Mercury Intrusion Porosimetry Analysis Research Articles

Thermal stability of geopolymers used as supporting materials for TiO2 film coating through sol-gel process: Feasibility and improvement

Thermal stability of geopolymers synthesized with fly ash, metakaolin as aluminosilicate sources was investigated in order to explore the feasibility of using geopolymers as supports for nano-titanium dioxide film coating via sol-gel process. Structural and compositional changes of geopolymers heated up to 800°C were examined by X-ray diffraction, Fourier transform infrared spectroscopy, mercury intrusion porosimetry and thermogravimetric analysis. Below 800°C, the loss of water is the main cause for the strength degradation and thermal shrinkage of geopolymers. Geopolymers synthesized with appropriate fly ash content possess good thermal stability because of high permeability arising from low reactivity of fly ash, filler effect provided by unreacted fly ash particles and original occurring minerals as quartz, mullite and hematite. TiO2 films were coated onto geopolymer derived from fly ash containing sources via sol-gel process. The grazing-incidence X-ray diffraction patterns of the films calcined at different temperatures show that anatase crystalizes well at 600°C. The study reveals the feasibility of using geopolymers with improved thermal stability as supports for TiO2 film coating via sol-gel process.

Microstructural insights into the lime mortars mixed with sticky rice sol–gel or water: A comparative study

This paper is dedicated to studying the effect of sticky rice sol–gel on the microstructure (including pore structure and texture) and properties of lime mortar. Uniaxial compressive strength tests, scanning electron microscopy (SEM), and mercury intrusion porosimetry (MIP) were utilized to investigate the macroscopic behaviors and microstructure, respectively. Based on the MIP data, a surface fractal dimension analysis is performed to study the impact of sticky rice sol–gel on pore structure. The addition of sticky rice sol–gel is demonstrated to improve the uniaxial compressive strength of lime mortar. The SEM, MIP and surface fractal dimension analysis results show that the addition of sticky rice sol–gel facilitates the formation of compact texture, fine pore structure and elevates the bonding strength of the lime mortar. A microstructrual mechanism is proposed to explain how properties of the lime mortar are affected by the addition of sticky rice sol–gel.

Value-added recycling of construction waste wood into noise and thermal insulating cement-bonded particleboards

Large amounts of waste wood formwork from construction sites end up with landfill disposal every day. This study aims to develop a practicable technology for recycling construction waste wood into formaldehyde-free cement-bonded particleboards that have value-added features of high strength, light weight, and thermal/noise insulation for reuse in building and construction applications. The mineralogy and microstructure of particleboards were characterized by X-ray diffraction, thermogravimetry, and mercury intrusion porosimetry analyses. Among the mineral admixtures, chloride accelerated precipitation of oxychlorides while sulphate produced calcium sulphoaluminate for promoting early strength development. The use of 2% CaCl2 proved to be sufficient for improving the wood-cement compatibility. At wood-to-cement ratio of 3:7 by weight (i.e., 3:1 by volume), cement hydrates in the porous structure ensured acceptable dimensional stability (<2% swelling). By adjusting the water-to-cement ratio to 0.3 and density of the particleboards to 1.54gcm−3, the volume of capillary pores was effectively reduced from 0.16mLg−1 to 0.02mLg−1. The more compact microstructure contributed to high fracture energy at 6.57Nmm−1 and flexural strength of 12.9MPa. Using the above optimal production conditions, the particleboards complied with the International Standard (9MPa) while enabling reuse as light-weight structure. The particleboards also manifested outstanding structure-borne noise reduction (at 32–100Hz) and low thermal conductivity (0.29Wm−1K−1), suggesting potential application as acoustic and thermal insulating materials. Preliminary cost-benefit analysis illustrated economic viability of the proposed approach. Therefore, technological innovation is crucial for delivering an eco-friendly solution to waste wood recycling for the building and construction industry.

Soil porosity in physically separated fractions and its role in SOC protection

Processes that lead to soil organic carbon (SOC) protection depend on both soil porosity and structure organization, as well as chemical and biological properties. In particular, the soil micro-nano porosity (<30 μm) regulates microorganism accessibility to the soil pore system and offers surfaces for organic carbon adsorption and intercalation into soil minerals. The aim of this work was to investigate how pore size distribution can selectively protect specific carbon pools in different aggregate size fractions, by considering the effects of long-term application of farmyard manure (FYM) and mineral (Min) fertilization. Macroaggregates (250–2000 μm), microaggregates (53–250 μm), and silt–clay (<53 μm) fractions of three different soils (clayey, peaty, and sandy) were separated by wet sieving technique and then subjected to chemical and physical analysis. Sample porosity and pore size distribution were analyzed using mercury intrusion porosimetry (MIP), while SOC chemical structure was characterized by means of nuclear magnetic resonance (13C cross-polarization–magic angle spinning nuclear magnetic resonance (CP MAS 13C NMR)) and diffuse reflectance infrared Fourier transform (DRIFT) spectroscopies. Results showed that FYM increased organic (OC) and humic carbon (HC) content compared to the Min fertilization and unfertilized soils. However, it caused a gradual decrease in O,N-alkyl C, and alkyl C of humic C from macroaggregate to silt–clay fractions, suggesting an advanced state of humic component degradation as revealed by CP MAS 13C NMR, DRIFT analyses. MIP analysis showed a clear increase of micropores (5–30 μm) and cryptopores (0.0035–0.1 μm) from macroaggregate to silt–clay fractions, while minor differences were observed among the treatments. The application of principal component analysis to mineral soil fractions identified the formation of three main clusters, where (i) macroaggregates of clayey soil were mainly associated to cryptopores and OC and (ii) microaggregates and silt–clay fraction were mainly isolated by carbonyl C, ultramicropores, and total porosity. The third cluster was associated with medium and fine sand of the sand soil fraction as coupled with O,N-alkyl C, anomeric C, mesopores, and HC/OC ratio. Overall, this study indicates that pore size distribution may be a valuable indicator of soil capacity to sequester carbon, due to its direct influence on SOC linkages with soil aggregates and the positive effects against SOC decomposition phenomena. In this context, micropore- to nanopore-dominated structures (e.g., clayey soil) were able to protect OC compounds by interacting with mineral surfaces and intercalation with phyllosilicates, while meso/macropore-dominated structures (i.e., sandy soil) exhibited their low ability to protect the organic components.

Recycling contaminated wood into eco-friendly particleboard using green cement and carbon dioxide curing

Landfill disposal of contaminated wood formwork from construction sites presents significant environmental burdens and economic wastage. This study proposed an innovative and low-carbon technology by using magnesia cement and CO2 curing to transform contaminated wood waste into eco-friendly cement-bonded particleboards, which demonstrated excellent compatibility and value-added properties. The microstructure characteristics and cement hydration chemistry were revealed by mercury intrusion porosimetry and X-ray diffraction analyses. At the optimal water to cement ratio of 0.3, the particleboards contained the lowest total pore area (10.2 m2 g−1) and porosity (26.1%), thereby successfully complying with the International Standards of mechanical strength (>9 MPa) and dimensional stability (<2% swelling after 24-h water immersion). An integration of 2-h CO2 curing facilitated carbonation at early stage and reduced the volume of mesopores and air pores, which contributed to strength development and carbon sequestration in the particleboards (8.78% by weight) helping to combat global warming. A subsequent 7-d air curing further enhanced the strength to outcompete those of 28-d air curing only, because rehydrated formation filled in capillary pores (reduced from 0.11 mL g−1 to 0.03 mL g−1). Moreover, fire resistance and thermal stability were improved by the chemistry of magnesia cement and accelerated carbonation. The carbonated particleboards retained high strength and stable dimension after 1-h heating up to 200 °C.

Experimental investigation of mechanical and microstructural properties of cemented paste backfill containing maple-wood filler

This experimental study investigates the influence of maple-wood sawdust addition on the mechanical and microstructural properties of cemented paste backfill (CPB). Mechanical properties of CPB were determined by uniaxial compressive strength (UCS) tests and microstructural changes were evaluated by mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM) analysis. Results indicate that the addition of 12.5% maple-wood sawdust (by dry mass of binder) improves the strength development of CPB specimens at later hydration age (91 curing days). However, at a higher maple-wood sawdust content of 14.5%, the UCS showed lower improvement. Moreover, MIP and SEM analysis results revealed that the 12.5% wood filler addition made the CPB material less porous and more compact by increasing the mineral content formed by cement hydration. The positive influence of maple-wood sawdust on CPB was associated with higher binder content (⩾5%) and mid- to long-term curing times (⩾56days).

Preparation of Porous Cellulose Beads via Introduction of Diamine Spacers.

The current work presents a synthesis route based on the reductive amination of 2,3-dialdehyde cellulose beads with diamines to render micrometer-sized beads with increased specific surface area (SSA) and porosity in the mesoporous range. Specifically, the influence of the reductive amination of 2,3-dialdehyde cellulose (DAC) using aliphatic and aromatic tethered mono- and diamines on bead microstructure was investigated. Aliphatic and aromatic tethered monoamines were found to have limited utility for producing porous beads whereas the introduction of diamines provided beads with a porous texture and an SSA increasing from <1 to >30 m(2)/g. Both aliphatic and aromatic diamines were found to be useful in producing porous beads having a pore size distribution range of 10 to 100 nm, as verified by N2 gas adsorption and mercury intrusion porosimetry analyses. The true density of the functionalized DAC beads decreased to an average of about 1.36 g/cm(3) as compared to 1.48 g/cm(3) for the unfunctionalized, fully oxidized DAC beads. The total porosity of the beads was, according to mercury porosimetry, in the range of 54-64%. Reductive amination with 1,7-diaminoheptane provided beads that were stable under alkaline conditions (1 M NaOH). It was concluded that the introduction of tethered diamines into DAC beads is a facile method for producing mesoporous beads.

Polymer scaffolds with no skin-effect for tissue engineering applications fabricated by thermally induced phase separation

Thermally induced phase separation (TIPS) based methods are widely used for the fabrication of porous scaffolds for tissue engineering and related applications. However, formation of a less-/non-porous layer at the scaffold’s outer surface at the air–liquid interface, often known as the skin-effect, restricts the cell infiltration inside the scaffold and therefore limits its efficacy. To this end, we demonstrate a TIPS-based process involving the exposure of the just quenched poly(lactide-co-caprolactone):dioxane phases to the pure dioxane for a short time while still being under the quenching strength, herein after termed as the second quenching (2Q). Scanning electron microscopy, mercury intrusion porosimetry and contact angle analysis revealed a direct correlation between the time of 2Q and the gradual disappearance of the skin, followed by the widening of the outer pores and the formation of the fibrous filaments over the surface, with no effect on the internal pore architecture and the overall porosity of scaffolds. The experiments at various quenching temperatures and polymer concentrations revealed the versatility of 2Q in removing the skin. In addition, the in vitro cell culture studies with the human primary fibroblasts showed that the scaffolds prepared by the TIPS based 2Q process, with the optimal exposure time, resulted in a higher cell seeding and viability in contrast to the scaffolds prepared by the regular TIPS. Thus, TIPS including the 2Q step is a facile, versatile and innovative approach to fabricate the polymer scaffolds with a skin-free and fully open porous surface morphology for achieving a better cell response in tissue engineering and related applications.

Pore structure of cement pastes through NAD and MIP analysis

Two cement pastes (water to cement ratio, w/c = 0·5, 0·3) were investigated through mercury intrusion porosimetry (MIP) and nitrogen adsorption/desorption (NAD) methods at different hardening ages. The pore structure is characterised by specific surface area, pore volume and pore size distribution. The results show that: (a) the pore structure has strong scale dependence and NAD–MIP joint measurement helps to identify the different pore structure patterns; (b) MIP total pore volume captures the global process of the hydrates filling process with curing age, the mesopore (2–70 nm) volume is dominated by hydrates filling for w/c = 0·5 but countered by high-density calcium-silicate-hydrate growth for w/c = 0·3; (c) specific surface area is sensitive to calcium-silicate-hydrate growth and specific surface area values are likely to confirm that high w/c (0·5) favours low-density calcium-silicate-hydrate growth whereas low w/c (0·3) facilitates high-density calcium-silicate-hydrate formation.

Predicting the uniaxial compressive strength of cemented paste backfill from ultrasonic pulse velocity test

The aim of this study is to investigate the predictability of the uniaxial compressive strength (UCS) of cemented paste backfill (CPB) prepared from three different tailings (Tailings T1, Tailings T2 and Tailings T3) using ultrasonic pulse velocity (UPV) test. For this purpose, 180 CPB samples with diameter × height of 5 × 10 cm (similar to NX size) prepared at different binder dosages and consistencies were subjected to the UPV and UCS tests at 7–56 days of curing periods. The effects of binder dosage and consistency on the UPV and UCS properties of CPB samples were investigated and UCS values were correlated with the corresponding UPV data. Microstructural analyses were also performed on CPB samples in order to understand the effect of microstructure (i.e. total porosity) on the UPV data. The UPV and UCSs of CPB samples increased with increasing binder dosage and reducing the consistency irrespective of the tailings type and curing periods. Changes in the mixture properties observed to have a lesser extent on the UPV properties of CPB, while, their effect on the UCS of CPB was significant. Empirical equations were produced for each mixture in order to predict the UCSs of CPB through UPV. The validity of the equations was also checked by t- and F-test. The results showed that a linear relation appeared to exist between the UPV and UCS with high correlation coefficients (r ≥ 0.79) and all models were valid by statistical analysis. Mercury intrusion porosimetry (MIP) and scanning electron microscope (SEM) analyses have revealed that the UPV properties of CPB samples were highly associated with their respective microstructural properties (i.e. total porosity). The major output of this study is that UPV test can be effectively used for a preliminary prediction of the strength of CPB.

Fabrication of an ionic liquid-based macroporous polymer monolithic column via atom transfer radical polymerization for the separation of small molecules

A polymer monolithic column was prepared in a stainless steel column (50×4.6mm i.d.) via atom transfer radical polymerization technique using triallyl isocyanurate and ionic liquid (1-allyl-3-methylimidazolium chloride) as co-monomers, ethylene dimethacrylate as cross linking agent, polyethylene glycol 200, 1,4-butanediol, and N, N- dimethylformamide as porogen system, CCl4 as initiator, and FeCl2 as catalyst. The optimized polymer columns were characterized by scanning electron microscope, nitrogen adsorption-desorption instrument, mercury intrusion porosimetry, infrared spectrometer, and thermogravimetric analysis technique. Respectively, all of these factors above could illustrate that the optimized columns had relative uniform macroporous structure and high thermal stability. A series of basic and acidic small molecules, isomers, and homologues were used to evaluate the performance of these monoliths and enhanced column efficiency was obtained.

Physical properties, electrical resistivity, and strength characteristics of carbonated silty soil admixed with reactive magnesia

Soil electrical resistivity has been used quite extensively for assessing mechanical properties of chemically treated soils in the recent past. One of the most innovative applications of this technique could be in the field of ground improvement wherein carbonated reactive magnesia (MgO) is employed for treating soils. With this in view, a systematic study that targets the application of electrical resistivity to correlate physical and strength characteristics of the carbonated reactive MgO-admixed silty soil is initiated, and its details are presented in this manuscript. To achieve this, reactive MgO-admixed soils were carbonized by exposing them to CO2 for different durations, and subsequently their electrical resistivity and unconfined compressive strength were measured. In this context, the role of a parameter, the ratio of the initial water content of the virgin soil to reactive MgO content (designated as w0/c), has been highlighted. It has also been demonstrated that w0/c is able to correlate, uniquely and precisely, with the physicochemical parameters of the soils (viz., unit weight, water content at failure, porosity, degree of saturation, and soil pH), electrical resistivity, and unconfined compressive strength at various carbonation times. In addition, microstructural properties have been obtained from the X-ray diffraction, scanning electron microscopy, and mercury intrusion porosimetry analyses. These properties have been used to substantiate the findings related to the carbonation of the reactive MgO-admixed soils.

Effect of glass powder on microstructure of cement pastes

The effect of glass powder (GP) on the microstructure of cement pastes was studied by using mercury intrusion porosimetry, thermogravimetric and differential thermal analysis, scanning electron microscopy, energy dispersive spectrum analysis and X-ray diffraction techniques. The compressive strength and alkali–silica reaction (ASR) expansion was also tested. The test results indicated that GP can increase the compressive strength of cement pastes and control the ASR expansion of mortars. With the increase in GP content, ASR expansion decreases sharply, although compressive strength decreases a little with a large amount of GP. The characteristic pore sizes decreased with some capillary pores transforming to interstitial pores or gel pores as GP content increased. GP could diminish pore size in cement pastes, which has important significance in improving durability. Incorporating GP in cement-based materials had little effect on the kinds of hydration products, but it significantly affected the amount of hydrates, especially calcium hydroxide. The amount of calcium hydroxide reduces with the increase in curing age and GP content. The microstructure of hardened pastes containing GP was relatively dense with an abundance of calcium silicate hydrate, whose morphology was different from the gel in pure cement systems. This kind of calcium silicate hydrate gel with a low calcium/silicon ratio had a network structure formed by irregular stumpy and lamelliform gel granules. GP has high pozzolanic activity.

Role of calcium sources in the strength and microstructure of microbial mortar

This study investigated the uniaxial compressive strength, splitting tensile strength and water absorption ratio of microbial mortars treated with three different calcium sources (CaCl2, Ca(CH3COO)2 and Ca(NO3)2). The results showed that the uniaxial compressive and splitting tensile strengths of microbial mortars treated with Ca(CH3COO)2 were about twice those of the microbial mortars treated with the other two calcium sources (‘the others’ hereafter). The results of mercury intrusion porosimetry analysis showed that the pore size distribution in the microbial mortar treated with Ca(CH3COO)2 was much more uniform than that of the others. The mineralogical compositions and the microstructure morphology of the microbially induced calcium carbonate precipitation were analyzed in detail. Scanning electron microscopy and X-ray diffraction revealed that the calcium carbonate cemented in the microbial mortar treated with Ca(CH3COO)2 were different from others. Besides the calcite and the vaterite crystals, aragonite crystals with an acicular mineral morphology were observed.Calcium acetate is a more appropriate calcium source than calcium chloride for the application of MICP technology in reinforced concrete structures because it avoids the corrosion of steel bars caused by chloride ion.

Green remediation and recycling of contaminated sediment by waste-incorporated stabilization/solidification

Navigational/environmental dredging of contaminated sediment conventionally requires contained marine disposal and continuous monitoring. This study proposed a green remediation approach to treat and recycle the contaminated sediment by means of stabilization/solidification enhanced by the addition of selected solid wastes. With an increasing amount of contaminated sediment (20–70%), the 28-d compressive strength of sediment blocks decreased from greater than 10MPa to slightly above 1MPa. For augmenting the cement hydration, coal fly ash was more effective than lime and ground seashells, especially at low sediment content. The microscopic and spectroscopic analyses showed varying amounts of hydration products (primarily calcium hydroxide and calcium silicate hydrate) in the presence of coal fly ash, signifying the influence of pozzolanic reaction. To facilitate the waste utilization, cullet from beverage glass bottles and bottom ashes from coal combustion and waste incineration were found suitable to substitute coarse aggregate at 33% replacement ratio, beyond which the compressive strength decreased accordingly. The mercury intrusion porosimetry analysis indicated that the increase in the total pore area and average pore diameter were linearly correlated with the decrease of compressive strength due to waste replacement. All the sediment blocks complied with the acceptance criteria for reuse in terms of metal leachability. These results suggest that, with an appropriate mixture design, contaminated sediment and waste materials are useful resources for producing non-load-bearing masonry units or fill materials for construction uses.

Characterization of Expanded Graphite Microstructure and Fabrication of Composite Phase-Change Material for Energy Storage

Phase-change composites for energy storage were prepared by the expanded graphite (EG) absorption method and their microstructures were analyzed. The organic phase-change materials (PCMs) were evaluated for their thermal and latent heat storage properties. The expanded graphite was prepared under the microwave irradiation. The scanning electron microscope (SEM) and mercury intrusion porosimetry analyses showed that expanded graphite had micron-size pores. The EG was able to easily absorb organic PCMs because of its nonpolarity and porosity. Composite PCMs for energy storage were fabricated with paraffin and the expanded graphite. The resulting material showed superior heat storage (releasing) effects and reduced large-range fluctuation in environmental temperature, thus achieving energy transfer simultaneously across different times and space.

On the crystallisation pressure of gypsum

We estimate the crystallisation pressure of gypsum quantitatively, with reference to the geological context of the Gypsum Keuper formation. The formation contains sulphatic claystones which have the property of swelling in the presence of water and have caused substantial structural damage to the linings of several tunnels in Switzerland and Germany. The swelling of these rocks is attributed to the transformation of anhydrite into gypsum, which occurs via the dissolution of anhydrite in pore water and the precipitation of gypsum from the solution. This simultaneous dissolution–precipitation process happens because the solubility of gypsum is lower than that of anhydrite under the conditions prevailing after tunnelling, and it does not cease until all of the anhydrite has been transformed. The elementary mechanism behind the development of the macroscopically observed swelling pressure is the growth of gypsum crystals inside the rock matrix: If a crystal is in contact with a supersaturated solution, but its growth is prevented by the surrounding matrix, it then exerts a so-called crystallisation pressure upon the pore walls. In the present paper, the crystallisation pressure is calculated by means of a thermodynamic model that takes coherent account of all relevant parameters, including the chemical composition of the pore water and pore size. Variations in these parameters lead to a very wide range of crystallisation pressures (from zero to several tens of megapascals). By using the results of mercury intrusion porosimetry and chemical analyses of samples from three Swiss tunnels, however, we show that the range of predicted values can be reduced significantly with the help of standard, project-specific investigations.

Monitoring hydration in lime-metakaolin composites using electrochemical impedance spectroscopy and nuclear magnetic resonance spectroscopy

AbstractThis paper describes a study of the hydraulic reactions between metakaolin (MK) and air lime using electrochemical impedance spectroscopy (EIS) and nuclear magnetic resonance spectroscopy (NMR). Tests were carried out at 20, 25 and 30°C on lime-MK pastes with 10:1 w/w ratio. Tests over 28 days allowed identification of relevant changes in the EIS signals and characterization of pastes using thermal analysis (TGA/DSC), scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP) and uni-axial compressive tests. Tests over shorter periods of time (up to 42 h) allowed more detailed studies of the hydraulic phases formed at the very beginning of the reactions.Results of thermal analyses demonstrate formation of hydraulic compounds such as CSH, C4AH13 and C3ASH6 and show their evolution over time. MIP analysis demonstrates changes in pore size distribution related to the formation and trasformation of hydraulic phases. Variations of impedance response with time are shown to be associated with reaction kinetics. Changes in the NMR signal within the first 42 h of reaction are shown to be associated with the dissolution of calcium hydroxide in the pore solution. Overall, this paper demonstrates the importance of NMR in the study of hydraulic reactions in lime based materials and the ability of EIS to detect the formation of hydraulic compounds and the end of the calcium hydroxide dissolution process.

Durability characteristics of fly ash concrete containing lightly-burnt MgO

There is a growing interest in the use of by-products in concrete for cost-reduction and performance enhancement. In China, lightly-burnt MgO (magnesium oxide), a by-product, has been used in dam concrete. Since lightly-burnt (850–1000°C) MgO tends to expand due to the hydrated product Mg(OH)2, and the hydration progresses at a lower rate than in cement, it can effectively compensate for concrete shrinkage. Many studies have been conducted to investigate the hydration and expansion properties of MgO, but few have attempted to examine the durability of concrete containing MgO.This study aims to investigate the durability properties of fly ash concrete containing 5% MgO by mass of binders as an expansive additive. To achieve this, the carbonation, freezing–thawing, chloride penetration, and sulfate resistance were tested on specimens cured for 28days or for 360days. In addition, MIP (Mercury Intrusion Porosimetry) analysis on the concrete specimens cured for up to 360days was conducted, and XRD (X-ray Diffraction) analysis of mortar containing 5% MgO and 20% fly ash was also carried out from 7 to 360days, to observe hydration products. The test results revealed that the compressive strength and durability characteristics of concrete in the long term age were slightly improved by the reduction in the porosity of the concrete due to the replacement of MgO.

Effect of Metakaolin Sand on Properties of Cement Composites

The Slovak natural raw material kaolin sand containing 36 wt.% of kaolinite from Vyšný Petrovec deposit was thermally transformed at 650 °C for 1 hour to the metakaolin sand with relevant content of metakaolinite. Behaviour of cement composites having replacement of Portland cement with metakaolin sand including 0; 5; 10 and 15 wt.% of metakaolinite and water to solids ratio of 0.5 cured in water for 28 days and 90 days was studied by thermal analysis, X-ray diffraction analysis and mercury intrusion porosimetry analysis. The study concerned calciumsilica hydrate and calcium aluminate hydrate formation, portlandite dehydroxylation and calcite decarbonation. The influence of curing time and metakaolinite content were estimated. The replacement of Portland cement by metakaolin sand led to positive effect on relevant compressive strengths. The changes in microstructure involved especially reduction in portlandite content and pore structure refinement.