Stabilization of Heavy Metals in Portland Cement Matrix: Effects on Paste Properties

2009 ◽  
pp. 147-147-16 ◽  
Author(s):  
JI Bhatty ◽  
PB West
Keyword(s):  
Heavy Metals ◽  
Portland Cement ◽  
Matrix Effects ◽  
Cement Matrix ◽  
Paste Properties

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 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 Performance of composite mineral adsorbents for removing Cu, Cd, and Pb ions from polluted water

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Woo-Ri Lim ◽  
Sung Wook Kim ◽  
Chang-Han Lee ◽  
Eun-Kyeong Choi ◽  
Myoung Hak Oh ◽  
...  
Keyword(s):  
Heavy Metals ◽  
Adsorption Isotherm ◽  
Portland Cement ◽  
Weight Percent ◽  
Adsorption Kinetic ◽  
Polluted Water ◽  
Isotherm Models ◽  
Kinetic Experiment ◽  
Pb Ions ◽  
Mineral Adsorbents

Abstract This study evaluated the efficiency of the removal of heavy metals from contaminated water via adsorption isotherm and kinetic experiments on two composite mineral adsorbents, CMA1 and CMA2. The developed CMA1 (zeolite with clinoptilolite of over 20 weight percent and feldspar of ~10 percent, with Portland cement) and CMA2 (zeolite with feldspar of over 15 weight percent and ~9 percent clinoptilolite, with Portland cement) were applied to remove Cu, Cd, and Pb ions. Based on the adsorption isotherm and kinetic experiments, the adsorbents CMA1 and CMA2 exhibited high removal efficiency for Cu, Cd, and Pb ions in solution compared to other adsorbents. In the adsorption kinetic experiment, CMA2 demonstrated better adsorption than CMA1 with the same initial concentration and reaction time, and Cu, Cd, and Pb ions almost reached equilibrium within 180 min for both CMA1 and CMA2. The results of the adsorption kinetic experiments with pseudo-first-order (PFO) and pseudo-second-order (PSO) models indicated that the PSO model was more suitable than the PFO model. Comparing the Langmuir and Freundlich adsorption isotherm models, the former showed a very slightly higher correlation coefficient (r2) than the latter, indicating that the two models can both be applied to heavy metal solutions on a spherical monolayer surface with a weak heterogeneity of the surface. Additionally, the adsorbents CMA1 and CMA2 demonstrated different removal abilities depending on which heavy metals were used.

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.

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.

Soundness in Mortars of Portland Cement with Substitutions Using Cactus (Opuntia ficus-indica) and Corn Starch

2018 ◽  
Vol 789 ◽  
pp. 150-154
Author(s):  
Victor Hugo Blancas-Herrera ◽  
Jorge Alberto Pacheco-Segovia ◽  
Wilfrido Martínez-Molina ◽  
Hugo Luis Chávez García ◽  
Mauricio Arreola-Sanchez ◽  
...  
Keyword(s):  
Portland Cement ◽  
Corn Starch ◽  
Weight Ratio ◽  
Physical And Mechanical Properties ◽  
Ultrasonic Pulse Velocity ◽  
Ultrasonic Pulse ◽  
Pulse Velocity ◽  
Electric Resistivity ◽  
Cement Matrix ◽  
Opuntia Ficus Indica

The use of dehydrated fibres of cactus, Opuntia ficus-indica (FN), and starch (corn starch,Zea Mays (MZ)) as partial substitutes for the total mass of Portland Cement (CP) in the making ofmortar, aims at modifying its physical and mechanical properties, reducing the amount of cementand the CO2 emission. Four mixtures of CP mortar were designed incorporating a superplasticizeradditive with a water/cement weight ratio of 0.68. To compare the results, there was a controlmortar; two mixtures with partial substitutions using fibres of FN, 0.5 and 1.5% (in weight of CP)respectively; and a substituted mixture with 2% of corn starch plus 0.5% of cactus fibre (MZ - FN).The test age was 180 days. The specimens were subjected to an accelerated attack of sodiumsulphate, quantifying the electric resistivity (ER) and the ultrasonic pulse velocity (UPV). Theresults indicate that the substitution of the materials, remarkably densify the cement matrix, whichresults in the improvement of the physical properties and the durability.

Dispersion of Multi-Walled Carbon Nanotubes in Portland Cement Concrete Using Ultra-Sonication and Polycarboxylic Based Superplasticizer

2015 ◽  
Vol 802 ◽  
pp. 112-117 ◽  
Author(s):  
Ali Yousefi ◽  
Norazura Muhamad Bunnori ◽  
Mehrnoush Khavarian ◽  
Taksiah A. Majid
Keyword(s):  
Mechanical Properties ◽  
Carbon Nanotubes ◽  
Portland Cement ◽  
Cement Matrix ◽  
Portland Cement Concrete ◽  
Cement Concrete ◽  
Uniform Dispersion ◽  
Multi Walled Carbon Nanotubes ◽  
Sonication Technique ◽  
Walled Carbon Nanotubes

The potential properties of carbon nanotube-cement based materials strongly depend on the dispersion of carbon nanotubes (CNTs) within the cement matrix and the bonding between CNTs and the hydrated cement. The homogeneous dispersion of CNTs in the cement matrix yet is one of the main challenges due to strong van der Waals forces between nanotubes. In this study, a polycarboxylic ether based superplasticizer and ultra-sonication technique was used for dispersion of multi-walled carbon nanotubes (MWCNTs). Portland cement concrete specimens with different concentrations of MWCNTs (0.04 and 0.1 % by the weight of cement), with and without the presence of superplasticizer were investigated. Compressive strength test results revealed a significant improvement in mechanical properties of sample containing 0.1 % MWCNTs and 0.2 % superplasticizer. Moreover, field emission scanning electron microscopy (FESEM) images of fractured surfaces of hardened specimens showed a good dispersion of MWCNTs within the cement matrix. This method was developed to facilitate the uniform dispersion of MWCNTs in the cementitious concrete for better reinforcement in nanoscale and mechanical properties enhancement by transfer of load between the nanotubes and matrix.

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