Green Innovations - A Change For Personal Life

The air we breathe, the water we drink, the security of all the living creatures on earth, the fertility of the land on which we grow our food, have all deteriorated in the past few years.'I'll go out for a breath of fresh air' is an often-heard phrase. But how many of us realize that this has become irrelevant in today's world, because the quality of air in our cities is anything but fresh. The moment you step out of the house and are on the road you can actually see the air getting polluted; a cloud of smoke from the exhaust of a bus, car, or a scooter; smoke billowing from a factory chimney, fly ash  generated by thermal power plants, and speeding cars causing dust to rise from the roads.

When the environment becomes less valuable or damaged, environmental degradation is said to occur. There are many forms of environmental degradation.  When habitats are destroyed, biodiversity is lost, or natural resources are depleted, the environment is hurt. .  The largest areas of concern at present are the loss of rain forests, pollution , ozone depletion, and the destruction of the marine environment. There are a number of serious issues that we, globally, have to deal with, for our own, our children's and our grand children's sake. Nature provides us with the very essence of life. However, the world is increasingly taking recourse to synthetic and toxic materials, which is polluting the atmosphere and curtailing human longevity.

Green issues In the broadest sense, all issues faced by a city relate to the environment in some way, even if only indirectly. At their core, green issues are about the choices we make and the impact those choices have on the environment around us. Below is a selection of major issue areas that demonstrate both the interconnectedness of green issues, as well as the many ways in which they intersect with our lives.

Green sleep Organic sleep system has been proven to provide a healthy, restorative sleep for our body and mind which is based on extensive studies and uses only the finest organic materials that nature has to offer.

-Even if we are sleeping enough hours, if we don't spend enough time in deep sleep, our body and mind will not be refreshed. Even in the absence of an obvious disorder, many things can disturb the quality and timing of sleep like medications, alcohol, stimulant use, even our exposure to strong lighting.

-Brewing a cup of tea made from relaxing, non-habit-forming herbs, which is a gentle sedative; chamomile, which helps calm our nerves and sooth the stomach; or passionflower, a safe sedative that eases anxiety, worry, or an overactive mind.

-Coffeealso promotes anxiety. It makes us constantly think about the next thing on  the  list so we cannot fall into a deep sleep.

-Sitting with our feelings for a bit at least 15 to 20 minutes a day and eventually we will see a huge improvement in our sleep. Meditation helps us remember that it's really just our monkey mind taking over and keeping us from relaxing.

-Millions of people complain about not being able to sleep or simply not feeling rested after a night of rest.

-Poor air quality is definitely one of the things that can be factored into not getting enough zzz's. Another method of breathing easier in the bedroom is to use a clay plaster that produces negative ions. It's thought by some that these negative ions can increase the flow of oxygen to the brain.

-Even a two-year-old pillow can attribute 10% of its weight to the critters and their droppings. So, if our mattress is old and heavy, we should get a new one. If absolutely cannot get a new one just, there is still a smaller step we can take; we can get a hypo-allergenic, natural mattress cover. The following are some of the tips for goodnight sleep.

-We must stick to a schedule. Erratic bedtimes do not allow for our body to align to the proper circadian rhythms.

-We should avoid daytime sleep if possible. Daytime naps steal hours from night time slumber.

-Twenty to thirty minutes of exercise every day can help us sleep. Exercise stimulates the body and aerobic activity before bedtime may make falling asleep more difficult. 
-Taking a hot shower or bath before bed helps bring on sleep because they can relax tense muscles. 
-We should avoid spicy foods before bedtime. Giving at least 2 hours from when we eat to when we sleep, allows for digestion to happen well before we go to sleep.

-Sleeping with no distractions is best for a clearer mind.
-We should avoid alcohol before bedtime. It's a depressant; although it may make it easier to fall asleep, it causes us to wake up during the night.

-Houseplants will purify the air in our bedroom, countering the stink of endless farts and abandoned socks. They filter out pollutants and toxins, add moisture to the air and reduce the incidence of allergies.

-We should avoid mothballs, as they are not just harmful to moths, but potentially bad for the environment. Mixing up cedar chips, rosemary, mint and peppercorns, and finishing off by sprinkling in a little dried tobacco will give a better result.

Green diet A green diet is a healthy, diverse diet that involves eating real foods. A green diet is a return to fresh, flavorful foods. Green Food stands edible produce and processed products produced in sustainable environment and technical standards with whole-some quality control, non-pollution, safety, quality and special logo. It is not about sacrificing an entire food group, or strictly eating vegetables, or giving up the foods we love.

Many people consider a vegetarian diet to be insufficient in terms of the major food groups. The biggest virtue of a vegetarian diet is that it allows for substantial add-ons to the total fibre intake while also allowing the incorporation of good quality fat. All wholegrain cereals and coarse grains like bajra, jowar, thalipeeth, oats, and pulses, as well as dals, nuts, oilseeds, and even green leafy vegetables, are not only full of soluble and insoluble fibre but also have good quality fats like omega 3 fatty acids and mono unsaturated. These are needed to prevent the onset of diabetes, heart diseases and cancers. A major benefit of including these foods in our daily diet is that they help to lower cholesterol and blood sugar, and also help in creating a protective environment in the body.

In order to aid the absorption of iron from these foods, vegetarians should also incorporate foods rich in vitamin C into their diets include capsicum, cabbage, drumstick leaves, guava, amla, orange juice, and sprouts. We should eliminate processed foods, high-fat foods, canned foods refined grain products such as white bread, white rice, pasta and all-purpose flour, which are less healthy and replace them with whole grain bread, whole wheat pasta, and brown rice, fresh fruits and vegetables that are in season, and preferably local and organic.

Green holiday Holidaying closer to home helps us cut down the emissions of our trips. It can also help minimise travel time and, in many cases, save money.
Closer to home, there are many simple ways to become a greener traveler –about shunning from cycling to driving efficiently; we can reduce the environmental impact of our travels at a stroke. If we have no choice but to drive a lot of miles regularly, then choosing a car with low emissions will lower our impact on the environment. Switching from model rated “fuel efficiency†will reduce the emissions per mile by around 40 per cent. If we drive only rarely, an even more ambitious move would be to get rid of our car altogether and join a car sharing club instead.   Idling should also be avoided – if a car is stationary for more than around ten seconds, it's usually greener to turn off the engine.

Green energyGreen energy is a term used to describe sources of energy that are considered to be environmentally friendly and non-polluting, such as geothermal, wind, and solar power. The more we use renewable energy, the more we benefit the global environment.

Solarenergy is created by heat and light radiated from the Sun.
Wind power is the conversion of wind energy into electricity using wind turbines. Groups of these turbines are called wind farms, which are connected to electrical grids.
Geothermal process uses energy generated by heat stored beneath the Earth's surface. Hydropower comes from the energy of dammed water driving a water turbine and generator.

Biomass produces energy which can reduce the use of fossil fuels and reduce greenhouse gas emissions as well as reducing waste management problems. Most electricity generated using biomass today is by the direct combustion method, primarily burning waste wood products generated by the agriculture and wood-processing industries.

Green fitness Exercise is important for health and keeping  less weight  Many people go to a gym, but gyms aren't the greenest places to  do it . Gyms use a huge amount of  air conditioning, operating the equipment, and heating pools.

We can get greener exercise in the nearest park or at home.  Housework is a good form of exercise and it's no more boring than spending time on the treadmill and we save on those gym fees. Personal fitness makes our body strong enough to better resist illness. We may need some basic equipment such as mats, bands, balls and other exercise and sports equipment.  Walking, biking, dance, yoga and Pilates are examples of exercise types that have good physical benefits without adding pollution to the environment.  “Green gyms†have emerged on the scene to help fitness buffs focus on natural healing fitness strategies.
Natural fitness gives us a greater chance to connect with the natural world around us.  Walking around the neighborhood, the park and other eco-friendly places is good for our spirit and the earth.   Taking friends or family members along when we exercise; it not only helps the entire family stay in shape, it promotes a green way of staying fit in a manner the entire family can enjoy.

Green communicationThe success of a green office policy is the active involvement of all members of staff, and this can be achieved by establishing good communication from the beginning. Office environmental policy is special because it needs everyone from the top of the organisation down to the junior office clerks at the bottom of the ladder to play their part. It is crucial to the success of a green office policy to maintain good communication between all levels of employee, and at all stages of the process. If employees are to embrace the green initiative, they need to be worked with rather than dictated to. Businesses that have implemented sustainable workplace initiatives and encouraged their staff to get involved have been pleasantly surprised by their enthusiasm and willingness to support the programme. Regular meetings or briefs should be held and newsletters or e-mail updates sent out, informing everyone what changes are going on, why, when and how they can contribute.

The relatively recent phenomenon of companies encouraging staff to speak out and tell them what they think is a positive development, but too often employees literally cannot because they work within their own little bubble unaware, and uninterested in anything going on in the rest of the workplace that doesn't directly affect them. Establishing a green network of communication will help give staff a power and interest beyond their desk.

Green areasspending time in green areas lowers stress levels. This could in part be due to our bodies being attuned to a more natural environment. Many of us know that being in pleasant natural surroundings can be relaxing. A walk in the countryside or through a leafy park feels as though it is doing us good.

It could be that the lack of crowding and lesser likelihood of crime in leafy areas give rise to less psychosocial stress; the poor are predominately urban dwellers. It can be refreshing and probably healthy to feel the wind, rain and cold on our bodies. We are also programmed to deal with danger. In urban environments, surrounded by strangers our stress response may be continually stimulated at a low level thereby providing a constant stream of stress hormones.

Green technologyGreen technology or clean technology is the application of the environmental science to conserve the natural environment and resources, and to curb the negative impacts of human involvement. Sustainable development is the core of environmental technologies.

-Hardware and software auditcould unveil inefficiencies in our business processes. We could steam-line our resources to make them more energy efficient.

-Printer & hardware maintenance will extend the life of the machine and save energy.

-By sending our incoming faxes straight to email, we save our business money on resources and enable electronic document organisation especially in combination with using document management software.

-By making an electronic filing system rather than a paper one, we can save printing resources, time and office space. With all our files stored in a categorised electronic system, we can search easily for our files and utilise the space that would normally be filled by filing cabinets.

-Allowing our employees to work from home can make them more efficient. By enabling our employees to manage their time better, eliminating commuting time and making family commitments easier to deal with, we could boost our business and reduce our office space, energy, bills and our company's overhead.

-Using mobile communications to work on the move can aid our employees in working more efficiently.

-Although face-to-face communication will always be vital to some sales, using video conferencing, we reduce the cost per sale through less travel time and more flexible customer engagement. Virtual seminars or product demonstrations can also be created using IP surveillance cameras which can be logged on to by the viewer from any Internet capable computer, eliminating the need to travel and allowing multiple persons to view at once.

- Having to call in emergency IT support costs our company time, energy and money. By having a facilities management agreement, our IT support service can monitor our company's technology remotely, alerting us to many problems before they occur, enabling a swift resolution before a call out has to be made.

About the Author

Physicochemical Properties of Metakaolin-lime Pastes at Different Calcination Temperatures of Kaolinite Clay

  Physicochemical Properties of Metakaolin-lime Pastes at Different Calcination Temperatures of Kaolinite clay

 

By

   

M.A.Taher, A.Y.El-Sayed , O.A.Farghaly and  M.R.Shatat

 

Chemistry Department. Faculty of Science, Al-Azhar University, Assiut,Egypt

 

 

Abstract

 

The study of metakaolin-lime hydration process is of great interest in the field of building materials technology.This study aimed to investigate experimentally the physicochemical properties of pastes containing metakaolin (MK) and lime as activator. MK was produced by calcining Kalabsha kaolinite clay (Aswan, Egypt) at different calcination temperatures 700,800,900 and 1000 oC for 2 hr. Five mixes were prepared by partial substitution of MK by 5,10,15,20 and 25% wt CaO ( from CaCO3) by weight, then hydrated up to 90 days . The characteristics of prepared specimens were investigated by measuring compressive strength and total porosity. The hydration kinetics were evaluated by determination of free lime contents. The change in phases was investigated by IR technique. The morphology and microstructure of hardened pastes were investigated by scanning electron microscopy (SEM) tests. The results show that, partial substitution of burnt kaolinite clay at 900oC with 15 % CaO improves the hydraulic properties of MK- lime pastes.

 

Keywords: Metakaolin, Pozzolan, Kaolin, Lime.

 

 

Abbreviations: C:CaO ; S:SiO2 ; H:H2O ; A:Al2O3 ; F:Fe2O3 ; CH: Ca(OH)2

Corresponding Author: M.A.Taher

E-mail Address: mahmoudtaher@hotmail.com

 

1- Introduction

The hydraulic reactivity of some artificial pozzolana made from burnt clay using lime as an activator was previously studied [1]. These pozzolans were made by firing of montmorillonite, montmorillonite-allite mixed layer, and kaolinite clay at 600, 700 and 800oC. Pozzolana-lime pastes with water were hydrated at room temperature for various time intervals. The hydration of calcined clays with Ca(OH)2 produces calcium silicate as well as calcium aluminosilicate hydrates as cementing materials. A study was carried out to determine the effect of curing temperature on the kinetics of reaction of a metakaolin (MK)/ lime mixture [2]. MK and analytical grade Ca(OH)2 were mixed in a ratio of 1:1 by weight and with a water/binder ratio of 2.37 then cured at 20 and 60°C. In the first case, the curing time varied from 2 h up to 180 days and, in the second case, from 2 h up to 123 days. A mathematical model was applied to calculate the rate constant for the hydration reaction. The identity and the amount of the phases present were determined from thermal analysis (TG and DTA) data. The results showed that the rate constant for the samples cured at 60 °C was 68 times greater than the rate constant at 20°C for the same curing period (up to 9 days). At 20 °C, the sequence of appearance of the hydrated phases was C–S–H, C2ASH8 and C4AH13; while at 60°C, the sequence was C–S–H, C2ASH8, C4AH13 and hydrogarnet (C3ASH6). 

  Ambroise, Joseph and Pera [3] used X-ray diffraction analysis to investigate the influence of temperature on thermal activation of two specimens of montmorillonite clay. The specimens were subjected to thermal activation for 5 hours at 650,750,780,800,820,850,900 and 950oC in fixed bed reactor. The XRD before and after heating showed that thermal activation did not produce a completely amorphous material. These activated specimens showed pozzolanic activity when mixed with lime and water. Measurement of compressive strength up to 90 days showed that the rate of strength development depends on the activation temperature. The maximum 28-days compressive strength was obtained when the material was activated at 800oC.

   Murat [4] found that when mixed with Ca(OH)2 and water, metakaolinite, obtained by fixed-bed calcination of kaolinite at 730oC and develops 28-days compressive strengths of 10-15 MPa. Hydration products are essentially 2CaO.Al2O3.SiO2.8H20 (gehlenite hydrate) and CSH. Four mixes were prepared of weight ratios 80:20, 70:30, 60:40 and 50:50 of China: pure Ca(OH)2 [5]. Each mix was calcined for 2 hours at 800oC and then paste hydrated in 100% relative humidity at room temperature up to 28 days. The hydration products were studied by XRD as well as DTA and TG techniques. The chemically-combined water and Ca(OH)2 contents were quantitavely determined from TG curves. The results illustrated the formation of gehlenite hydrate (C2ASH8) as the main hydration product; its amount increases with curing time. Cabrera and Frias [6] made a detailed study of the pozzolanic reaction between MK and lime, showing the main phases produced at early hydration times from 2hours to 9 days. It was reported that C2ASH8 and C4AH13 were stable under the condition of the study, and there was no evidence of a possible conversion reaction from the phase to hydrogarnet. Also, the study focuses on the influence of curing temperature on the mechanism of reaction in MK-lime systems which gives valuable information about the nature of the reaction products and their stability with hydration time. At early stages of the reaction, the C-S-H was the main phases for both temperatures. Subsequently, C2ASH8 (stratlignite) and C4AH13 appear, and finally the C3ASH6 (hydrogarnet) was the predominant phase in the samples cured at 60oC. No hydrogarnet formation was detected. At 20oC, there is clear evidence of the existence of C4AH13 in the absence of Ca(OH)2 [7].

   The effect of calcination temperature on clay and limestone as well as hydration characteristics of calcined products were investigated [8]. Three mixes 50/50, 60/40, 70/30 wt.% clay-limestone were calcined at 700, 800, 900, and 1000°C for 2 h, then hydrated for up to 90 days. The degree of calcination was investigated from the free lime content and the ignition loss for each mixture. Also, the mineralogical composition of the fired mixes was investigated with the aid of X-ray diffractometry. The results revealed that the free lime of each mix increased up to 800°C then decreased gradually up to 1000°C. Mix 60/40 clay-limestone fired at 800°C shows the presence of Ca(OH)2 with quartz. As the firing temperature increased gehlenite appeared and increased up to 1000°C with the disappearance of lime. Mix 50/50 gave the highest hydration kinetics as measured from the determination of free lime and combined water contents. As the limestone decreased, the rate of hydration decreased. The suitable firing temperature of the clay-limestone mixes was 800°C for 2 hours.

2- Experimental:

 

2.1- Materials:

The materials used in this investigation were Kalabsha kaolinite clay (KK) and CaO prepared from CaCO3 BDH grade. The chemical oxide compositions of Kalabsha kaolinite clay used in this study are shown in Table (1).

 

Table (1): Chemical oxide composition of Kalabsha kaolinite clay, (% weight).

 

Oxide contents

Kalabsha kaolinite  clay

SiO2

Al2O3

Fe2O3

CaO

SO3

MgO

Na2O

K2O

TiO2

L.O.I

Total

44.18

36.75

1.36

0.26

-----

0.16

0.18

0.25

2.94

13.55

99.63

 

 

2.2- Methods:

2.2.1- Preparation of calcined clay (MK) and CaO:

Kalabsha Kaolinite clay (KK) was dried at 110oC for 48 hours, then crushed and passed completely through 1mm B.S. sieve. The crushed clay was burnt at 700,800, 900 and 1000oC for a soaking period of 2 hours and then quenched in air. The burnt clay (MK), after air quenching, was subjected to ball mill grinding for 20 minutes and passed through a 75 ?m B.S. sieve; the processes of grinding and sieving were repeated until the sample is completely passed through a 90 ?m sieve. CaO was prepared by firing CaCO3 (BDH grade) at 1000 oC in muffle furnace for 2 hrs and kept in desiccators until mixing with MK for the preparation of different specimens.

 

2.2.2- Preparation of MK- CaO specimens:

CaO was mixed with four types of MK produced by burning Kalabsha kaolinite clay at 700,800,900 and 1000oC. Five dry mixtures were prepared from various proportions of MK and CaO with the mass ratios 100:0(B), 95:5(KI), 90:10(KII), 85:15(KIII), 80:20(KIV) and 75:25(KV),  respectively, using ethanol to obtain complete homogeneity then dried overnight at 105oC. Each dry mixture was mixed for three minutes at different workability water/solid ratios by weight. The resulting mass was molded in 1-inch cubic moulds. The moulds were vibrated for one minute to remove any air bubbles and voids. Immediately after molding, the specimens were cured in humidity cabinet at 100% relative humidity at room temperature for 24 hours in order to attain the setting of the specimens. The specimens then were demolded and cured under tap water for various hydration periods: 3, 7, 28 and 90 days. After the predetermined curing time, three specimens were used to determine the residual compressive strength according to ASTM specification (ASTM, 1992 C). Total porosity was determined after any time of hydration as described elsewhere [9]. The hydration of pastes was stopped by employing alcohol–ether method [10]. The samples were dried at 105oC for one hour and then collected in polyethylene bags, sealed and stored in desiccators for analysis. The degree of hydration was followed by determination of free lime [11, 12]. The hydration products were analyzed by FTIR spectrophotometric technique using a Perkin-Elmer System 2000 FTIR spectrometer. The morphology and microstructure of some dry samples were investigated using scanning electron microscope (JEOL JSM-840SEM).

 

3- Results and discussion:

 

3.1- Compressive strength:

The compressive strength values of the various hardened pastes made from MK (produced by firing KK at different temperatures  700,800,900 and 1000 oC) and CaO as a function of curing time  are graphically represented in Figs. 1, 2, 3 and 4, respectively. The results indicate that, the compressive strength increases gradually from 3 t0 90 days curing for all mix composition and all firing temperatures of clay. This result might be attributed to the increase of hydration products which act as binding centers in the cured specimens with time of hydration. The reduction in compressive strength value in some mixes in the early stage of hydration (3-7days) is mainly due to the interaction between the initially formed calcium silicate hydrates and the remaining parts of pozzolanic grains leading to a decrease of the lime content of theses hydrates. At later ages (28-90 days), the hardened specimens process high strength values due to the accumulation and later stabilization of the hydration reaction products. Moreover, the strength values are higher for specimens prepared from mixes KIII, KIV and KV with higher lime contents ( 15%, 25% and 25% , respectively ) as compared with the strength values of specimens made from  mixes KI and KII with low lime contents( 5% and 10%, respectively) at all firing temperature of clay . This result may be attributed to the increase of the formation of stabilized hydrates in presence of high lime contents. Mix KIII(85% MK:15% CaO) has the highest compressive strength values at all curing ages and  firing temperatures of clay and the optimum value for this mix was at 900oC after 90 day curing. Also, mix KI (95% MK: 5% CaO) has the lowest compressive strength values at all curing ages and firing temperatures. Although mix KV has the highest lime contents, but it possessed compressive strength lesser than mixes KIII and mix KIV at all curing ages and firing temperatures. This may be attributed to the presence of high lime contents which causes formation and later accumulation of calcium aluminosilicate hydrates (hydrogarnet) having weak hydraulic properties. Accordingly, mix KIII at firing temperature 900oC of KK was suitable for the production of building materials containing lime and fired KK.

 

                          Fig.(1): Compressive strength of hardened specimens ( mixes KI-KV ) made   

                                       from MK (burnt  KK at 700oC) and CaO as a function of curing time

 

           Fig.(2): Compressive strength of hardened specimens ( mixes KI-KV ) made

                            from MK (burnt KK at 800oC) and CaO as a function of curing time

 

             Fig.(3): Compressive strength of hardened specimens ( mixes KI-KV ) made

                                        from MK (burnt KK at 900oC) and CaO as a function of curing time

 

           Fig.(4): Compressive strength of hardened specimens ( mixes KI-KV) made

                           from MK (burnt KK at 1000oC) and CaO as a function of curing time

 

 

3.2 - Total Porosity:

The total porosity values of the hardened specimens made from MK fired KK at different temperatures 700,800,900 and 1000 oC) and CaO at different proportions are graphically represented in Figs.5, 6, 7 and 8, respectively. The results show that the total porosity decreases with curing time for all MK- CaO pastes at all mix composition and firing temperatures of KK as a result of progress of hydration. The hardened pastes of mixes KIII ( 85% MK:15% CaO ) give the lower porosity values up to 90 days at all firing temperatures, while mixes KI (95% MK:5% CaO) give the highest porosity values. This may be due to the products of the MK-lime pozzolanic reaction, which have high molecular weight silicate chains in presence of high lime contents [13]. This may be also due to the decrease of hydration products formed at lower values of CaO. Generally, the total porosity of metakaolin fired at 1000oC is higher than the other firing temperatures due to the formation of some crystalline phases which retards the hydration of MK-lime mixes.

 

 

                      Fig.(5): Total porosity of hardened specimens ( mixes KI-KV ) made from  

                                        MK (burnt KK at 700oC) and CaO as a function of curing time

 

             Fig.(6): Total porosity of hardened specimens ( mixes KI-KV ) made from

                             MK (burnt KK at 800oC) and CaO as a function of curing time

 

          Fig.(7): Total porosity  of hardened specimens ( mixes KI-KV ) made from

                                      MK (burnt KK at 900oC) and CaO as a function of curing time

 

             Fig.(8): Total porosity of hardened specimens ( mixes KI-KV) made from

                          MK (burnt KK at 1000oC) and CaO as a function of curing time

 

 

3.3 - Free lime contents:

The free lime (CaO%) values of the hardened pastes made from MK( burned KK at 700,800,900 and 1000 oC) and CaO as a function of mix composition and curing time are graphically represented in Figs. 9,10,11 and 12, respectively. The free lime was consumed gradually during the hydration process of all mixes and at all firing temperatures of KK. Obviously, all of MK-CaO pastes possess extremely very low free lime content values at all stages, a result of the immediately complete reaction of liberated lime with active SiO2, Al2O3 of the decomposed MK. Generally, pastes containing mix KI (95% MK: 5% CaO) possess low free lime contents; while that containing mix KV (75% MK: 25% CaO) possess the highest free lime contents at all curing stages and all firing temperatures of KK. This is mainly attributed to the low lime content in mixes KI which is immediately complete consumed with decomposed MK. As the lime content increases in the MK pastes the free lime increases due to the decrease of retarded lime with CaO to form hydration products such as CSH, C4AH13, C2ASH8 and C3AS3H6.

 

            Fig.(9): Free lime contents of hardened specimens ( mixes KI-KV) made

                          from  MK (burnt KK at 700oC) and CaO as a function of curing time

 

              Fig.(10): Free lime contents of hardened specimens ( mixes KI-KV) made

                                           from  MK (burnt KK at 800oC) and CaO as a function of curing time

 

              Fig.(11): Free lime contents of hardened specimens ( mixes KI-KV) made

                                            from MK (burnt KK at 900oC) and CaO as a function of curing time

 

 

            Fig.(12): Free lime contents of hardened specimens ( mixes KI-KV) made

                                          from MK (burnt KK at 1000oC) and CaO as a function of curing time

 

3.4 - Infra Red Spectroscopic Analysis:

The infrared spectroscopic analysis was carried out on some selected samples of hardened MK-lime pastes of mix KIII containing fired KK clay at 800oC as a function of curing time and mixes (KI-KV) containing fired KK clay at 900oC and 1000oC after 90 days to identify the phases coexisting during the hydration process. The IR spectra of hydrated MK-lime paste (KK fired at 900oC) after 3,7,28 and 90 days are shown in Fig.13. It is clear that the intensity of broad band at 3484 cm-1 due to combined water [14] increased with curing time due to acceleration of hydration process with curing time. The intensity of  1438 cm-1 band due carbonation[15] decreases with curing time which gives advantage for the  reaction of lime with pozzolana grains in MK. The 1038 cm-1 band which is attributed to CSH (tobermorite) formation increases with curing time and 544 cm-1 band which is attributed to Al-O, hydrogarnet or Ca-O in C-A-H increases with curing time due to accumulation of CSH in the hydration process [16] . Figs.(14&15) illustrated the IR spectra of mixes KI-KV containing fired KK clay at 900oC and 1000oC after 90 days curing respectively. The bands at 3456&1650 cm-1 for 900oC and 3420 &1654 cm-1 for 1000oC due to combined water increased with curing time due to increasing in the rate of hydration process in presence of higher lime content [15]. There are two bands appear due to carbonation[14] at 1438 & 876 cm-1  for 900oC and three bands at 1430,874and 712 cm-1 for 1000oC, the intensities of these bands increased with curing time due to increasing of lime contents causes increase the carbonation . It is clear that there is increasing in the intensities of 1034 & 540 cm-1 bands of 900oC and 1030& 536 cm-1 bands for 1000oC with increasing lime content (KI- KV) due to the accumulation of CSH (tobermorite) and presence of hydrogarnet, Al-O and Ca-O in

C-A-H[16]. Mix KIII show higher intensity bands in these cases at 900 & 1000oC. Accordingly, mix KIII improves the hydraulic properties of theses mixes which is in harmony with other measurements in this investigation.

   

 

 

 

          Fig.(13) : IR spectra of mix KIII contains fired KK at 900oC after 3,7,28

                          and 90 days curing.

 

                      ( 1= 3484 cm-1, 2= 1438 cm-1, 3= 1038 cm-1 , 4= 544 cm-1 )

 

 

            Fig.(14) : IR spectra of mixes (KI-KV) contains fired KK at 900oC

                 after 90 days curing

(1= 3456 cm-1, 2= 1650 cm-1, 3= 1438 cm-1, 4= 1034 cm-1, 5= 876 cm-1, 6= 540 cm-1)

        

           Fig.(15) : IR spectra of mixes (KI-KV) contains fired KK at 1000oC

                after 90 days curing

          ( 1= 3420 cm-1, 2= 1654 cm-1, 3= 1430 cm-1, 4= 1030 cm-1, 5= 874 cm-1,

           6= 712 cm-1, 7= 536 cm-1)

3.5 -- Morphology and microstructure:

Six samples were investigated using scanning electron microscopy (SEM) as representatives for the hardened MK-lime pastes in this study. Three of these samples were made from mix KI (95% MK: 5% CaO) at the firing temperatures of KK clay 800,900 and 1000oC after 90 days curing; their SEM micrographs are shown in Figs. 16, 18 and 20, respectively. The other three samples were made from mix KIII (75% MK: 25% CaO) at the firing temperature of KK clay 800,900 and 1000 oC after 90 days curing; their SEM micrographs are shown in Figs.17, 19 and 21, respectively.    Comparing the SEM micrographs obtained for the specimens of mix KI [Fig.16 (a&b)] and mix KIII [Fig.17 (a&b)] at firing temperature 800oC after 90 days, it is clear that mix KI showed formation of nearly amorphous CSH as well as some cubic crystal of hydrogarnet-like calcium alumino-silicate hydrate, while mix KIII showed formation ill-crystallized and fibrous particles of CSH; which appeared as a clear binder between fibrous clay grains; these hydrates  mainly as CSH-(I) were engulfed with small hexagonal particles of Calcium hydroxide. The SEM micrographs of specimens made from mix KI containing burnt KK at 900oC after 90 days indicated formation of irregular hydration products without any interlocking binder [Fig.18 (a&b)]. The micrographs of mix KIII [Fig.19 (a&b)] at the same firing temperature and curing time, showed formation of dense structure and fully crystalline hydrates having close texture structure with interlocking arrangements. Also, there is appearance of hexagonal phases of CAH10 beside mixture of ill-crystallized and amorphous phases which means that these pastes have high hydraulic properties [17]. The SEM micrographs obtained after 90 days curing of specimens made from mix KI containing calcined KK at 1000oC [Fig.20 (a&b)] displayed a dense and massive structure composed of interlocking fibers and crumpled foils as well as particles with irregular appearance. In the same firing temperature and curing time, specimens of mix KIII [Fig.21] displayed mainly ill-crystallized and well-crystallized hydration products; these are a massive calcium silicate hydrates and appreciable amounts of calcium aluminate hydrates (C3AH13) [18]. From the morphology and microstructure studies of MK-lime pastes, it is clear that specimens made from mix KIII (85% MK: 15% CaO) possess the highest hydraulic properties than those made from mix KI (95% MK: 5% CaO) for all firing temperatures of KK and all curing time.. These results are in a good agreement with the obtained physico-chemical measurements of MK- lime pastes.

                         

                            (a)                                                                    (b)

Fig.(16): SEM micrographs of mix KI contain fired KK at 800oC after 90 days curing 

                   

 

                        

                           (a)                                                                (b)

Fig.(17): SEM micrographs of mix KIII contain fired KK at 800oC after 90 days curing

 

            

                               (a)                                                            (b)

 Fig.(18): SEM micrographs of mix KI contain fired KK at 900oC after 90 days curing

 

 
                              (a)                                                          (b)

 Fig.(19): SEM micrographs of mix KIII contain fired KK at 900oC after 90 days curing

 

 

                                 (a)                                                            (b)

 Fig.(20): SEM micrographs of mix KI contain fired KK at 1000oC after 90 days curing

 

 

                              (a)                                                                    (b)

Fig.(21): SEM micrographs of mix KIII contain fired KK at 1000oC after 90 days curing

 

Conclusion:

 

1- The compressive strength of the various MK-lime pastes increased continuously with increasing age of hydration up to 90 days for all firing temperatures of clay and mix composition. Mix KIII(85% MK:15% lime) has the highest compressive strength values at all curing ages and firing temperatures of clay and the optimum value for this mix was at 900oC after 90 days curing.

 

2- The results of free lime contents indicated that the free lime was gradually consumed with the time of hydration for all MK-lime pastes up to 90 days, which indicate clearly the high pozzolanic reactivity of artificial pozzolana made from burnt Kalabsha kaolinite clay and lime.

 

3-The infrared spectroscopic analysis of some MK-lime pastes indicated the formation of bands at different wave lengths due to the formation of different phases. At all selected samples there are different bands appear due to combined water, carbonation, CSH and CAH formation with variation of intensities according to the mix composition, firing temperature and curing time. Generally, mix KIII (85% MK : 15% CaO) has  the hydraulic properties of MK-lime mixes .

 

4- The morphology and microstructure of hardened MK-lime pastes indicated the formation of various hydration products having different degrees of crystallinity. Mixes KI showed formation of nearly amorphous CSH as well as some cubic crystal of hydrogarnet-like calcium alumino-silicate hydrate, irregular hydration products without any interlocking binder and particles with irregular appearance.  Mixes KIII showed formation of ill-crystallized and fibrous particles of CSH and fully crystalline hydrates having close texture structure with interlocking arrangements. According to these results; pastes made from mixes KIII (85% MK: 15% lime) show the higher hydraulic properties of prepared artificial pozzolana made from burnt Kalabsha kaolinite clay and lime.

 

5-Finally, we can conclude that, partial substitution of burnt Kalabsha kaolinite clay at 900oC with 15% CaO improves its hydraulic properties and it can be used as building material.

 

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About the Author

AMK Thermal Bivvy (Adventure Medical Kits)