Influence of Thermal Preconditioning on the Mechanism of External Sulphate Attack

2019 ◽  
pp. 71-80
Author(s):  
S. Boudache ◽  
E. Rozière ◽  
A. Loukili ◽  
H. Colina
Keyword(s):  
Sulphate Attack ◽  
Thermal Preconditioning

Influence of thermal preconditioning on anticonvulsive effects of valproate and memantine

2008 ◽  
Author(s):  
A. A. Yakimchuk ◽  
Yu F. Pastukhov ◽  
N. A. Frolova
Keyword(s):  
Thermal Preconditioning

The Effect of Cassava Starch on the Durability Characteristics of Concrete

2020 ◽  
Vol 14 (1) ◽  
pp. 289-301
Author(s):  
Daniel Oni ◽  
John Mwero ◽  
Charles Kabubo
Keyword(s):  
Cement Hydration ◽  
Research Work ◽  
Cassava Starch ◽  
Chloride Penetration ◽  
Hardened Concrete ◽  
Sulphate Attack ◽  
Marine Structures ◽  
Durability Properties ◽  
Chloride Attack ◽  
Starch Gel

Background: Concrete is a common material used in the construction of marine structures, such as bridges, water treatment plants, jetties, etc. The use of concrete in these environment exposes it to attack from chemicals like sulphates, chlorides and alkaline, thereby causing it to deteriorate, and unable to perform satisfactorily within its service life. Hence, the need to investigate the durability properties of concrete has become necessary especially when admixtures are used to modify some of its properties. Objective: This research work investigates the effect of Cassava Starch (CS) on the durability characteristics of concrete. Methods: The durability properties investigated in this work are water absorption, sorptivity, resistance to sulphates, sodium hydroxides and chloride penetration. The specimens were prepared by adding CS by weight of cement at 0.4, 0.8, 1.2, 1.6 and 2.0% respectively. The concrete specimens were cured for 28 days, tested for compressive strength before ponding in ionic solutions of sodium hydroxide, sulphuric acid and sodium chloride. Six (6) concrete mixes were prepared, five of which were used to evaluate the effect of CS on the durability characteristics of concrete. Results: The slump values reduced with the increasing dosage of CS due to the viscous nature of the CS paste. Generally, the addition of CS in concrete tends to improve the resistance of concrete to sulphate and chloride attack due to the ability of the muddy-like starch gel to block the pore spaces of hardened concrete, hence, reduces the rate at which water and other aggressive chemicals penetrate the concrete. In addition, the retarding ability of CS impedes the formation of mono-sulphate aluminates during cement hydration, thereby making the concrete less susceptible to sulphate attack. Conclusion: The addition of CS to concrete by weight of cement generally improved the durability characteristics of concrete, while the relative performances of the concrete mixes showed that CS 2.0 gave a better resistance to chloride penetration and sulphate attack.

scholarly journals Physical-Mechanical Properties of Cupola Slag Cement Paste

2021 ◽  
Vol 11 (15) ◽  
pp. 7029
Author(s):  
Carlos Thomas ◽  
José Sainz-Aja ◽  
Israel Sosa ◽  
Jesús Setién ◽  
Juan A. Polanco ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Circular Economy ◽  
Setting Time ◽  
Casting Process ◽  
Industrial Sector ◽  
Sulphate Attack ◽  
Experimental Campaign ◽  
High Consumption ◽  
Superior Mechanical Properties ◽  
Environmental Savings

The high consumption of natural resources in the industrial sector makes it necessary to implement measures that enable the reuse of the waste generated, seeking to achieve circular economy. This work assesses the viability of an alternative to the use of CEM III B 32.5 R cement in mortars for the internal coating of centrifugally spun cast iron pipes for water piping. The proposal is to reuse the slag generated in the casting process after being finely ground, as an addition mixed with CEM I 52.5 R cement, which is basically Portland clinker. In order to analyse this possibility, an extensive experimental campaign was carried out, including the analysis of the cupola slag (micro-structural and chemical composition, leachates, setting time, vitrification, puzzolanicity and resistance to sulphate) and regarding the mortars (workability and mechanical properties). The experimental programme has shown that the optimum substitution is achieved with a replacement percentage of 20% of the cement, with which similar workability, superior mechanical properties and guaranteed resistance to sulphate attack are obtained. In addition, both economic and environmental savings are achieved by not having to transport or landfill the waste. In addition, the new cement is cheaper than the cement currently used.

Monitoring of Chemical Resistance of New Grouting Materials

2021 ◽  
Vol 898 ◽  
pp. 27-33
Author(s):  
Petr Figala ◽  
Rostislav Drochytka ◽  
Vit Černý ◽  
Radek Hermann ◽  
Jiří Kolísko
Keyword(s):  
Fly Ash ◽  
Chemical Resistance ◽  
Raw Materials ◽  
Waste Glass ◽  
Sulphate Solution ◽  
Sulphate Attack ◽  
Glass Waste ◽  
Foundry Sand ◽  
Waste Foundry Sand ◽  
Grouting Materials

This paper deals with the study of chemical resistance of new cement-based grout for invert grouting. The aim of this work is to verify new mixtures with specific admixtures. The study monitors resistance to external sulphate attack. Specimens were placed into sulphate solution 29.8 g∙l-1 (44 g∙l-1 Na2SO4) according to DIN19753 standard. Based on the results gained, new mixtures will be designed and optimized by addition of suitable secondary raw materials (fly ash, waste foundry sand, waste glass, waste filers).

Combustion of Coal/Water Mixtures With Thermal Preconditioning

1987 ◽  
Vol 109 (3) ◽  
pp. 313-318 ◽  
Author(s):  
M. Novack ◽  
G. Roffe ◽  
G. Miller
Keyword(s):  
Gas Turbine ◽  
Combustion Efficiency ◽  
Experimental Program ◽  
Water Mixture ◽  
Gas Turbine Combustor ◽  
Hydrocarbon Gases ◽  
Sampling Probe ◽  
Stable Flame ◽  
Thermal Preconditioning ◽  
Gaseous Form

Thermal preconditioning is a process in which coal/water mixtures are vaporized to produce coal/steam suspensions, and then superheated to allow the coal to devolatilize producing suspensions of char particles in hydrocarbon gases and steam. This final product of the process can be injected without atomization, and burned directly in a gas turbine combustor. This paper reports on the results of an experimental program in which thermally preconditioned coal/water mixture was successfully burned with a stable flame in a gas turbine combustor test rig. Tests were performed at a mixture flowrate of 300 lb/hr and combustor pressure of 8 atm. The coal/water mixture was thermally preconditioned and injected into the combustor over a temperature range from 350°F to 600°F, and combustion air was supplied at between 600°F to 725°F. Test durations varied between 10 and 20 min. Major results of the combustion testing were that: A stable flame was maintained over a wide equivalence ratio range, between φ = 2.2 (rich) and 0.2 (lean); and combustion efficiency of over 99 percent was achieved when the mixture was preconditioned to 600°F and the combustion air preheated to 725°F. Measurements of ash particulates, captured in the exhaust sampling probe located 20 in. from the injector face, show typical sizes collected to be about 1 μm, with agglomerates of these particulates to be not more than 8 μm. The original mean coal particle size for these tests, prior to preconditioning, was 25 μm. Results of additional tests showed that one third of the sulfur contained in the solids of a coal/water mixture with 3 percent sulfur was evolved in gaseous form (under mild thermolized conditions) mainly as H2S with the remainder as light mercaptans.

Fired Brick and Sulphate Attack

2007 ◽  
Vol 13 (1) ◽  
pp. 69-80 ◽  
Author(s):  
Enrico Fodde
Keyword(s):  
Sulphate Attack

Sulphate Attack in Lime-Treated Marine Clay

2005 ◽  
Vol 23 (1-2) ◽  
pp. 93-116 ◽  
Author(s):  
G. Rajasekaran ◽  
S. Narasimha Rao
Keyword(s):  
Sulphate Attack ◽  
Marine Clay
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