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
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
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
It is well-known that a product or a system is sustainable if it is economically viable, socially acceptable and environmentally friendly. Load bearing masonry is one such example which is quite sustainable, especiall...It is well-known that a product or a system is sustainable if it is economically viable, socially acceptable and environmentally friendly. Load bearing masonry is one such example which is quite sustainable, especially if the masonry units are locally available. It is important to quantify the environmental benefits and cost, if an alternative to an existing technology is to be suggested. Of course the issues related to acceptance have to be discussed and addressed. This paper presents the quantification of embodied energy and cost of lime-pozzolana-cement (LPC) geopolymer based masonry units made using locally available bulk ingredients viz. tank-bed soil (TBS) and brick-powder (BP). The masonry adobe units developed have achieved the target performance in terms of strength, low water absorption and relative ease of production. Simultaneously the issues related to cost are also discussed in this paper. The studies have revealed that the bulk contributor to embodied energy and cost of geopolymer adobes are the alkaline materials viz sodium hydroxide and sodium silicate. However, the embodied energy and cost per unit strength appears to be better than that of conventional table moulded bricks in south India, especially when alkaline solution at 2M concentration is used with LPC.展开更多
The growing concern for the environment all over the world, as well as the high cost of Portland cement has placed limitation on its use as the sole binding material in concrete. This work has shown that ashes from so...The growing concern for the environment all over the world, as well as the high cost of Portland cement has placed limitation on its use as the sole binding material in concrete. This work has shown that ashes from some agricultural or other biogenic wastes when mixed with appropriate amounts of ordinary Portland cement (OPC) can be used as low-cost, environmentally, more friendly binders for concrete production, than using OPC alone. Experimental determination of requisite properties of the ashes of rice husk, coconut husk, palm leaf, bamboo leaf and peanut shell revealed that they satisfy the essential requirements for pozzolans. Further experimental work was carried out on OPC/rice husk ash (RHA) and OPC/coconut husk ash (CHA) concretes to determine their essential properties in fresh and hardened states. Although the initial and final setting times of OPC/RHA and OPC/CHA pastes were longer than the setting times of 100% OPC paste, they are all within the limits specified by relevant standards. The workability of fresh concrete produced by partially replacing OPC with either of RHA and CHA was found to be better than with 100% OPC. It was also shown that the porosity of OPC/RHA and OPC/CHA concretes was less than the porosity of OPC concrete. Strength tests using very finely ground RHA and CHA to partially replace Portland cement in concrete production showed that at up to 15% replacement the strength activity index of each of them is greater than 100%, which indicating that they are excellent pozzolans.展开更多
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.
文摘It is well-known that a product or a system is sustainable if it is economically viable, socially acceptable and environmentally friendly. Load bearing masonry is one such example which is quite sustainable, especially if the masonry units are locally available. It is important to quantify the environmental benefits and cost, if an alternative to an existing technology is to be suggested. Of course the issues related to acceptance have to be discussed and addressed. This paper presents the quantification of embodied energy and cost of lime-pozzolana-cement (LPC) geopolymer based masonry units made using locally available bulk ingredients viz. tank-bed soil (TBS) and brick-powder (BP). The masonry adobe units developed have achieved the target performance in terms of strength, low water absorption and relative ease of production. Simultaneously the issues related to cost are also discussed in this paper. The studies have revealed that the bulk contributor to embodied energy and cost of geopolymer adobes are the alkaline materials viz sodium hydroxide and sodium silicate. However, the embodied energy and cost per unit strength appears to be better than that of conventional table moulded bricks in south India, especially when alkaline solution at 2M concentration is used with LPC.
文摘The growing concern for the environment all over the world, as well as the high cost of Portland cement has placed limitation on its use as the sole binding material in concrete. This work has shown that ashes from some agricultural or other biogenic wastes when mixed with appropriate amounts of ordinary Portland cement (OPC) can be used as low-cost, environmentally, more friendly binders for concrete production, than using OPC alone. Experimental determination of requisite properties of the ashes of rice husk, coconut husk, palm leaf, bamboo leaf and peanut shell revealed that they satisfy the essential requirements for pozzolans. Further experimental work was carried out on OPC/rice husk ash (RHA) and OPC/coconut husk ash (CHA) concretes to determine their essential properties in fresh and hardened states. Although the initial and final setting times of OPC/RHA and OPC/CHA pastes were longer than the setting times of 100% OPC paste, they are all within the limits specified by relevant standards. The workability of fresh concrete produced by partially replacing OPC with either of RHA and CHA was found to be better than with 100% OPC. It was also shown that the porosity of OPC/RHA and OPC/CHA concretes was less than the porosity of OPC concrete. Strength tests using very finely ground RHA and CHA to partially replace Portland cement in concrete production showed that at up to 15% replacement the strength activity index of each of them is greater than 100%, which indicating that they are excellent pozzolans.
