Ismail Aiad

Influence of time addition of superplasticizers on the rheological properties of fresh cement pastes

It is well known that the fluidity and the fluidity loss of fresh cement pastes are affected by the kind and the time of addition of organic admixtures. The influence of the time addition of two chemical admixtures, namely, melamine formaldehyde sulfonate (MFS) and naphthalene formaldehyde sulfonate (NFS), on the rheological properties of ordinary Portland and sulfate-resisting cement pastes through the first 120 min of hydration was investigated. The admixture addition was delayed by 0, 5, 10, 15, 20, and 25 min. Shear stress and apparent viscosity of the cement pastes were determined at different shear rates (3–146 s−1) and hydration times of 30, 60, 90, and 120 min. The concentration of Ca2+ and the combined water content of the cement pastes were determined after 120 min. Yield stress and plastic viscosity values were also determined by using the Bingham model. The results show that an increase in the addition time of the admixture reduces the shear stress, the yield stress, and the plastic viscosity of the cement pastes at the early ages (15 min) as well as at later early ages (120 min). The optimum delaying time of admixture addition is found to be 10–15 min. This time does not depend on the cement and superplasticizer type.

Effect of delaying addition of some concrete admixtures on the rheological properties of cement pastes

The effect of delayed addition of two concrete admixtures, namely melamine formaldehyde sulfonate (MFS) and naphthalene formaldehyde sulfonate (NFS), on the rheological and adsorption properties of ordinary Portland cement (OPC), sulfate-resisting cement (SRC) and silica fume-ordinary Portland cement (SF-OPC) pastes was investigated. The admixture addition was delayed by 1, 3, 6, 10 and 13 min after the addition of mixing water. The shear stress, as well as the apparent viscosity of these cement pastes, was determined at different shear rates. Total organic carbon (TOC), Ca2+ concentration and conductivity of the filtrate and the combined water content of the precipitated cement pastes were determined. The results show that delaying the admixtures addition increases the cement pastes workability than that of simultaneous addition.

Portland cement clinker, granulated slag and by-pass cement dust composites

Three blends of slag cement were prepared, namely 70/30, 50/50 and 30/70 mass% of Portland cement clinker and granulated slag, respectively. Each blend was mixed with 2.5, 5.0, 7.5 and 10.0 mass% by-pass cement dust. The physical properties of cement pastes were studied, including setting times, electrical conductivity and fluidity. The results indicated that the rheological properties of Portland cement clinker were enhanced by partial replacement by granulated slag. By-pass cement dust affects the rheological properties of Portland cement clinker/granulated slag composites and depends on its amount as well as mix composition. The increase in the amount of by-pass cement dust increases the required water of normal consistency. The setting time of Portland slag cement paste was extended with the increase in slag content. The addition of 2.5 mass% by-pass cement dust to M.1 (70 mass% Portland cement clinker/30 mass% granulated slag) and M.2 (50 mass% Portland cement clinker/50 mass% granulated slag) retards the initial and final setting time, whereas it accelerates the final setting time of M.3 (30 mass% Portland cement clinker/70 mass% granulated slag). The presence of by-pass cement dust affects the location and height of the conductivity peaks. By increasing the by-pass cement dust from 2.5 to 7.5 mass%, the conductivity maximum increases. With further addition (10.0 mass%), the height of the conductivity maximum decreases.

Synthesis and Biocidal Activity of Some Naphthalene-Based Cationic Surfactants

In this study, different cationic surfactants were prepared by reacting dodecyl bromide with tertiary amines to produce a series of quaternary ammonium salts that were converted subsequently to stannous and cobalt cationic complexes via complexing them with stannous (II) or cobalt (II) ions. Surface properties such as surface- and interfacial-tension, and the emulsifying power of these surfactants were investigated. The surface parameters including critical micelle concentration, maximum surface excess, minimum surface area, tension lowering efficiency and effectiveness were studied. The free energy of micellization and adsorption were calculated. Antimicrobial activity was determined via the inhibition zone diameter of the prepared compounds, which was measured against six strains of a representative group of microorganisms. The antimicrobial activity of some of the prepared surfactants against sulfate reducing bacteria was determined by the dilution method. FTIR spectra, elemental analysis and a H1 NMR spectrum were examined to confirm compound structure and purity. The results obtained indicate that these compounds have good surface properties and good biocidal effect on broad spectrum of micro organisms.

The Preparation and Characterization of Some Novel Quaternary Iminium Salts Based on Schiff-base as a Corrosion Inhibitor

Abstract Novel quaternary iminium compounds, namely, N-(4-methoxybenzylidene)-N-benzyldodecyliminium chloride (Ia), N-(4-methoxybenzylidene)-N-benzylhexadecyl iminium chloride (Ib), N-(4-methoxybenzylidene)-N-benzyloctadecyliminium chloride (Ic), and N-benzylidene-N-benzyldodecyliminium chloride, were prepared. The surface properties such as surface and interfacial tension, foaming, and emulsifying power of these surfactants were investigated. The surface parameters including critical micelle concentration (CMC), maximum surface excess (Γmax), minimum surface area (Amin), efficiency (PC20), and effectiveness (πCMC) were calculated. Free energy of micellization (ΔG°mic) and adsorption (ΔG°ads) were calculated.

Rheological properties of cement pastes admixed with some alkanolamines

Abstract The influence of addition of some alkanolamines, namely, monoethanolamine (MEA), triethanolamine (TEA) and polytriethanolamine (PTEA) on the rheological properties of the fresh pastes made of sulfate resisting cement (SRC) and ordinary Portland cement (OPC) was investigated. Different cement pastes made with and without these alkanolamines were prepared at a water/cement (w/c) ratio of 0.40. The shear rate–shear stress relationship was established by a co-axial cylindrical Rheotest. It was found that the rheological properties of the various cement pastes were affected by (i) the type and amount of alkanolamine, (ii) the type of cement and (iii) the applied shear rate. The alkanolamines were found to possess a significant retarding effect on the hydration of SRC in the order: TEA>PTEA>MEA.

Some Corrosion Inhibitors Based on Schiff Base Surfactants for Mild Steel Equipments

Two series of Schiff base amphiphiles were prepared throughout condensation of benzaldehyde or anisaldehyde and three different fatty amines with various alkyl chain length; namely: dodecyl, hexadecyl and octadecyl amine. The chemical structures of the prepared Schiff bases were confirmed using elemental analysis, FTIR, and 1H-NMR spectra. The data of structural analysis for these compounds were confirmed the chemical structures and the purity of the synthesized amphiphiles. The synthesized Schiff base amphiphiles were evaluated as corrosion inhibitors for low carbon steel (mild steel) in various acidic media (HCl and H2SO4) using weight loss technique. The corrosion inhibition measurements of these inhibitors showed high protection of the low carbon steel alloys against corrosion process in the tested acidic media at different periods as well as they have good biocidel effectagainest SRB. The discussion was correlated the efficient corrosion inhibition of these inhibitors to their chemical structures.

Molecular, Surface, and Thermodynamic Properties of Nonionic Surfactants Based on Castor Oil

A series of nonionic surfactants containing different chains of polyethylene oxide monomethyl ether [‒O(CH2CH2O)x CH3, x = 7, 12, 16, 44, and 112] based castor oil were synthesized. Their structures were confirmed using FTIR, H1-NMR, and C13-NMR spectra. Structural effects of the synthesized surfactants on surface tension γ, critical micelle concentration (CMC), and hydrophile lipophile balance (HLB) were investigated. The effect of structural features on their surface behavior is analyzed through changes in surface properties, including the surface excess concentration (Γmax), the effectiveness of adsorption, the area per surfactant molecule at the air/water interface at surface saturation (A min). Thermodynamic properties; adsorption and micellezation were also investigated. Biodegradation of these nonionic surfactants were studied.

Experimental Investigation of Newly Synthesized Gemini Cationic Surfactants as Corrosion Inhibitors of Mild Steel in 1.0 M HCl

Three Gemini cationic surfactants named N1,N1,N3,N3-tetramethyl-N1,N3-bis(3-octanamidopropyl) propane-1,3-diaminium bromide (C8-S3-C8), N1,N1,N3,N3-tetramethyl-N1,N3-bis(3-dodecanamidopropyl) propane-1,3-diaminium bromide (C12-S3-C12) and N1,N1,N3,N3-tetramethyl-N1,N3-bis(3-hexadecanamidopropyl) propane-1,3-diaminium bromide (C16-S3-C16) were evaluated as corrosion inhibitors for mild steel in 1.0 M HCl. The corrosion rate of mild steel in 1.0 M HCl at three different temperatures 25, 45 and 60oC was investigated gravimetrically. The corrosion rate of mild steel was confirmed electrically at 25oC. The corrosion inhibition efficiency directly proportionally with the hydrophobic chain length of inhibitors. The inhibition efficiency exhibit a positive trend with raising the solution temperatures. The potentiostatic polarization study revealed that the tested gemini cationic surfactants act as mixed type inhibitors with predominant control of cathodic reaction. The Villamil isotherm provide the best describing of the adsorption process on the selected steel in 1.0 M HCl. The adsorption of the tested inhibitors on the steel surface is a mixture of chemical and physical adsorption.

Protection of carbon steel against corrosion in hydrochloric acid solution by some synthesized cationic surfactants

A series of some cationic surfactants was synthesized namely: N,N,N-tris(hydroxymethyl)-2-oxo-2-(2-(2-(dodecanoyloxy)ethoxy)ethoxy)ethanaminium chloride (DDAC); N,N,N-tris(hydroxymethyl)-2- oxo-2-(2-(2-(tetradecanoyloxy) ethoxy) ethoxy) ethanaminium chloride (TDAC) and N,N,Ntris( hydroxymethyl)-2-oxo-2-(2-(2-(hexadecanoyloxy)ethoxy)ethoxy)ethanaminium chloride (HDAC). Their chemical structures were characterized using FTIR and 1HNMR spectroscopy. Corrosion inhibition performance of these compounds on carbon steel in 0.5 M HCl was studied using weight loss and potentiodynamic polarization methods. It was seen that the three synthesized cationic surfactants decreased the corrosion rate of mild steel in acidic medium due to the adsorption on the metal surface. And it was found that the inhibition efficiency increased with increasing the inhibitor concentration. The adsorption of inhibitors on the carbon steel surface obeys modified Langmuir equation which named Villamil isotherm adsorption. Polarization curves show that the synthesized inhibitors are mixed-type inhibitors in 0.5 M HCl. ΔGads0 were ranged from–31.65 to–33.40 kJ mol–1 which indicate that the adsorption process is mixture between physical and chemical adsorption.