scholarly journals Hydration Properties of Portland Cement Paste with Boron Gangue

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Quan Zhao ◽  
Jianwei Tu ◽  
Weiwei Han ◽  
Xi Wang ◽  
Youzhi Chen
Keyword(s):  
Portland Cement ◽  
Cement Hydration ◽  
Setting Time ◽  
High Strength ◽  
Cementitious Materials ◽  
Radiation Shielding ◽  
Boron Compounds ◽  
Hydration Properties ◽  
Materials Used ◽  
Low Solubility

In order to prepare a good radiation shielding concrete with a proper setting time and a high strength, the hydration properties of cement with boron gangue were investigated by the methods of XRD, isothermal microcalorimetry, TG/DSC, and FTIR. The results demonstrated that it was mainly related to the insoluble matter CaB2O4·4H2O and Ca(H2BO3)2·4H2O that boron gangue could severely inhibit the cement hydration. Boron gangue made a significant retardation on Portland cement hydration with the form of BO33− and BO45−, which caused an obvious retardation of C3A and C3S hydration with an insoluble coat and a low solubility of calcium ion in the solution. Therefore, it is important and necessary to take into consideration the chemistry of borates in aqueous and the kind of cement-based or cementitious materials used for radiation shielding concrete with boron or boron compounds, especially for the materials with a high content of C3A and C3S.

Evaluation of strength of concrete on different initial exposure condition

2020 ◽  
Vol 13 ◽  
Author(s):  
Sri Ram Krishna Mishra ◽  
Pradeep Kumar Ghosh ◽  
Manoj Kulshreshtha
Keyword(s):  
Portland Cement ◽  
High Strength ◽  
Cementitious Materials ◽  
General Purpose ◽  
Supplementary Cementitious Materials ◽  
Exposure Condition ◽  
Portland Cement Concrete ◽  
Initial Exposure ◽  
Skilled Manpower ◽  
Standard Practices

Background: The previous studies have focused curing effect of mainly on high strength concrete, where strict supervision is maintained. This study is based upon general purpose concreting work for commercial and residential construction in absence of skilled manpower and supervision. Objective: The objective of this study is to establish a thumb rule to provide 7 days initial curing for maintaining quality for unsupervised concreting irrelevant to type of cement and grading. Methods: In this study concrete samples made with locally available commercial cements were cured for various initial exposure. Results: The results shows that concrete cured after a gap of 4 days from the time of de-moulding have given lowest strength as compared to concrete cured in standard practices i.e. where proper curing protocol had been followed. Conclusion: Initial curing is most important aspect of gaining desired strength. The findings after this study shows that curing affects the strength of concrete in variable grading. Initial curing has great importance for concrete with all types of Portland cement. Concrete with supplementary cementitious materials gives lowest strength initially but results higher strength after 28 days as compared to Portland cement.

scholarly journals Effect of TiO2 Nanoparticles on Physical and Mechanical Properties of Cement at Low Temperatures

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Li Wang ◽  
Hongliang Zhang ◽  
Yang Gao
Keyword(s):  
Mechanical Properties ◽  
Low Temperatures ◽  
Cement Hydration ◽  
Setting Time ◽  
Physical And Mechanical Properties ◽  
Xrd Analysis ◽  
Cementitious Materials ◽  
Strength Test ◽  
Hydration Degree ◽  
Time Test

Low temperature negatively affects the engineering performance of cementitious materials and hinders the construction productivity. Previous studies have already demonstrated that TiO2 nanoparticles can accelerate cement hydration and enhance the strength development of cementitious materials at room temperature. However, the performance of cementitious materials containing TiO2 nanoparticles at low temperatures is still unknown. In this study, specimens were prepared through the replacement of cement with 1 wt.%, 2 wt.%, 3 wt.%, 4 wt.%, and 5 wt.% TiO2 nanoparticles and cured under temperatures of 0°C, 5°C, 10°C, and 20°C for specific ages. Physical and mechanical properties of the specimens were evaluated through the setting time test, compressive strength test, flexural strength test, hydration degree test, mercury intrusion porosimetry (MIP), X-ray diffraction (XRD) analysis, thermal gravimetric analysis (TGA), and scanning electron microscopy (SEM) in order to examine the performance of cementitious materials with and without TiO2 nanoparticles at various curing temperatures. It was found that low temperature delayed the process of cement hydration while TiO2 nanoparticles had a positive effect on accelerating the cement hydration and reducing the setting time in terms of the results of the setting time test, hydration degree test, and strength test, and the specimen with the addition of 2 wt.% TiO2 nanoparticles showed the superior performance. Refined pore structure in the MIP tests, more mass loss of CH in TGA, intense peak appearance associated with the hydration products in XRD analysis, and denser microstructure in SEM demonstrated that the specimen with 2 wt.% TiO2 nanoparticles exhibited preferable physical and mechanical properties compared with that without TiO2 nanoparticles under various curing temperatures.

scholarly journals Effect of nano-SnO2 on early-age hydration of Portland cement paste

2019 ◽  
Vol 11 (6) ◽  
pp. 168781401985194 ◽  
Author(s):  
Jianping Zhu ◽  
Genshen Li ◽  
Ruijie Xia ◽  
Huanhuan Hou ◽  
Haibin Yin ◽  
...  
Keyword(s):  
Portland Cement ◽  
Cement Paste ◽  
Cement Hydration ◽  
Cementitious Materials ◽  
Hydration Process ◽  
Strength Development ◽  
Early Age ◽  
Test Machine ◽  
Portland Cement Paste ◽  
Scanning Electron

Nanomaterial, as a new emerging material in the field of civil engineering, has been widely utilized to enhance the mechanical properties of cementitious material. Nano-SnO2 has presented high hardness characteristics, but there is little study of the application of nano-SnO2 in the cementitious materials. This study mainly investigated the hydration characteristics and strength development of Portland cement paste incorporating nano-SnO2 powders with 0%, 0.08%, and 0.20% dosage. It was found that the early-age compressive strength of cement paste could be greatly improved when nano-SnO2 was incorporated with 0.08% dosage. The hydration process and microstructure were then measured by hydraulic test machine, calorimeter, nanoindentation, X-ray diffraction, scanning electron microscope, and mercury intrusion porosimetry. It was found that the cement hydration process was promoted by the addition of nano-SnO2, and the total amount of heat released from cement hydration is also increased. In addition, the addition of nano-SnO2 can promote the generations of high density C-S-H and reduce the generations of low density C-S-H indicating the nucleation effect of nano-SnO2 in the crystal growth process. The porosity and probable pore diameter of cement paste with 0.08% nano-SnO2 were decreased, and the scanning electron microscopic results also show that the cement paste with 0.08% nano-SnO2 promotes the densification of cement microstructure, which are consistent with the strength performance.

scholarly journals Effect of boron-containing aggregates on setting and hardening of Portland cement mortars

2018 ◽  
Vol 163 ◽  
pp. 04003 ◽  
Author(s):  
Aneta Antolik ◽  
Michał A. Glinicki ◽  
Marek Gawlicki
Keyword(s):  
Isothermal Calorimetry ◽  
Setting Time ◽  
Radiation Shielding ◽  
Boron Compounds ◽  
Concrete Technology ◽  
Neutron Shielding ◽  
Mortar Strength ◽  
Cement Mortars ◽  
Isothermal Calorimeter ◽  
Cement Setting

Multicomponent cement-based composites are known as versatile structural materials for enhanced radiation shielding. The use of selected elements, like boron, cadmium, or rare earth elements, provides an increased neutron shielding capacity. Because of profusion, reasonable costs and large cross-section for neutron capture, boron containing minerals are suggested as aggregates for radiation shielding concrete. Despite many advantages, boron additives may act as cement setting retarders. Uncontrolled setting and hardening is not acceptable in radiation shielding concrete technology. In this work we present results from isothermal calorimetry measurements on cement mortars with boron-containing aggregates. Four types of boron aggregates were used in the studies: colemanite, ulexite, borax and boron carbide. Based on calorimetric curves, the beginning of setting time was determined. Additionally early mortar strength was investigated and linear relationship between the heat generated in the isothermal calorimeter and the early compressive strength has been observed. The use of isothermal calorimetry allowed us to estimate the limits for the content of boron compounds to be used cement mortar.

Influence of Clutch Disc Waste (Grinding Dust) on Portland Cement Hydration

2019 ◽  
Vol 803 ◽  
pp. 284-288
Author(s):  
José da Silva Andrade Neto ◽  
Tiago Assunção Santos ◽  
Raphael Dias Mariano ◽  
Marcio Raymundo Morelli ◽  
Daniel Véras Ribeiro
Keyword(s):  
Portland Cement ◽  
Propagation Velocity ◽  
Pulse Propagation ◽  
Cement Hydration ◽  
Setting Time ◽  
Reference Sample ◽  
Ultrasonic Pulse ◽  
X Ray Diffraction ◽  
Copper Zinc ◽  
Portland Cement Hydration

This paper evaluates the effect of grinding dust (GD), a waste generated in the clutch disc finishing process, on Portland cement hydration. For this, pastes with additions of 5%, 10% and 15% GD, relative to cement weight, were molded and compared with a reference sample. Tests of setting time determination by Vicat needle, calorimetry, monitoring the ultrasonic pulse propagation velocity and mineralogical analysis (X-ray diffraction) in pastes with 1 day of hydration were carried out. It was observed that GD, due to the presence of copper, zinc and phenolic resin in its composition, is responsible for retarding cement hydration and thus increases the setting time and delays the evolution of heat release and pulse propagation velocity. However, the formation of new crystalline phases was not observed.

Effect of Calcined Red Mud Addition on the Hydration of Portland Cement

2012 ◽  
Vol 727-728 ◽  
pp. 1408-1411 ◽  
Author(s):  
Daniel Véras Ribeiro ◽  
João A. Labrincha ◽  
Márcio Raymundo Morelli
Keyword(s):  
Portland Cement ◽  
Red Mud ◽  
Setting Time ◽  
Cementitious Materials ◽  
Adiabatic Calorimeter ◽  
Hydration Process ◽  
Early Hydration ◽  
Bauxite Ore ◽  
Calorimetric Studies ◽  
Reference Mixture

The red mud (RM) is a solid waste derived from the processing of bauxite ore to produce alumina and it is considered a hazardous waste due to its high pH. This paper describes the use of mud untreated and after calcination at distinct temperatures (450, 650, and 1000°C) attempting to improve its reactivity. The Portland cement was replaced up to 30 wt% red mud, and its addition changed the hydration process, evaluated by calorimetric studies of early hydration and setting time. By comparing with the reference mixture (without red mud), the obtained results confirm the potential of the red mud to be used as pozzolanic additive to cementitious materials. Temperature of hydration was monitored by a quasi-adiabatic calorimeter (Langavant). The hydration temperature increases with RM addition, particularly if calcined in the same interval (450-650°C). In this condition, the hydration process is accelerated.

The Evolution of Cementitious Materials Through History

1994 ◽  
Vol 370 ◽  
Author(s):  
David Bonen ◽  
Mehmet A. Tasdemir ◽  
Shondeepl. Sarkar
Keyword(s):  
Portland Cement ◽  
High Strength ◽  
Cementitious Materials ◽  
Portland Cement Concrete ◽  
Slaked Lime ◽  
Cracking Pattern ◽  
The 19Th Century ◽  
Highly Porous ◽  
Microstructural Examination

AbstractThe use of cementitious materials dates back to the beginning of the Epipaleolithic period. Examples for ancient cementitious materials from Israel, Egypt, Turkey, and Italy are numerous.Prior to Aspdin's patent of portland cement at the first half of the 19th century, cementitious materials were composed of earth, mixture of earth and limestone, calcium sulfates, and slaked lime with and without pozzolans. The latter comprises pozzolanic materials from volcanic and sedimentary origin, crushed burnt clay brick, and dust brick. Frequently, organic fibers were incorporated for reinforcement. This paper describes the evolution of the cementitious materials through time and highlights the durability of ancient cementitious materials as compares to that of portland cement concrete.Although modem concrete is characterized by its high strength and low permeability, it often faces durability problems. In turn, ancient concretes examined exhibit low strength but have proved to be durable materials. Microstructural examination reveals that the groundmass of the latter has been carbonated and is highly porous. Nevertheless, no specific cracking pattern could be observed. The outstanding performance of ancient concrete structures implies that thermodynamic stability rather that mechanical strength is a key point for a long-term durability.

scholarly journals Valorisation of fly ashes by geopolymerisation

2013 ◽  
Vol 11 (2) ◽  
pp. 147-154 ◽  
Keyword(s):  
Portland Cement ◽  
Setting Time ◽  
Cementitious Materials ◽  
Alkaline Solutions ◽  
Strength Development ◽  
Fly Ashes ◽  
Concrete Production ◽  
Metallurgical Slags ◽  
Coal Fly Ashes ◽  
Intrinsic Reactivity

Coal fly ashes and metallurgical slags are currently widely used as supplementary cementitious materials in production of Portland cement-based concretes. However, this application makes very poor use of the intrinsic reactivity of the glassy phases present in the waste materials, and can hardly therefore be considered ‘valorisation’ in the true sense of the word. Addition of these materials to Portland cements can also cause difficulties in early strength development, limiting their use to certain applications. Geopolymerisation, on the other hand, makes full use of the glassy ash and slag materials by using them as the key reactants in synthesis of aluminosilicate gel binders for waste-based concrete production. The activation of the glassy phases by alkaline solutions provides the opportunity to greatly reduce the Portland cement content of a concrete, but requires a sound understanding of the ash chemistry and its effects on workability, water demand and setting time if it is to be implemented successfully on a commercial scale. In this paper, various aspects of fly ash valorisation via geopolymerisation are discussed, including in particular the determination of ash reactivity by a recently-developed technique utilising dilatometric data. The correlations between ash reactivity as measured by dilatometry and geopolymer mechanical strength are discussed in detail, and comparisons with other measures of ash reactivity presented. Some commercial examples of geopolymer concrete in-place are also discussed to highlight these differences in real world usage.

scholarly journals Peculiarities of hydration of Portland cement with synthetic nano-silica

2017 ◽  
Vol 12 (2) ◽  
pp. 101-106 ◽  
Author(s):  
Galyna Kotsay
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Portland Cement ◽  
Cement Hydration ◽  
Physical And Mechanical Properties ◽  
The Other ◽  
Nano Materials ◽  
Nano Silica ◽  
Other Hand ◽  
Materials Used

Abstract Application of nano-materials in cement products significantly, improves their properties. Of course, the effectiveness of the materials depends on their quantity and the way they are introduced into the system. So far, amongst nano-materials used in construction, the most preferred was nano-silica. This research investigated the effect of synthetic precipitated nano-silica on the cement hydration as well as, on the physical and mechanical properties of pastes and mortars. Obtained results showed that admixture of nano-silica enhanced flexural and compressive strength of cement after 2 and 28 days, however, only when admixture made up 0.5% and 1.0%. On the other hand, the use of nano-silica in the amount 2% had some limitations, due to its ability to agglomerate, which resulted in deterioration of the rheological and mechanical properties.

Retarding Action of Various Lead (II) Salts on Setting of Portland Cement

2018 ◽  
Vol 760 ◽  
pp. 43-48
Author(s):  
Martin Keppert
Keyword(s):  
Portland Cement ◽  
Ordinary Portland Cement ◽  
Cement Hydration ◽  
Setting Time ◽  
Lead Sulfate ◽  
Cementitious Material ◽  
Secondary Product ◽  
Experimental Conditions ◽  
Anion Effect ◽  
High Instability

Lead is an example of heavy metal, which influences the course of silicate cement hydration resulting to retardation of setting and hardening. This topic become of importance when a cementitious material is intended to be used as solidification/stabilization matrix for a waste or secondary product containing some lead species. There are literature data on the effect of Pb retarding action but they are incomparable each other due to uneven experimental conditions, used Pb salts, types of cement etc. The present paper aims to describe influence of various lead(II) compounds (nitrate, sulfate and lead(II) oxide) on setting course of Ordinary Portland cement (OPC). The setting was monitored by Vicat apparatus, the dosage of salts (expressed as wt. % of elementary Pb to OPC) was 0.5, 1, 2 and 5%. Obviously the present anions may also influence the setting time; the set of control experiments with sodium salts of above given anions was performed in order to eliminate the anion effect. The PbO was found to be most detrimental towards retarding of setting, while lead sulfate at higher dosages caused high instability of setting (oscillation). The effect of Pb was, in all cases, more important than influence of given anion.

Sign in / Sign up

Export Citation Format

Share Document