The effects of silica fume and ground granulated blast furnace slag on rheology and hardened properties of superplasticized grouts were studied. Silica fume and slag improved impermeability, strength, and wet-dry durability of grouts. The physical and mechanical properties of slag- and silica fume-modified grouts compared favorably with those of grouts prepared with Type II and V cements. Silica fume was found to have a more pronounced impact on shear stress-shear rate relationships than slag. Gel strength was decreased by slag and increased by silica fume. The rheological properties of the grouts were sensitive to the sequence of superplasticizer addition. Slag- and silica fume-modified grouts are suitable for use in structural and environmental applications.

Blast furnace slag-modified grouts were used to stabilize soils contaminated with trivalent and hexavalent chromium. Slag content, grout/soil ratio and water/cementitious material ratio were varied to determine the effects on leachability of chromium, permeability and compressive strength. Slag-modified grouts successfully stabilized Cr(VI)-contaminated soil to give low leachability, thereby allowing omission of the pretreatment stage to reduce Cr(VI) to Cr(III) necessary with lime and ordinary Portland cement stabilization procedures. Leachability of both Cr(III) and Cr(VI) decreased with increasing slag content. The permanence of leach resistance is enhanced by higher slag levels in grout. Compressive strength of grout-treated soil ranges from 6 to 36 MPa and permeability is of the order of 10(-11) to 10(-7) cm/s, depending on mix proportions. Slag-modified grouts have potential for in situ stabilization of Cr(III)- or Cr(VI)-contaminated landfills.

Fibrillated polypropylene fibres were added to cementitious grouts to determine whether improved mechanical properties and durability could be achieved. The grouts were studied for suitability as subsurface containment barriers around stabilized hazardous waste landfills. Strength, wet-dry and freeze-thaw durability and shrinkage crack control were investigated. Fibres added at volume fractions of 0.1 and 0.2% were found to reduce crack widths of restrained shrinkage specimens by bridging action. compressive and flexural strengths were not consistently affected by incorporation of fibres. Fibres did not significantly change the residual compressive strength of air entrained grouts subjected to freeze-thaw cycles.

In-situ remediation of a chemical waste landfill with excessive chromium levels is being investigated as part of the Mixed Waste Landfill Integrated Demonstration. This paper is concerned with the design of advanced cementitious grouts for in-situ stabilization of chromium contaminated soil and in-situ installation of subsurface containment barriers. Grouts have been developed to improve the performance and cost effectiveness of remediation compared with conventional materials. In addition to restoration of chromium contaminated soils, the developed grouts have applications in other environmental operations where superior properties are required.

Superplasticized cementitious grouts were tested for constructing subsurface containment barriers using jet grouting in July, 1994. The grouts were developed in the Department of Applied Science at Brookhaven National Laboratory. The test site was located close to the Chemical Waste Landfill at Sandia National Laboratories, Albuquerque, NM. Sandia was responsible for the placement contract. The jet grouted soil was exposed to the service environment for one year and core samples were extracted to evaluate selected properties. The cores were tested for strength, density, permeability (hydraulic conductivity) and cementitious content. The tests provided an opportunity to determine the performance of the grouts and grout-treated soil. Several recommendations arise from the results of the core tests. These are: (1) grout of the same mix proportions as the final grout should be used as a drilling fluid in order to preserve the original mix design and utilize the benefits of superplasticizers; (2) a high shear mixer should be used for preparation of the grout; (3) the permeability under unsaturated conditions requires consideration when subsurface barriers are used in the vadose zone; and (4) suitable methods for characterizing the permeability of barriers in-situ should be applied.

Calcium phosphate cements were investigated as potential lost circulation control materials for geothermal wells. The calcium phosphate cements were produced by reacting calcium aluminate (high alumina) cement with sodium phosphate compounds. Pumpable formulations with thickening times of up to 2 h at temperatures between 25 and 90°C were developed and characterized. The materials showed rapid set behavior, early strength development, low permeability and acceptable durability in hydrothermal environments. Strengths up to 4 MPa were achieved 4 h after mixing and permeabilities were of the order of 10−9–10−7 cm/s at 24 h. Partial replacement of calcium aluminate cement with ground granulated blast furnace slag was found to reduce the amount of borax retarder required to maintain pumpability at elevated temperatures and pressures.

Cement-based containment barriers for waste landfills are at risk of cracking, thereby reducing effectiveness. Improved resistance to formation of permeable cracks will enhance the performance of cementitious hydraulic barriers exposed to excessive drying or to wet-dry cycles. Addition of fibre reinforcement was investigated as a potential means of improving crack resistance. Grout and soil cements with and without polypropylene fibres were subjected to different curing and exposure conditions and tested for initial and final permeability. Permeabilities under saturated flow conditions were compared to determine whether fibres could control permeable microcracking of subsurface containment barriers. Fibrillated polypropylene fibres reduced the relative change in permeability for grout and soil cement cured in water and subjected to wet-dry cycles, but did not show significant benefit for materials cured in soil and allowed to dry. Addition of monofilament fibres to barrier materials caused an increase in post-cracking permeability compared with unreinforced materials. This was attributed to increased flow paths created at failed fibre/matrix interfaces.

The objective of this work was to produce grout-treated soils with permeability coefficients less than 10(-7) cm/sec that would be suitable as containment barriers around hazardous waste landfills. The role of such admixtures as superplasticizers and silica fume in grouts for mixing with soil was investigated. Grouts were designed to be used with soil-mixing or jet-grouting techniques for in situ installation of barriers. Materials with a range of soil-cement ratios were tested for permeability and strength under wet and simulated subsurface curing conditions. Permeability coefficients of the order of 10(-10) cm/sec were measured for soil cements with soil-cement ratios by mass up to 5, depending on how the materials were cured. The use of superplasticizers in parent grouts to reduce water-cement ratio decreases permeability up to four orders of magnitude compared to soil cements produced from conventional high water-cement ratio grouts. The significant improvement in performance results in reduced thickness of barriers for hydraulic and physical isolation of contaminants, and hence greater cost effectiveness.

The objective of the project was to develop, demonstrate and implement advanced grouting materials for the in-situ installation of impermeable, durable subsurface barriers and caps around waste sites and for the in-situ stabilization of contaminated soils. Specifically, the work was aimed at remediation of the Chemical Waste (CWL) and Mixed Waste Landfills (MWL) at Sandia National Laboratories (SNL) as part of the Mixed Waste Landfill Integrated Demonstration (MWLID). This report documents this project, which was conducted in two subtasks. These were (1) Capping and Barrier Grouts, and (2) In-situ Stabilization of Contaminated Soils. Subtask 1 examined materials and placement methods for in-situ containment of contaminated sites by subsurface barriers and surface caps. In Subtask 2 materials and techniques were evaluated for in-situ chemical stabilization of chromium in soil.

Cementitious grouts with and without polypropylene fibres were evaluated for use as containment barriers around waste landfills located in an arid environment. Viscosity, flow time, water permeability and microstructure of the grouts were investigated. Low permeabilities of the order of 10−11 to 10−10 cm/s were measured on cement-sand grouts. Permeability was influenced by curing conditions and water/cement ratio. Variation of sand/cement ratio by mass from 1 to 1.2 and addition of 0.1 to 0.2% volume fraction fibres did not affect permeability significantly.

Well cements resistive to high-temperature (∼300 °C) brines containing carbon dioxide (CO2) are needed for use in the completion of geothermal wells. Recent attempts to complete wells through aquifers containing ∼1000 p.p.m. concentrations of CO2 at ∼130 °C have shown severe deterioration of all conventional cement systems, with resulting cement and casing failures after only 90 days in service. As part of an ongoing research programme to develop hydrothermally and CO2-resistant cement formulations, studies were performed to determine the rate of alkali carbonation of autoclave-treated polymer-calcium aluminate cement composites upon exposure to Na2CO3-laden water at 300 °C. The results indicated that the formation of a calcium-complexed carboxylate polymer structure, resulting from the addition of an acrylic polymer in the cement, improved the compressive strength of the composite after a 1 day autoclave exposure, and minimized the carbonation rate over 30 days. However, biccholite→wairakite and triclinic→hexagonal anorthite transformations resulted in strength degradation after exposure for times up to 30 days. The polymer system found to be most effective for minimizing strength degradation and carbonation reactions was a carboxylated styrene-butadiene copolymer.

Polyaryl thermoplastic adhesives (polyetheretherketone, PEEK, polyphenylene sulfide PPS, polyphenylethersulfone, PES) were evaluated for ability to bond elastomer to metal for use in geothermal environments. Strength of elastomer-to-metal joints adhesives blends (such as in drill pipe or casing protectors) were determined using peel tests. Parameters involved in making the joints were temperature, time and atmosphere, in addition to type of adhesive. Physical chemical analyses have aided endeavors to determine the cause of adhesion failure in the joint: differential thermal analyses, thermal gravimetric analyses, infrared spectroscopy and electron spectroscopy for chemical analysis. Tests showed that joints made of adhesive blends which contained greater than 50% PES survived simulated geothermal conditions (200C, water vapor pressure 200 psi) for weeks without significant decrease in peel strength. Chemical components of the adhesive appear to be highly stable under the conditions required to make the joints and in subsequent exposure to the simulated geothermal environment.

This specification covers styrene-butadiene latex modified concrete as an overlay on concrete bridge decks. It applies to both new construction and rehabilitation of existing decks. It includes certification requirements of the latex products, storage, handling, surface preparation, mixing, application, and limitations.

An anhydrous α-Zn3(PO4)2 phase converted by the dehydration of hydrous zinc phosphate, Zn3(PO4)2·2H2O, crystal coatings in air at a temperature of approximately 300 °C, significantly enhances the corrosion resistance of steel, and also reduces the susceptibility of the crystals to alkaline dissolution. A subsequent α→γ phase transition at approximately 500 °C results in a poor protection behaviour, because of the formation of numerous microcracks on the crystal faces.

AbstractPolymide (PI) resins which are produced by an in situ imidization condensation reaction of polyamic acid (PAA) precursors were evaluated for use as binders in high‐temperature performance lightweight cement‐filled material systems. Unfortuanately, the presence of partially hydrated cement in the system led to strength retrogression at room temperature. Significant mechanical failure was observed upon exposure of the specimens to steam at > 150°C. This was found to be due mainly to alkali catalyzed hydrolysis of the functionaries of unreacted PAA adjacent to the cement surfaces and the imide rings of PI matrices. The formation of Ca‐complexed carboxylate salts derived from the hydrolysis resulted in chain scission of the polymer, thereby decreasing the mechanical strength, and making the composites unsuitable for use in aqueous environments.

Amorphous polytitanosiloxane (PTS) was formed by hydrolysis-polycondensation and hydrolysis-polycondensation-pyrolysis reactiomechanisms of precursor sol solutions consisting of monomeric organosilanes, Ti(OC2H5)4, methanol, water and hydrochloric acid, over the temperature range 100–500 °C. These reaction processes which are responsible for the assemblage of PTS networks were found to depend mainly on the species of organosilane used.

Calcium aluminate cement pastes containing hydrous titania sol-gel particles that were produced by hydrolysis of Ti(OR)4, (R:C2H5, C3H7 and C4H9) were exposed to steam and air at temperatures up to 1000°C. It was determined that agglomerate particles of anatase crystalline units formed by in-situ sintering in the cement matrices at temperatures ranging from 300° to 850°C, perferentially react with the Ca in the cement. The extent of the interaction between the titania aggregate and the cement was enhanced as the in-situ anatase→rutile phase conversion occured at temperatures > 850°C. This was due to the reactive feature of rutile evolved by the intra-agglomerate densification and crystallite growth of anatase. The titania-cement interaction played a major role in improving the mechanical properties of cement composites at elevated temperatures.

In an attempt to better understand interactions occuring at hydrated cement/organic polymer interfaces, the reaction mechanism and products formed at the interfaces between poly(acrylic acid), p(AA) or poly(acrylamide), p(AM), and Ca(OH)2 or gibbsite, Al2O3·3H2O, were explored using x-ray photoelectron spectroscopy (XPS). It was estimated that at p(AA)/Ca(OH)2 interfaces, a Ca-complexed carboxylate interfacial reaction product was formed by an ionic reaction between the COOH in p(AA) and Ca2+ ions from Ca(OH)2. A similar reaction product was formed at p(AM)/Ca(OH)2 interfaces as a result of an inter-facial transformation of amide in p(AM) into carboxylic acid, caused by the alkali-catalyzed hydrolysis of the amide. The proton-accepting hydroxyl groups existing at the outermost surface sites of Al2O2·3H2O react favorably with proton-donating COOH groups in p(AA). This acidbase interaction at the p(AA)/Al2O3·3H2O joint formed hydrogen bonds. Whereas, when the p(AM) was applied on Al2O3·3H2O surfaces, interfacial electrostatic bonds were formed through charge-transferring reaction mechanisms in which the charge density was transferred from the Al in Al2O3·3H2O to the C=0 oxygen in p(AM).