To provide basic data for the reasonable mixing design of the alkali-activated (AA) foamed concrete as a thermal insulation material for a floor heating system, 9 concrete mixes with a targeted dry density less than 4...To provide basic data for the reasonable mixing design of the alkali-activated (AA) foamed concrete as a thermal insulation material for a floor heating system, 9 concrete mixes with a targeted dry density less than 400 kg/m3 were tested. Ground granulated blast-furnace slag (GGBS) as a source material was activated by the following two types of alkali activators: 10% Ca(OH)2 and 4% Mg(NO3)2, and 2.5% Ca(OH)2 and 6.5% Na2SiO3. The main test parameters were water-to-binder (W/B) ratio and the substitution level (RFA) of fly ash (FA) for GGBS. Test results revealed that the dry density of AA GGBS foamed concrete was independent of the W/B ratio an RFA, whereas the compressive strength increased with the decrease in W/B ratio and with the increase in RFA up to 15%, beyond which it decreased. With the increase in the W/B ratio, the amount of macro capillaries and artificial air pores increased, which resulted in the decrease of compressive strength. The magnitude of the environmental loads of the AA GGBS foamed concrete is independent of the W/B ratio and RFA. The largest reduction percentage was found in the photochemical oxidation potential, being more than 99%. The reduction percentage was 87% - 93% for the global warming potential, 81% - 84% for abiotic depletion, 79% - 84% for acidification potential, 77% - 85% for eutrophication potential, and 73% - 83% for human toxicity potential. Ultimately, this study proved that the developed AA GGBS foamed concrete has a considerable promise as a sustainable construction material for nonstructural element.展开更多
This paper presents the findings of an experimental program seeking to understand the effect of mineral admixtures on fresh and hardened properties of sustainable self-consolidating concrete （SCC） mixes where up to ...This paper presents the findings of an experimental program seeking to understand the effect of mineral admixtures on fresh and hardened properties of sustainable self-consolidating concrete （SCC） mixes where up to 80% of Portland cement was replaced with fly ash, silica fume, or ground granulated blast furnace slag. Compressive strength of SCC mixes was measured after 3, 7, and 28 days of moist curing. It was concluded in this study that increasing the dosage of fly ash increases concrete flow but also decreases segregation resistance. In addition, for the water-to-cement ratio of 0.36 used in this study, it was observed that the compressive strength decreases compared to control mix after 28 days of curing when cement was partially replaced by 10%, 30%, and 40% of fly ash. However, a fly ash replacement ratio of 20% increased the compressive strength by a small margin compared to the control mix. Replacing cement with silica fume at 5%, 10%, 15%, and 20% was found to increase compressive strength of SCC mixes compared to the control mix. However, the highest 28 day compressive strength of 95.3 MPa occurred with SCC mixes in which 15% of the cement was replaced with silica fume.展开更多
The mechanical performances and water retention characteristics of clays,stabilised by partial substitution of cement with by-products and inclusion of a nanotechnology-based additive called RoadCem(RC),are studied in...The mechanical performances and water retention characteristics of clays,stabilised by partial substitution of cement with by-products and inclusion of a nanotechnology-based additive called RoadCem(RC),are studied in this research.The unconfined compression tests and one-dimensional oedometer swelling were performed after 7 d of curing to understand the influence of addition of 1%of RC material in the stabilised soils with the cement partially replaced by 49%,59%and 69%of ground granulated blast furnace slag(GBBS)or pulverised fuel ash(PFA).The moisture retention capacity of the stabilised clays was also explored using the soil-water retention curve(SWRC)from the measured suctions.Results confirmed an obvious effect of the use of RC with the obtained strength and swell properties of the stabilised clays suitable for road application at 50%replacement of cement.This outcome is associated with the in-depth and penetrating hydration of the cementitious materials by the RC and water which results in the production of needle-like matrix with interlocking filaments e a phenomenon referred to as the‘wrapping’effect.On the other hand,the SWRC used to describe the water holding capacity and corresponding swell mechanism of clays stabilised by a proportion of RC showed a satisfactory response.The moisture retention of the RC-modified clays was initially higher but reduced subsequently as the saturation level increased with decreasing suction.This phenomenon confirmed that clays stabilised by including the RC are water-proof in nature,thus ensuring reduced porosity and suction even at reduced water content.Overall,the stabilised clays with the combination of cement,GGBS and RC showed a better performance compared to those with the PFA included.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
The effect of fly ash (FA) and ground granulated blast furnace slag (GGBFS) on chloride migration through concrete subjected to repeated loading was examined. Portland cement was replaced by three percentages (20%, 30...The effect of fly ash (FA) and ground granulated blast furnace slag (GGBFS) on chloride migration through concrete subjected to repeated loading was examined. Portland cement was replaced by three percentages (20%, 30%, and 40%) of mineral admixtures. Five repeated loadings were applied to concrete specimens using a WHY series fully automatic testing machine. The maximum loadings were 40% and 80% of the axial cylinder compressive strength (f′c). Chloride migration through concretes was evaluated using the rapid chloride migration test and the chloride concentration in the anode chamber was measured. The results showed that the replacement percentages of mineral admixtures, the curing time and repeated loading had a significant effect on chloride migration through concrete. The transport number of chloride through concrete cured for 28 d increased with increasing FA replacement and markedly decreased with extension of the curing time. 20% and 30% GGBFS replacement decreased the transport number of chloride through concrete, but 40% GGBFS replacement increased the transport number. Five repeated loadings at 40% or 80% f′c increased the transport number of chloride for all mixes.展开更多
This research studies the impact of different types of coarse aggregate on the behavior of geopolymer concrete based on both fly ash (FA) and ground granulated blast furnace slag (GGBFS) in different marine environmen...This research studies the impact of different types of coarse aggregate on the behavior of geopolymer concrete based on both fly ash (FA) and ground granulated blast furnace slag (GGBFS) in different marine environments. Aiming to solve the problems caused by the construction and demolition waste and the depletion of natural aggregates, in the present study coarse recycled aggregates is used to produce new green concrete with a fly ash-slag based geopolymer. By this examination, the research seeks to improve the quality and productivity of concrete used in construction and hydraulic projects. For this research, four mixtures containing different types of coarse aggregate in two different water environments were used. The utilized mixtures contained natural aggregate concrete (NAC) such as basalt and crushed marble. Also, recycled coarse aggregate concrete (RAC), which totally replaced natural aggregate, was presented in this paper such as crushed concrete and crushed ceramic. For this study, in the sieve analysis;specific and unit weights, was recorded. Furthermore, the mechanical properties were determined, using a compressive test that was conducted on the 7th, 28th, 56th and 90th days at different water environments;potable water (PW) and sea water (SW). Durability test was also performed for total absorption measurement. Results indicated that geopolymer concrete exhibits better strength in marine environments than in those of potable water. Results also showed that crushed marble (CMA) exhibits higher compressive strength and durability.展开更多
文摘To provide basic data for the reasonable mixing design of the alkali-activated (AA) foamed concrete as a thermal insulation material for a floor heating system, 9 concrete mixes with a targeted dry density less than 400 kg/m3 were tested. Ground granulated blast-furnace slag (GGBS) as a source material was activated by the following two types of alkali activators: 10% Ca(OH)2 and 4% Mg(NO3)2, and 2.5% Ca(OH)2 and 6.5% Na2SiO3. The main test parameters were water-to-binder (W/B) ratio and the substitution level (RFA) of fly ash (FA) for GGBS. Test results revealed that the dry density of AA GGBS foamed concrete was independent of the W/B ratio an RFA, whereas the compressive strength increased with the decrease in W/B ratio and with the increase in RFA up to 15%, beyond which it decreased. With the increase in the W/B ratio, the amount of macro capillaries and artificial air pores increased, which resulted in the decrease of compressive strength. The magnitude of the environmental loads of the AA GGBS foamed concrete is independent of the W/B ratio and RFA. The largest reduction percentage was found in the photochemical oxidation potential, being more than 99%. The reduction percentage was 87% - 93% for the global warming potential, 81% - 84% for abiotic depletion, 79% - 84% for acidification potential, 77% - 85% for eutrophication potential, and 73% - 83% for human toxicity potential. Ultimately, this study proved that the developed AA GGBS foamed concrete has a considerable promise as a sustainable construction material for nonstructural element.
文摘This paper presents the findings of an experimental program seeking to understand the effect of mineral admixtures on fresh and hardened properties of sustainable self-consolidating concrete （SCC） mixes where up to 80% of Portland cement was replaced with fly ash, silica fume, or ground granulated blast furnace slag. Compressive strength of SCC mixes was measured after 3, 7, and 28 days of moist curing. It was concluded in this study that increasing the dosage of fly ash increases concrete flow but also decreases segregation resistance. In addition, for the water-to-cement ratio of 0.36 used in this study, it was observed that the compressive strength decreases compared to control mix after 28 days of curing when cement was partially replaced by 10%, 30%, and 40% of fly ash. However, a fly ash replacement ratio of 20% increased the compressive strength by a small margin compared to the control mix. Replacing cement with silica fume at 5%, 10%, 15%, and 20% was found to increase compressive strength of SCC mixes compared to the control mix. However, the highest 28 day compressive strength of 95.3 MPa occurred with SCC mixes in which 15% of the cement was replaced with silica fume.
文摘The mechanical performances and water retention characteristics of clays,stabilised by partial substitution of cement with by-products and inclusion of a nanotechnology-based additive called RoadCem(RC),are studied in this research.The unconfined compression tests and one-dimensional oedometer swelling were performed after 7 d of curing to understand the influence of addition of 1%of RC material in the stabilised soils with the cement partially replaced by 49%,59%and 69%of ground granulated blast furnace slag(GBBS)or pulverised fuel ash(PFA).The moisture retention capacity of the stabilised clays was also explored using the soil-water retention curve(SWRC)from the measured suctions.Results confirmed an obvious effect of the use of RC with the obtained strength and swell properties of the stabilised clays suitable for road application at 50%replacement of cement.This outcome is associated with the in-depth and penetrating hydration of the cementitious materials by the RC and water which results in the production of needle-like matrix with interlocking filaments e a phenomenon referred to as the‘wrapping’effect.On the other hand,the SWRC used to describe the water holding capacity and corresponding swell mechanism of clays stabilised by a proportion of RC showed a satisfactory response.The moisture retention of the RC-modified clays was initially higher but reduced subsequently as the saturation level increased with decreasing suction.This phenomenon confirmed that clays stabilised by including the RC are water-proof in nature,thus ensuring reduced porosity and suction even at reduced water content.Overall,the stabilised clays with the combination of cement,GGBS and RC showed a better performance compared to those with the PFA included.
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.
基金Project (No. 50808045) supported by the National Natural Science Foundation of China
文摘The effect of fly ash (FA) and ground granulated blast furnace slag (GGBFS) on chloride migration through concrete subjected to repeated loading was examined. Portland cement was replaced by three percentages (20%, 30%, and 40%) of mineral admixtures. Five repeated loadings were applied to concrete specimens using a WHY series fully automatic testing machine. The maximum loadings were 40% and 80% of the axial cylinder compressive strength (f′c). Chloride migration through concretes was evaluated using the rapid chloride migration test and the chloride concentration in the anode chamber was measured. The results showed that the replacement percentages of mineral admixtures, the curing time and repeated loading had a significant effect on chloride migration through concrete. The transport number of chloride through concrete cured for 28 d increased with increasing FA replacement and markedly decreased with extension of the curing time. 20% and 30% GGBFS replacement decreased the transport number of chloride through concrete, but 40% GGBFS replacement increased the transport number. Five repeated loadings at 40% or 80% f′c increased the transport number of chloride for all mixes.
文摘This research studies the impact of different types of coarse aggregate on the behavior of geopolymer concrete based on both fly ash (FA) and ground granulated blast furnace slag (GGBFS) in different marine environments. Aiming to solve the problems caused by the construction and demolition waste and the depletion of natural aggregates, in the present study coarse recycled aggregates is used to produce new green concrete with a fly ash-slag based geopolymer. By this examination, the research seeks to improve the quality and productivity of concrete used in construction and hydraulic projects. For this research, four mixtures containing different types of coarse aggregate in two different water environments were used. The utilized mixtures contained natural aggregate concrete (NAC) such as basalt and crushed marble. Also, recycled coarse aggregate concrete (RAC), which totally replaced natural aggregate, was presented in this paper such as crushed concrete and crushed ceramic. For this study, in the sieve analysis;specific and unit weights, was recorded. Furthermore, the mechanical properties were determined, using a compressive test that was conducted on the 7th, 28th, 56th and 90th days at different water environments;potable water (PW) and sea water (SW). Durability test was also performed for total absorption measurement. Results indicated that geopolymer concrete exhibits better strength in marine environments than in those of potable water. Results also showed that crushed marble (CMA) exhibits higher compressive strength and durability.
