The effect of grinding process on mechanical properties and alkali–silica reaction resistance of fly ash incorporated cement mortars

The effect of fineness of fly ash on mechanical properties and alkali–silica reaction resistance of cement mortar mixtures incorporating fly ash has been investigated within the scope of this study. Blaine fineness of fly ash has been increased to 907 m²/kg from its original 290 m²/kg value by a ball mill. Test samples were prepared by replacing cement 20, 40 and 60%, with finer and coarser fly ashes and kept under standard and steam curing conditions until testing. Test results showed that grinding process improved the mechanical properties of all samples significantly. The beneficial effect of grinding fly ash, may increase utilization of this by-product in precast and ready-mix concrete industries. Incorporation of fly ash with different fineness values and ratios also decreased the expansions to harmless levels of cement mortars due to alkali–silica reaction.     

Effect of large amounts of natural pozzolan addition on properties of blended cements

In this study, the effects of 35, 45, and 55 wt.% natural pozzolan addition on the properties of blended cement pastes and mortars were investigated. Blended cements with 450 m²/kg Blaine fineness were produced from a Turkish volcanic tuff in a laboratory mill by intergrinding portland cement clinker, natural pozzolan, and gypsum. The cements were tested for particle size distribution, setting time, heat of hydration, compressive strength, alkali-silica activity, and sulfate resistance. Cement pastes were tested by TGA for Ca(OH)₂ content and by XRD for the crystalline hydration products. The compressive strength of the mortars made with blended cements containing large amounts of natural pozzolan was lower than that of the portland cement at all tested ages up to 91 days. Blended cements containing large amounts of pozzolan exhibited much less expansion with respect to portland cement in accelerated alkali-silica test and in a 36-week sulfate immersion test.     

Effect of clinker grinding aids on flow of cement-based materials

Grinding aids (GAs) are increasingly used during cement production to reduce energy consumption and/or optimize clinker factor. This paper seeks to assess the effect of such additions on variations in flow of cement pastes, including static yield stress (τ₀) and viscosity (η). Grinding tests were performed at fixed specific energy consumption (Ec) or Blaine cement fineness. For fixed Ec, tests have showed that the increase in cement fineness resulting from the addition of higher GA concentration leads to reduced flow and increased τ₀ and η values. Conversely, cement ground for fixed Blaine fineness exhibited an improvement in flowability together with reduction in τ₀ and η values. This was related to a dispersion effect of cement agglomerates in the presence of GA molecules. Special emphasis is placed throughout this paper regarding the effect of GAs on ASTM C465 requirements.     

Influence of the fineness of sewage sludge ash on the mortar properties

Sewage sludge ash (SSA) is a recycled material and can be used in cement mortar as pozzolan. To improve the mortar properties, this research utilized mechanical grinding to adjust the fineness of SSA. Finely ground SSA with Blaine fineness of 500-1000 m²/kg was added to mortar to replace 20% of portland cement. The initial and final setting times of SSA-cement paste simultaneously prolonged when SSA fineness increased. Because of the lubricant effect and morphology improvement, the workability of SSA mortar increased when fineness increased. In addition, the pozzolanic activity of SSA and the compressive strength of mortar increased when SSA fineness did. The strength activity index (SAI) value approximately increased 5% when SSA fineness increased per 100 m²/kg. According to the results, the application of mechanical grinding to adjust SSA fineness was an effective modification to improve SSA mortar properties including workability and compressive strength.     

助磨介质作用下旋窑熟料微细化过程及其效果评价

通过对助磨介质作用下不同粉磨细度的旋窑熟料所配制的硅酸盐水泥的物理性能检测,对助磨介质作用下旋窑熟料的微细化效果进行了评价。结果表明,对水泥熟料来说,早期的快速水化不一定能得到高强度的水泥,因此熟料微细化的评价要从水化性能和粉磨能耗上综合考虑,在实验中,旋窑熟料的最佳粉磨细度为5 000m2/g,而加入助磨剂可显著降低粉磨能耗,在达到同样效果时缩短25％的粉磨时间。     

利用工业废渣制备复合水泥的研究

采用分别粉磨再混合的方式,利用正交试验方法,研究了熟料、矿渣及粉煤灰的不同细度组合对复合硅酸盐水泥物理性能的影响。结果表明,熟料细度是影响复合水泥3d强度的决定因素;影响水泥28d强度的主次因素依次为:矿渣细度、熟料细度、粉煤灰细度。得到了复合水泥3种主要组分的细度最佳控制参数为:熟料420m2/kg,矿渣500m2/kg,粉煤灰400m2/kg。并对复合水泥水化各龄期的试样进行了SEM分析。     

Superplasticized portland cement: production and compressive strength of mortars and concrete

This paper deals with the effect of intergrinding different percentages of a naphthalene-based superplasticizer with Portland cement clinker and gypsum on the fineness of the product, and on the water requirement and the compressive strength of the mortars made with the superplasticized cement. The properties of the fresh and hardened concrete made with the superplasticized cements were also investigated. The results showed that the intergrinding of a given amount of a naphthalene-based superplasticizer with Portland clinker and gypsum reduced the grinding time required for obtaining the same Blaine fineness as that of the control Portland cement without the superplasticizer. The water requirement of the mortars made with the superplasticized cements was similar to that of the mortars made with the control Portland cements when the same amount of the superplasticizer was added at the mortar mixer; for a given grinding time and a Blaine fineness of 4500 cm²/g, the mortars made with the superplasticized cement had higher compressive strength than those made with the control Portland cement. For a given grinding time or Blaine fineness of cement ≥5000 cm²/g, the slump loss, air content stability, bleeding, autogenous temperature rise, setting times, and compressive strength of the concrete made with the superplasticized cements were generally comparable to those of the concrete made with the control Portland cements when the superplasticizer was added at the concrete mixer.     

Removal of Organic Acids from Wine by Adsorption on Weakly Basic Ion Exchangers: Equilibria for Single and Binary Systems

Abstract

In order to remove or reduce the organic acids from wine and liqueur, we investigated their adsorption on weakly basic resins. CC-S, WA-10, and WA-30, which were made from chitosan, acryl, and styrene, respectively, appeared technically feasible. The concentration of the fixed amino group in CC-S, WA-10, and WA-30 is 3.31, 2.37, and 2.81 kmol/m³, respectively. These resins adsorbed citric acid and malic acid from wine selectively. The equilibrium isotherms for single component systems of citric acid or malic acid were little affected by the initial concentration (C ₀ = 0.01, 0.02, and 0.03 kmol/m³) and by ethanol. The equilibrium data were correlated by the Langmuir equation. The equilibrium data were correlated by the Langmuir equation. The equilibrium isotherms for the binary system of citric and malic acids were affected by the initial concentration (C _A0 = 0.02, C _B0 = 0.03 kmol/m³; C _A0 = 0.014, C _B0 = 0.004 kmol/m³). The equilibrium data were correlated reasonably well by the Markham-Benton equation. The equilibrium constants for citric acid were much larger than those for malic acid. By using these constants, the equilibrium data for adsorption of citric and malic acids from wine could be adequately correlated by the Markham-Benton equation.     

The effect of particle size distribution on the properties of blended cements incorporating GGBFS and natural pozzolan (NP)

This paper investigates the effect of particle size distribution on the properties of blended cements incorporating ground granulated blast-furnace slag (GGBFS) and natural pozzolan (NP). Pure Portland cement (PPC), NP and GGBFS were used to obtain blended cements that contain 10, 20, 30% additives. The cements were produced by intergrinding and separate grinding and then blending. Each group had two different Blaine fineness of 280 m²/g and 480 m²/g. According to the particle size distribution (PSD) curves, 46% of the coarser specimens and 69% of the finer specimens passed through the 20 μm sieve. It was observed that the separately ground specimens were relatively finer than the interground ones and had higher compressive strength and sulfate resistance. The separately ground coarser specimens had the lowest heat of hydration. The separately ground finer specimens, which had the highest compressive strength and sulfate resistance, had the highest percent passing for each sieve size. For these specimens 34, 69, 81 and 99% passed through 5, 20, 30 and 55 μm sieves, respectively. For the interground specimens, which had the same fineness, the respective values for the same sieves were 32, 68, 75 and 94%.     

Adsorption equilibrium constants of methyl oleate and methyl linoleate in vapor phase on supported copper and nickel catalysts

Adsorption equilibrium constants for methyl oleate and methyl linoleate in vapor phase on supported copper and nickel catalysts have been determined using the technique of pulse gas chromatography. The results are discussed in relation to selectivity in fat hydrogenation. Notation: A, column cross-section, m₂ ; a_n,b_n, nth Fourier coefficients; c, concentration of adsorbate in bulk flow, mol/m³ ; c^* = c/ ∫ ₀ ^∞ cdt, normalized concentration of adsorbate in bulk flow; C_i, concentration of adsorbate in catalyst pores, mol/m³ ; c_a, concentration of adsorbate on catalyst surface, mol/kg; c_TOT, active area of catalyst as measured by hydrogen adsorption, mol/kg; D_e, effective diffusion coefficient of adsorbate in catalyst, m²/s; D_ea, axial dispersion coefficient based on void cross-section, m²/s; h_n, nth coefficient in Hermite polynomial expansion; H_n nth Hermite polynomial; ΔH_A, adsorption enthalpy, kJ/mol; ΔH_vap , heat of vaporization, kJ/moll; k_a, adsorption rate constant, m³/kgs;K_A, adsorption equilibrium constant, m³/kg; K₀ , preexponential factor defined in Eqn. 8, m³/kg; k_f, mass transfer coefficient, m/s; L, bed length, m; q, flow rate, m³/s; R, particle radius, m; R_g, gas constant; t, time, s; T, temperature, K; T_F, period of Fourier expansion, s; u = q/A, linear velocity, m/s; z, length coordinate in packed column, m. Greek symbols: δ(t), Dirac delta function; ∈_B, void fraction of bed; ∈_-p, particle void fraction, ρ_rp, particle density, kg/m³ ; ξ, radial coordinate in particle, m; μ₁, first absolute moment, μ₂, second central moment.     

Studies on electrochemical treatment of dairy wastewater using aluminum electrode

This study reports results of electrochemical treatment to the synthetic dairy wastewater using aluminum electrode. Response surface methodology with four factors and five level full factorial central composite design has been used to design the experiments. Four operational parameters, namely current density (J): 61.73–308.64 A/m²; dosage of sodium chloride (NaCl) (m): 0–2 g/l; electrolysis time (t): 10–90 min and initial pH (pH_o): 5–11, have been taken as input parameters and percentage chemical oxygen demand (COD) removal (Y₁) and the specific energy consumed (kWh per Kg of COD removed, Y₂) have been taken as responses of the system. Multiresponse optimization technique has been applied to find values of operational parameters which maximize the Y₁ and simultaneously minimize Y₂. The optimum values of operational parameters were found to be J = 123.46 A/m², m = 2.0 g/l, t = 74 min, and pH_o = 6.5. Optimum Y₁ and Y₂ were found to be 70.91% and 1.32 kWh/kg COD removed. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Effect of the clinker composition on the threshold limits for Cu,Sn or Zn

The threshold limit corresponds to the maximum amount of trace element that could be incorporated into clinker whilst reaching the limit of solid solution of its four major phases (C₃S, C₂S, C₃A and C₄AF). For Cu, Zn or Sn, these threshold limits in a standard clinker (65% C₃S, 18% C₂S, 8% C₃A and 8% C₄AF) were equal to 0.35, 0.7 and 1 wt.% respectively (Gineys et al., in press). This paper presents the effect of the clinker composition on these threshold limits. Laboratory made clinkers having different mineralogical compositions was characterised by XRD and SEM. Results showed that the threshold limits for Cu, Zn or Sn were consistent. The threshold limit for Sn was affected by the Bogue content in interstitial phases. On the other hand, the threshold limit for Zn was affected by the Bogue content in C₃S of clinker while that of Cu was unaffected by any modifications of clinker composition.     

Differential comminution of gypsum in cements ground in different mills

Identical mixes containing fixed amounts of ordinary Portland cement clinker and gypsum were ground in two types of industrial cement mills—viz. ball mill (BM) and vertical roller mill (VRM)—to identical Blaine fineness to examine the effect of any possible differential comminution of gypsum on cement setting times. The present investigation demonstrates that during comminution of cements, the degree of crystallinity of gypsum, as determined by X-ray diffraction (XRD), changes with used grinding mills and this causes changes in setting times of similar cements even when ground to identical Blaine fineness.     

The effect of cement particle size distribution upon properties of pastes and mortars with low water-to-cement ratio

Technological properties of pastes and mortars (viscosity, time development of strengths) with low water-to-cement ratio (the clinker-sodium lignosulfonate-alkali carbonate or bicarbonate-H₂O system) depend upon clinker particle size distribution. These properties cannot be described explicitly as a function of specific surface measured according to Blaine. The granulometric composition of clinker particles according to idealised curves (Fuller, EMPA recommendation) represent a specific optimum state, permitting minimum viscosities to be reached at given water volume as well as maximum short-term strength values.     

采用攀枝花煤矸石替代砂岩配料的生产实践与效益分析

攀枝花钢城集团瑞丰水泥有限公司采用当地煤矸石替代砂岩配料,在2500t/d新型干法水泥生产线上进行了普通水泥熟料的煅烧研究和应用实践.结果表明,这一方案工艺技术上完全可行;且可获得巨大的经济效益和社会效益.其中,年可消耗攀枝花煤矸石超过110000t,同时可使熟料综合标煤耗下降12.55kg/t以上,吨熟料的余热发电提高量9.57 kWh/t,吨熟料综合电耗减少3.40 kWh/t,由此吨熟料生产成本下降18.21元;同时回转窑产量提高5.42t/h,且使熟料28d抗压强度提高了1.5 MPa.     

Electrochemical oxidation of tannery wastewater

Tannery wastewater was treated by an electrochemical oxidation method using Ti/Pt, Ti/PbO₂ and Ti/MnO₂ anodes and a Ti cathode in a two‐electrode stirred batch reactor. The changes in colour concentration, chemical oxygen demand (COD), ammonia (NH₄⁺), sulfide and total chromium have been determined as a function of treatment time and applied current density. Gas chromatography–mass spectrometry (GC–MS) analysis, performed on the wastewater samples before and after treatment, as well as on foam samples, is reported. Anode efficiency, rate constants and energy consumption were estimated and discussed. The efficiency of Ti/Pt was 0.802 kgCOD h^?1 A^?1m^?2 and 0.270 kgNH₄⁺ h^?1 A^?1m^?2, and the energy consumption was 5.77 kWh kg^?1 COD and 16.63 kWh kg^?1 of NH₄⁺. The order of efficiency of anodes was found to be Ti/Pt ? Ti/PbO₂ > Ti/MnO₂. The results indicate that the electro‐oxidation method could be used for effective oxidation of tannery wastewater and a final effluent with substantially reduced pollution load can be obtained. © 2001 Society of Chemical Industry     

Application of rigid polyurethane integral-skin foams to thermal insulating unit cases for car air conditioners

Integral-skin foams of rigid polyurethane are sandwich structures consisting of a core layer of closed cells enclosed in rigid surface layers on both sides. We examined the layer composition of integral-skin foam with the objective of maximum flexural strength, and then studied possibilities of reconciling the strength and thermal insulating properties in housings for evaporators in car air conditioners; i.e., unit cases. This examination showed that the most practical density range (250 ≦ ρ_pall ≦ 500 kg/m³) provides vibratile resistance and thermal insulating properties. In actual car-running tests, a maximum 0.1 MPa stress was generated on unit cases with overall densities of 350 kg/m³, We found this to be 0.4% of the flexural strength of an integral-skin foam and 2% of the fatigue strength. In the forcible vibratile test, a stress of 0.5 to 1.0 MPa was generated at the resonance point of a unit case with 250 to 500 kg/m³ overall density. We found that these values are 2 to 5% of integral-skin foam's flexural strength and 10 to 25% of its fatigue strength. These values are of the same level as the conventional unit case made of polypropylene blended with talc. An integral-skin foam with an overall density of 250 kg/m³, nearly equal to half the weight of polypropylene, has the same level of resistance to vibration.     

Modeling a perforated bipole trickle bed electrochemical reactor for the generation of alkaline peroxide

This paper describes the modeling of a novel perforated bipole electrochemical reactor with trickle-bed cathodes employed in the electrosynthesis of alkaline peroxide solutions. The model engages an electronic analogue of the 3D electrode/bipoles to solve the coupled material, energy and voltage (charge) balances that estimate the potential, current density, composition, pressure and temperature profiles through the reactor. The predictions of this model are compared to the performance of a bench scale experimental reactor operating at superficial current densities up to 5 kA m⁻². With eddy diffusion through the diaphragm as the single adjustable parameter the model shows good agreement with peroxide current efficiency but underestimates the electrochemical specific energy consumption by about 2 kWh/kg H₂O₂ at 5 kAm⁻².     

Cement pastes and mortars with low water-to-cement ratio I

Clinkers of nominal Czechoslovak production were ground in presence of grinding aid (derivative of lignin) to specific surfaces 400 – 2700 m²/kg and were processed in presence of sodium lignosulfonate and alkali carbonate (resp. bicarbonate) into pastes and mortars with low water-to-cement ratio. The clinker lignosulfonate-carbonate-H₂O system (further under “A”) is qualitatively different to the clinker-gypsum-H₂O system in rheological properties and in reaching short and long-term strengths. The volume changes (A) are similar to volume changes in Portland cements. The properties of system A are affected by concentration and type of carbonate and lignosulfonate.     

New AMP/polyamine blends for improved CO2 capture: Study of kinetic and equilibrium features

2-Amino-2-methyl-1-propanol (AMP), which is the sterically hindered form of monoethanolamine (MEA), is a credible substitute to conventional CO₂-capturing solvents. Its performance can be improved by blending with a highly reactive polyamine promoter. Two such aqueous blends of AMP/TETA and AMP/TEPA were chosen here (TETA = triethylenetetramine and TEPA = tetraethylenepentamine). The kinetics of CO₂ absorption in the proposed blends was investigated at 308, 313, and 318 K using the stirred cell technique. The concentrations of AMP and polyamine were varied between 2 to 3 kmol/m³ and 0.1 to 0.5 kmol/m³, respectively. From the measured values of the fast pseudo-first order constants, the second-order rate constants for the reactions of CO₂ with TETA (14 695 m³/(kmol s)) and TEPA (19 250 m³/(kmol s)) were determined at T = 313 K. Both TETA and TEPA react faster with CO₂ than MEA. Further, the respective activation energy values were found (40 and 37 kJ/mol). Finally, the equilibrium solubility of CO₂ for both blends was measured at T = 303 K. The loading capacity was higher than that for the aqueous blends of AMP/MEA, AMP/DEA, and AMP/MDEA (here, DEA and MDEA denote diethanolamine and N-methyldiethanolamine). The highest value of loading capacity (1.12 mol CO₂/mol amine at 2.01 kPa equilibrium partial pressure of CO₂) was noted in AMP/TEPA mixtures. The new findings on our proposed blends will strengthen the AMP/polyamine application in CO₂ separation.