Physico-chemical Studies on Some CementitiousProducts Based on Some Industrial Solid Wastes
Doaa Mohamed Sayed Ibrahiem Teleb;
Abstract
The accumulation of different industrial solid wastes and by-products in several industrial plants represent a severe pollution problem which have negative effect to the environment. Some of it these solid wastes might have pozzolonic activity by inter grinding of a mixture of ordinary Portland cement (OPC) and pozzolana or by intermixing of the pozzolana with calcium hydroxide (hydrated lime) or any other alkaline activator which may be other by-product.
The objectives of the present investigation are to study the main hydration characteristics of hardened pastes derivedfrom ground granulated blast-furnace slag (GGBFS),lime-rich sludge (LRS), ordinary Portland cement (OPC),fine kaolinite sand (FKS) and fired fine kaolinite sand (FFKS).
Different series of dry mixtures were investigated in the present study. First series was prepared from lime rich sludge (LRS) and ground granulated blast-furnace slag (GGBFS). Second series was prepared from lime rich sludge (LRS),ground granulated blast-furnace slag (GGBFS) and fine kaolinite sand (FKS).Third series was prepared from lime rich sludge (LRS),ground granulated blast-furnace slag (GGBFS) and fired fine kaolinite sand(FFKS),and the fourth series was prepared from ground granulated blast-furnace slag (GGBFS),ordinary Portland cement (OPC),with and without kaolinite sand.Various hardened pastes were prepared from the different drymixtures by mixing each dry solid mixture with water (Water/Solid ratio= 0.2) and the cylindrical specimens having 2cm diameter and about 2cm height were mouldedfrom the fresh pastes under a hydraulic pressure of 50kg/cm2. The specimens of each mixture,thus obtained,were first cured at 100% relative humidity at room temperature for 24hours and the hardened cement pastes were cured under tap water.
Various physico-chemical and mechanical investigations were studied for the hardened pastes made of these series of mixes with respect to hydration kinetics,development of compressive strength and changes in the phase composition and microstructure of the formed hydration products.
The hardened pastes were hydrated for various time intervals of 1,3,7,28 and 90 days. At each time interval,the hydrated pastes were tested for their compressive strength; then,the following studies were carried out on the ground dried specimens:
1- Kinetics ofhydration were studied by the determination of chemically combined (non-evaporable) water (Wn, %) and free lime (CaO, %) contents at the different times of hydration.
2- Phase composition of the formed hydration products was investigated by means of X-ray diffraction (XRD) and differential scanning calorimetry (DSC).
3- Morphology and microstructure of the hardened pastes were studied using scanning electron microscopy (SEM).
The results of physicochemical and mechanical studies obtained from this investigation were divided into four parts; theseare:
In first part,the results of the main physicochemical and mechanical characteristicsof the hardened pastes made of LRS-GGBFS (mixes I, II and III) indicated the following:
1- The results of compressive strengthshowed three stages of strength development with increasing hydration ages; these are: pre-dormant period,dormant period and acceleration period.The hardened specimens made from mix II (25% LRS and 75% GGBFS) showed higher compressive strength values than those of the hardened specimens made from mixes I and III especially at later ages of hydration. This indicates that the percentage ratio of GGBFS - LRS blend in mix II represents the optimum composition required for activation of GGBFS that led to the formation of larger amounts of hydration products having considerable hydraulic character.
2- The variations of the combined water values (Wn,%) with age of hydration are in agreement with the variations of the compressive strength values.
3- The free lime contents(CaO,%) showed a continuous decrease with increasing age of hydration. The main observation showed that the hardened cement pastes made from mixes II and III possess slightly higher values of free lime (CaO,%)than those of mix I. That could be related to the increased percentage composition of LRS,as the lime source,in mixes II and III than that in mix I.
4- The higher strength values of the hardened pastesmade of LRS-GGBFS (mixesI,II and III) aremainly attributed to the formation of CSHhydratesat all ages of hydration as confirmed by the results of XRD, DSC and SEM studies.
The objectives of the present investigation are to study the main hydration characteristics of hardened pastes derivedfrom ground granulated blast-furnace slag (GGBFS),lime-rich sludge (LRS), ordinary Portland cement (OPC),fine kaolinite sand (FKS) and fired fine kaolinite sand (FFKS).
Different series of dry mixtures were investigated in the present study. First series was prepared from lime rich sludge (LRS) and ground granulated blast-furnace slag (GGBFS). Second series was prepared from lime rich sludge (LRS),ground granulated blast-furnace slag (GGBFS) and fine kaolinite sand (FKS).Third series was prepared from lime rich sludge (LRS),ground granulated blast-furnace slag (GGBFS) and fired fine kaolinite sand(FFKS),and the fourth series was prepared from ground granulated blast-furnace slag (GGBFS),ordinary Portland cement (OPC),with and without kaolinite sand.Various hardened pastes were prepared from the different drymixtures by mixing each dry solid mixture with water (Water/Solid ratio= 0.2) and the cylindrical specimens having 2cm diameter and about 2cm height were mouldedfrom the fresh pastes under a hydraulic pressure of 50kg/cm2. The specimens of each mixture,thus obtained,were first cured at 100% relative humidity at room temperature for 24hours and the hardened cement pastes were cured under tap water.
Various physico-chemical and mechanical investigations were studied for the hardened pastes made of these series of mixes with respect to hydration kinetics,development of compressive strength and changes in the phase composition and microstructure of the formed hydration products.
The hardened pastes were hydrated for various time intervals of 1,3,7,28 and 90 days. At each time interval,the hydrated pastes were tested for their compressive strength; then,the following studies were carried out on the ground dried specimens:
1- Kinetics ofhydration were studied by the determination of chemically combined (non-evaporable) water (Wn, %) and free lime (CaO, %) contents at the different times of hydration.
2- Phase composition of the formed hydration products was investigated by means of X-ray diffraction (XRD) and differential scanning calorimetry (DSC).
3- Morphology and microstructure of the hardened pastes were studied using scanning electron microscopy (SEM).
The results of physicochemical and mechanical studies obtained from this investigation were divided into four parts; theseare:
In first part,the results of the main physicochemical and mechanical characteristicsof the hardened pastes made of LRS-GGBFS (mixes I, II and III) indicated the following:
1- The results of compressive strengthshowed three stages of strength development with increasing hydration ages; these are: pre-dormant period,dormant period and acceleration period.The hardened specimens made from mix II (25% LRS and 75% GGBFS) showed higher compressive strength values than those of the hardened specimens made from mixes I and III especially at later ages of hydration. This indicates that the percentage ratio of GGBFS - LRS blend in mix II represents the optimum composition required for activation of GGBFS that led to the formation of larger amounts of hydration products having considerable hydraulic character.
2- The variations of the combined water values (Wn,%) with age of hydration are in agreement with the variations of the compressive strength values.
3- The free lime contents(CaO,%) showed a continuous decrease with increasing age of hydration. The main observation showed that the hardened cement pastes made from mixes II and III possess slightly higher values of free lime (CaO,%)than those of mix I. That could be related to the increased percentage composition of LRS,as the lime source,in mixes II and III than that in mix I.
4- The higher strength values of the hardened pastesmade of LRS-GGBFS (mixesI,II and III) aremainly attributed to the formation of CSHhydratesat all ages of hydration as confirmed by the results of XRD, DSC and SEM studies.
Other data
| Title | Physico-chemical Studies on Some CementitiousProducts Based on Some Industrial Solid Wastes | Other Titles | دراسات فيزيوكيميائية على بعض منتجات البناء المبنية علي بعض المخلفات الصناعية الصلبة" | Authors | Doaa Mohamed Sayed Ibrahiem Teleb | Issue Date | 2016 |
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