The strength and durability of concrete will be significantly reduced at high volume of mineral admixture,and the poor early strength of concrete also still needs to be solved.In this investigation,a highly active alk...The strength and durability of concrete will be significantly reduced at high volume of mineral admixture,and the poor early strength of concrete also still needs to be solved.In this investigation,a highly active alkaline electrolyzed waters was used as mixing water to improve the early strength and enhance the durability of green concrete with high volume mineral admixture,the influences of alkaline electrolyzed water(AEW)on hydration activity of mineral admixture and durability of concrete were determined.The results showed that compared with natural tap water,AEW can accelerate early hydration process of cement in concrete and produce comparatively more hydrated products,leading to a 13.6%higher compressive strength than that of ordinary concrete at early age,but the improvement effect of AEW concrete was relatively reduced at long-term age.Meanwhile,the activity of mineral admixtures could be stimulated by AEW to some extent,the strength and durability performance of AEW concrete after double doping 25%slag and 25%fly ash can still reach the level of ordinary cement concrete without mineral admixtures.The SEM micromorphology of 7 d hydrated natural tap water cement paste was observed to be flaky and tabular,but the AEW cement pastes present obvious cluster and granulation phenomenon.The SEM microstructure of AEW concrete with mineral admixtures is more developed and denser than ordinary tap water concrete with mineral admixtures.Therefore,the AEW probably could realize the effective utilization of about 50%mineral admixture amount of concrete without strength loss,the cement production cost and associated CO_(2) emission reduced,which has a good economic and environmental benefit.展开更多
The effect of ultra-fine fly ash (UFFA),steel slag (SS) and silica fume (SF) on packing density of binary,ternary and quaternary cementitious materials was studied in this paper in terms of minimum water requirement o...The effect of ultra-fine fly ash (UFFA),steel slag (SS) and silica fume (SF) on packing density of binary,ternary and quaternary cementitious materials was studied in this paper in terms of minimum water requirement of cement. The influence of mineral admixtures on the relative density of pastes with low water/binder ratios was analyzed and the relationship between paste density and compressive strength of the corresponding hardened mortars was discussed. The results indicate that the incorporation of mineral admixtures can effectively improve the packing density of cementitious materials; the increase in packing density of a composite with incorporation of two or three kinds of mineral admixtures is even more obvious than that with only one mineral admixture. Moreover,an optimal amount of mineral admixture imparts to the mixture maximum packing density. The dense packing effect of a mineral admixture can increase the packing density of the resulting cementitious material and also the density of paste with low water/binder ratio,which evidently enhances the compressive strength of the hardened mortar.展开更多
Self-consolidating concrete(SCC)with manufactured sand(MSCC)is crucial to guarantee the quality of concrete construction technology and the associated property.The properties of MSCC with different microlimestone powd...Self-consolidating concrete(SCC)with manufactured sand(MSCC)is crucial to guarantee the quality of concrete construction technology and the associated property.The properties of MSCC with different microlimestone powder(MLS)replacements of retreated manufactured sand(TMsand)are investigated in this study.The result indicates that high-performance SCC,made using TMsand(TMSCC),achieved high workability,good mechanical properties,and durability by optimizing MLS content and adding fy ash and silica fume.In particular,the TMSCC with 12%MLS content exhibits the best workability,and the TMSCC with 4%MLS content has the highest strength in the late age,which is even better than that of SCC made with the river sand(R sand).Though MLS content slightly affects the hydration reaction of cement and mainly plays a role in the nucleation process in concrete structures compared to silica fume and fly ash,increasing MLS content can evidently have a significant impact on the early age hydration progress.TMsand with MLS content ranging from 8%to 12%may be a suitable alternative for the Rsand used in the SCC as fine aggregate.The obtained results can be used to promote the application of SCC made with manufactured sand and mineral admixtures for concrete-based infrastructure.展开更多
This paper presents quantitatively the results of an experimental investigation on influence of mineral admixtures and superplasticizers on Vickers micro hardness(HV) of aggregate-paste interface in cement concrete. T...This paper presents quantitatively the results of an experimental investigation on influence of mineral admixtures and superplasticizers on Vickers micro hardness(HV) of aggregate-paste interface in cement concrete. The HV was measured by Vickers hardness testing equipment.The results indicate that addition of fly ash decreases HV of the concrete.Although it decreases with the increase of ground granulated blast furnace slag (GGBS) replacement,the HV is higher than that of concrete containing fly ash at all replacements.The flying ash and GGBS composition increases HV in later curing ages,but does not improve it in early curing ages.Aminosulfonic acid based superplasticizer and aliphatic hydroxy sulphonate condensate superplasticizer can enhance HV in early curing ages.The HV of concrete with polycarboxylic acid superplasticizer is higher in later curing ages.展开更多
Compared with the control sample without limestone powder(LP), the mechanical properties of the sample with 30% LP can be significantly improved by using a small amount of water reducer to reduce the water-cement rati...Compared with the control sample without limestone powder(LP), the mechanical properties of the sample with 30% LP can be significantly improved by using a small amount of water reducer to reduce the water-cement ratio, without significantly affecting the fluidity of the fresh mixture and increasing the economic cost. In addition, compared with the sole addition of limestone powder, dual addition of metakaolin and limestone powder can effectively improve the strengths. The reason of this phenomenon was investigated by means of XRD, TG-DTG, SEM, LF-NMR and isothermal calorimetry, etc. The reactive aluminum-rich phases in metakaolin react with limestone powder in the hydration process, and the formed calcium carboaluminate reduces the porosity and makes the hardened paste denser. The addition of ground granulated blast furnace slag can also improve the strength of the specimen added with limestone powder, whereas, the effect is inferior to that of metakaolin, for the ground granulated blast furnace slag contains less reactive aluminate phases, and accordingly, the amount of calcium carboaluminate generated is lower than that of metakaolin.展开更多
Improving the activity of Iron Ore Tailings(IOTs)to utilize them as a mineral admixture in cement-based minerals is still challenging.In this paper,the wet grinding technology was employed to stimulate the activity of...Improving the activity of Iron Ore Tailings(IOTs)to utilize them as a mineral admixture in cement-based minerals is still challenging.In this paper,the wet grinding technology was employed to stimulate the activity of IOTs,and the traditional dry grinding method was used as a reference.The effect of wet grinding on the activation of IOTs was evaluated through ion leaching from an alkaline solution and the reactivity index.Additionally,a detailed comparison between Dry-grinding Iron Ore Tailings(DIOTs)and Wet-grinding Iron Ore Tailings(WIOTs)was made.This comparison was based on particle characteristics,crystal structures,chemical structure,and surface properties.The results showed that the particle size of IOTs reduced rapidly during wet grinding.In addition,WIOTs had a higher activity index compared to DIOTs.The storage of lattice distortions in the quartz crystal structure was also more significant during the wet grinding process than during the dry grinding process.Moreover,both prolonged dry and wet grinding could destabilize the Si-O bond and decrease the surface binding energy.展开更多
This study evaluated the influence of the Portland cement replacement by 0, 5</span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span sty...This study evaluated the influence of the Portland cement replacement by 0, 5</span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">%</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">, 10</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">%</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">, 15</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">%</span></span></span><span><span><span style="font-family:""><span style="font-family:Verdana;"> and 20% of Construction and Demolition Waste (CDW) filler </span><span style="font-family:Verdana;">contents in the production of self-compacting concrete (SCC). The SCC mixtures </span><span style="font-family:Verdana;">were evaluated on fresh state by slump flow, J-ring, resistance of segre</span><span style="font-family:Verdana;">gation, specific gravity, and on hardened state by compressive and splitting tensile </span><span style="font-family:Verdana;">strength, specific gravity, air voids and absorption rate. The results indicated that all SCC produced with CDW filler met the limits established at any level of substitution without changes of the w/c ratio or superplasticizer content. It was possible to verify that the presence of CDW filler, in substitution of cement, by volume, improves the resistance to segregation and up to 5% of CDW filler decreases the loss of fluidity with time as compared to reference. It was found that all SCC mixtures, at 28 days, had the average compressive strength above 50 MPa, without showing significant loss with up to 20% of CDW filler. For splitting tensile strength, SCC recycled mixtures reached up to 92.5% of the SCC used as reference. Absorption rate and air voids index of SCC recycled mixtures had a maximum increase of 1.60%Compared to the reference one. So, it is possible to conclude that the use of the CDW filler up to 20% in substitution of cement, by volume, is feasible for SCC production.展开更多
The cost of cement has made concrete production expensive such that the housing deficit in developing countries is on the rise despite all the efforts by governments and other stakeholders to produce affordable housin...The cost of cement has made concrete production expensive such that the housing deficit in developing countries is on the rise despite all the efforts by governments and other stakeholders to produce affordable housing units for the populace. Ashes of agricultural products such as rice husk, known as mineral admixtures may have pozzolanic characteristics which would be more beneficial to the housing industry in terms of strength gain and economy than being pollutants to the environment. Rice Husk Ash (RHA), because of its finely divided form and very high silica content and amorphousness, proved to be useful for strength gain of Rice Husk Ash Concrete (RHAC). Rice husk ash was manufactured by uncontrolled burning, ground, sieved and replaced with cement at 0%, 5%, 10%, 15%, 20% and 25% in mass for the mixes C20, C25, C30 and C35 where their compressive strengths were verified at 3, 7, 14, 21, 28, 56, 90 and 180 days. The X-ray diffraction pattern list indicated amorphous as well as diffused peak of about 8000 counts of SiO</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;"> representing crystalline structures identified as cristobalite. A physical examination of the RHA showed very fine appearance, grey color and specific gravity of 2.06. The chemical analysis also revealed the existence of oxide content to be 55.8% representing 0.78% of Fe</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">O</span><sub><span style="font-family:Verdana;">3</span></sub><span style="font-family:Verdana;">, 54% of SiO</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;"> and 1.06% of Al</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">O</span><sub><span style="font-family:Verdana;">3</span></sub><span style="font-family:Verdana;"> representing 20.23% lower than the minimum value of 70% required for pozzolans. Generally, the compressive strength values decreased as the RHA content in the mixes increased but when compared to the control concrete the optimum replacement percentage of Ordinary Portland Cement (OPC) with RHA at 5% showed an increase above the control concrete for C20 mix. The increase in the RHA in the mixes resulted in the high demand for water in all the mixes.展开更多
The results of investigation to assess the possibility of copper slag with high MgO to be used as a mineral admixture in concrete were reported in this study. The soundness of cement paste containing the slag has been...The results of investigation to assess the possibility of copper slag with high MgO to be used as a mineral admixture in concrete were reported in this study. The soundness of cement paste containing the slag has been examined by autoclave test. Pozzolanic activity of the slag was studied in comparison to fly ash. The slag was mixed calcium hydroxide and water,and the progress of the pozzolanic reaction was determined by X-ray diffraction,differential thermal analysis-thermogravimetry and scanning electron microscopy from 28 to 90 d. The experimental results showed that the autoclave expansion value of cement paste containing the slag was far below the expansion limit (0.8%). It can be conclude that the slag has little periclase content. The consumption of calcium hydroxide showed the slag exhibits high pozzolanic activity,which was higher than that of fly ash. Hence,use of the copper slag with high MgO but low periclase content as a mineral admixture in concrete seems feasible.展开更多
基金funded by National Natural Science Foundation of China(Grant Nos.51808310,51878366)Natural Science Foundation of Shandong Province(Grant Nos.ZR2019PEE007,ZR2020ME036)High-level Scientific Research Foundation for the introduction of talent of Qingdao Agricultural University(Grant No.1118034).
文摘The strength and durability of concrete will be significantly reduced at high volume of mineral admixture,and the poor early strength of concrete also still needs to be solved.In this investigation,a highly active alkaline electrolyzed waters was used as mixing water to improve the early strength and enhance the durability of green concrete with high volume mineral admixture,the influences of alkaline electrolyzed water(AEW)on hydration activity of mineral admixture and durability of concrete were determined.The results showed that compared with natural tap water,AEW can accelerate early hydration process of cement in concrete and produce comparatively more hydrated products,leading to a 13.6%higher compressive strength than that of ordinary concrete at early age,but the improvement effect of AEW concrete was relatively reduced at long-term age.Meanwhile,the activity of mineral admixtures could be stimulated by AEW to some extent,the strength and durability performance of AEW concrete after double doping 25%slag and 25%fly ash can still reach the level of ordinary cement concrete without mineral admixtures.The SEM micromorphology of 7 d hydrated natural tap water cement paste was observed to be flaky and tabular,but the AEW cement pastes present obvious cluster and granulation phenomenon.The SEM microstructure of AEW concrete with mineral admixtures is more developed and denser than ordinary tap water concrete with mineral admixtures.Therefore,the AEW probably could realize the effective utilization of about 50%mineral admixture amount of concrete without strength loss,the cement production cost and associated CO_(2) emission reduced,which has a good economic and environmental benefit.
文摘The effect of ultra-fine fly ash (UFFA),steel slag (SS) and silica fume (SF) on packing density of binary,ternary and quaternary cementitious materials was studied in this paper in terms of minimum water requirement of cement. The influence of mineral admixtures on the relative density of pastes with low water/binder ratios was analyzed and the relationship between paste density and compressive strength of the corresponding hardened mortars was discussed. The results indicate that the incorporation of mineral admixtures can effectively improve the packing density of cementitious materials; the increase in packing density of a composite with incorporation of two or three kinds of mineral admixtures is even more obvious than that with only one mineral admixture. Moreover,an optimal amount of mineral admixture imparts to the mixture maximum packing density. The dense packing effect of a mineral admixture can increase the packing density of the resulting cementitious material and also the density of paste with low water/binder ratio,which evidently enhances the compressive strength of the hardened mortar.
基金All the authors appreciate the supports from the Australian Research Council(DEI50101751,IH150100006)University of Technology Sydney Research Academic Program at Tech Lab(UTS RAPT),University of Technology Sydney Tech Lab Blue Sky Research Scheme.
文摘Self-consolidating concrete(SCC)with manufactured sand(MSCC)is crucial to guarantee the quality of concrete construction technology and the associated property.The properties of MSCC with different microlimestone powder(MLS)replacements of retreated manufactured sand(TMsand)are investigated in this study.The result indicates that high-performance SCC,made using TMsand(TMSCC),achieved high workability,good mechanical properties,and durability by optimizing MLS content and adding fy ash and silica fume.In particular,the TMSCC with 12%MLS content exhibits the best workability,and the TMSCC with 4%MLS content has the highest strength in the late age,which is even better than that of SCC made with the river sand(R sand).Though MLS content slightly affects the hydration reaction of cement and mainly plays a role in the nucleation process in concrete structures compared to silica fume and fly ash,increasing MLS content can evidently have a significant impact on the early age hydration progress.TMsand with MLS content ranging from 8%to 12%may be a suitable alternative for the Rsand used in the SCC as fine aggregate.The obtained results can be used to promote the application of SCC made with manufactured sand and mineral admixtures for concrete-based infrastructure.
基金the Special Foundation for Basic Scientific Research of Central Colleges of China (No:CHD2011ZD011)the Special Foundation of Basic Research for Chang'an University
文摘This paper presents quantitatively the results of an experimental investigation on influence of mineral admixtures and superplasticizers on Vickers micro hardness(HV) of aggregate-paste interface in cement concrete. The HV was measured by Vickers hardness testing equipment.The results indicate that addition of fly ash decreases HV of the concrete.Although it decreases with the increase of ground granulated blast furnace slag (GGBS) replacement,the HV is higher than that of concrete containing fly ash at all replacements.The flying ash and GGBS composition increases HV in later curing ages,but does not improve it in early curing ages.Aminosulfonic acid based superplasticizer and aliphatic hydroxy sulphonate condensate superplasticizer can enhance HV in early curing ages.The HV of concrete with polycarboxylic acid superplasticizer is higher in later curing ages.
基金Funded by the National Natural Science Foundation of China (Nos.51972249, 52172026, 51772226)。
文摘Compared with the control sample without limestone powder(LP), the mechanical properties of the sample with 30% LP can be significantly improved by using a small amount of water reducer to reduce the water-cement ratio, without significantly affecting the fluidity of the fresh mixture and increasing the economic cost. In addition, compared with the sole addition of limestone powder, dual addition of metakaolin and limestone powder can effectively improve the strengths. The reason of this phenomenon was investigated by means of XRD, TG-DTG, SEM, LF-NMR and isothermal calorimetry, etc. The reactive aluminum-rich phases in metakaolin react with limestone powder in the hydration process, and the formed calcium carboaluminate reduces the porosity and makes the hardened paste denser. The addition of ground granulated blast furnace slag can also improve the strength of the specimen added with limestone powder, whereas, the effect is inferior to that of metakaolin, for the ground granulated blast furnace slag contains less reactive aluminate phases, and accordingly, the amount of calcium carboaluminate generated is lower than that of metakaolin.
基金This work was supported by University Natural Science Research Project of Anhui Province(KJ2019A0171).
文摘Improving the activity of Iron Ore Tailings(IOTs)to utilize them as a mineral admixture in cement-based minerals is still challenging.In this paper,the wet grinding technology was employed to stimulate the activity of IOTs,and the traditional dry grinding method was used as a reference.The effect of wet grinding on the activation of IOTs was evaluated through ion leaching from an alkaline solution and the reactivity index.Additionally,a detailed comparison between Dry-grinding Iron Ore Tailings(DIOTs)and Wet-grinding Iron Ore Tailings(WIOTs)was made.This comparison was based on particle characteristics,crystal structures,chemical structure,and surface properties.The results showed that the particle size of IOTs reduced rapidly during wet grinding.In addition,WIOTs had a higher activity index compared to DIOTs.The storage of lattice distortions in the quartz crystal structure was also more significant during the wet grinding process than during the dry grinding process.Moreover,both prolonged dry and wet grinding could destabilize the Si-O bond and decrease the surface binding energy.
文摘This study evaluated the influence of the Portland cement replacement by 0, 5</span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">%</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">, 10</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">%</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">, 15</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">%</span></span></span><span><span><span style="font-family:""><span style="font-family:Verdana;"> and 20% of Construction and Demolition Waste (CDW) filler </span><span style="font-family:Verdana;">contents in the production of self-compacting concrete (SCC). The SCC mixtures </span><span style="font-family:Verdana;">were evaluated on fresh state by slump flow, J-ring, resistance of segre</span><span style="font-family:Verdana;">gation, specific gravity, and on hardened state by compressive and splitting tensile </span><span style="font-family:Verdana;">strength, specific gravity, air voids and absorption rate. The results indicated that all SCC produced with CDW filler met the limits established at any level of substitution without changes of the w/c ratio or superplasticizer content. It was possible to verify that the presence of CDW filler, in substitution of cement, by volume, improves the resistance to segregation and up to 5% of CDW filler decreases the loss of fluidity with time as compared to reference. It was found that all SCC mixtures, at 28 days, had the average compressive strength above 50 MPa, without showing significant loss with up to 20% of CDW filler. For splitting tensile strength, SCC recycled mixtures reached up to 92.5% of the SCC used as reference. Absorption rate and air voids index of SCC recycled mixtures had a maximum increase of 1.60%Compared to the reference one. So, it is possible to conclude that the use of the CDW filler up to 20% in substitution of cement, by volume, is feasible for SCC production.
文摘The cost of cement has made concrete production expensive such that the housing deficit in developing countries is on the rise despite all the efforts by governments and other stakeholders to produce affordable housing units for the populace. Ashes of agricultural products such as rice husk, known as mineral admixtures may have pozzolanic characteristics which would be more beneficial to the housing industry in terms of strength gain and economy than being pollutants to the environment. Rice Husk Ash (RHA), because of its finely divided form and very high silica content and amorphousness, proved to be useful for strength gain of Rice Husk Ash Concrete (RHAC). Rice husk ash was manufactured by uncontrolled burning, ground, sieved and replaced with cement at 0%, 5%, 10%, 15%, 20% and 25% in mass for the mixes C20, C25, C30 and C35 where their compressive strengths were verified at 3, 7, 14, 21, 28, 56, 90 and 180 days. The X-ray diffraction pattern list indicated amorphous as well as diffused peak of about 8000 counts of SiO</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;"> representing crystalline structures identified as cristobalite. A physical examination of the RHA showed very fine appearance, grey color and specific gravity of 2.06. The chemical analysis also revealed the existence of oxide content to be 55.8% representing 0.78% of Fe</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">O</span><sub><span style="font-family:Verdana;">3</span></sub><span style="font-family:Verdana;">, 54% of SiO</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;"> and 1.06% of Al</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">O</span><sub><span style="font-family:Verdana;">3</span></sub><span style="font-family:Verdana;"> representing 20.23% lower than the minimum value of 70% required for pozzolans. Generally, the compressive strength values decreased as the RHA content in the mixes increased but when compared to the control concrete the optimum replacement percentage of Ordinary Portland Cement (OPC) with RHA at 5% showed an increase above the control concrete for C20 mix. The increase in the RHA in the mixes resulted in the high demand for water in all the mixes.
文摘The results of investigation to assess the possibility of copper slag with high MgO to be used as a mineral admixture in concrete were reported in this study. The soundness of cement paste containing the slag has been examined by autoclave test. Pozzolanic activity of the slag was studied in comparison to fly ash. The slag was mixed calcium hydroxide and water,and the progress of the pozzolanic reaction was determined by X-ray diffraction,differential thermal analysis-thermogravimetry and scanning electron microscopy from 28 to 90 d. The experimental results showed that the autoclave expansion value of cement paste containing the slag was far below the expansion limit (0.8%). It can be conclude that the slag has little periclase content. The consumption of calcium hydroxide showed the slag exhibits high pozzolanic activity,which was higher than that of fly ash. Hence,use of the copper slag with high MgO but low periclase content as a mineral admixture in concrete seems feasible.
