Initial Curing Period Research Articles

Impacts of alkaline washing pretreatment on municipal solid waste incineration fly ash (MSWI FA) and resulting geopolymers

The safe disposal and utilization of municipal solid waste incineration fly ash (MSWI FA) has emerged as a crucial challenge, primarily due to elevated levels of heavy metals and chlorides. In this study, the influence of key factors in different pretreatment methods on the physicochemical properties of MSWI FA was analyzed, and the effects and mechanism of different pretreatment methods on the resulting geopolymers were studied. Under the conditions of a liquid-solid ratio (L/S) of 7 mL/g, a rotational speed of 500 r/min, and a stirring time of 20 min, the alkali washing with 1 mol/L NaOH solution exhibited better effect than water washing. The total content of chlorides and the content of soluble chloride in AFA (MSWI FA with alkali washing) were 1.53 % and 0.85 %, respectively. Alkali washing had a greater influence on the migration of heavy metals from MSWI FA to filtrate than water washing. Meanwhile, alkaline washing exhibited better effect in calcium retention and sulfur removal. The pretreatment process enhanced the gel formation in geopolymers, subsequently exerting a significant influence on the compressive strength and leaching concentration of heavy metals. Thermogravimetric analysis showed the bound water content in AG (8.46 %) was the greatest in all simples, indicating that exerted the most pronounced impact on the gel formation during geopolymerization. And, the lower ratio of Si-O-Na to Si-O-T in AG (0.20) indicated a longer geopolymeric chains, which explained the higher compressive strength of geopolymers during the initial curing period. This article provides a new pretreatment method to promote the resource utilization of MSWI FA.

Characterization of cement–slime mixture using time domain reflectometry

This study explores the electromagnetic characteristics of five cement–slime mixtures using two types of time domain reflectometry sensors. For 28 days of curing, compressive strength tests are conducted and electromagnetic signals are measured. The electromagnetic wave velocity and corresponding apparent permittivity are calculated, and the relationships between these properties and the compressive strengths of the mixtures are established. Results show that in the initial curing period, capturing the apparent permittivity using a conventional probe proves difficult due to the high electrical conductivity of the mixtures. In contrast, an insulated electrical wire can detect reflected signals across all slime ratios, but it exhibits less sensitivity to changes in the electromagnetic signal. The apparent permittivity decreases exponentially over the curing time, influenced by the hydration process. Strong correlations are found between the apparent permittivities derived from both sensors and between decreasing apparent permittivity and increasing compressive strength.

Influences of pretreatment methods on the mechanical and environmental behaviors of PG-GGBS-LM ternary stabilizer.

Phosphogypsum is a kind of acidic industrial byproducts with high content of soluble phosphorus and fluorine pollutants, which requires to be pretreated when used as cementitious material to (partial) replace traditional Portland cement. In this study, five different pretreatment methods were proposed for comparative analysis to examine the pretreatment effect on the mechanical and environmental behaviors of ternary phosphogypsum (PG), ground granulated blast-furnace slag (GGBS), and lime (LM) mixed stabilizer. Series laboratory tests, including unconfined compressive strength (UCS), pH, phosphorus (P)/fluorine (F) leaching, scanning electron microscopy (SEM), and X-ray diffraction (XRD) tests, were conducted to comprehend the macro- and microscopic mechanism. The results show that it is essential to grind raw PG to finer powdered state, so that it reacts more easily and quickly with LM and water. In addition, it was noticed that the UCS and P/F leaching concentration are not only affected by the mixing proportion of the PG-GGBS-LM ternary stabilizer, but also by the curing duration. The UCS increases rapidly from initial curing period and then grows slowly after 28days of curing. From the perspective of strength evolution, mixing proportion of PG: GGBS: LM = 15:80:5 is optimal, but considering the economy and environmental related issues, PG: GGBS: LM = 30:65:5 was regarded as a more attractive choice. The findings can provide a reference for the selection of pretreatment methods and design of PG-based cementitious materials suited for stabilized soils.

THE EFFECT OF SHRINKAGE CONTACT STRESSES ON THE ADHESION STRENGTH OF THE WATERPROOFING COMPOSITION AND THE «OLD» CONCRETE

The paper is devoted to the study of the effect of shrinkage contact stress on the bonding strength of the waterproofing composition of fine-grained cement concrete and «old" concrete. In order to obtain a strong contact when adhering old and new concrete, it is necessary to minimize the amount of internal stress in it. The cause of concrete shrinkage during the initial curing period is the reduction of the cement stone gel, the amount of free water that is consumed by evaporation and hydration of the cement. The semi-bound water (film water) surrounding the gel particles is then consumed. This causes the gel particles to come closer together and shrink further. In addition, the capillary pressure in the pores is very significant and increases with decreasing pore size. Since the micropores are scattered in the cement stone in different directions, the pressure, balancing each other, acts as a comprehensive compression, which also causes volumetric deformation. With further drying of the concrete, the moisture gradient decreases, the growing crystal growths provide more and more resistance to internal pressure and the shrinkage deformation gradually subsides. Thus, the more intensive the hydration processes in the waterproofing coating and the more crystalline hydrates are formed at earlier curing times, the earlier the resistance to comprehensive compression in the coating will be, and as a result, the crack resistance of the coating and the strength of its adhesion to the «old» concrete will increase. As a result of the research carried out in this work, it was found that the compaction of the waterproofing composition, which helps to reduce internal stresses during curing and thus increases the amount of its adhesion to old concrete, is achieved by introducing a finely ground calcium carbonate filler and a complex of chemical water-soluble additives of the second class. The mineral filler and chemical additives allow for the additional synthesis of etringite, calcium hydrocarbonate and calcium hydrochloraluminate, low-base calcium hydrosilicates, and calcite during cement hydration in its pores and capillaries. The developed permeable waterproofing composition in the form of a mortar has high adhesion strength to old concrete and can be used in repair, restoration and protection of building structures, buildings and structures from external influences related to the water environment.

STRUCTURAL CHARACTERISTICS AND PERFORMANCE OF CONCRETE WITH A COMPOSITE MODIFYING ADDITIVE

Introduction: The paper addresses the effect of a composite modifying mineral additive based on waste — tailings from the Balkhash Mining and Processing Plant — and microsilica on the structural characteristics and performance of heavy concrete. Purpose of the study: We aimed to select optimal B25 and B35 concrete mixes based on the MV-D20 modified binder with the composite additive in its composition and evaluate the characteristics of concrete. Methods: In the course of the study, standard methods were used to design concrete mixes and test the characteristics of concrete. Proportioning was performed in accordance with State Standard GOST 27006-86 “Concretes. Rules for Mix Proportioning”. The physical and mechanical properties of heavy concrete were determined in accordance with State Standard GOST 10180-2012 “Concretes. Methods for Strength Determination Using Reference Specimens”. The strength of concrete was assessed in accordance with State Standard GOST 18105-2018 “Concretes. Rules for Control and Assessment of Strength”. Results: It was established that in terms of the rate of strength gain, the designed heavy concrete mixes are fast-curing. In the initial curing period of 7 days, B25 and B35 concretes gain 90.1 and 85.4% of the required standard strength, respectively. The average values of water absorption in B25 and B35 concretes are 4.20 and 3.46%, respectively. In terms of water tightness, concrete mixes have W10 and W12 grades. The application of the MV-D20 modified binder with the composite additive consisting of tailings and microsilica instead of standard sulfate-resistant Portland cement will reduce the relative deformation of B35 concrete in an aggressive environment by 12%.

Effect of initial curing period on the behavior of mortar under sulfate attack

The infrastructures in the ocean and salt lake areas are usually subjected to sulfate attack shortly after casting. But the influence of early exposure is unclear yet. This study aims to evaluate the influence of early exposure on mortar properties under sulfate attack and to identify the degradation mechanism under this condition. The mortar specimens with different initial curing periods (1, 3, 7, 14 and 28 days) were immersed in 10% Na2SO4 solution for equal time periods (60, 90, 150, 240 and 360 days). Evaluation of the influence of early exposure on mortar behavior under sulfate attack was based on changes in physical properties and mechanical strengths. The degradation mechanism of the mortar specimens was analyzed by X-ray diffraction (XRD), and scanning electron microscopy (SEM) with energy-dispersive spectrometry (EDS). The results showed that the shortening of the initial curing period led to more sulfate ions penetrating into the specimen, resulting in more serious surface spalling, higher expansion rate and mass growth rate, lower mechanical strength. Microscopic images showed that the cement matrix of the early exposed specimen was much looser. In addition, the relationships between compressive strength and other mechanical strengths considering the initial curing period were established and fitted reasonably well with other data sources.

Recycle of large amount cathode ray tube funnel glass sand to mortar with supplementary cementitious materials

Utilizing acid treated CRT funnel (T-CRTF) glass sand in mortar is a feasible option to lower natural resource consumption and protect the environment. In this study, T-CRTF glass sand replaces river sand in mortar at four levels (0, 25 %, 50 %, 75 %). The inclusion of T-CRTF glass sand improves the fluidity properties of mortar. At the initial curing period (3 days), T-CRTF glass sand mortar exhibits the larger hardened density, mechanical strength than river sand-based mortar. After all mortars cured in water for 90 days, the hardened densities and the mechanical strength of mortars with 25 %, 50 % T-CRTF glass sand are the slightly higher than control mortar. The use of the excessive T-CRTF glass sand can no increase anyway the long-term hardened density and mechanical strength of mortars. The recycle of T-CRTF glass sand to mortars reduces the water absorption, the chloride ion penetration, enhances the drying shrinkage, the alkali-silica reaction (ASR) expansion and the lead leaching amount. FA, GGBS mortars with 75 % T-CRTF glass sand have the lowest water absorption, chloride ion penetration in all mortars. The introduction of large amount T-CRTF glass sand to FA, GGBS mortars is more easily to induce the drying shrinkage, the ASR expansion and the long-term lead leaching from mortar. Considerations from the long- term mechanical strength, durability behaviors and environmental compatibility of mortar mixture, the application of 50 % T-CRTF glass sand in FA mortar is the sustainable method to dispose CRT funnel glass.

Effect of Initial Curing Period on the Behavior of Mortar Under Sulfate Attack

Effect of Initial Curing Period on the Behavior of Mortar Under Sulfate Attack

Fiber cement boards modified with styrene-acrylic copolymer: An approach to address dimensional stability and cellulose fiber preservation

The performance of polymers such as acrylics, styrene-acrylics, styrene-butadiene, ethylene vinyl acetate, type added in cementitious composites are well reported in the literature to boost properties in the fresh mortar stage as workability, anti-bleeding, and hard stage as deformation, adhesion strength, crack bridging, cohesion, durability and reduced water uptake. Polymer treatment was performed in fiber cement boards by adding 5% w/w (dry basis) of styrene-acrylic copolymer aiming to investigate the impact on the mechanical and physical properties at initial curing period (28 days) and after the 200 soak and drying ageing cycles. Dimensional stability at 28 days and the cellulose fiber/cement interface transition zone were assessed by scanning electron microscopy combined with dispersive energy X-ray spectroscopy (EDS). These experiments confirmed that the water absorption value in polymer modified cement boards was reduced by 50% after the ageing cycles when compared to the unmodified boards. Additionally, improvements on board’s rigidity with reduction of modulus of elasticity (MOE) values up to 40% and 15% reduction of board shrinkage was noticed, enhancing boards dimensional stability and preventing fibers from the mineralization process by keeping the cellulose fiber adhered on the cementitious matrix, providing a dense and cohesive fiber-cement interface transition zone after the ageing cycles. This achievement can open important fields of application for the reinforcement of flat panels.

Cements with supplementary cementitious materials for high-temperature geothermal wells

This paper discusses self-healing ability, characterized by the strength recovery and crack sealing, thermal shock and acid resistance of several cementitious composites in water, alkali carbonate or geothermal brine at 300 °C. The tested formulations included a common high-temperature OPC/SiO2 formulation, a calcium-aluminate cement with alkali activated FAF blend (TSRC), alkali-activated granulated blast furnace slag (GBFS/SiO2) and fly ash C/fly ash F (FAC/FAF) cementitious blends. Compressive strength recoveries and visual observations of cracks sealing using 3D imaging after the compressive damage and then after the 5-day healing period were used to evaluate the self-healing abilities of these composites. The strength recoveries were evaluated for composites after 1-, 5-, 10-, 15-, and 30- day initial curing periods at 300 °C and after repeated damage and 5-day healing treatments. The nature of the failure was classified depending on the Young’s modulus (YM) of the tested blends. Composites with moderate values of YM, such as OPC/SiO2 and TSRC developed slim cracks while brittle and very brittle FAC/FAF and GBFS/SiO2 cementitious blends produced multidirectional cracks or near-fragment failures resulting in poor strength recoveries. In comparison with the common high-temperature OPC/SiO2 blend, composites with alkali activated pozzolanic materials demonstrated a decrease in crack size during the short healing periods. Fly ash-containing composites showed better acid resistance surviving 28 days in sulfuric acid (pH 0.2) at 90 °C. The TSRC demonstrated the best thermal shock resistance losing only about 20 % of the original strength in five 350 °C heat→25 °C water thermal cycles. In all the tests the TSRC outperformed the rest of the composites with average strength recoveries of more than 85 %. Alkali carbonate was the most favorable for both strength recovery and crack sealing. The short-term strength recoveries could be further improved to above 100 % by addition of micro-glass fibers (MGF). However, the MGF raised the brittleness of the samples after longer initial curing times, which decreased recovery rates of the aged samples. Crystalline phase analysis demonstrated that different products assisted in strength recoveries and crack sealing. The later included for the most part silica and analcime while the former were hydrogrossulars (ferrian) with various stoichiometries, iron-magnesium minerals, cancrinite, quartz and boehmite. These phases formed thanks to the slow high-temperature alkaline reactions of fly ash and glass fibers for MGF-modified samples.

Effect of initial curing conditions on air permeability and de- icing salt scaling resistance of surface concrete

Enhancing the surface quality of concrete is a key to improve the durability of reinforced concrete. Surface concrete can protect steel bars from corrosion due to the migration of gas, water and ion from the surrounding environment. Therefore, the influence of the initial curing on air permeability and the de-icing salt scaling resistance of surface concrete were investigated in this paper. Firstly, existing bridge structures in the cold region of Japan were surveyed with visual rating and non-destructive test (NDT) for the surface quality of concrete. Secondly, the concrete specimens were prepared for different curing conditions and methods including cold weather concreting, heat or non-heat-supply curing, ex- tending demold period and water-retention sheet. These results showed that concrete curing with sheet or permeability formwork was better than curing in air. Especially, utilizing permeability formwork is greatly effective for the attainment of high surface quality of concrete. Simultaneously, focus on cold weather concreting, could evaluate the appropriate curing period combining with the surface air perme- ability and the de-icing salt scaling resistance of concrete. The surface concrete has better de-icing salt frost resistance, when the surface air permeability coefficient is below 1×10-16m2 or the initial curing period is more than three weeks.

Combined effects of mineral additions and curing conditions on strength and durability of self-compacting mortars exposed to aggressive solutions in the natural hot-dry climate in North African desert region

The long-term behavior of self-compacting concrete (SCC) or mortar (SCM) in standard climate is relatively well studied. However, the performance of SCM under hot-dry climate is little investigated. In fact, strength and durability of SCM can be affected by climatic conditions and can be enhanced by the use of the mineral additives. The present paper analyses the combined effects of both mineral additions and curing conditions on the properties of self-compacting mortar exposed to natural hot-dry climate. Ten mixtures were prepared using blended binder containing three types of mineral additives (marble powder (MP), brick powder (BP) and metakaolin (MK)) in various proportions. In order to evaluate compressive and flexural strengths and ultrasonic pulse velocity (UPV), mortar specimens were stored in water for an initial curing period of 0, 1, 3, 7 and 28 days (T = 20 ± 2 °C and RH = 30%–50%), before being exposed to natural hot-dry climate in a North African desert region (T = 25–48 °C and RH = 8%–33%) until 28 days. The durability against sulfate and acid attacks was assessed by curing mortar specimens in water for seven days, followed by immersion-drying cycles for 56 days and then total immersion in MgSO4, Na2SO4, HCl and H2SO4 solutions until 360 days. The results showed an enhancement in hardened properties of SCM with increasing water-curing period. A water-curing period for a minimum 7 days appears to be necessary in hot-dry climate to achieve acceptable mechanical performances. Metakaolin seems to exhibit the best performance regarding mechanical properties and durability in sulfate mediums. Mineral additions show little influence in reducing damage due to acid attacks.

Chloride diffusion and oxygen permeability of mortars with low active blast furnace slag

Depending on its hydraulic activity, the use of Granulated Blast Furnace Slag (GBFS) in cementitious materials contributes to improve their durability performances. In this paper, a low reactive Granulated Blast Furnace Slag with is used in modifying mortar composition. Some durability properties of mixes containing 0, 30 and 50% of slag as substitution to OPC are studied. Diffusion and conduction of chlorides at long term are analyzed with different initial wet curing periods. Microstructure of mortars after 360 days of diffusion is observed by means of Mercury Intrusion Porosimetry. The oxygen permeability is analysed at 90 and 360 days of wet curing. The results indicate good performances to chloride diffusion of the mortars with GBFS, especially for a prolonged wet curing. Moreover, the GBFS are inefficient for oxygen permeability at 90 days but they however allow a decreasing over long term.

A new meta-model to calculate carbonation front depth within concrete structures

Carbonation processes cannot be ignored as regards durability and service-life of new concrete structures, and their correct understanding and quantification are essential for maintenance and repair works on existing structures. This paper initially presents a new meta-model developed to calculate carbonation front depth based on the analytic solution of Fick’s first law. The only input data required by this non numerical model are: (i) material variables (concrete mix design, maximum nominal aggregate size, cement type, and chemical composition of cement type CEM I and cement density); (ii) technological parameters (initial curing period (tc)); (iii) environmental parameters (ambient temperature (T), relative external humidity (RH) and CO2 concentration in the air ([CO2]ext)). Consequently, this model is fully suitable for the prediction of carbonation depth in the case of new reinforced concrete structures, for which these required parameters are well-known. The meta-model is validated using data from the literature on short and long-term natural carbonation exposure conditions. Most of the experimental data concern CEM I, CEM II, CEM III cement types, and CEM I additives (fly ash (FA)) with various water to cement (W/C) ratios and tc. The meta-model is also compared with two already available models: Papadakis’ model and Yang’s model. The three model predictions are compared with the corresponding values found in the literature. The results confirm that the prediction of the new meta-model proposed here for estimation of carbonation depth is the most accurate in every case.

Evaluation of compressive strength development and carbonation depth of high volume slag-blended concrete

Compressive strength development and carbonation are critical topics for using high volume slag concrete rationally. The objective of this study is to present a numerical procedure that evaluates compressive strength and carbonation depth of high volume slag concrete. This numerical procedure consists of a blended hydration model and a carbonation reaction model. The amount of carbonatable materials, such as calcium hydroxide (CH) and calcium silicate hydrate (CSH), is calculated using the blended hydration model. Compressive strength development of cement-slag blends is evaluated from CSH content. By considering the effects of material properties and environmental conditions, the carbonation reaction model analyzes the diffusivity of carbon dioxide and the carbonation depth of concrete. The results of the analysis show that regarding compressive strength, the contribution of slag mixes prepared at a lower water to binder ratio was greater than the contribution of slag mixes prepared at a higher water to binder ratio. Regarding carbonation, with an increase in slag content or reducing the initial curing period, carbonation depth increases. The results of this study are useful for optimum mixing proportional design and carbonation durability design of concrete incorporating a high volume slag.

Experimental Research on Alkaline Residue Concrete Dry Shrinkage Performance

Shrinkage performance of alkaline residue concrete is researched in different conditions, it found that different alkaline residue proportions concrete dry shrinkage increases with the growth of the curing time increasing, but the dry shrinkage changes of different alkaline residue proportions are different, the dry shrinkage of low proportions of 8-12% concrete is similar with that of plain concrete, therefore, to the high content of concrete, its dry shrinkage significantly increase. The dry shrinkage of low incorporation proportion (8-12%) concrete increases quickly in the initial curing period (3-7 days), its shrinkage rate changes stabilized in the subsequent conservation period; to high incorporation proportion (20-30%) concrete, its dry shrinkage increases rapidly in the curing period of 7-14 days, then it stabilized. compared with the low proportion of concrete, its growth is faster in the late curing period. Water-cement ratio is very important factor of the shrinkage performance of concrete, dry shrinkage curve of alkaline residue concrete present concave, when water-cement ratio are in 0.52-0.57, the shrinkage of alkaline residue concrete is minimum.

Natural and accelerated carbonation of concrete containing fly ash and GGBS after different initial curing period

This paper presents a study of the carbonation process of concrete with different initial curing periods consisting of fly ash and ground granulated blast furnace slag (GGBS). Both are exposed in a natural indoor environment for 720 days and at accelerated conditions. The relationship between compressive strength and carbonation depth is analysed. The factors affecting the carbonation of high-volume mineral admixture concrete in a natural environment and accelerated conditions are discussed using the orthogonal method. The factors include: water–binder ratio, content of mineral admixtures, total amount of cementitious materials and fly ash–slag ratio. The influence of different initial curing periods at early ages on carbonation depth is also reported. The results show that there is not always a linear rule between compressive strength and carbonation depth of high-volume mineral admixture concrete. Adequate curing at an early age can decrease the carbonation resistance of concrete significantly. For insufficiently cured concrete, the early stage before 56 days is the main developing stage of carbonation in a natural environment. An evident decrease of carbonation depth can be observed after exposure for 180 days and this will make the carbonated area turn to a red colour again when sprayed with phenolphthalein. In order to guarantee the excellent anti-carbonation ability of concrete in field structure, it is very important to ensure the initial curing time, except for restricting the water–binder ratio and the content of mineral admixtures.

치아 와동의 복합레진 수복시 음향방출의 시간적 발생 특성

Acoustic emission (AE) signals were detected and analyzed in real time during the polymerization shrinkage of composite resin restoration in an artificial dental ring with a class I cavity. Most AE hit events were observed in the initial curing period of the 1st region with high contraction rate. The range of the region for the stainless steel specimen was shorter than that for the PMMA specimen but longer than that for the human dentin specimen. AE hit events showed a blast-type signal having an amplitude in the range of 25.45 dB and a frequency band of 100.200 kHz or 240.300 kHz. These values of amplitude and frequency indicated the fracture of resin or of the adhesive layer.

Role of Gypsum in the Strength Development of Fly Ashes with Lime

The strength of fly ash mixture often needs to be enhanced for its better utilization in geotechnical and environmental applications. Many fly ashes often improve their strength with lime but may not meet the requirements. Gypsum, which reduces the lime leachability, further improves the strength. An attempt is made in this paper to study the effect of gypsum on the strength development of two Class F fly ashes with different lime contents after curing them for different periods. The sustainability of improved strength has been examined after soaking the cured specimens in water and with different leachates containing heavy-metal ions. The strength of both the fly ashes investigated improved markedly up to a particular amount of the lime content, which can be taken as optimum lime content, and thereafter the improvement is gradual. The improvement in strength at higher lime contents continues for a longer period (even up to 180 days). Gypsum accelerates the gain in strength for lime-stabilized fly ashes, particularly in the initial curing periods at about optimum lime content. At high lime contents gypsum attributes very high strength after curing for long periods mainly due to the alteration of fly ash lime reaction compounds. Gypsum not only improves the reduction in the loss of strength due to soaking even at low curing periods but also improves the durability of stabilized fly ashes due to repeated cycles of wetting and drying.

Utilization of industrial waste products as pozzolanic material in cemented paste backfill of high sulphide mill tailings

In this study, the potential use of the industrial waste products including waste glass (WG), fly ash (FA), granulated blast furnace slag (GBFS) and silica fume (SF) as pozzolanic additive for the partial replacement of ordinary Portland cement (OPC) in cemented paste backfill (CPB) of sulphide-rich mill tailings was investigated. The influence of these industrial waste products on the short- and long-term mechanical performance of CPB was demonstrated. The rate of development of strength of CPB samples tended to slow down when the pozzolanic wastes were incorporated or increased in dosage in the binder phase. Severe losses (by 26%) in the strength of CPB samples produced from exclusively OPC occurred after an initial curing period of 56 days. The addition of WG (10–30 wt%) as a partial replacement of OPC was observed to aggravate further the strength losses of CPB samples. GBFS, FA and SF appeared to improve the long-term performance of CPB samples; albeit, only GBFS and SF could be incorporated into the binder phase only at certain levels i.e. up to 20 wt% GBFS and 15 wt% SF in order to maintain a threshold strength level of 0.7 MPa over 360 days. SEM studies have provided further insight into the microstucture of CPB and confirmed the formation of deleterious gypsum as the expansive phase. These findings have demonstrated that the industrial waste products including GBFS and SF can be suitably used as mineral additives to improve the long-term mechanical performance of CPB produced from sulphide-rich tailings as well as to reduce the binder costs in a CPB plant.