Effect Of Metakaolin Research Articles

Microstructure, electrical and mechanical properties of steel fibres reinforced cement mortars with partial metakaolin and limestone addition

This paper investigates binary and ternary binders of ordinary Portland cement, metakaolin and limestone as a possible solution to reduce the amount of cement content in mortar mixes. Furthermore, the mortar mixtures were reinforced with steel fibres and their properties were investigated. The effectiveness of metakaolin and limestone on compressive and flexural strength of mortar samples as mechanical properties was analysed. Results indicated that partial substitution of metakaolin in mortar mixtures provides higher compressive strength values at early ages; combined mixtures of limestone and metakaolin enhanced compressive strength comparing with 100% ordinary Portland cement (OPC) as the binder. Flexural strength values improved by increasing the number of steel fibres in mixtures; variations in metakaolin and limestone on mixtures seemed not to affect on final flexural results significantly. Electrical resistivity results revealed substantial improvements on the likelihood corrosion and corrosion rate of mortar mixtures. The addition of steel fibres to the admixture significantly decreased the ER mainly due to the conductivity of the fibres.

Water Absorption and Hydration Products of Metakaolin Modified Mortar

The compressive strength, water absorption and hydration products of mortar with metakaolin addition were characterized by a range of techniques to evaluate the effect of metakaolin on the properties and hydration of mortar. Metakaolin is more effective on the improvement of compressive strength of mortar after curing for 7 days, due to the refinement of pore structure and pozzolanic reaction between metakaolin and calcium hydroxide. Water absorption of mortar was reduced by introducing metakaolin, especially in the very early age, due to the optimization of packing density of mortar by superfine metakaolin particles. There is no correlation between compressive strength and water absorption of mortar due to the differences between mechanisms affecting the compressive strength and water absorption of mortar by metakaolin. The hydration products of mortar without metakaolin were Portlandite and ettringite. Additional hemicarboaluminate and monocarboaluminate were identified in mortar with metakaolin addition. Metakaolin addition reduced the calcium hydroxide content due to the pozzolanic reaction.

Properties, microstructure and hydration products of lightweight aggregate concrete with metakaolin and slag addition

The effects of metakaolin (MK) and slag on the strength, shrinkage, chloride resistance and interfacial transition zone microstructure of lightweight aggregate concrete were characterized by a range of analytical techniques. Slag decreased early age strength while MK increased late age strength, which was further increased by the combination of MK and slag. MK was more effective on reducing chloride diffusion coefficient and shrinkage than slag. These properties were further improved by the combination of MK and slag. Linear correlation was observed between strength and chloride diffusion coefficient with higher strength presenting lower diffusion coefficient. Portlandite, ettringite, hemicarboaluminate and monocarboaluminate were identified as hydration products. MK promoted the formation of hemicarboaluminate and monocarboaluminate. Portlandite content decreased at 28days in concrete with MK and slag, resulting in an interfacial transition zone with denser microstructure and lower Ca/Si ratio, due to the pozzolanic reaction.

Use of metakaolin on enhancing the mechanical properties of self-consolidating concrete containing high percentages of crumb rubber

This research aimed to investigate the mechanical properties of self-consolidating rubberized concrete (SCRC) mixtures with high percentages of crumb rubber (CR). The effect of metakaolin (MK) compared to other supplementary cementing materials (SCMs) on enhancing the mechanical properties and stability of SCRC mixtures was highlighted in this research. The variables were percentage of CR (0–50% by volume of sand), type of SCM (fly ash, slag, and metakaolin), binder content (500–550 kg/m3), coarse aggregate size (10–20 mm), and air entrainment. The mechanical properties of the tested mixtures were investigated based on their compressive strength, flexural strength, splitting tensile strength, and modulus of elasticity. The results indicated that using MK improved the mixture stability and particle suspension, which facilitated the development of SCRC mixtures with a high percentage of CR (30%) and with enhanced mechanical properties. Adding entrained air to SCRC mixtures with MK further enhanced the fresh properties and stability, and allowed a higher percentage of CR (40%) to be used safely in SCRC with acceptable stability/strength and with a density of less than 2100 kg/m3. The results also indicated that although SCRC mixtures had slightly higher mechanical properties compared to vibrated rubberized concrete (VRC), the problems associated with the fresh properties and stability of SCRC mixtures were reduced in VRC, which allowed up to 50% CR to be used in this mixture with acceptable stability/strength and with further reduction of the mixture density (less than 2050 kg/m3).

Investigation of the properties of high-porosity cement foams based on ternary Portland cement–metakaolin–silica fume blends

High-porosity cement foams based on ternary blends of Portland cement, metakaolin and silica fume were prepared by the pre-foaming method. The effects of ternary blends on the early-age properties, air-void structure and hardened state properties of cement foams were investigated. The effect of metakaolin and silica fume on stabilizing air-voids was observed, and the collapse of cement foams during the hardening process was avoided by addition of metakaolin. Moreover, the compressive strength of the prepared 91% high-porosity cement foams was enhanced by addition of metakaolin and silica fume. The compressive strength and thermal conductivity reached 0.74MPa and 0.054W/mK, respectively. However, metakaolin and silica fume had a negative impact on the workability of the cement foam.

PROPERTIES OF SELF COMPACTING CONCRETE WITH METAKAOLIN REPLACING SAND WITH GBFS

After Agriculture Industry in India. Construction sector contribute 11% to the GDP. Hence construction Industry plays a crucial role in economic development for any construction. Sand is the major material for preparation of mortar and self compacting concrete. But the problem here is sand is largest basic consumer non-renewable resource. Hence it is our responsibility to safeguard the sand for future generation. Today this is an almost scarcity of national sand and due to continuous excavation of river beds there is some serious effect on ecology ever. It’s the time to think for alternate material to replace the river sand and for any mix design of self compacting concrete higher %age of powder content & sand is required. In the present paper we have put an effort to replace the sand with GBFS by–product of steel and iron manufacturing plant. Test result of GBFS meets the national standard of fine aggregates (IS 38 3 1970) GBFS does not contain material that may affect the strength and durability of concrete such as chlorides, organics impurities. It is free from emission of Co2. In the present paper M40 grade of SCC was considered with different replacement of sand with G.B.F.S. Further it is studied that the effect of MetaKaolin on the properties of GBFS self compacting concrete, the studies include the effect of GBFS and MetaKaolin on the fresh and hardened mechanical properties of SCC made with GBFS and MetaKaolin. The observation made that river sand can be replaced up to 60% with constant W/C ratio 0.38% the only problem with GBFS, it takes long time to gain strength. If we add the admixtures METAKAOLIN by 10%, then quick setting & early strength is possible. The GBFS is free from Co2, Alkalis and silt, Co2.The fresh properties & compressive strength of SCC increases with the increase in the percentage of GBFS. But limited to 60% replacement provided by adding 10% MetaKaolin. It is found that 70% replacement not reached satisfactory results. It is economical when compared with natural sand and also reliable alternative material in terms of workability, strength and durability. As there is broader slope for advancement in construction Industry. Therefore there is an immense necessity to know for alternative to natural river sand, this paper further detail about the fresh and hardened properties chemical properties briefly in full length submission. The fresh properties and compressive strength of self compacting concrete is improved as percentage of GBFS increases with constant MetaKaolin (%). The study has revealed that using MetaKaolin in the replacement f river sand with GBFS gives better flow properties and compressive strength in comparison to only GBFS

Effect of Metakaolin on the geotechnical properties of Expansive Soil

Expansive soil spreads in Iraq and some countries of the world. But there are many problems can be occurred to the structures that built on, so we must study the characteristics of these soils due to the problems that may be caused to these structures which built on these kinds of soil and then study the methods of treatment. The present study focuses on improving the geotechnical properties of expansive soils by treating it Metakaolin(M). Metakaolin (M) has never been used before as an improvement material for stabilizing the expansive soil . Metakaolin is a pozzolanic material. It’s obtained by calcination of kaolinite clay at temperatures from 700°C to 800°C. Kaolin chemical composition is basically aluminous silicates hydrates associated with Mn, Fe, Ca, K, Na. Its crystal has a lattice structure of tetrahedral and octahedral layers with interplanar distance of 7.2 Å. The soil used in the present study can be classified according to the Unified Soil Classification System as clay with high plasticity (CH) .
 

Effect of metakaolin on the chloride ingress properties of concrete

Research and practical experience have shown that partial replacement of cement by metakaolin improves concrete durability as a result of the refinement of the pore structure. While much research has been presented on concrete performance with metakaolin, it is scarce concerning the transport properties of chlorides in concrete with metakaolin, in natural conditions (i.e., un-accelerated). This study determines the chloride diffusion coefficients for several concretes with vary levels of cement replacement with metakaolin, and compares these results with chloride migration coefficients obtained from accelerated laboratory testing. In this study, two cement types (CEM I 42,5R and CEM IV/A 42,5) and two cement contents levels where used with metakaolin replacement levels varying from 10-20%. Concretes where tested for fresh properties, compressive strength, electrical resistivity, chloride ingress characteristics (natural diffusion and migration), and mercury intrusion porosimetry. The results show improved strength, durability properties and chloride penetration resistance of concretes with metakaolin. Furthermore, the use of metakaolin in fly ash concrete improves the early age performance of the concrete (<90 days), counteracting the delay in strength and durability gain typically associated with fly ash concrete. The results obtained from this study fulfil the lack of critical input for service life design models of reinforced concrete structures in chloride environments, with emphasis on concretes with metakaolin replacement.

Properties of Lime Plaster with Hydrophobic Admixture

The effect of metakaolin and hydrophobic agent admixture on properties of newly designed lime plasters is analysed in the paper. The overall majority of physical - chemical building deterioration is related to the penetration of moisture and soluble salts into the building structure. For that reason, the modified lime plasters were in the wide range of various properties tested. Comparative measurement declared the usage of metakaolin and zinc stearate does not significantly influenced basic physical parameters and water vapour transport, but reduced the liquid water transport which is very positive finding.

Fresh, micro- and macrolevel studies of metakaolin blended self-compacting concrete

This investigation focuses on the effect of metakaolin (MK) on the fresh, micro- and macrolevel properties of self-compacting concrete (SCC). Cement content of 500kgm−3 was considered, while the MK was used to replace cement by 5, 10 and 15wt.%. To assess the fresh concrete properties tests like slump flow, T50 cm time, V-funnel flow times, L-box and blocking ratio were performed. The macrolevel properties studied were compressive strength and split tensile strength. The microstructural changes were studied using a Scanning Electron Microscope (SEM), X-ray Diffraction Analysis (XRD) and Energy Dispersive X-ray Analysis (EDX). The fresh concrete results show that SCC mixes prepared at different Water:Powder (W:P) ratios satisfied the rheological properties without addition of Viscosity Modifying Admixture (VMA). MK inclusion enhanced the macrolevel properties. The microlevel studies indicated that microcrack width was reduced due to inclusion of MK in the control mix. In addition pozzolanic action of MK reduces the calcium hydroxide (CH) and lowers the calcium:silicate (Ca:Si) ratio of calcium silicate hydrate (C–S–H). The optimum replacement of MK was 10wt.% regarding micro- and macrolevel properties. As a result of this evaluation, inclusion of MK improved the micro- and macrolevel properties.

Effects of metakaolin on mechanical properties, pore structure and hydration heat of mortars at 0.17 w/b ratio

In the last two decades, metakaolin (MK) has received considerable attention as a supplementary cementitious material. However, few studies have evaluated the performance of cementitious composites employing MK under a very low water to binder (w/b) ratio. This paper presents our findings on the pozzolanic reactivity of MK and the effects of MK on mechanical properties, pore structure and hydration heat of mortars by replacing the cement with MK at 0%, 6%, 10%, and 14% by weight at a constant 0.17 w/b ratio. The experimental results show that the pozzolanic reactivity of MK is higher than that of silica fume (SF), especially at 28d. For mortars without steel fibers, the flexural strength decreases with the inclusion of MK, whereas 10% MK blended mortars show the highest compressive strength (96.1MPa at 90d) compared to the others. For reinforced mortars with 2% steel fibers by volume, both flexural and compressive strength are remarkably enhanced. In addition, three-point bending tests demonstrate that the flexural toughness is improved with the addition of MK as well, although MK decreases the flexural strength of plain mortars. Mercury intrusion porosimetry (MIP) results indicate that increase tendency in porosity is detected with the elevating MK contents. Heat of hydration tests results show that 6% MK accelerates the cement hydration, with an advanced accelerating period starting time, and maximize the heat flow which indicates maximum temperature rise. Although 14% MK blended mortar minimizes the total heat evolved, the optimal MK content is 10% with the consideration of mechanical properties.

Effect of metakaolin on the corrosion resistance of structural lightweight concrete

In this study, the mechanical and physical properties of structural lightweight concrete (SLC) specimens produced by substituting cement with metakaolin (MK) at ratios of 5%, 10%, 15% and 20% w/w were examined, and the corrosion behavior of the reinforcing steel bars embedded in these specimens was investigated. Corrosion rates of the bars were determined by using galvanic current measurement method. Furthermore, the corrosion potential of the steel bars in these specimens was measured daily for a period of 90d based on ASTM C876 standard test method. As a result of this study, it was found that the MK improved the mechanical and physical properties of the SLC and the 15% w/w MK addition showed the optimum contribution to the strength development. Furthermore, the use of MK in SLC specimens, as a cement replacement up to 15% w/w, improved the corrosion resistance of the specimens, while there was no positive effect when MK was added in greater ratios. The conclusions were also supported with scanning electron microscope (SEM) studies.

The effect of metakaolin on the durability of concrete hollow blocks used in masonry: evaluation of degradation caused by driving rain

Driving rain, considered one of the major factors in the degradation of external seals, may cause esthetic problems and material decomposition to facades and masonry. In the present research, the production of concrete hollow blocks for masonry underwent testing for which 20 years of exposure have been considered, taking into account the annual precipitation in the State of Paraíba. This was assessed by replacing 10, 15 and 20% of cement for metakaolin using as parameter the specimen’s mass loss at end of the test. It has was found that the concrete with metakaolin revealed values of weight loss greater than those of the reference concrete, without metakaolin, and that these values increased as the level of substitution increased. However, for mixtures with lower cement content, the use of 10% by metakaolin promoted results that have been considered similar to the reference. The test results are, therefore, consistent with those reported in literature for assessment studies on actual exposure situations; however, further studies will be developed to correlate the laboratory results obtained and from the resulting exposure to natural weather conditions.

The Impact of Metakaolin on Early Days Strength of Nanotechnology Modified Sandwich ECC

Metakaolin is a produce from Kaolinite. Meanwhile, Kaolinite is a natural clay mineral that consists of so many mineral materials, metakaolin inclusive, that can be used in many areas of life and hence sustainable in contents if process adequately. The issue of global warming coupled with a general belief of greenhouse gas emission through the production and usage of cement, a main building and infrastructures construction materials, necessitate for the substitution of cement in building materials most especially concrete. This study focused on the effect of metakaolin on the early day's strength of sandwich engineered cementitious concrete modified with nanosilica particles. The nanosilica in this mix served two purposes, one as a cementitious substitute and secondly as to increase the silica content of the normal sand used. The fresh and engineering properties of samples with 12% weight replacement of ordinary Portland cement with metakaolin was also evaluated. The surface area of metakaolin used in this experiment was 25.4m2/g. The result shows that the sandwich ECC samples modified with nanosilica produced higher strength compared with the base standard M45 ECC.

Effect of Metakaolin on the Strength and Pore Size Distribution of Concrete

Metakaolin, a supplementary cementitious material, together or separately with silica fume and fly ash, has been widely used as a replacement material for cement. This research is to determine the effect of metakaolin replacement of cement (0%, 7%, 9% and 12 %) to the 3, 7, 14 and 28-day compressive strengths of wet cured concrete at water/cement ratio of 0.4 and design strength of 40 MPa. The workability of the fresh concrete was measured through slump and compacting factor tests. Results show that the workability of the fresh concrete decreased up to 80% at metakaolin replacement of 12%. Replacing metakaolin by 12 %, on the other hand, had resulted in the highest compressive strength, which is 48.5 MPa at 28 days compared to control and other percentages of replacement. The porosity measured on the broken samples taken from the compressive strength test shows that the pore diameter size of metakaolin concrete is almost 93% finer than the controlled concrete, which had contributed to the increased in the strength. The use of metakaolin as supplementary cementitiuos material is hoped to be able to replace or stand tall as others similar to it in the market either due to its strength or cost.

Effect of Metakaolin and PVA Fibres on the Workability and Mechanical Properties of Concrete

Locally produced metakaolin (MK) as the cement replacing material and PVA fibres has been used. The effect on workability and on the mechanical properties of concrete has been investigated. Total fifteen (15) mixes of concrete have been examined using MK 5 to 10% and PVA fibres of aspect ratio 45, 60, 90 and 120 with 1% volume fraction. Three (03) mixes without PVA fibre have been used as control mixes. For each mix, test for slump, cube compressive strength and splitting tensile strength has been performed. It has been found that MK and PVA fibres causes decrease in slump but use of MK and PVA fibres together improves the workability. The use of MK and PVA fibres has advantageous in increasing compressive strength and splitting tensile strength.

Strength and Porosity of Cement Mortar Blended with Metakaolin

An experimental investigation was carried out to assess the effect of metakaolin (MK) on the compressive strength, flexural strength and porosity of cement mortar. The cement was partially substituted with MK at 0-30% replacement levels. The results show that the strengths and porosity of mortar containing up to 20% were superior to that of control (0% MK). The Balshin equation fits the experimental results of compressive strength and porosity of the specimens containing MK and there is a strong quantitative relationship between compressive strength and porosity of the specimens.

The use of electrical impedance spectroscopy for monitoring the hydration products of Portland cement mortars with high percentage of pozzolans

In this paper, mortars and pastes containing large replacement of pozzolan were studied by mechanical strength, thermogravimetric analysis (TGA), scanning electronic microscopy (SEM), mercury intrusion porosimetry (MIP) and electrical impedance spectroscopy (EIS). The effect of metakaolin (35%) and fly ash (60%) was evaluated and compared with an inert mineral addition (andalusite). The portlandite content was measured, finding that the pozzolanic reaction produced cementing systems with all portlandite fixed. The EIS measurements were analyzed by the equivalent electrical circuit (EEC) method. An EEC with three branches in parallel was applied. The dc resistance was related to the degree of hydration and allowed us to characterize plain and blended mortars. A constant phase element (CPE) quantified the electrical properties of the hydration products located in the solid–solution interface and was useful to distinguish the role of inert and pozzolanic admixtures present in the cement matrix.

Effects of metakaolin, silica fume and slag on pore structure, interfacial transition zone and compressive strength of concrete

The pore structure and interfacial transition zone (ITZ) of concrete incorporating slag, silica fume and metakaolin were analyzed in this study. Some techniques such as mercury intrusion porosimetry (MIP), microhardness testing and scanning electronic microscopy (SEM) were employed to characterize the effects of slag, silica fume and metakaolin on the pore structure, microhardness and morphology of the ITZ at 28 and 180days. The traditional properties such as compressive strength were experimentally evaluated in relation to pore characteristics and ITZ. Meanwhile, the influence of silicon, as the major component of slag, silica fume and metakaolin, on thermodynamic stability of hydrate phases was further investigated. The experimental results show that mineral admixtures have positive impact on pore refinement and ITZ enhancement of concrete especially at later curing stages. The effect of the mineral admixtures on microstructure is in the sequence: metakaolin>silica fume>slag. The development of the compressive strength is related to the evolution of the pore structure and ITZ. Thermodynamic stability analysis indicates that if mineral admixtures are added to the CaO–Al2O3–CaSO4–H2O system, the phase assemblage of C6AsH32 and C3AS0.8H4.4, which represents a member of the solid solution series Ca3Al2(SiO4)3−x(OH)4x, has a lower Gibbs free energy of reaction and is therefore thermodynamically more stable than monosulfoaluminate at temperatures from 1 to 99°C.

Effect of Metakaolin on the Physical Properties and Setting Time of High Performance Concrete

Abstract. Kaolin native to Jilin Province was calcined at the constant temperature of 750°C for 4 hours to obtain the high pozzolanic metakaolin(Al2Si2O7). The effects of metakaolin (MK) on the static flow expansion of cement paste and the workability and setting time of concrete were studied with the content of 0, 5%, 10% and 15% by weight of cementitious material. The test results show that: when the dosage of superplasticizer is 2% by weight of cementitious material, the setting time of concrete shortens obviously and the slump and expansion decrease with the raising of MK content. When 5% of cement is replaced by MK, the setting time of concrete shortens by 5%; the slump and the slump flow decrease by 5.5% and 4.4% respectively.