscopy. The results show the formation of ternesite at 800°C and the stabilization of clinker containing y’elminite, belite and ternesite at temperatures between 1100 and 1250°C.

scholarly journals Properties of cement composites based on limestone depending on their granulometric composition

Vestnik MGSU ◽  
2020 ◽  
pp. 999-1006
Author(s):  
Svetlana V. Samchenko ◽  
Olga V. Alexandrova ◽  
Anton Yu. Gurkin
Keyword(s):  
Composite Materials ◽  
Portland Cement ◽  
Granulometric Composition ◽  
Coarse Grained ◽  
Cement Matrix ◽  
Cement Composites ◽  
Construction Costs ◽  
Initial Strength ◽  
Fine Grained ◽  
Additional Formation

Introduction. The use of limestone in cement compositions as an additional cementing agent solves both environmental and economic problems, namely, reduction of construction costs. In this regard, the study of the properties of the granulometric composition and volumetric content of cement composites, containing limestone, becomes increasingly important. The mission of this research is to optimize the properties of composite materials containing Portland cement and limestone by changing the granulometric composition of flour limestone. Materials and methods. Limestone, having three different Blaine milling fineness values of 250, 300 and 450 m2/kg, was used; its content reached 10, 15, 25 and 35 %. Cement and sand mortars were applied for testing purposes. The influence of the granulometric composition of limestone on the workability and compressive strength of composite cement was determined. Results. The effect of limestone on the limit shear stress becomes more pronounced when the amount of limestone increases to 25 and 35 %. This is most noticeable for limestone with a high content of fine fractions of 5–20 µm. The use of finely milled limestone increases the initial strength of the composite material. By adding 10 and 15 % of such limestone we can increase the strength by 16–20 %, and supplementary 25–35 % of limestone increases strength by 5–8 %. Strength enhancement is due to the reactivity of limestone and formation of calcium hydrocarbon aluminate 3CaO∙Al2O3∙СаСО3∙12H2O, which promotes formation of the crystal framework of the cement matrix. Additional formation of crystalline hydrates in the initial coagulation structure deteriorates the mortar workability, but increases its strength. Conclusions. The use of coarse-grained limestone significantly improves mortar workability, while the use of fine-grained limestone increases its content without reducing its strength. The granulometric composition of ground limestone shall be as close as possible to the granulometric composition of cement for the properties of composite materials containing Portland cement and limestone to be optimized.

scholarly journals AN EFFECTIVE WAY TO RECYCLE 3D PRINTING CONCRETE SCRAP

2021 ◽  
Vol 4 (2) ◽  
pp. 12-18
Author(s):  
D.A. Tolypin ◽  
N. Tolypina
Keyword(s):  
Compressive Strength ◽  
3D Printing ◽  
Portland Cement ◽  
Quartz Sand ◽  
Raw Materials ◽  
Electricity Consumption ◽  
Cement Matrix ◽  
Fine Aggregate ◽  
Fine Grained ◽  
Control Samples

the article proposes a rational method for processing 3D printing concrete scrap using vibration equipment, which allows obtaining a multicomponent building material with minimal electricity consumption. As a crite-rion for the degree of grinding of concrete scrap, it is proposed to use the specific surface area of the finely dispersed part of concrete scrap, which should correspond to 400-500 m2/kg. The possibility of reusing the resulting product instead of the traditional fine aggregate of quartz sand is shown. It was found that the con-crete scrap without the addition of Portland cement hardens, reaching up to 48% of the compressive strength of the control samples by 28 days. When 10% of the binder CEM I 42.5 N was added to the concrete scrap processing product, the compressive strength of fine-grained concrete increased by 106.6%, and 20% of Portland cement - by 112.2 %, compared to the strength of control samples of a similar composition on tra-ditional quartz sand after 28 days of hardening. It is noted that this is primarily due to the weak contact zone of quartz sand and the cement matrix of concrete. The use of the product of processing concrete scrap al-lows obtaining building composites based on it with the complete exclusion of natural raw materials

scholarly journals Thermodynamic analysis of copper(I) sulfide chlorination by calcium chloride in the presence of oxygen

1999 ◽  
Vol 64 (5-6) ◽  
pp. 365-374 ◽  
Author(s):  
Rajko Vracar ◽  
Katarina Cerovic
Keyword(s):  
Calcium Chloride ◽  
Thermodynamic Analysis ◽  
Chemical Reactions ◽  
Phase Stability ◽  
Log P ◽  
Temperature Range ◽  
Stability Diagrams

This paper presents a thermodynamic analysis of possible, but insufficiently studied, chemical reactions occurring during the chlorination of copper(I) sulfide by calcium chloride in the presence of oxygen. It formed the basis for assessing the probability and priority of their occurrence. Phase stability diagrams have been plotted for the Cu-S-O-Cl system in the coordinates log p(S2)-log p(O2)-log p(Cl2) in the temperature range from 473 to 773 K.

Studies on recycling spent compost for mushroom cultivation

1976 ◽  
Vol 27 (6) ◽  
pp. 857 ◽  
Author(s):  
NG Nair
Keyword(s):  
Electrical Conductivity ◽  
Calcium Chloride ◽  
Calcium Nitrate ◽  
Peat Moss ◽  
Mushroom Cultivation ◽  
Soluble Salts ◽  
Rice Hulls ◽  
Mushroom Production ◽  
Commercial Cultivation ◽  
Casing Layer

Natural weathering of spent compost for 2 years resulted in a lowering of electrical conductivity which enabled it to be used as a casing material in mushroom cultivation. Spent compost and peat moss had different optima of electrical conductivity values for normal mushroom production. Relatively high levels of soluble salts such as calcium nitrate and calcium chloride reduced the yield of mushrooms. The addition of rice hulls and peat moss to spent compost overcame the effect of sealing caused by watering. These amendments improved aeration of the casing layer and increased the number of pseudomonads. Pasteurized, spent compost, aged for 2 years, at a moisture level of 65% saturation, was shown to be a suitable casing material for obtaining relatively good yields of mushrooms. It is suggested that this material may find an application in commercial cultivation of mushrooms.

scholarly journals Dielectric Dissipation of Fibre-modified Hydraulic Concretes

1998 ◽  
Vol 7 (6) ◽  
pp. 096369359800700
Author(s):  
J.B. Hernández ◽  
F.A. Aguirre ◽  
J.L. Martínez ◽  
C. E. Caballero ◽  
L. Pérez-Rea ◽  
...  
Keyword(s):  
Portland Cement ◽  
Dielectric Behavior ◽  
Hydration Process ◽  
Cement Matrix ◽  
Polypropylene Fibers ◽  
Polypropylene Fibres ◽  
Polar Surfaces ◽  
Definitive Role

Dielectric behavior of Portland cement-based concretes, modified with either polyester or polypropylene fibers was studied by measuring their dissipation factors at different frequencies. The results show that the fibers with non-polar surfaces (polyester) do not influence the hydration process of the cement matrix, whereas polypropylene fibres, with polar surfaces, have a definitive role on the curing properties of the composites.

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