Clayey soils in Syria cover a total area of more than 20,000 km2 of the country, most of which are located in the southwestern region. In many places of the country, the clayey soils caused severe damage to infrastruc...Clayey soils in Syria cover a total area of more than 20,000 km2 of the country, most of which are located in the southwestern region. In many places of the country, the clayey soils caused severe damage to infrastructures. Extensive studies have been carried out on the stabilization of clayey soils using lime. Syria is rich in both lime and natural pozzolana. However, few works have been conducted to investigate the influence of adding natural pozzolana on the geotechnical properties of lime-treated clayey soils. The aim of this paper is to understand the effect of adding natural pozzolana on some geotechnical properties of lime-stabilized clayey soils. Natural pozzolana and lime are added to soil within the range of 0%–20% and 0%–8%, respectively. Consistency, compaction, California bearing ratio （CBR） and linear shrinkage properties are particularly investigated. The test results show that the investigated properties of lime-treated clayey soils can be considerably enhanced when the natural pozzolana is added as a stabilizing agent. Analysis results of scanning electron microscopy （SEM） and energy-dispersive X-ray spectroscopy （EDX） show significant changes in the microstructure of the treated clayey soil. A better flocculation of clayey particles and further formation of cementing materials in the natural pozzolana-lime-treated clayey soil are clearly observed.展开更多
Thermodynamic stability, microvoid distribution and phases transformation of natural pozzolana opal shale（POS） were studied systematically in this work. XRD analysis showed that opal-CT, including microcrystal crist...Thermodynamic stability, microvoid distribution and phases transformation of natural pozzolana opal shale（POS） were studied systematically in this work. XRD analysis showed that opal-CT, including microcrystal cristobalite and tridymite, is a major component of POS. DTA and FT-IR indicated that there were many hydroxyl groups and acid sites on the surface of amorphous SiO2 materials. FE-SEM analysis exhibited amorphous SiO2 particles（opal-A） covering over stacking sequences microcrystal cristobalite and tridymite. Meanwhile, MIP analysis demonstrated that porosity and pore size distribution of POS remained uniform below 600 ℃. Because stable porous microstructure is a key factor in improving photocatalyst activity, POS is suited to preparing highly active supported.展开更多
Burnt clay pozzolana produced from a clay deposit at Mankranso in Ghana has been activated by mechanical means through roll milling and ball milling as well as chemically by the addition of 1% - 4% m/m Na2SO4. The poz...Burnt clay pozzolana produced from a clay deposit at Mankranso in Ghana has been activated by mechanical means through roll milling and ball milling as well as chemically by the addition of 1% - 4% m/m Na2SO4. The pozzolana sample was chemically suitable with total SiO2 + Al2O3 + Fe2O3 content ≥70% as stipulated by the ASTM C 618 standard. The particle sizes, surface characteristics and specific surface areas obtained by the types/degrees of milling were analyzed and their effect on the strength development of Portland pozzolana cement mortar cubes prepared from the pozzolana samples was evaluated. Compressive strengths obtained showed that the activated pozzolana could be used to replace up to 40% ordinary Portland cement (OPC) and satisfy the EN 197-1 and ASTM C 595 standard requirements. Comparatively, the chemically activated pozzolana cement mortars attained higher compressive strengths than the mechanically activated pozzolana cement mortars at equal ages of tests and the same pozzolana content levels. The chemically activated pozzolana cement mortars attained higher 2 day strengths than OPC at sulphate concentrations of 3% and 4% for all pozzolana content levels between 30% - 40%. SEM image and insoluble residue in HCl of a 2 day old chemically activated pozzolana cement paste confirmed dissolution of fine pozzolana particles in the alkaline media which influenced higher early age strengths. The highest 28 day compressive strength of 54.2 MPa was obtained at 4% sulphate concentration and 30% pozzolana content for the chemically activated pozzolana. The highest 28 days compressive strength for the mechanically activated pozzolana was 35.6 MPa—obtained for the roll milled product at 30% pozzolana content. Standard consistence of the pozzolana cement pastes increased with increasing pozzolana fineness and pozzolana content. Increasing Na2SO4 concentration however had no effect on standard consistence. Setting times decreased with increase in both fineness and sulphate concentration. The EN 197-1 standard for initial setting time was satisfied by the chemically activated pozzolana cement mortars at all pozzolana content levels. Pozzolana samples activated by roll milling and 36 h ball milling had faster initial setting times than the EN 196-1 standard at all pozzolana content levels beyond 30%. The ASTM C 595 requirement for initial set was however satisfied at all pozzolana content levels.展开更多
Concrete, widely used construction material suffers from cracks and low tensile strength that cut down the load capacity resulting in shortening of self-life. Biologically modified construction materials become more p...Concrete, widely used construction material suffers from cracks and low tensile strength that cut down the load capacity resulting in shortening of self-life. Biologically modified construction materials become more popular for higher strength and long-term sustainability. This investigation deals with the compressive and flexural strengths increment of a novel bacterial protein (bioremediase) incorporated pozzolana cement based mortar specimens. This protein also increases durability and crack repairing attributes that is more effective in pozzolana cement. Higher constituent percentage of silicate in pozzolana cement leads to higher silica leaching activity within the matrix manifesting of higher strength and durability of the samples. Eco-friendliness and wide range temperature stability lead added advantage to the protein for potential additive in high performance concrete technology. This means in practice that a substantial part of the cement of the mortar/concrete mixtures can be left out while still obtaining needed final strength. This would substantially improve the ecological footprint (sustainability) of mortar/concrete, as it is particularly cement that causes (during its production) massive CO2 emission what negatively affects the global climate (significantly contributes to global warming).展开更多
Pozzolana which is an eco-friendly and cheap supplementary cementious material has not been established on a commercial scale in the construction industry in Nigeria. Hence, this paper is aimed at presenting a feasibi...Pozzolana which is an eco-friendly and cheap supplementary cementious material has not been established on a commercial scale in the construction industry in Nigeria. Hence, this paper is aimed at presenting a feasibility study to show the viability and highlight the business opportunities available for local and foreign investors in the area of pozzolana production in Nigeria. The paper discussed the technical requirements and estimated start-up capital for setting up a Pozzolana production plant from calcinated of Fifteen Thousand Tonnes Annual Production Capacity. An outline for start-up capital identified building and civil work, furniture and fixtures, machinery and equipment requirement, intangible assets, and seed fund. Raw materials/utilities and organizational requirement for annual production were also presented. The investment is viable with a total investment cost of $507,321.23, annual net profit of $107,961.70 and a payback period of 4.7 years. The net profit ratio and rate of return are 16.28% and 21.28% respectively. The findings and understanding of the technical and financial requirements from this work will aid investors in making decisions. The project if carried out will reduce cement contents in concrete and mortar structures, with eco-friendly cement admixtures and subsequently reduce the cost of construction in general.展开更多
Sustainable concepts and practices have taken a centre-stage in different fields of studies and professions. This is because human activities continue to threaten the carrying capacity of earth resources as well as li...Sustainable concepts and practices have taken a centre-stage in different fields of studies and professions. This is because human activities continue to threaten the carrying capacity of earth resources as well as life basic needs such as shelter. Ghana, a developing nation, has been characterized with a boom in construction activities. In almost every constructional work, Portland cement remains the main binding agent that is used to bind aggregates together in a monolithic unit. The overdependence of the Ghanaian construction industry on Portland cement has contributed to huge sums of foreign exchange used to import cement ingredients, high cost of buildings and annual artificial shortages of cement which leads to high cost of the product. In this work, alternative binding agent—pozzolana cement, is reported with regards to the theory behind its utilization, laboratory results and practical applications. Results obtained from both the laboratory and the field works have shown that the future binder for the Ghanaian construction industry is pozzolana cement. CSIR-Building and Road Research Institute recommends it for the construction industry for use in various forms of construction such as block making, concrete and mortar works.展开更多
Chemical compositions, mineral compositions and the activated mechanism of the coal-gangue were analyzed. And pozzolana activities of the coal-gangue were evaluated after activated. Moreover, hydration heat and hydrat...Chemical compositions, mineral compositions and the activated mechanism of the coal-gangue were analyzed. And pozzolana activities of the coal-gangue were evaluated after activated. Moreover, hydration heat and hydration compositions of activated coal-gangue-calcium oxide system, as well as hydration degree and hardened paste microstructures of activated coal-gangue-cement system were studied. Results show that pozzolana activities of the activated coal-gangue root in amorphous SiO2 and activated Al2O3. With the exciting of gypsum, the reaction of activated coal-gangue and Ca（OH） 2 would produce hydration products as ettringite, calcium silicate hydrate, and calcium aluminate. The relationship between the curing age and the content of Ca （OH）2 in coal-gangue-cement system was ascertained. Unhydrated particles in the coalogangue-cement paste were more than that in the neat cement paste at the same hydration periods, and even existed at the later stage of hydration. Furthermore, the activated coal-gangue could inhibit growth and gathering of the calcium oxide crystal, and improve the structure of hardened cement paste.展开更多
基金financial support of this research from Damascus University
文摘Clayey soils in Syria cover a total area of more than 20,000 km2 of the country, most of which are located in the southwestern region. In many places of the country, the clayey soils caused severe damage to infrastructures. Extensive studies have been carried out on the stabilization of clayey soils using lime. Syria is rich in both lime and natural pozzolana. However, few works have been conducted to investigate the influence of adding natural pozzolana on the geotechnical properties of lime-treated clayey soils. The aim of this paper is to understand the effect of adding natural pozzolana on some geotechnical properties of lime-stabilized clayey soils. Natural pozzolana and lime are added to soil within the range of 0%–20% and 0%–8%, respectively. Consistency, compaction, California bearing ratio （CBR） and linear shrinkage properties are particularly investigated. The test results show that the investigated properties of lime-treated clayey soils can be considerably enhanced when the natural pozzolana is added as a stabilizing agent. Analysis results of scanning electron microscopy （SEM） and energy-dispersive X-ray spectroscopy （EDX） show significant changes in the microstructure of the treated clayey soil. A better flocculation of clayey particles and further formation of cementing materials in the natural pozzolana-lime-treated clayey soil are clearly observed.
基金Funded by the National Natural Science Foundation of China(Nos.51278086,51578108)Special Fund for Scientific Research in the Public Interest by Ministry of Water Resource of the People’s Republic of China(No.201501003)
文摘Thermodynamic stability, microvoid distribution and phases transformation of natural pozzolana opal shale（POS） were studied systematically in this work. XRD analysis showed that opal-CT, including microcrystal cristobalite and tridymite, is a major component of POS. DTA and FT-IR indicated that there were many hydroxyl groups and acid sites on the surface of amorphous SiO2 materials. FE-SEM analysis exhibited amorphous SiO2 particles（opal-A） covering over stacking sequences microcrystal cristobalite and tridymite. Meanwhile, MIP analysis demonstrated that porosity and pore size distribution of POS remained uniform below 600 ℃. Because stable porous microstructure is a key factor in improving photocatalyst activity, POS is suited to preparing highly active supported.
文摘Burnt clay pozzolana produced from a clay deposit at Mankranso in Ghana has been activated by mechanical means through roll milling and ball milling as well as chemically by the addition of 1% - 4% m/m Na2SO4. The pozzolana sample was chemically suitable with total SiO2 + Al2O3 + Fe2O3 content ≥70% as stipulated by the ASTM C 618 standard. The particle sizes, surface characteristics and specific surface areas obtained by the types/degrees of milling were analyzed and their effect on the strength development of Portland pozzolana cement mortar cubes prepared from the pozzolana samples was evaluated. Compressive strengths obtained showed that the activated pozzolana could be used to replace up to 40% ordinary Portland cement (OPC) and satisfy the EN 197-1 and ASTM C 595 standard requirements. Comparatively, the chemically activated pozzolana cement mortars attained higher compressive strengths than the mechanically activated pozzolana cement mortars at equal ages of tests and the same pozzolana content levels. The chemically activated pozzolana cement mortars attained higher 2 day strengths than OPC at sulphate concentrations of 3% and 4% for all pozzolana content levels between 30% - 40%. SEM image and insoluble residue in HCl of a 2 day old chemically activated pozzolana cement paste confirmed dissolution of fine pozzolana particles in the alkaline media which influenced higher early age strengths. The highest 28 day compressive strength of 54.2 MPa was obtained at 4% sulphate concentration and 30% pozzolana content for the chemically activated pozzolana. The highest 28 days compressive strength for the mechanically activated pozzolana was 35.6 MPa—obtained for the roll milled product at 30% pozzolana content. Standard consistence of the pozzolana cement pastes increased with increasing pozzolana fineness and pozzolana content. Increasing Na2SO4 concentration however had no effect on standard consistence. Setting times decreased with increase in both fineness and sulphate concentration. The EN 197-1 standard for initial setting time was satisfied by the chemically activated pozzolana cement mortars at all pozzolana content levels. Pozzolana samples activated by roll milling and 36 h ball milling had faster initial setting times than the EN 196-1 standard at all pozzolana content levels beyond 30%. The ASTM C 595 requirement for initial set was however satisfied at all pozzolana content levels.
文摘Concrete, widely used construction material suffers from cracks and low tensile strength that cut down the load capacity resulting in shortening of self-life. Biologically modified construction materials become more popular for higher strength and long-term sustainability. This investigation deals with the compressive and flexural strengths increment of a novel bacterial protein (bioremediase) incorporated pozzolana cement based mortar specimens. This protein also increases durability and crack repairing attributes that is more effective in pozzolana cement. Higher constituent percentage of silicate in pozzolana cement leads to higher silica leaching activity within the matrix manifesting of higher strength and durability of the samples. Eco-friendliness and wide range temperature stability lead added advantage to the protein for potential additive in high performance concrete technology. This means in practice that a substantial part of the cement of the mortar/concrete mixtures can be left out while still obtaining needed final strength. This would substantially improve the ecological footprint (sustainability) of mortar/concrete, as it is particularly cement that causes (during its production) massive CO2 emission what negatively affects the global climate (significantly contributes to global warming).
文摘Pozzolana which is an eco-friendly and cheap supplementary cementious material has not been established on a commercial scale in the construction industry in Nigeria. Hence, this paper is aimed at presenting a feasibility study to show the viability and highlight the business opportunities available for local and foreign investors in the area of pozzolana production in Nigeria. The paper discussed the technical requirements and estimated start-up capital for setting up a Pozzolana production plant from calcinated of Fifteen Thousand Tonnes Annual Production Capacity. An outline for start-up capital identified building and civil work, furniture and fixtures, machinery and equipment requirement, intangible assets, and seed fund. Raw materials/utilities and organizational requirement for annual production were also presented. The investment is viable with a total investment cost of $507,321.23, annual net profit of $107,961.70 and a payback period of 4.7 years. The net profit ratio and rate of return are 16.28% and 21.28% respectively. The findings and understanding of the technical and financial requirements from this work will aid investors in making decisions. The project if carried out will reduce cement contents in concrete and mortar structures, with eco-friendly cement admixtures and subsequently reduce the cost of construction in general.
文摘Sustainable concepts and practices have taken a centre-stage in different fields of studies and professions. This is because human activities continue to threaten the carrying capacity of earth resources as well as life basic needs such as shelter. Ghana, a developing nation, has been characterized with a boom in construction activities. In almost every constructional work, Portland cement remains the main binding agent that is used to bind aggregates together in a monolithic unit. The overdependence of the Ghanaian construction industry on Portland cement has contributed to huge sums of foreign exchange used to import cement ingredients, high cost of buildings and annual artificial shortages of cement which leads to high cost of the product. In this work, alternative binding agent—pozzolana cement, is reported with regards to the theory behind its utilization, laboratory results and practical applications. Results obtained from both the laboratory and the field works have shown that the future binder for the Ghanaian construction industry is pozzolana cement. CSIR-Building and Road Research Institute recommends it for the construction industry for use in various forms of construction such as block making, concrete and mortar works.
基金the National Basic Reasearch Program of China(Grant No.2001CB610704).
文摘Chemical compositions, mineral compositions and the activated mechanism of the coal-gangue were analyzed. And pozzolana activities of the coal-gangue were evaluated after activated. Moreover, hydration heat and hydration compositions of activated coal-gangue-calcium oxide system, as well as hydration degree and hardened paste microstructures of activated coal-gangue-cement system were studied. Results show that pozzolana activities of the activated coal-gangue root in amorphous SiO2 and activated Al2O3. With the exciting of gypsum, the reaction of activated coal-gangue and Ca（OH） 2 would produce hydration products as ettringite, calcium silicate hydrate, and calcium aluminate. The relationship between the curing age and the content of Ca （OH）2 in coal-gangue-cement system was ascertained. Unhydrated particles in the coalogangue-cement paste were more than that in the neat cement paste at the same hydration periods, and even existed at the later stage of hydration. Furthermore, the activated coal-gangue could inhibit growth and gathering of the calcium oxide crystal, and improve the structure of hardened cement paste.
