Harvill C. Eaton

Microstructure, strength, and reaction products of ground granulated blast-furnace slag activated by highly concentrated NaOH solution

Ground granulated blast-furnace slag was reacted in 5 M (pH 14.7) and 1.5 M (pH 14.2) NaOH solutions at a water/slag ratio of ∼0.4, and characterized by unconfined compressive strength testing, scanning electron microscopy, energy dispersive spectroscopy, and x-ray diffraction. The reacted material consisted of a dense layered matrix interspersed with unreacted glass particles and regions of reaction products with higher porosity. CSH(I) and (C, M) 4 AH 13 were identified by x-ray diffraction. The C-S-H (calcium silicate hydrate) phase is proposed to consist mainly of structurally imperfect layers of tobermorite, interleaved with layers of (C, M) 4 AH 13 . Other cations, most significantly Na + , are incorporated into the structure. Use of the highly concentrated solution (5 M) produced a higher degree of reaction and, consequently, higher compressive strength (38 MPa after 28 days for 5 M solution vs 21 MPa for 1.5 M).

The effect of sodium sulfate on solidification/stabilization of a synthetic electroplating sludge in cementitious binders

Abstract The effect of sodium sulfate on the solidification/stabilization of a large quantity of a synthetic electroplating sludge in cementitious binders was s

Evaluation of the leaching properties of solidified heavy metal wastes

Abstract The effects of three inorganic materials on the leaching properties of Type I Portland cement solidification matrix were studied. Also, possible effects on the cement chemistry were suggested. Cadnium nitrate and hydroxide sludges of cadmium and lead were used as the inorganic materials. Cure times of i, 7, and 28 days were studied. Leachability effects were determined by the Toxicity Characteristic Leaching Procedure (TCLP). Hydroxide sludges were added in hydroxide to cement weight percentages of 10% and 30%. A control group containing no additives were also prepared. A control group containing only hydroxide sludges was also tested by the TCLP to determine the amount of metal leached from the sludges alone. Cadmium (Cd+2), in hydroxide or nitrate form, was found by leaching results to be well contained in the cement matrix. All of the TCLP leaching results for Cd+2 were well below the 1.0 mg/L guideline established in the procedure. Lead (Pb+2) was found not to be readily contained as was seen...

Organic interference of solidified/stabilized hazardous wastes

Liquid hazardous waste disposal in landfills is usually allowed only after solidification/stabilization. Although various procedures are commonly practiced, little is known about the mechanism(s) of the processes. A particular problem is the interference of organics. Small amounts of organics can interfere with the reaction between inorganic sludges and cementitous matrices. The present communication reports studies of the interaction between selected organic hazardous wastes and Type I Portland cement. Microscopic studies of the structural differences between cements set with water and those set with water plus organic liquids are discussed. In these studies the scanning electron microscope is used to observe samples fractured at 78K. The results provide technical background data on the ultimate stability of critical waste constituents solidified by various binding agents.

Scanning electron microscopy/energy dispersive X-ray analysis of type I portland cement pastes containing parachlorophenol

Abstract Four mixtures of Type I Portland Cement, parachlorophenol (pCP) and water were examined by scanning electron microscopy and energy dispersive x-ray analysis after hydrating 7, 28, and 90 days. All mixtures were prepared with a water/cement weight ratio of 0.4. Weight ratios of pCP/cement were as follows: 0, 0.04, 0.1 and 0.2. Samples were polished and examined for morphological differences and compositional variations. The smoothness of the polished surface was found to increase with hydration time as well as pCP concentration. X-ray dot maps and microprobe analyses indicate an even distribution of pCP within the hydrated cement paste. However, there is an increase in the mean and standard deviation of the Ca+Mg)/Cl atomic ratio with increasing hydration time for all pCP containing specimens. Although this ratio was higher for inclusions than for the matrix, the detection of Cl in the inclusions suggests a possible interaction between pCP and unhydrated clinker.

Solidification/stabilization of a synthetic electroplating sludge in cementitious binders containing NaOH

Abstract Solidification/stabilization of a highly concentrated synthetic electroplating waste sludge by cementitious mixtures containing NaOH was studied. The sludge contained 86.2 mg/g Ni, 84.1 mg/g Cr, 18.8 mg/g Cd, and 0. 137 mg/g Hg and before mixing was dewatered to 25% solids. It was stabi- lized by ordinary Type I portland cement (OPC), an OPC/Class F fly ash mixture (referred to as CFA), and a lime/Class C fly ash mixture (referred to as LFA). Mix ratios of OPC: sludge of 0.3: 1, OPC:fly ash:sludge of 0.2:0.5: 1, and lime:fly ash:sludge of 0.3:0.5:1 were used, respectively. NaOH was added to each mix at 0 (control sample), 2, 5 and 8% by weight of solidified binder. A set of binder samples without sludge, but con- taining 8% NaOH, was also prepared. The microstructure, microchemistry, and component phases present in the binders after curing were determined by scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffractometry. The chemical species present in the sludge were not significantly affected by the high pH produced by NaOH; the sample showing the least effect was CFA/sludge. Ettringite was formed in CFA /sludge samples containing up to 5% NaOH, and in CFA/sludge and LFA/sludge containing up to 2% NaOH. NaOH reacted with the binders to produce phases containing Na plus minor amounts of Cr and Ni.

Effects of additives on solidification of API separator sludge

API separator sludge was solidified with various combinations of binders and absorbent soil additives. The binders utilized were Type I Portland Cement, Type C Flyash, and a 1:1 combination of the two. The soil additives used were bentonite, diatomite, Fullers earth, and two brands of chemically altered bentonites, or organoclays. The effectiveness of the solidification materials was based on their effect on the physical and leaching characteristics of the sludge.It was determined the Portland cement and combination binders provided the sludge with adequate physical and strength characteristics. It was also determined the affinity of each additive for water had an important influence on the physical characteristics of the solidified sludge. The results of the leaching procedure indicated the binders alone reduced the leachability of organic constituents from the sludge by 1/5 to 1/10. It appeared the use of the additives with the binders may have further reduced the leachability of constituents from sludge, with the incorporation of the organoclay additives further reducing leachability by up to 1/2. Also, it appeared the absorbing capacity of the additives was directly related to their ability to reduce the leachability of organic constituents from the sludge.

Solidification/stabilization of a synthetic electroplating waste in lime-fly ash binder

Abstract A synthetic electroplating sludge was solidified in a binder which was a mixture of lime and Class C fly ash (LFA). The sludge contained 86.2, 84.1, 18.8 and 0.137 mg/g of nickel, chromium, cadmium, and mercury, respectively. The binder contained lime and Class C fly ash in the ratio 3:5, and the waste to binder ratio was 1.0:0.8. The microstructure and microchemistry of the solidified samples were studied by scanning electron microscopy, energy dispersive x-ray microanalysis, and x-ray diffractometry. The sludge was composed of impure, complex species of the heavy metals. The microstructure and phase composition of LFA were not affected by sludge. The sludge/LFA mixtures were simple mechanical mixtures of the binder and sludge. The heavy metals existed as large particles embedded in the binder, and uniformly mixed in the matrix at low concentrations, and with particle sizes smaller than those resolvable by the microscope under the conditions dictated by the specimen type and form. Fly ash spheres acted as sites of adsorption for the heavy metals.

COD and TOC analysis of leachate from a solidified organic waste.

Several combinations of binders and absorbent additives were utilized to solidify a typical organic waste, API Separator sludge. The effectiveness of the materials was based on the waste leachability from the solidified samples. COD and TOC analyses were used to determine the organic content of the leachate samples.The ability of the COD and TOC analyses to assess waste leachability was limited. The inability of the COD and TOC tests to differentiate between organic compounds made the results difficult to interpret. This was due to organic contaminants from the solidification materials contributing to the COD and TOC contents of the leachates. Also, the COD test may have be influenced by reduced inorganic compounds contained in the flyash binder and the sludge. Representative samples for the TOC analysis were difficult to obtain for the leachates containing oils or suspended particles. It is recommended that the COD and TOC tests only be used as a screening method for determining solidified organic waste leachability and other methods need to be employed to obtain more accurate results.