Reactive Clay Research Articles

The role of ferrous clays in the interpretation of wettability – a case study

Clean sandstone, with minimal clay content, is expected to be strongly water wet once the rock has been through an effective cleaning process. Even samples containing significant clay minerals are usually expected to be water wet after appropriate cleaning. However, tests carried out on core samples from Fields in three different global locations show mixed indices, even for clean state samples where no aging with crude oil has taken place. A few hypotheses for this behaviour considered herein are: whether the cleaning method was adequate, whether wettability was altered by an external factor, or if wettability was due to mineral composition. This paper presents the results obtained from wettability studies on fresh, clean and restored state core plug samples from three different Fields. Wettability indices were obtained by using the combined Amott-USBM method. Petrography was performed on sample end-trims to investigate the possible presence of halite or barite in the clean state samples, thought to be from drilling fluid infiltration, which should have been removed by the methanol cleaning cycle. This showed no organic material or salt (halite), negating wetting change from inefficient cleaning. From a reactive clays [1] model perspective, these rock samples are considered clean-sand (i.e. illite/ smectites- as total clay content), determined by XRD analysis, are lower than 10%. SEM and XRD results showed the presence of grain-coating chlorite in one sample set and glauconite grains in the others. Only once the unusual wettability indices were obtained was the grain-coating chlorite identified as chamosite by SEM/EDX, which is an iron-rich form of chlorite. The presence of chamosite or glauconite appears to influence the wetting tendency. In summary, USBM vs Amott wettability indices of the analysed samples are consistent between both methods, showing a mixed to oil-wet tendency for all samples where chamosite was identified, regardless of the initial test condition. Samples with glauconite appeared to be more mixed wet after wettability restoration. The results suggest that iron rich clay/mineral content is the main contributor to the oil wet tendency of the evaluated rocks.

Interaction of Dissolved CO2, SOx and NOx with the Moolayember Formation Underlying the Precipice Sandstone

An injected CO2 or greenhouse gas (GHG) stream will dissolve into formation water forming carbonic acid, especially in the case of low salinity reservoir storage. Industrial GHG streams from coal combustion, cement or streel production may contain accessory gases including N2, Ar, SOx, NOx, or O2, several including SOx and NOx form stronger acids. The dissolved GHG stream will have reactivity to some rock forming minerals, potentially modifying porosity or water chemistry, or mineral trapping CO2. The Precipice Sandstone in the Surat Basin, Australia, is a low salinity target reservoir for CO2 storage. The Surat CCS project proposes to a demonstration-scale injection test of 60,000 t per year of a GHG stream captured from black coal PCC into the quartz rich Lower Precipice Sandstone. The dissolved GHG stream is expected to interact with the Lower and Upper Precipice Sandstone and sink to interact with the underlying Moolayember Formation of the Bowen Basin. However little was known about the lithologies of the Moolayember Formation which unconformably underlies the projects proposed injection site. Drill cores from the Moolayember Formation were sampled and characterized: indicating a high proportion of carbonate cements, potentially reactive clays, feldspars, and trace amounts of sulphides and coal. Complex carbonate assemblages and secondary textures indicate this may already be a valuable example of a natural analogue of CO2 alteration. Kinetic geochemical modelling was performed to predict the CO2 or CO2-SO2-NO reactivity of several lithologies. This indicted that after 30 years, low concentrations of SOx and NO (100 ppm) had minimal effect on the pH which was buffered to similar values relative to pure CO2 for these reactive mineralogies. The pH was instead controlled by the carbonate mineral content, which buffered acidity. Reaction of clay and feldspar rich lithologies resulted in dissolution of K-feldspar, chlorite, and plagioclase to form kaolinite, smectite, and additionally siderite mineral trapping CO2. SO2 was predicted to be mineral trapped as pyrite or alunite. The net predicted mineral volumes or porosities however did not change significantly. Experiments at reservoir conditions and further characterization are planned to validate and improve model predictions.

Volumetric Behavior and Soil Water Characteristic Curve of Untreated and Lime-Stabilized Reactive Clay

This paper investigates the influence of lime stabilization of an expansive clay based on volumetric behavior and the soil- water characteristic curve (SWCC). The selected soil was a residual clay located in Victoria, Australia. Specimens treated with an optimum lime content (OLC) that was found to reduce swell potential were selected to investigate the SWCCs. Static compaction tests were conducted to establish the virgin compression surface. Hyprop (Meter Group, Pullman, Washington), filter paper, and the chilled mirror hygrometer were used to measure the SWCC at and below the surface at different net stress levels. To interpret the volumetric behavior of untreated and treated soil using the SWCC, swelling and collapse values were measured at various initial moisture contents and stress levels. The test results found that although the treated specimens were stabilized with lime at OLC, significant collapse and swelling potential were obtained when the lime-treated specimens were prepared at high suction value and wetted under low net stresses.

Cationic starch derivatives as reactive shale inhibitors for water‐based drilling fluids

ABSTRACTOne of the major problems associated with the use of water‐based drilling fluids is the interaction of water with specific rock formations, such as shales, and the consequent swelling of reactive clays that may be present in that type of rock. Several types of clays reactivity inhibitors have been used by the oil industry, and the most effective ones are the cationic polyelectrolytes, such as the poly(diallyldimethylammonium chloride) (PDADMAC). However, this polyelectrolyte is very toxic. In this work, a series of cationic starch derivatives with different cationic degrees were synthesized with the objective of evaluating their potential as environmentally correct shale reactivity inhibitors. The results showed that the synthesized derivatives presented a good capacity of adsorption on bentonite and an efficient inhibition of the shale reactivity. The derivative with an intermediate cationic degree presented the best performance. In the tests with the formulated fluids this derivative provided an intact cuttings recovery of 84.8% and a total recovery of 92.3%. These values are very close to those found for the PDADMAC additive, therefore indicating that this cationic starch derivative presents a good potential as inhibitor of the shale reactivity. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46621.

A robust and parsimonious model for caesium sorption on clay minerals and natural clay materials

Caesium (Cs) is one of the most studied radionuclides in the fields of nuclear waste disposal and environmental sciences. The overall objective of this work is to improve the tools designed to describe and predict migration, retention, and bioaccumulation processes in the geosphere and the biosphere, particularly in the soil/solution soil/plant roots systems. Cs sorption on clay minerals has been extensively measured and modeled because these minerals control Cs mobility and (bio)availability in the environment.A critical analysis of published experimental data on Cs sorption by clay minerals and natural clay materials along with the different models was performed in an attempt to elaborate and evaluate a generic model for Cs sorption. This work enabled us to propose a robust and parsimonious model for Cs sorption, which combines the surface complexation and cation exchange approaches invoking only two types of surface sites: frayed edge and exchange sites. Our model, referred to as the “1-pK DL/IE model”, takes into account the competition between Cs and other cations as well as the influence of the ionic strength and pH of the solution.This model was successfully calibrated for Cs sorption on three reference clay minerals (illite, montmorillonite and kaolinite), in a wide range of Cs concentrations and physicochemical conditions. Using the same parameters, we tested our model on several natural clayey materials containing a single to several clay minerals. The goodness-of-fit obtained with natural materials containing a single clay mineral demonstrates the robustness of the model. The results obtained with natural mixed clay materials confirm the predictive capability of the model and also allowed us to test the sensitivity to the mineral composition of these materials (uncertainties). We found that illite is usually the most reactive clay mineral with respect to Cs sorption and that component additivity is applicable when the contribution of other clay minerals becomes non negligible. The whole set of model-measurement comparisons performed in this study provides a high level of confidence in the capabilities of the 1-pK DL/IE model as an interesting predictive tool.

Valorization of KCl/PHPA system of water-based drilling fluid in presence of reactive clay: Application on Algerian field

During the drilling when using water-based drilling fluid, the swelling issue is encountered, particularly in reactive clay section. After a bibliographical review showing a fundamental divergence from already published results depending on the type of system and shale inhibitors products used, this paper describes an experimental plant to measure inhibition level of KCl/PHPA system on reactive clays. For this, the current study provides more information on the potential of the mud system as well as its influence on the essential properties of drilling fluids. Qualification testing reported here shows that the use of combination of PHPA product and KCl meets the characteristics of performance. The series of X-rays Diffraction analysis were conducted on cutting samples collected from different depths of Ain Amenas field, the results obtained allowed to say that all the samples have different percentages of swelling clay that represent a source Potential of high-reactivity clay materials. Moreover, a series of physico-chemical and rheological analysis were performed on these cutting samples, in order to allow the valuation of the KCl/PHPA system in water based drilling fluids.

Understanding the clay-PEG (and hydrophobic derivatives) interactions and their effect on clay hydration and dispersion: A comparative study

In oil and gas well drilling, the effective minimization of clay-water interactions is an essential function that water-based drilling fluids must meet in order to maintain the integrity of the shale formations as well as suitable rheological properties. In this work, the protective effect of poly(ethylene glycol) 2000 (PEG2000) and two hydrophobic derivatives on the hydration and dispersion of reactive clay materials was investigated. Thus, conventional inhibition tests were combined with adsorption measurements and analyses by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and thermogravimetry (TGA) in an attempt to establish structure-performance relationships. It was found that both PEG2000 and its hydrophobic derivatives can strongly adsorb, in equimolar amounts, on mineral clay following a Langmuir type behavior, in which bilayers are formed in the clay interlayer region at surface saturation. It was found that the PEG backbone rules the adsorption process, while the hydrocarbon tails of the hydrophobically modified products do not play a decisive role. However, it was verified that hydrocarbon tails play a central role in the mechanism of inhibition of clay particles hydration. Bentonite inhibition test revealed that the incorporation of two hydrocarbon tails at the PEG2000 chain ends duplicate the performance of oligomer, regarding the product with just one tail.

Development of innovative environmental applications of attapulgite clay

In this paper we present a series of laboratory and field, pilot- scale applications of attapulgite clay as an amendment for the stabilization of metals in contaminated soil and sewage sludge. Attapulgite’s structure together with its fine particle size and fibrous habit are responsible for its high specific surface area and sorption properties. A pilot scale application of attapulgite clay as a binder for in situ stabilization of toxic metals in contaminated land showed significant reduction in the water leachable metal fraction (Cu: 17%, Pb: 50%, Zn: 45%, Cd: 41%, Ag: 46%, As: 18%, Mn: 47%, Ba: 45%, Sb: 29%). In a second pilot scale environmental application, an innovative attapulgite “Geosynthetic Reactive Clay - GRC” was designed and developed for “capping” and “stabilization”of toxic metals in contaminated soil. Also, laboratory scale experiments with fresh sewage sludge from a municipal water treatment plant showed that addition of attapulgite clay in sludge, significantly reduced the leachable concentrations of phenol, DOC, Hg, Cu, Mo, Pb, Se, As, Zn and pathogen population over a 4 weeks observation period. The developed soil remediation techniques are promising and cost-effective under present market conditions. Concerning treatment of sewage sludge, attapulgite clay is an effective additive that could enhance the composting procedure creating an environmental added value, final compost product.

Formulation of a water based drilling fluid system with synthesized graft copolymer for troublesome shale formations

Shale formations consisting of reactive clay mineral of smectite group like montmorillonite may lead to severe wellbore instability problems with conventional water based drilling fluids. This may be due to their high magnitude of rock-fluid interaction inside the wellbore. Problems like hole enlargement, pipe sticking, high toque and drag etc. may escalate drilling cost and time. The present study deals with the applicability of synthesized polyacrylamide/dially dimethyl ammonium chloride-grafted-gum acacia copolymer in formulation of novel water based drilling mud system (WBDMS) for troublesome shale formations. The mechanism behind the synthesis was free radical polymerization. The structural information and morphological properties of copolymer were determined by Fourier transform infrared spectroscopy (FTIR) and Field emission scanning electron microscopy (FESEM). Further, its effect on filtration and rheology of developed mud system was analyzed thoroughly as per API standard procedures. Further, effectiveness of graft copolymer on the shale stabilization was investigated using shale dispersion and slake durability tests. The reactivity of core sample with the developed drilling fluid system was analyzed using core flooding experimental setup. The experimental investigations showed that synthesized graft copolymer has significant effect on rheological parameters and filtration characteristics of the system due to its synergistic effects in the developed system. Also, its shale stabilization property was superior to the commercially used shale stabilizer (partially hydrolyzed polyacrylamide polymer). It was evident from the high values of shale recovery and slake durability index. This was achieved due to the presence of cationic ions and formation of a protective coating on shale cuttings. It has also resulted in the low magnitude of rock-fluid interaction. The developed drilling fluid system exhibited low reactivity with the core sample during core flow studies. Thus, the synthesized graft copolymer can be utilized as an additive in the formulation of water based mud system customized for reactive shale formations.

A New Matrix/Fracture Multiscale Coupled Model for Flow in Shale-Gas Reservoirs

Summary A new computational model for coupled gas flow in hydraulic fractures and multiporosity shale matrix is developed within the framework of multiscale modeling. The hydrodynamics in the network of hydraulic fractures are constructed by averaging the mass-conservation equation across the fracture aperture, giving rise to an averaged balance law supplemented by a source term arising from the jump in the gas flux from the shale matrix. The resultant flow equation in the fracture is coupled with a new pressure equation that governs the averaged gas movement in the shale matrix. Such a pressure equation exhibits a new storage coefficient and is rigorously derived by homogenizing the pore-scale model of gas flow in the interparticle pores, partially saturated with water, lying adjacent to the nanopores within the kerogen and impermeable inorganic matter composed of a reactive clay and an inert solid. The free gas at the interparticle pores is assumed at local thermodynamic equilibrium with the dissolved gas in the water and adsorbed gas lying in the nanopores of the kerogen aggregates and at the surface of the active clay. The constitutive laws for the partition coefficients, which appear in the pressure equation, are derived from the adsorption isotherms, which are rigorously constructed from the thermodynamics of confined gases on the basis of the density-functional-theory (DFT) approach. Numerical simulations of both canonical and real computational examples of gas primary recovery in the Barnett, Marcellus, and Eagle Ford formations illustrate the potential of the multiscale approach proposed herein in computing production in different flow regimes.

Interpretation of the loading–wetting behaviour of compacted soils within the “MPK” framework. Part I: Static compaction

Depending on the state paths, loading–wetting of compacted unsaturated soils can exhibit complex volumetric behaviour, such as swelling, collapse, collapse followed by swelling, swelling followed by collapse, and swelling pressure development. Microscopically, these behaviours arise from complex interactions among applied stresses, air–water pressure deficit or suction at the water menisci, moisture content or degree of saturation in the voids, and the nature of the micro- and macrosoil aggregates of compacted soils that depend on the level of suction. While significant advances have been made in modelling hydromechanical behaviour of compacted unsaturated soils taking these interactions into account, input parameter determination requires advanced testing equipment and the testing processes can be very time-consuming. In 2012, a relatively simple and practical framework within the void ratio – moisture ratio (water volume / solid volume) – net stress space (referred to as the MPK framework) has been proposed by Kodikara to explain–predict these state paths. A desirable feature of this framework is that it identifies a direct link between the well-known compaction curve and the compacted soil constitutive behaviour. This paper presents a comprehensive series of tests on statically compacted soils, the results of which are in close agreement with this framework. Two soil types, namely lightly reactive kaolin and more reactive clay (referred to as Merri Creek soil), were used in the testing. The soils were prepared with different moisture contents from the dry state and statically compacted at constant water content to obtain void ratio – moisture ratio – net stress constitutive surfaces, as well as soil specimens for state path tests. The state path test results of yielding under loading, collapse under wetting, swelling pressure development, and change in yield pressure due to wetting are explained within this framework. In addition, some published data on a silty soil mixture were also analysed, highlighting that the framework is valid, regardless of the degree of reactivity of the soil. Suction was not measured in the authors’ experiments, as it was not required to explain the above state paths according to this framework. However, it is recognised that suction is the conjugate state variable to the moisture content. Therefore, in future experiments, suction will be measured and its role will be fully explained within the framework, adding more generality.

Field Performance of In-Service Cast Iron Gas Reticulation Pipe Buried in Reactive Clay

AbstractField instrumentation of an in-service cast iron gas pipe buried in a residential area is detailed in this paper. The aim of the study was to monitor the long-term pipe behavior to understand the mechanisms of pipe bending in relation to ground movement as a result of seasonal fluctuation of soil moisture content. Field data showed that variation of soil temperature, suction, and moisture content are closely related to the prevailing climate. Change of soil temperature is generally related to the ambient air temperature, with a variation of approximately −3°C per meter depth from the ground surface in summer (decrease with depth) and winter (increase with depth). Seasonal cyclic variation in moisture content was observed with maxima in February and March, and a minimum around September. The pipe top was under tensile strain during summer and subsequently subjected to compressive strain as soil swelling occurred as a result of increase in moisture content. The study suggests that downward pipe bend...

Addition of low reactive clay into metakaolin-based geopolymer formulation: Synthesis, existence domains and properties

This paper investigates the addition of low reactive Tunisian clay into metakaolin-based geopolymer as a valorization way in alkaline media. To conduct this investigation, the aluminosilicate precursors used were primarily characterized. Then, several samples were prepared by varying the amounts of metakaolin and clay in the mixture as well as the Si/K molar ratio of the alkaline solution. Correlations between (i) the polycondensation rate of the synthesized mixtures, followed by FTIR spectroscopy; (ii) the working properties, evaluated by the compression test; and (iii) the chemical composition were established, and a model of reactivity was proposed to elucidate the different networks formed for each sample. It appears that the Tunisian clay, after heat treatment, exhibits some reactivity that allows for the formation of consolidated materials. The associated minerals present in the clay seem not to participate in the polycondensation reaction and are simply agglomerated by the alkaline solution. However, the increase of the proportion of metakaolin in the mixture and the depolymerized species in the alkaline solution may improve the polycondensation rate and the working properties of the final materials. The optimal properties were obtained for a mixture of 50% low reactive Tunisian clay and 50% metakaolin and a Si/K ratio of the alkaline solution of 0.50.

Field performance of in-service cast iron water reticulation pipe buried in reactive clay

Field monitoring is an important means for understanding soil behaviour and its interaction with buried structures such as pipeline. This paper details the successful instrumentation of a section of an in-service cast iron water main buried in an area of reactive clay where frequent water pipe breakage has been observed. The instrumentation included measurement of pipe strain; pipe water pressure and temperature; soil pressure, temperature, moisture content, and matric suction; as well as the meteorological conditions on site. The data generally indicated that changes in soil temperature, suction, and moisture content were directly related to the local climatic variations. The suction and moisture content data indicated that the soil profile at the site down to around 700 mm, and probably down to 1000 mm, is affected by changes in surface weather, while soil conditions below this depth appear to be more stable. Analysis of pipe strain indicated that the pipe behaves like a cantilever beam, with the top experiencing predominantly tensile strains during summer. Subsequently, these trends reduce to compressive strains as soil swelling occurs because of the increase of moisture content with the onset of winter.

Blended Cements Elaborated with Kaolinitic Calcined Clays

In the clinker production process, the main component of Portland cement (PC), large amount of CO2 are emitted into the atmosphere. The use of calcined kaolinitic clays as supplementary material of cement is an alternative to mitigate the environmental impact. In this paper, the influence of the replacement of PC by two calcined kaolinitic clays (15 and 30%), with high content of metakaolinite and different reactivity was studied. Calcined kaolinitic clays were characterized, the pozzolanic activity usingFrattini test, the compressive strength, rate of water absorption (sorptivity), the assemblage of hydration products and the pore size distributionwere determined at28 days. The results show that the replacement of high percentage (30%) of very reactive clays improves the mechanical behavior and durable parameters compared with those obtained for plain PC

Field Performance of Five Soil Moisture Instruments in Heavy Clay Soils

The increased use of soil moisture retrieval from satellites has heightened the need for improved accuracy of point measurements that are used to validate remotely sensed soil moisture products. A wide range of devices can be installed for operational monitoring of soil moisture; however, many of these devices have not been tested in situ in soils with a very high reactive clay content. The objective of this study was to evaluate the accuracy in field performance of five soil moisture sensors: the EnviroSCAN probe, the Diviner 2000 (both from Sentek Technologies), the Hydra Probe soil sensor (Stevens Water Monitoring Systems), the ThetaProbe ML2x (Delta-T Devices), and the ECH2O EC-5 (Decagon Devices) in soils that had about 71% clay content. The instruments' default calibrations were tested against observed soil moisture from core samples using the thermogravimetric method. New calibration equations were developed for each device, which were evaluated using an independent data set. The ThetaProbe had the lowest root mean square error (RMSE) of 0.025 m3 m−3 and mean bias error (MBE) of 0.002 m3 m−3 in the precalibration analysis. Although the Hydra Probe showed the highest precalibration errors, the instrument made the greatest improvement in post-calibration analysis, with an RMSE of 0.129 m3 m−3 using the default equation reduced to 0.014 m3 m−3 using in situ calibration, and the 0.110 m3 m−3 MBE was reduced to 0 after applying in situ calibration.

High-Performance Water-Based Drilling Fluids Offshore Cameroon

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 163502, ’High-Performance Water-Based Drilling Fluids: An Environmentally Friendly Fluid System Achieving Superior Shale Stabilization While Meeting Discharge Requirement Offshore Cameroon,’ by Anuradee Witthayapanyanon, SPE, Baker Hughes; Jerome Leleux, SPE, Julien Vuillemet, Ronan Morvan, and Andre Pomian, Perenco; and Alain Denax and Ronald Bland, SPE, Baker Hughes, prepared for the 2013 SPE/IADC Drilling Conference and Exhibition, Amsterdam, 5-7 March. The paper has not been peer reviewed. Historically, invert-emulsion drilling fluids are the preferred system for drilling offshore Cameroon. However, with a regulatory environment moving toward zero discharge, associated costs are rising. Therefore, an operator planning to drill in this environment investigated high-performance water-based-mud (HPWBM) -system alternatives. HPWBM systems offer the potential advantage of offshore discharge of drilled cuttings and effluents (owing to the absence of oil contamination) and lowered waste-management costs. Experience in the field demonstrated that the selected drilling fluid met expectations by achieving the required drilling performance and high shale stabilization with zero environmental impact. Introduction Drilling with an overbalanced pressure is a common operational technique used to prevent formation fluids or gas from entering the wellbore, thereby minimizing the risk of well kick and blowout. However, overbalanced drilling can cause drilling fluid to invade the formation, resulting in formation damage, differential sticking, and sloughing if the formation consists of highly reactive clay and shale. To avoid these consequences, invert-emulsion drilling fluids have always been preferable for drilling highly reactive clays and shale formations. The HPWBM system is formulated with a concept of total inhibition. Unlike a conventional water-based-mud system, designed chemical additives are used explicitly in the formulation to achieve desired drilling characteristics that are similar to those of invert-emulsion mud. The key features of HPWBM systems include high shale stability, clay and cuttings inhibition, rate-of-penetration (ROP) enhancement, minimized bit balling and accretion, torque and drag reduction, and environmental compliance. A complementary benefit of its aqueous base is that HPWBM captures the growing need for more-environmentally- friendly drilling fluids. During the past 10 years, more-stringent regulations on drilling-waste disposal have been implemented worldwide. The industry anticipates that the zero discharge of oil-contaminated drilling wastes will soon be the global standard. By switching from invert-emulsion drilling fluids (oil-/synthetic- based mud) to an HPWBM system, operators can achieve substantial cost savings on waste management and logistics. These savings result from the use of on-site, offshore discharge allowed by an absence of oil contamination.

Hyperbranched polyglycerols, obtained from environmentally benign monomer, as reactive clays inhibitors for water‐based drilling fluids

ABSTRACTTo prevent the degradation of the borehole and also the disintegration and dispersion of drilled cuttings, different shale stabilizing additives are used in water‐based drilling fluids (WBFs). Glycols, poly(ethylene glycol), glycerols, and polyglycerol derivatives, also called polyols, have been used to inhibit shales containing reactive clays in WBF. These additives are normally used in conjunction with KCl to reduce clay swelling and dispersion of drilled cuttings. Highly branched polymers have become an important field in current polymer science. Such materials typically exhibit compact, globular structures in combination with an exceptionally high number of sites with functional groups. They have unique properties that differ significantly from their linear counterparts, and the hyperbranched polyglycerol (hPG) is an important hyperbranched polymer that can be produced from an environmentally benign monomer, the glycerol carbonate. In this article, the clay inhibitive properties of hPG were evaluated by different test methods including bentonite inhibition test, cuttings recovery, and X‐ray diffraction measurements. The results show that the hPG has a great potential to be used as an environmental friendly inhibitor additive in WBFs. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40384.

Crumpled highly filled poly(styrene-co-butyl acrylate)/clay hybrid latexes

Abstract The encapsulation of laponite in poly(styrene-co-butyl acrylate) nanoparticles to obtain hybrid latexes with ultra-high clay contents is described. In-situ intercalative ad-miniemulsion polymerisation was used to prepare these hybrid latexes facilitating encapsulation up to 50 wt% of laponite clay. The encapsulation of clay platelets resulted in latexes with crumpled particle morphology. Besides the polymerisation method, the encapsulation of clay was facilitated by careful choice modifier and use of non-dried modified clay. TEM and SAXS showed that the clay platelets were exfoliated and homogeneously distributed within the transparent polymer/clay nanocomposites films. The use of reactive clay modifier enhanced the clay exfoliation and polymer–clay interactions resulting in material showing significant storage modulus improved of up to 5000%. The high clay content incorporated was above the percolation threshold and the materials exhibited solid-like viscoelastic behaviour.

Comparing the performance of different commercial clays in fly ash-modified mortars

Three different commercially available clays (Actigel, Concresol, and Metamax) were compared based on their performance and effect on fly ash-modified mortars prepared with a consistent w/b of 0.45 and s/b of 2.75. Three fly ashes (FA1–3) from different sources were selected to evaluate the performance of these three clays. Ternary mortar blends were formed at various addition and replacement levels of these clays to study their performance in terms of the heat of hydration, thermal setting time, air content, flow ability, and compressive strength development up to 90 days. Results indicated that slight addition of Actigel or Palygorskite significantly affects the rheology as well as decreases the setting time of fresh mortar, the clay being able to alter the fresh state properties to a great extent. All the clays accelerated the cement hydration process as well as decreased the flow ability of mortars. Metamax or metakaolin was found to be the most reactive clay among the three clays in terms of its pozzolanic behavior.