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.     

The effect of porosity on the strength of foamed concrete

A study has been undertaken to investigate the effects of replacing large volumes of cement on the properties of foamed concrete (up to 75% by weight) with both classified and unclassified fly ash. This is the third paper in a series; it investigates the relationship between porosity and compressive strength and presents mathematical models that have been developed to describe this relationship. The compressive strength of the foamed concrete was shown to be a function of porosity and age, and a multiplicative model (such as the equation derived by Balshin) was found to best fit the results at all ages up to 1 year. In addition, it was concluded that the equation derived by Hoff could effectively be used to predict the compressive strength of foamed concrete mixtures containing high percentages of ash.     

Properties of volcanic pumice based cement and lightweight concrete

The results of investigations on the suitability of using volcanic pumice (VP) as cement replacement material and as coarse aggregate in lightweight concrete production are reported. Tests were conducted on cement by replacing 0% to 25% of cement by weight and on concrete by replacing 0% to 100% of coarse aggregate by volume. The physical and chemical properties of VP are critically reviewed to evaluate the possible influence on both fresh and hardened state of cement and concrete. The standard tests on different Portland cement-volcanic pumice powder (VPP) mixes provided encouraging results and showed good potential of manufacturing Portland volcanic pumice cement (PVPC) with higher setting time using up to 15% of VPP. The properties of volcanic pumice concrete (VPC) using different percentages of volcanic pumice aggregate (VPA) were evaluated by conducting comprehensive series of tests on workability, strength, drying shrinkage, surface absorption and water permeability. It is concluded that the VPC has sufficient strength and adequate density to be accepted as structural lightweight concrete. However, compared to control concrete, the VPC has lower modulus of elasticity and has more permeability and initial surface absorption.     

High-strength lightweight concrete made with scoria aggregate containing mineral admixtures

This paper presents a part of the results of an ongoing laboratory work carried out to design a structural lightweight high strength concrete (SLWHSC) made with and without mineral admixtures. In the mixtures, basaltic-pumice (scoria) was used as lightweight aggregate.A control lightweight concrete mixture made with lightweight basaltic-pumice (scoria) containing normal Portland cement as the binder was prepared. The control lightweight concrete mixture was modified by replacing 20% of the cement with fly ash. The control lightweight concrete mixture was also modified by replacing 10% of the cement with silica fume. A ternary lightweight concrete mixture was also prepared modifying the control lightweight concrete by replacing 20% of cement with fly ash and 10% of cement with silica fume. Two normal weight concrete (NWC) were also prepared for comparison purpose.Fly ash and silica fume are used for economical and environmental concerns. Cylinder specimens with 150 mm diameter and 300 mm height and prismatic specimens with dimension 100×100×500 mm were cast from the fresh mixtures to measure compressive and flexural tensile strength. The concrete samples were cured at 65% relative humidity with 20 °C temperature. The density and slump workability of fresh concrete mixtures were also measured.Laboratory test results showed that structural lightweight concrete (SLWC) can be produced by the use of scoria. However, the use of mineral additives seems to be mandatory for production of SLWHSC. The use of ternary mixture was recommended due to its satisfactory strength development and environmental friendliness.     

Performance of volcanic ash and pumice based blended cement concrete in mixed sulfate environment

The deterioration of concrete structures due to the presence of mixed sulfate in soils, groundwater and marine environments is a well-known phenomenon. The use of blended cements incorporating supplementary cementing materials and cements with low C₃A content is becoming common in such aggressive environments. This paper presents the results of an investigation on the performance of 12 volcanic ash (VA) and finely ground volcanic pumice (VP) based ASTM Type I and Type V (low C₃A) blended cement concrete mixtures with varying immersion period of up to 48 months in environments characterized by the presence of mixed magnesium-sodium sulfates. The concrete mixtures comprise a combination of two Portland cements (Type I and Type V) and four VA/VP based blended cements with two water-to-binder ratio of 0.35 and 0.45. Background experiments (in addition to strength and fresh properties) including X-ray diffraction (XRD), Differential scanning calorimetry (DSC), mercury intrusion porosimetry (MIP) and rapid chloride permeability (RCP) were conducted on all concrete mixtures to determine phase composition, pozzolanic activity, porosity and chloride ion resistance. Deterioration of concrete due to mixed sulfate attack and corrosion of reinforcing steel were evaluated by assessing concrete weight loss and measuring corrosion potentials and polarization resistance at periodic intervals throughout the immersion period of 48 months. Plain (Type I/V) cement concretes, irrespective of their C₃A content performed better in terms of deterioration and corrosion resistance compared to Type I/V VA/VP based blended cement concrete mixtures in mixed sulfate environment.     

矿物外掺合料对箱梁C50混凝土工作及力学性能影响

利用粉煤灰/矿渣粉作为复合外掺料等量替代部分水泥,探究外掺合料的组成及掺量对箱梁C50混凝土工作性及力学性能的影响,并通过SEM观察混凝土微观结构,结果表明:复合掺合料中,粉煤灰与矿渣粉最佳质量比为1∶2.外掺合料掺量从0%增至30%过程中,C50混凝土工作性有所改善,但混凝土3 d、10 d、28 d、56 d强度均随外掺合料掺量增加而降低.通过SEM观察,掺外掺合料体系水化生成的C-S-H凝胶数目较少,使得混凝土界面粘接强度不高,导致抗压强度降低.     

掺合料对硫铝酸盐水泥基混凝土耐久性影响的研究

研究了掺合料复掺(矿渣∶粉煤灰=2∶1)、单掺矿渣、单掺粉煤灰对硫铝酸盐水泥基混凝土强度、抗渗性、抗冻性的影响,并与相同水灰比下掺合料复掺对普通硅酸盐水泥基混凝土对应性能的影响进行对比。结果表明:在硫铝酸盐水泥基混凝土中,掺合料的加入使混凝土的早期和后期强度都明显降低,抗渗性稍微降低,抗冻性明显降低,且掺量越高,其强度、抗渗性、抗冻性降低越明显;但复掺时的效果比单掺时的效果好,粉煤灰的效果最差;而在普通硅酸盐水泥基混凝土中,掺合料的加入使混凝土的早期强度降低,但后期强度超过空白样的强度,抗渗性、抗冻性明显提高,但是,在无掺合料时其抗渗性、抗冻性大大低于相同水灰比下硫铝酸盐水泥基混凝土的抗渗性、抗冻性。     

纳米秸秆灰对多孔混凝土路面力学性能的影响

本文主要研究了掺加纳米秸秆灰后对多孔混凝土路面性能的影响。根据抗压强度，弯曲强度和抗拉强度来测试多孔混凝土。结果表明，使用纳米秸秆灰材料极大提高了多孔混凝土路面的力学性能，其中纳米秸秆灰以10％质量分数替代水泥制备的多孔混凝土与其它比例制备的样品相比，表现出更加优异的强度；并且测试发现纳米秸秆灰多孔混凝土路面的抗压强度，弯曲强度和抗拉强度随着养护时间的增加而增加。     

粉煤灰掺量对高性能自密实混凝土抗压强度发展影响分析

粉煤灰对自密实混凝土的工作性能、抗压强度和耐久性能等有着显著的影响。为了探究粉煤灰掺量对自密实混凝土抗压强度发展规律的影响,配制了粉煤灰掺量为30%、45%、60%(体积分数),水灰比为1.05、1.15、1.25(体积比)的自密实混凝土并进行立方体抗压强度试验,对其3 d、7 d、28 d、90 d抗压强度的变化规律进行了分析。结果表明,随着粉煤灰掺量的增加,混凝土抗压强度逐渐减小。然后对3 d/28 d、7 d/28 d、90 d/28 d的强度比值进行分析,结果表明,粉煤灰对混凝土早期强度影响较小,对后期影响较大。最后借鉴欧洲规范CEB-FIP探究了粉煤灰与水泥混合下的复合粉体对自密实混凝土抗压强度影响系数,为相关工程应用提供理论依据。     

Effect of fine aggregate replacement with Class F fly ash on the abrasion resistance of concrete

This paper presents the abrasion resistance of concrete proportioned to have four levels of fine aggregate replacement (10%, 20%, 30%, and 40%) with Class F fly ash. A control mixture with ordinary Portland cement was designed to have 28 days compressive strength of 26 MPa. Specimens were subjected to abrasion testing in accordance with Indian Standard Specifications (IS: 1237). Tests were also performed for fresh concrete properties and compressive strength. Tests on compressive strength and abrasion were performed up to 365 days.Test results indicated that abrasion resistance and compressive strength of concrete mixtures increased with the increase in percentage of fine aggregate replacement with fly ash. Abrasion resistance of concrete was improved approximately by 40% over control mixture with 40% replacement of fine aggregate with fly ash, and concrete with fine aggregate replacement could be suitably used.     

Utilization of coal combustion byproducts in building blocks

Some mechanical and durability properties of composite material produced with by-products of Orhaneli power plant (flue gas desulfurization sludge, fly ash and bottom ash), cement and hydrated lime were investigated. To improve the mechanical properties (compressive and flexural strength) of this material, steam curing was applied and the effect of chemical admixture (high water reducing agent) was investigated. Some physical properties and water resistance of the mixtures were also determined. Furthermore, microstructure of the specimens was investigated using scanning electron microscopy. Finally, to produce construction elements, prototypes of building blocks were manufactured by using some of these mixtures. All kind of power plant wastes (flue gas desulfurization sludge, fly ash, bottom ash) can be utilized with these mixtures, which consist of 90% of coal combustion byproducts. It seems to be a promising material for composite construction elements such as building blocks.     

Studies on high-performance blended/multiblended cements and their durability characteristics

Number of blends were prepared by intergrinding clinker, gypsum, fly ash, calcined clay, microsilica and limestone in laboratory ball mill in varying percentages, and their physical properties such as fineness, consistency, setting time and compressive strength have been determined. The durability tests on selected compositions were also conducted by exposing the mortar cubes separately in 5% Na₂SO₄ and 5% NaCl solutions till the age of 90 and 180 days. The performance was observed by compressive strength development criteria after various length of exposure. Results have been discussed and found that the durability of blended cement is higher than the ordinary Portland cement.     

利用电炉氧化钢渣制备混凝土矿物掺合料的研究

研究了磨细电炉氧化钢渣对水泥标准稠度需水量、水泥净浆流动度以及混凝土抗压强度、抗渗性、抗冻性、抗碳化等性能指标的影响.研究结果表明,磨细钢渣具有令人满意的减水效果且与混凝土减水剂有较好的适应性;适量磨细钢渣掺入混凝土中对混凝土抗压强度以及耐久性能影响不大;将磨细钢渣与磨细粉煤灰或矿渣混掺可以发挥复合效应,提高掺合料的活性,改善混凝土的性能.     

Treated Oil Shale Ashes as a Substitute for Natural Aggregates,Sand, and Cement in Concrete

Oil shales are rocks that contain organic matter and are used as a low-grade fuel for energy production. The oil shale combustion process produces large quantities of ash as combustion wastes. These residues contain a high concentration of calcium anhydrite (CaSO₄) and calcium carbonate (CaCO₃), which can be utilized to neutralize acidic wastes (e. g., wastes from the phosphate industry) .Using untreated oil shale bottom ash as partial substitutes for aggregates, natural sand, and cement in concrete mixtures has resulted in a significantly decreased performance of the concrete mixtures. However, by blending the oil shale with acidic materials, the concrete properties improved, as manifested by the development of compressive strength and the workability of the concrete mixtures. In the current study, it was shown that treatment of the oil shale ash with the acidic waste of the Israeli phosphate industry or with phosphoric acid significantly improves the properties of the concrete mixtures, by partial replacement of the natural aggregates and sand by the treated oil shale ash.     

An investigation on the use of tincal ore waste, fly ash, and coal bottom ash as Portland cement replacement materials

The possibility of using tincal ore waste (TW), coal bottom ash (BA), and fly ash (FA) as partial replacement in concrete was examined through a number of tests. The properties examined include setting time, compressive strength, mortar expansion, water consistency of mortar, and microstructure. The results showed that compressive strength of all specimens containing 1 wt.% of TW was higher than that of the control at the 28th day of curing. At 90 days, the contribution to strength by BA+TW and FA+TW was higher than in the concrete-prepared equivalent TW beyond 3 wt.% of Portland cement (PC) replacement. With the replacement of 3-5 wt.% of PC by TW, the compressive strength of the concrete decreased compared to control concrete. However, the values obtained are within the limit of Turkish Standards (TS). Adding BA or FA with TW improved the performance relative to TW replacement only. Increasing replacement of TW gives rise to a higher setting time. As a result, TW, BA, and FA samples may be used as cementitious materials.     

石灰石粉对水泥-粉煤灰混凝土性能的影响

本文主要研究了石灰石粉对水泥-粉煤灰混凝土工作性、抗压强度、耐久性能(抗水渗透性能、抗碳化性能和抗冻性能)的影响,并利用SEM-EDS和孔结构微观分析仪对其进行了机理分析.试验结果表明:石灰石粉应用于水泥-粉煤灰混凝土,不仅可改善混凝土的工作性能,而且可提高混凝土的抗压强度,但对混凝土的耐久性能影响不大.     

Ash content for optimum strength of foamed concrete

A study has been undertaken into the properties of foamed concrete in which large volumes of cement (up to 75 wt.%) have been replaced with both classified and unclassified fly ash. This fourth paper in the series examines the effects of increasing the levels of ash on the compressive strength of the concrete. Twenty-seven different mixtures were cast with varying ash contents and densities, and the results used to develop models that have been used to predict the compressive strength of the foamed concrete. The output from the models predicts an optimum ash content for maximum strength at a given porosity and age and shows that the optimum value increases with increasing age.     

掺合料对再生混凝土强度和耐久性的影响

对掺入磨细掺合料的再生混凝土的抗压强度及抗渗性、抗冻性、抗碳化等耐久性能进行了研究。结果表明,适量磨细粉煤灰掺入再生混凝土中对混凝土抗压强度及耐久性能影响不大;将磨细粉煤灰与矿渣混掺可以发挥复合效应,提高掺合料的活性,改善再生混凝土的性能。     

Effect of lime putty addition on structural and durability properties of concrete

The effect of lime putty addition on main structural and durability properties of concrete was studied. Different types of cement were used for concrete preparation: a Portland cement, a pozzolanic cement and a Portland cement with the addition of 20% fly ash. The measured concrete properties were compressive strength, setting times, length change, porosity, carbonation depth and degree of steel bar corrosion. It was found that the lime putty addition has a positive effect on the properties of concrete that contain pozzolans and a slightly negative effect on the properties of pure Portland cement. This behavior was correlated with the availability of active silica of cementitious materials. The active silica of pozzolans reacts with the added calcium hydroxide giving constituents, which improve the concrete stability and durability.     

Utilisation of Turkish fly ashes in cost effective HVFA concrete production

High-volume fly ash (HVFA) concrete is an economical and durable option for structural as well as general concreting purposes, if properly controlled ashes are employed. The aim of this study was to investigate the possibility of the use of three types of Turkish fly ashes from different sources in cost effective high-volume fly ash concrete production. For this purpose HVFA concrete mixtures were prepared by substituting 40, 50, 60 and 70% of cement by fly ash. The mechanical properties and material costs of mixtures were compared with conventional concrete at the same strength grade at 28 days. It should be noted that as an additional benefit, the long-term strength development and durability advantageous of HVFA concrete is not taken into consideration in cost analysis. Results showed that for structural applications a technically suitable and cost effective HVFA concrete can only be produced by using the fly ashes within the limits of specific chemical and physical properties. It may be possible to use other fly ashes with rehabilitation and pre-process, which may reduce the economical feasibility of fly ash usage.