Utilization of trommel sieve waste as an additive in Portland cement production

Large quantities of industrial wastes form in boron industry in Turkey every year. These wastes have dual problems of disposal and health hazards. The wastes such as borax slime, tincal waste, concentration wastes and thromel sieve waste (TSW) contain impurities that accelerate the normal setting and hardening of building materials produced from them. In this study, it was aimed to stabilize TSW produced during manufacture of borax from tincal. The effects of TSW added on the mechanical properties of Portland cement prepared by adding TSW to clinker were investigated. The utilization of TSW in cement industry as an additive was tested and compared with other materials.     

Utilization of weathered phosphogypsum as set retarder in Portland cement

In this study, usability of weathered phosphogypsum (PG) from residue areas as set retarder in Portland cement was investigated. The effects on the setting and mechanical properties of PG added in ratios 1, 3, 5, 7, 10, and 12.5 wt.% to Portland cements were studied and compared with a Portland cement containing natural gypsum (NG). It was found that PG can be used in place of NG for Portland cement according to Turkish standards. The highest 28-day compressive strength was found in the sample with 3 wt.% PG.     

Utilization of clay wastes containing boron as cement additives

The utilization of clay wastes (CW) containing boron as cement additives was investigated. The effect of CW on mechanical and chemical properties of cement prepared by adding CW to clinker and gypsum was determined. The results obtained were compared with Portland cement properties and Turkish standards (TS) values. It was determined that the first clay waste (CW1) and the second clay waste (CW2) may be used as cement additives up to 5% and 10%, respectively.     

Effect of waste aluminosilicate material on cement hydration and properties of cement mortars

The effect of waste material (catalyst used previously in catalytic cracking of petroleum in fluidized bed—fluidized bed cracking catalyst denoted as FBCC) on cement hydration kinetics was investigated in terms of fineness of this admixture. The compressive strength and microstructure of cement mortars were also examined. Variable percentage of this aluminosilicate admixture, originating from batches of quite different grain size composition, was introduced to cement pastes. Further on, cement mortars were produced using the material of higher activity, as it has been found in admixtured cement investigations. The waste was added as cement replacement or, partially, as sand replacement. The activity of waste catalyst was strongly related to the fineness—finer grains indicate better activity. In the presence of a FBCC admixture, the Ca(OH)₂ content decrease in cement pastes due to the pozzolanic reaction is observed. The surface area of hydrated paste becomes higher and, simultaneously, the mean pore diameter decreases, as compared to reference sample, without admixture. The strength improvement is observed particularly when the aluminosilicate material is introduced as partial sand replacement.     

Utilization of borogypsum as set retarder in Portland cement production

Boron ores are used in the production of various boron compounds such as boric acid, borax and boron oxide. Boric acid is produced by reacting colemanite(2CaO·3B₂O₃·5H₂O) with sulphuric acid and a large quantity of borogypsum is formed during this production. This waste causes various environmental problems when discharged directly to the environment. Portland cement is the most important material in the building industry. This material is produced by adding about 3-5% gypsum (CaSO₄·2H₂O) to clinker as a set retarder. The aim of this study was to stabilize borogypsum, and to produce cements by adding borogypsum instead of natural gypsum to clinker. Concrete using cement produced with borogypsum was tested to find the mechanical properties and the test values were compared with those of concrete from cement with natural gypsum. Compressive strength of concrete from cement produced with borogypsum was found to be higher than that of natural gypsum. Also, the setting time of cement with borogypsum was longer than that of the Portland cement.     

The effect of waste oil-cracking catalyst on the compressive strength of cement pastes and mortars

Epcat, one of the spent fluid catalytic cracking (FCC) catalysts from oil-cracking refineries, shows pozzolanic activity. In this study, pastes and mortars with Epcat were prepared and cured, and their compressive strengths after 3, 7 and 28 curing days were measured. The water/binder (W/B) ratios were 0.2, 0.25 and 0.3, and the replacement levels of cement by Epcat were 0, 5, 10 and 15 wt.%. Proper amount of superplasticizer was added into each mix to ensure similar workability.The results indicate that the presence of Epcat would increase the compressive strength of mortars substantially, but increase the compressive strength of the related pastes only slightly. Epcat mortars with W/B=0.25 show more strength-enhancing effect than those with W/B=0.3, and this effect increases with the catalyst content. Therefore, the mix (W/B=0.25) incorporated 15% Epcat exhibits the greatest compressive strength (92.3 MPa). For mortars with W/B=0.2, the strength-enhancing effect occurs only for those containing 5% catalyst; this effect becomes unclear when mixes containing 10% Epcat or more because high dosage of superplasticizer was added in obtaining proper workability and that affects the strength development. The improvement in the mechanical properties of mortars is attributed to the increase in the hydrated cement paste itself and, more importantly, improved bonds between the cement paste and aggregate.     

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

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 study of limestone blended cement in the presence of hazardous wastes containing Cr(VI)

Considering the increasing use of limestone cement manufacture, the present paper tends to characterize limestone behavior in the presence of Cr(VI). The research reported herein provides information regarding the effect of Cr(VI) from industrial wastes in the limestone cement hydration.The cementitious materials were ordinary Portland cement, as reference, and limestone blended cement.The hydration and physicomechanical properties of cementitious materials and the influence of chromium at an early age were studied with X-ray diffraction (XRD), infrared spectroscopy (FTIR), conductimetric and mechanical tests. Portland cement pastes with the addition of Cr(VI) were examined and leaching behavior with respect to water and acid solution were investigated.This study indicates that Cr(VI) modifies the rate and the components obtained during the cement hydration.     

Treating waste phosphogypsum for cement and plaster manufacture

In the investigation reported in this paper, treatment of phosphogypsum with aqueous citric acid solution was attempted to purify phosphogypsum and improve its quality to make it fit for manufacture of cement and gypsum plaster for the first time. The treatment of gypsum converts phosphatic and fluoride impurities into water-removable citrates, aluminates and ferrates. The findings of chemical and physical tests and differential thermal analysis of the phosphogypsum with and without citric acid treatment established improvement of the treatment for purifying phosphogypsum. The purified phosphogypsum was found to have lesser amount of impurities of phosphates, fluorides and organic matter than the impure material. The Portland and Portland slag cements produced with purified phosphogypsum were found to have strength properties similar to those produced from mineral gypsum, whereas gypsum plaster produced conformed to the relevant Indian Standards.     

Calcium sulfoaluminate cement blended with OPC: A potential binder to encapsulate low-level radioactive slurries of complex chemistry

Investigations were carried out in order to solidify in cement a low-level radioactive waste of complex chemistry obtained by mixing two process streams, a slurry produced by ultra-filtration and an evaporator concentrate with a salinity of 600 gxL^− 1. Direct cementation with Portland cement (OPC) was not possible due to a very long setting time of cement resulting from borates and phosphates contained in the waste. According to a classical approach, this difficulty could be solved by pre-treating the waste to reduce adverse cement–waste interactions. A two-stage process was defined, including precipitation of phosphates and sulfates at 60 °C by adding calcium and barium hydroxide to the waste stream, and encapsulation with a blend of OPC and calcium aluminate cement (CAC) to convert borates into calcium quadriboroaluminate. The material obtained with a 30% waste loading complied with specifications. However, the pre-treatment step made the process complex and costly. A new alternative was then developed: the direct encapsulation of the waste with a blend of OPC and calcium sulfoaluminate cement (CS̄̄A) at room temperature. Setting inhibition was suppressed, which probably resulted from the fact that, when hydrating, CS̄̄A cement formed significant amounts of ettringite and calcium monosulfoaluminate hydrate which incorporated borates into their structure. As a consequence, the waste loading could be increased to 56% while keeping acceptable properties at the laboratory scale.     

The effect of boron waste in phase and microstructural development of a terracotta body during firing

In the present study, a dewatering sieve waste (TSW) of Etibor Kırka Borax company (Turkey) was employed in different amounts in order to develop an experimental terracotta floor tile body composition in combination with a feldspathic waste provided from a local sanitaryware plant and a ball clay. Several formulations were prepared and shaped by dry pressing under laboratory conditions. The obtained samples were fired at selected peak temperatures (1050, 1100 and 1150 °C) to establish their optimum firing temperatures. Some technological properties of the resultant products, namely linear firing shrinkage, water absorption and breaking strength were determined as a function of increasing TSW content in place of the sanitaryware waste at these temperatures. The phase content of the starting raw materials and that of the fired compositions was determined by XRD. The relevant polished surfaces of selected fired samples were also examined using SEM. According to the results, increased presence of TSW compared to the standard mixture of clay and the sanitaryware waste, as a co-fluxing material, in the experimental terracotta body considerably accelerated the vitrification process. The overall results indicated a prospect for using the TSW as a raw material in mixtures with both clay and sanitaryware waste for the production of a terracotta floor tile body.     

Replacement of raw mix in cement production by municipal solid waste incineration ash

The feasibility of municipal solid waste incineration (MSWI) ash utilized as the replacement of raw mix in cement production is investigated. Result shows that sieving, self-grinding, and magnet separation processes are necessary to remove the debris, salt, and metallic contents that existed in the MSWI ash. By using the pretreated MSWI ashes, the produced cement specimens were in compliance with the unconfined compression strength (UCS) standard in Taiwan at small replacement percentage (<5%). When ash replacement percentage is large (more than 10%), the strength development of specimens would be hindered due to the deficient formation of the calcium silicate. Calculation on lime saturation factor (LSF) also shows a descending trend in consequence of the increase in replacement percentage. Thus, compositional effect should be taken into consideration for promoting the calcium silicate formation at the case of large ash replacement. In this research, adjustment of chemical composition was achieved by adding 183 g calcium oxide per kilogram of cement raw mixture with 15% ash replacement. After adjustment, the produced cement could develop seven- and fivefold increase on UCS compared with those without calcium oxide supplement at 3 and 7 days of curing, respectively. Results concluded that the MSWI ash was suitable in reuse for cement production under a well-conditioned situation.     

Portland cement clinker, granulated slag and by-pass cement dust composites

Three blends of slag cement were prepared, namely 70/30, 50/50 and 30/70 mass% of Portland cement clinker and granulated slag, respectively. Each blend was mixed with 2.5, 5.0, 7.5 and 10.0 mass% by-pass cement dust. The physical properties of cement pastes were studied, including setting times, electrical conductivity and fluidity. The results indicated that the rheological properties of Portland cement clinker were enhanced by partial replacement by granulated slag. By-pass cement dust affects the rheological properties of Portland cement clinker/granulated slag composites and depends on its amount as well as mix composition. The increase in the amount of by-pass cement dust increases the required water of normal consistency. The setting time of Portland slag cement paste was extended with the increase in slag content. The addition of 2.5 mass% by-pass cement dust to M.1 (70 mass% Portland cement clinker/30 mass% granulated slag) and M.2 (50 mass% Portland cement clinker/50 mass% granulated slag) retards the initial and final setting time, whereas it accelerates the final setting time of M.3 (30 mass% Portland cement clinker/70 mass% granulated slag). The presence of by-pass cement dust affects the location and height of the conductivity peaks. By increasing the by-pass cement dust from 2.5 to 7.5 mass%, the conductivity maximum increases. With further addition (10.0 mass%), the height of the conductivity maximum decreases.     

Properties of ceramic fiber reinforced cement composites

Mechanical properties and preliminary durability of ceramic fiber reinforced Portland cement composites tested with wet-hot accelerating method were investigated. The results showed that the flexural strength of mortar could be increased obviously by adding ceramic fiber into it, but the effect of the flexural reinforcement was influenced by various factors, including fiber length, fiber content and kinds of matrices; the preliminary durability of ceramic fiber in ordinary Portland cement tested with wet-hot accelerating method was much better than that of alkali-resistant (AR) glass fiber. The mechanism of the durability of ceramic fiber in ordinary Portland cement is also discussed.     

Bone cement strength after different methods of mixing

During the mixing of methyl methacrylate bone cement for use in orthopaedic surgery, unpleasant and possibly harmful fumes are emitted. In an attempt to overcome this problem, three samples of bone cement were prepared by two methods. The effect on the duration of curing and the mechanical properties of the cement after curing have been studied. The samples showed to significant variation in strength when prepared by the different routes. The unconventional method of preparing the cement in a polythene sachet is particularly recommended for Simplex bone cement.     

Blended cement using volcanic ash and pumice

This paper reports the results of investigation to assess the suitability of volcanic ash (VA) and pumice powder (VPP) for blended cement production. Tests were conducted on cement where Portland cement (PC) was replaced by VA and VPP within the range of 0 to 50%. The physical and chemical properties of VA and VPP were critically reviewed to evaluate the possible influences on cement properties. The investigation included testing on both fresh and hardened states of cement paste. The standard tests conducted on different PC-VA and -VPP mixtures provided encouraging results, comparable to those for fly ash (FA) cement, and showed good potential of manufacturing blended Portland volcanic ash cement (PVAC) and Portland volcanic pumice cement (PVPC) with higher setting time and low heat of hydration using up to 20% replacement.     

硫铝酸盐水泥与硅酸盐水泥复配性能研究

基于硫铝酸盐水泥、硅酸盐水泥各自的特点,研究了二者复配后的标准稠度用水量、凝结时间、水化热效应、胶砂强度、膨胀性、水化产物的物相及微观形貌。结果表明,复配水泥的标准稠度用水量因复配比例不同而变化,凝结时间相对于占主导地位的单组分水泥明显缩短;复配水泥的早期水化速率得到提高,1d、7d的水化放热量均低于占主导地位的单组分水泥;28d抗压、抗折强度低于任何单组分水泥;膨胀性的大小取决于两种水泥的复配比例;硫铝酸盐水泥与硅酸盐水泥的复配使二者的水化相互促进,随着硫铝酸盐水泥掺量的增加,Ca(OH)2相的衍射峰减弱,AFt相的衍射峰增强;纯硅酸盐水泥水化后的微观形貌是致密的,而与硫铝酸盐水泥复配后则出现微观裂纹。     

Reuse of heavy metal-containing sludges in cement production

The feasibility of the replacement of raw material for cement production by heavy metal-containing sludge from surface finishing and electroplating industries was investigated. The effect of heavy metal content in the cement raw mix on the crystalline formation in cement production was also examined by XRD analyses. It was found that both sludges were applicable for the replacement of raw mix for cement production by moderate conditioning of the sludge compositions with several compositional parameters. As the replacement of raw mix by sludge was within 15%, the formation of tricalcium silicate (C₃S) phase in cement would be enhanced by the introduced heavy metals. While owing to a high level of heavy metals concentration (> 1.5%) in cement raw mix, C₃S crystalline in cement would be inhibited by a large sludge replacement (> 15%). During the sintering process, over 90% of the high volatile elements such as Pb would evaporate in high temperature, yet 90% of the less volatile elements such as Cu, Cr and Ni would be trapped in clinkers. Most of all, the results of leaching test shows that the trapped elements in hydrated samples would not leach out under acidic conditions. The reuse of heavy metal-containing sludges as cement raw material would not cause leaching hazard from sintered clinkers. Heavy metal-containing sludges thus should have the potential to be utilized as alternative raw materials in cement production.     

分别粉磨对粉煤灰水泥性能及能耗的影响

在半工业化试验球磨机中对粉煤灰水泥的组分进行了单独粉磨,然后在混合机中进行混合配制,研究了分别粉磨工艺和传统共同粉磨工艺磨制的粉煤灰水泥在颗粒分布、水泥性能及粉磨电耗等方面的差异,探讨了利用分别粉磨工艺生产粉煤灰水泥的最佳技术方案。结果表明,采用分别粉磨工艺,是解决传统共同粉磨的粉煤灰水泥需水量大、早期强度低等缺点的有效措施。选择合适的配制方案,不仅能够显著改善水泥的物理性能和与减水剂的适应性,也可适当提高水泥中粉煤灰的掺量和节约一定的粉磨电耗。