P.C. Borthakur

Characterization, beneficiation and utilization of a kaolinite clay from Assam, India

Abstract Kaolin available in Deopani, Assam of northeastern region of India was characterized by FTIR, XRD, DTA and by wet chemical analysis methods. The major impurities in the clay are quartz and siderite. Wet sieving of the clay by −53-μm sieve removes almost all the quartz and a major amount of Fe bearing impurities. The iron content of the clay may be reduced further by treating with wet high intensity magnetic separator (WHIMS) or leaching with organic acids. The effectiveness of various leachants follows the order: Oxalic>Oxalic+EDTA>Malonic>Citric acid. Almost all the nonstructural iron may be removed at room temperature by using 0.4 M oxalic acid solution. The leached clay may find use as a ceramic raw material and filler material for paper and other materials.

Kinetics of dehydroxylation of kaolin in presence of oil field effluent treatment plant sludge

Abstract Oil field effluent treatment plant (ETP) sludge contains high amounts of hydrocarbon and its disposal by land filling is a problem. Various methods to utilize the sludge and circumvent the disposal problem have been suggested. The high calorific value of the sludge may be used in calcination of clay and manufacture of ceramic materials. This communication reports the kinetics of dehydroxylation of a kaolin clay in presence of ETP sludge. Nonisothermal methods are applied to obtain the thermal curves. Nine solid-state mechanisms are applied for analysing the data obtained in the temperature range of 450–750 °C. Random nucleation is the major process of decomposition in both the clay and clay–sludge mixture at the lower temperature range (450–600 °C). At higher temperatures (600–750 °C), the thermal decomposition of the sludge follows a three-dimensional diffusion process and occurs at the phase boundary with spherical symmetry. The thermal decomposition of the clay–sludge mixture, in the temperature range of 600–750 °C, occurs at the phase boundary with cylindrical symmetry. The kinetic parameters follow the kinetic compensation effect.

Cementitious properties of metakaolin-normal Portland cement mixture in the presence of petroleum effluent treatment plant sludge

Abstract The physicochemical characteristics of cocalcined kaolin and petroleum effluent treatment plant (ETP) sludge and its effect on the technological and hydration characteristics of cement have been presented. Conductivity measurements indicate that both the sludge ash (SA) and cocalcined kaolin–sludge mixtures in aqueous medium are reactive in nature. The rate of hydration was investigated by determining the combined water (CW) and Ca(OH) 2 content in the hydration products. The hydration products were characterized by FTIR spectrophotometric method and XRD analysis technique. The rates of hydration of cement containing cocalcined kaolin–sludge mixtures are comparatively higher than the others. Blended cements with improved technological properties may be prepared by replacing 20% cement with cocalcined kaolin–sludge mixtures containing up to 30% sludge.

Hydration behaviour of lime–co-calcined kaolin–petroleum effluent treatment plant sludge

Abstract Petroleum effluent treatment plant (ETP) sludge contains hydrocarbons and its ash is pozzolanic in character. The hydrocarbon may be utilized in the calcination of clay. The present communication reports on the hydration behaviour of lime–metakaolin mixtures produced in the presence of the sludge. The hydration products were characterized by using FTIR, TG, DTA and XRD methods. Use of sludge in metakaolin preparation increases the initial hydration rate and enhances the production of C–S–H or C–A–S–H gel.

Activation of low lime high alumina granulated blast furnace slag by anhydrite

Abstract Activation of low lime high alumina granulated blast furnace slag by anhydrite has been investigated with an objective to prepare supersulphated slag cement. The optimum amount of anhydrite required for the purpose is found in the range of 15–20%. An attempt has been made to interpret the hydration characteristics of a typical supersulphated slag cement composition by means of chemical, thermal, infrared spectroscopic and X-ray analyses.

Paddy husk as raw material and fuel for making Portland cement

Abstract Paddy husk has been finding world wide attention for its utilization in various applications. Most of the research in this area, particularly in the field of cement and building materials has been carried out in the development of lime-rice husk ash cementitious materials. However, the strengths of these cements are low. The present paper deals with the utilization of both calorific value and reactive silica of paddy husk for producing Portland cement type clinkers. The physico-chemical and minerological properties of the clinkers and cements produced are presented. The burnability of the raw mixes containing husk as fuel is found to be better than those prepared with other fuels following the same process. This is attributed to the high reactivity of the insitu generated silica in the ash and rapid burning and cooling schedule maintained in the process of clinkerisation. Cements of various technological properties comparable to ordinary Portland cement can be produced using paddy husk as fuel at a significantly low LSF and low temperature of around 1300 deg.C. The clinkers generated are soft and porous and the fuel also being a waste material, the cement produced is expected to be of low cost.

Physicochemical and cementitious properties of sludge from oil field effluent treatment plant

Abstract Sludge generated in the effluent treatment plants (ETPs) of oil fields contain calcite, clay and other inorganic materials as well as hydrocarbon oil. The amount of the latter is often more than the permissible level for safe disposal by landfilling. The thermoanalytical characteristics of the sludge generated in the ETP of Lakwa oil field, Assam, India were investigated by using TG, DTG, DTA, XRD, FTIR techniques and chemical methods. The lime reactivities of the sludge ash and the physical properties of blended cement containing the ash were evaluated. Decomposition of calcite starts from above 550°C and it is succeeded by several solid state reactions involving CaO and aluminosilicates forming new phases. Gehlenite (Ca 2 Al 2 SiO 7 ) has been identified as one of the products and it forms above 750°C. Sludge ash prepared at 750°C consumes considerable amount of lime but it is not suitable for preparation of blended cement.

Investigation on reduction of cement binder in cold bonded pelletization of iron ore fines

Abstract Cold bonded pelletization processes developed for utilization of iron ore fines and slimes require about 10% or more cementitious binders. Reduction of the cost of the pellet and its gangue content require reduction of the amount of binder. This communication reports the results of an investigation on reduction of binder requirement in cold bonded pelletization of iron ore fines by using cement clinker alone or mixed with silica of different characteristics. Pellets with crushing strength of 100–200 kg/pellet could be obtained even using about 4–6% binders consisting of Portland cement clinker/cement of appropriate chemical characteristics and fineness either alone or mixed with silica fines. The binder requirement may be curtailed by about 4% by increasing its surface area. The physico-metallurgical properties of the cured pellets indicate potentiality for use as burden material in low/moderate shaft furnaces.

Hydration of Portland cement clinker in the presence of carbonaceous materials

Abstract An investigation of the hydration behaviour of ordinary Portland cement clinker in the presence of coal, coke, and charcoal has been carried out. The physico-chemical characteristics of cement are greatly influenced by these materials. The water requirement and setting times are increased. The 1–28 day compressive strength of the mortars are invariably lowered by the carbonaceous materials but the 90 day strength depends upon the nature of the materials. The hydration characteristics of different cementitious compositions have been investigated with the help of infrared spectroscopy, X-ray diffraction and SEM analysis.

Investigation on cold bonded pelletization of iron ore fines using Indian slag-cement

Abstract Cold bonded pelletization of iron ore fines using ordinary portland cement binder is emerging as a potential energy saving agglomeration process for proper utilization of Indian iron ore fines. The possibility of substituting ordinary portland cement/clinker by cheaper low grade Indian granulated blast furnace slag is investigated. The strength development characteristics of pellets containing slag-clinker is similar to those containing clinker as the binder. Around 50% of the ordinary portland cement required for making pellets of desired properties can be stubstituted by slag. The crushing strength of the pellets is found to increase with increase of diameter of the pellets. The green pellets on normal curing for 5–7 days develop crushing strength of 60–90 kg/pellet which enhances to 125–175 kg/pellet or 140–220 kg/pellet, respectively on prolonging the normal curing to 28 days or subjecting to heat/steam treatment for a few hours. Slag-clinker containing pellets are slightly less basic but are more reducible than those of clinker containing pellets.