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In this article, the physico-mechanical properties and hydration processes of cement pastes containing three additives are introduced. Cement was replaced with pumice, trass, waste chalcedonite powder at 30% by mass and a combination of pumice or trass and waste chalcedonite powder in the amounts of 15% each. The main aim of this research was to assess the properties of two- or three-component binders to save cement in these binders. Rheological properties such as consistency, yield stress, viscosity and thixotropy were determined, in addition to porosity, 7-day and 28-day flexural and compressive strength and bulk density. Additionally, the heat evolution and degree of hydration of the tested pastes were compared. The use of all additives resulted in a reduction in the consistency of the tested pastes. The highest compressive strength measured after 28 days was observed for the cement paste with a 30% content of waste chalcedonite powder, which is related to it having the best pozzolanic activity of the materials used. The results of this research have confirmed that pumice, trass and waste chalcedonite powder can be used as components of blended Portland cements. [ABSTRACT FROM AUTHOR]

The article presents the influence of pumice, trass and chalcedonite powder on rheological properties of cement pastes. Cement was being replaced both of additions 10% or 20% by mass and combination of pumice or trass and chalcedonite powder in the amount 5% or 10% of each of them. The main purpose of the publication was to assess the effects of chalcedonite powder with selected mineral additions in terms of rheological properties and compare them with the results obtained for pastes modified with only one of the additions. In each case, the additive or combination of additives introduced into the paste reduced the flow, compared to the result of paste without additive(s). Rheological properties varied depending on type and amount of additive(s). [ABSTRACT FROM AUTHOR]

Cement production causes serious environmental problems and requires large amounts of energy. Studies have proven that the use of geopolymers can significantly reduce carbon dioxide emission and energy consumption arisen from cement production. Although there are many studies on the geopolymers, the number of studies dealing with geopolymers containing natural pozzolans other than metakaolin is very limited. In this study, the compressive strength and pore structure of geopolymers produced with trass (a type of natural pozzolan) were investigated. The mineralogical composition of trass, morphology of trass, and microstructure of geopolymer paste as well as the weight loss of the paste were determined using XRD, SEM, and TGA examinations, respectively. Moreover, the pore size distribution of the paste mixtures was obtained with Micro-CT analysis. The trass was used both in the natural form and after calcining at 550 °C for 6 h. The strength of geopolymer mortars produced with calcined trass, cured at 90 °C for 24 and 96 h, was found to be 86.7% and 81.6% higher than that of their counterparts containing natural trass. In addition, calcination of the trass resulted in 12.8–22.9% reduction in the porosity of geopolymer paste, compared to that of the paste containing natural trass. In XRD and TGA investigations, it was determined that the trass calcination performed at 550 °C did not make a significant change in the paste crystal structure and the weight loss-temperature graphs. SEM images proved that the reactivity of trass in geopolymerization increased with calcination and the matrix structure became denser and more homogeneous. [ABSTRACT FROM AUTHOR]

Pozzolans are used as additives in stabilizing clayey soils and as trass in cement production. Natural and unnatural pozzolans added to the ground in the stabilization process increase the bearing strength and strength of the soil, reduce the deformations that will occur as a result of stresses, settlements, swelling potential, liquefaction potential and permeability. It Pozzolans, which are used in cement and called trass, reduce the heat of hydration, increase the resistance of concrete against cracking, increase the waterproofing of the concrete and prevent the expansion caused by the alkaliaggregate reaction. For this reason, researching materials with natural pozzolanic properties and examining their pozzolanic properties are important for the country's economy. In this study, chemical and mineralogical studies were carried out to determine the pozzolanic properties of acidic and basic tuffs, and pozzolanic activity tests were carried out on the tuffs. As a result of the studies, although the acidic character tuffs belonging to the Kızılkaya Formation meet the conditions for use as an additive in the stabilization and cement production recommended in the standards, they cannot provide sufficient compressive strength in the pozzolanic activity test. This is due to the low CaO ratio. For this reason, it is necessary to increase the CaO ratio with lime additives in the use of acidic tuffs. It has been concluded that the chemical properties of the basic character tuffs of the Karabakır Formation are not in accordance with the limit values given in the standards, they will not create sufficient pozzolanic reaction and cannot be used as an additive material. [ABSTRACT FROM AUTHOR]

Landslides from Mount Bawakaraeng caldera in 2004 has caused high dam sedimentation at the lower reaches of the Jeneberang River. The availability of this large sedimentary material makes this material need to be considered as an alternative to new materials in the geotechnical field. However, the results of laboratory tests applied to sedimentary materials show that the mechanical characteristics of these materials are not sufficient for construction materials. Therefore, it is very important to conduct a study on how to improve the quality of dredged soil by adding Trass as stabilizing agent to improve the quality of the mechanical properties of the dredged soil. This study aims to analyze the mechanical characteristics of the dredged soil stabilized with Trass. The research was conducted by adding Trass with composition 3%; 6%; 9% and 12%; respectively to the dry weight of the dredged soil. The curing time was applied for a period of 3, 7 and 14 days to analyze the significant binding of Trass to the stabilized dredged soil. Laboratory tests was conducted to the density test and unconfined compression test. The results showed that there was an increase in the maximum dry density of the dredged soil between 1.41% - 3.56% due to the addition of trass, and a decrease in the optimum water content between 0.8% - 2.7%. In addition, there was an increase in the value of free compressive strength from 47.76% to 388.89% in the trass stabilized dredged soil during the curing period of 3, 7 and 14 days. The use of dredged soil and trass as stabilizing agent can be an alternative option in soil improvement efforts based on the utilization of waste material and local content potential.

Community involvement gained momentum after the establishment of the Terrestrial Restoration Action Society Seychelles (TRASS) in 2009 to address the concerns of forest rehabilitation on the fire ravaged lands on Praslin. This study assesses issues pertaining to community participation in forest rehabilitation and proposes strategies for improvement. Three shared-dialogue workshops and 180 household surveys conducted via a stratified random sampling was applied for the data collection. The collected data was analyzed using the Statistical Package for Social Sciences (SPSS) version 20. Results indicated that arson, accidents during agricultural practices, negligence during rubbish burning, cigarettes butts on trails and harvesting wild honey as well as the extended drought period during the dry season are the predominant causes of forest fires on Praslin. Membership in a community-based organization was the only determinant that influenced household participation in forest rehabilitation while other factors such as household size, age, gender and number of schooling years were not significant. Most benefits of forest rehabilitation were perceived in-kind rather than financial through the provisioning of ecosystem goods and services. Technical challenges manifesting in the form of inadequate knowledge and skills for tree planting on very steep slopes often covered with boulders and also exposed to soil erosion were of greater concern. This reinforces the point that forest rehabilitation needs to be adaptive to local conditions in order for it to prevail and it is a learning-by-doing process to develop the best practices that can ensure greater success. Lastly, some proposed strategies for improvement of rehabilitation programmes include awareness and education campaigns, additional manpower, the development of an efficient monitoring and evaluation system, conducting regular enrichment planting, and also greater involvement of community members at the planning stage but also during the execution of forest rehabilitation programmes. [ABSTRACT FROM AUTHOR]

The article presents a comparison of pozzolanic activity of R-Mud, which is a by-product of TiO2, with known and long-used additives to cement and concrete. Tests were carried out comparing the amount of heat of the hydration of cement and cement with added R-Mud, silica fume, fly ash and trass. The reaction susceptibility of these additives with calcium hydroxide has also been studied using the thermogravimetric method. Results from this method have shown that the reactivity of R-Mud is high and at a similar level to silica fume, while it is much higher than the reactivity of fly ash or natural trass. The high level of pozzolanic reactivity of R-Mud has been confirmed by both isothermal calorimetry and thermogravimetry. [ABSTRACT FROM AUTHOR]

The use of Cement Treated Recycling Base (CTRB) material in Indonesia, is a very well established practice in Indinesia. This mixture containing Reclaimed Asphalt Pavement (RAP) and Reclaimed Aggregate Materials (RAM) and stabilized with portland cement as pavement structural base layer. This technique has been applied in the field in some pavement major rehabilitationand reconstruction projects successfully. However, identical to other cementitious stabilized materials, this CTRB material is prone to cracks during service. For that reason, the use of cement as a stabilized material in CTRB has to be reviewed thoroughly before implementation in the field. The use of recyclable materials in pavement applications is not only environmentally friendly, but also can reduce the cost of materials in a particular project. In addition, a reduction in the use of cement in the CTRB material has a potential to reduce anticipated cracks that influence the physical characteristic of the mixtures. In this research project, the Indirect Tensile Strength (ITS) Test was conducted to review the influence of partial cement replacement with natural pozzolan (trass) to the mechanical properties of the CTRB to withstand tensile stress. A lower ITS value correlates to the shrinkage cracking tendency of the material. The results show that the increase in the percentage of cement replacement correlates well to the increase of the ITS values. Direct correlations exist for 15% and 30% cement replacement of the 4% to 6% CTRB cement content with 40% RAP-60% RAM and 60% RAP – 40% RAM combinations.

The influence of natural pozzolans on the controlling of the alkali-carbonate reaction (ACR) and the alkali-silica reaction (ASR) has not been studied comprehensively, regardless of the research studies conducted on utilizing natural pozzolans as supplementary cementitious materials. Nevertheless, the performance of natural pozzolans toward the ACR and ASR was investigated in recent studies. The primary purpose of this research is to evaluate the alkali-carbonate expansion of mortar specimens, which contain trass and fly ash in the short-term. For the short-term, the extent of expansion due to ACR was monitored for fourteen 7-day intervals. Based on the test result, fly ash and trass meaningfully reduced the expansion due to ACR in the short-term. Moreover, long-term test results for trass were presented as well. For the long-term, samples were kept at 80 °C in NaOH solution for curing in 56 days according to ASTM C1260 and 390 days according to ASTM C1293 . The observations by optical microscopy have been conducted on thin sections. [ABSTRACT FROM AUTHOR]

Roller compacted concrete pavement is a cost effective and beneficial pavement system which needs fewer material and less energy than other kinds of pavements. An important problem with the pavements is salt scaling that occurs due to a saline solution on cementitious surfaces. In order to reduce the negative effects of salt scaling, the influence of cement replacement by trass, a natural pozzolan, has been investigated. Mechanical and durability tests and salt scaling with air void analysis on hardened concrete were carried out to evaluate the effect of ordinary/trass selected mixes with/without air entraining agents. Results generally showed that although usage of air entraining agents reduced compressive and tensile strengths and increased water permeability and capillary absorption, it performed well against salt scaling in freeze-thaw cycles. The control samples with less w/c performed better than trass samples. In this research, spacing factor obtained about 0.07 mm and 0.1 mm for air-entrained and non air-entrained samples respectively. [ABSTRACT FROM AUTHOR]

Our study was directed to the analysis of the influence of various types of cements on the behaviour of concrete at high temperatures. In our experiments binary blended and ordinary Portland cements were involved: two Portland cements with different clinker compositions and Portland cements containing pozzolanic additives as replacement of clinkers. In the first part of the study we focused on the influence of cement types where cement paste specimens were investigated. Then, based on the results of cement paste specimens, concretes specimens were prepared with some selected types of cements. Most important observation of our experimental study was that the pozzolanic additives and their increased amount have a favourable effect on the heat resistance (fire resistance) properties of concrete. [ABSTRACT FROM AUTHOR]

This paper presents an investigation into the applicability of the dynamic approach of the Taguchi method to optimize alkali-activated mortar utilizing ground granulated blast-furnace slag and natural pozzolan from Germany called trass (hereafter, AAGT). The volume ratio of powder to alkaline activating solution ( V p / V aas ) was chosen as an input signal, while flow value and flexural and compressive strengths were considered as output values. The concentration of sodium hydroxide solution, mass ratio of sodium silicate to sodium hydroxide solution, ground granulated blast-furnace slag replacement ratio, mixing regime, mixing time, curing temperature, and cumulative temperature in heat curing were taken into account as design parameters. Based on the experiments conducted using an L 18 orthogonal array and the calculated results of signal to noise (SN) ratios and sensitivities, input–output relationships between V p / V aas and the output values were optimized. Long-term tests on the optimized specimens revealed the applicability of AAGT as a construction material; however, expansion cracks due to a gypsum formation were noticed after long-term immersion in a 10% sulfuric acid solution. [ABSTRACT FROM AUTHOR]

This paper describes the influence of the producing method (inter-grinding and separate grinding) and particle size distribution (PSD) on long term properties of blended cements. Portland cement (PC), limestone and a natural pozzolan (Trass) were used in binary and ternary cementitious blends. In this study, 14 types of cements including two types of Portland cement (PC), four types of Portland-limestone cement (PLC), four types of Portland-pozzolan cement (PPC), and four types of Portland-composite cement (PCC) were used. The results show that for achieving the same percentage of 45-μm residue in blended cements containing Trass, inter-grinding was less energy-demanding than separate grinding (shorter grinding time was required). Also, PPC and PCC provided better durability properties compared to PC and PLC properties. In addition, particle size distribution (PSD) and long term properties of blended cements with same percentage of 45-μm residue were not affected significantly by grinding method. Furthermore, the use of cements with high fineness seems not economically beneficial due to its low effect on long term properties. [ABSTRACT FROM AUTHOR]

In this study, the development of hydration of Portland cement and trass substituted cements containing super plasticizer was investigated. The effects of super plasticizer and trass substitution on the compressive strength, water demand, volume expansion and setting time was determined by the experiments the standard cement. Cement pastes were prepared with Portland cement and trass containing super plasticizer were performed using X-Ray diffraction, Fourier transform infrared spectroscopy and Simultaneous thermal analysis in order to determine their the phases developed during the hydration. Furthermore, microstructures by scanning electron microscope 28-days of hydration of cement pastes were determined and cement mortars were examined with strength tests. As a result, with the amount of trass, water needs and setting time have increased and volume expansion values remained between the standards. Also, the amount of Ca(OH)2 which is formed during the reaction was decreased. All these differences influenced the compressive strength of mortar samples. [ABSTRACT FROM AUTHOR]

Beberapa penelitian menunjukkan bahwa kuat tekan beton geopolimer sangat bergantung pada sifat material pozolan dan larutan aktivator yang digunakan pada campuran pastanya. Dalam paper ini disampaikan beberapa cara untuk memanfaatkan Lumpur Sidoarjo (Lusi) dan trass sebagai material substitusi fly ash di dalam campuran pasta untuk dianalisa sifat mekaniknya. Larutan NaOH yang dicampur dengan Na2SiO3 digunakan sebagai aktivator yang konsentrasinya divariasikan dari 8M sampai 14M. Perbandingan berat Na2SiO3 terhadap berat larutan NaOH juga bervariasi dari 0.5 sampai 2.5. Tes kuat tekan, tes belah dan tes porositas dilakukan untuk membandingkan setiap benda uji dari komposisi yang berbeda. Hasil studi menunjukkan bahwa kuat tekan beton dipengaruhi oleh konsentrasi NaOH, perbandingan Na2SiO3 terhadap larutan NaOH dan penyusun material dasar bindernya.

Bu çalışmada, Osmaniye-Delihalil Trasının çimento üretiminde kullanılabilirliği deneysel olarak ele alınmıştır. Osmaniye Delihalil Trası ile halen çimento üretiminde kullanılmakta olan bazı tras materyallerinin puzolanik aktiviteleri ve mineralojik özellikleri incelenmiştir. Portland çimentosu ile üretilen örneklerle, Portland çimentosuna değişik oranlarda tras katılarak üretilen örneklerin karşılaştırmaları yapılmıştır. Puzolanların aktiflikleri konusunda hala yeterli bilgi elde edilememiştir. Kimyasal ve fiziksel tepkime oldukça komplekstir. Puzolanik aktivitenin belirlenmesinde standartlarda yer alan her iki yöntem de kullanılmıştır. Tras-kireç karışımıile elde edilen numunelerin 7-28 günlük basınç dayanımları ASTM C618'e göre belirlenmiştir. Çalışmada % 10, % 20, % 30 ve % 40 tras kullanılarak üretilen örneklerin 28, 90 ve 180 günlük basınç dayanımları test edilmiştir. Yapılan karşılaştırmalar Delihalil Trasının çimento üretiminde kullanılmaya uygun olduğunu göstermiştir.

• Effects of trass on micro- and macro-level properties of cement paste were evaluated. • Blending cement with trass accelerated the C 3 S and C 3 A hydration. • Higher nonevaporable water contents were detected in blended sample compared to plain one. • The values of compressive strength activity index fluctuated between 106.7 and 124.6%. • Incorporating trass into cement can lead to a cleaner, cheaper, and less energy consumer construction. Due to some physical or chemical incompatibility issues between supplementary cementitious materials (SCMs) and cement, it is necessary to investigate the microscopic properties and macroscopic performance of cement composites containing such blends before their incorporation in construction. Hence, in this study, the hydration kinetics, degree of hydration, microstructural morphology, and pore structure of cement paste blended with trass, as well as its mechanical and transport properties, were profoundly evaluated. Moreover, the potential of trass for enhancing the sustainability of construction was also assessed. The physical properties of trass accelerated the C 3 S hydration, while its chemical composition led to the reduction of induction period, in addition to the acceleration of C 3 A hydration. Significant refinement of pore structure characteristics was found in blended sample after 90 days, when the threshold and critical pore diameters were reduced by respectively 27.7 % and 10.7 %, compared to those of the plain sample. This denser microstructure was reflected in superior electrical resistivity of the blended sample, which was 2.1 times of the plain one at 90 days. Furthermore, the inclusion of trass through refining the morphology of CH crystals in the microstructure, besides lowering the calcium hydroxide (CH) content by 12.1–63.3 % and increasing the nonevaporable water content by 2.1–8.0 %, led to 6.7–24.6 % higher compressive strengths in blended sample. Regarding the sustainability, at a similar 90-day compressive strength of 40 MPa, using trass results in an approximately 21.7 % less energy consumer, 20.3 % cleaner, and 15.8 % cheaper construction. Moreover, at equal levels of energy consumption or CO 2 emission, the blended sample has greater compressive strength and electrical resistivity than the plain one, which can be indicative of an extended service life. Accordingly, the utilization of trass is recommended since it has the potential to improve the sustainability both directly and indirectly. [ABSTRACT FROM AUTHOR]

In this study, instead of clay the effect of trass - which is used as a component for clinker production in the cement industry and has properties that are significant for agriculture - are researched. The clinkering properties of raw material compositions which are prepared according to the constant Lime Saturation Factor (LSF) degree were considered in relation to sintering at fixed temperature (1450 °C). Two different clinkers - namely trass 1 which is added to clinker 1 and trass 2 which is added to clinker 2 - were produced from the raw material compositions prepared at a constant LSF. The clinkering reaction was determined by the measurement of the free CaO (FCaO) value. According to the FCaO content and the amount of C3S test results, clinker 1 is preferable to clinker 2. Because of the C3S phases are 70,43 % and 42,72 % respectively. [ABSTRACT FROM AUTHOR]

This paper presents the results of an investigation on the compressive strength and weight loss of mortars containing three types of fillers as cement replacements; Limestone Filler (LF), Silica Fume (SF) and Trass (TR), subjected to elevated temperatures including 400°C, 600°C, 800°C and 1000°C. Results indicate that addition of TR to blended cements, compared to SF addition, leads to higher compressive strength and lower weight loss at elevated temperatures. In order to model the influence of the different parameters on the compressive strength and the weight loss of specimens, artificial neural networks (ANNs) were adopted. Different diagrams were plotted based on the predictions of the most accurate networks to study the effects of temperature, different fillers and cement content on the target properties. In addition to the impressive RIVISE and R2 values of the best networks, the data used as the input for the prediction plots were chosen within the range of the data introduced to the networks in the training phase. Therefore, the prediction plots could be considered reliable to perform the parametric study. [ABSTRACT FROM AUTHOR]

The active puzzolanic additives decrease the participation of clinker in the cement composition by decreasing the calcium hydrate products and improving the chemical, acidic and sulphate stability and mechanical properties. In this paper the properties of cement containing natural puzzolanic additives trass and zeolite are studied. The experimental part comprises two stages. In the first stage, a complete mineralogical characterization of the puzzolanic additives trass and zeolite was performed. In the second stage, the mechanical and physical properties of blended cements incorporating 0 to 30 %mass of fine puzzolanic additives (trass and zeolite) were determined. It is technologically and economically mass effective to use active puzzolanic additives in the cement production. [ABSTRACT FROM AUTHOR]

• The ettringite content in blended sample was quantified more than the plain one. • The pore size distribution shifted toward smaller pore diameters with the inclusion of trass. • The rise of UPV values was more pronounced during 3–28 days compared to 28–90 days. • The compressive strengths of samples correlated closely with their UPV values. • Strong linear correlations between acid-induced performance losses of samples were observed. This study comprehensively investigated the viability of binary blended trass-cement system for being used as a competitive alternative to cement or other traditional blended cements. Concerning the phase composition, the trass blended sample had not only higher gel contents, but also faster rates of gel formation, which were 1.5 and 1.2 times greater than those of the plain cement sample during the periods of 7–28 and 28–90 days, respectively. Regardless of the samples types, the increase rate of ultrasonic pulse velocity was highest within the interval of 3–7 days, then decreased during the period of 7–28 days, and almost approached zero at 28–90 days. This indicated the minor change of the samples microstructure at prolonged ages compared to those earlier ones. Due to the pozzolanic effect of trass, the pore size distribution significantly shifted toward smaller pore diameters and also became more uniform. Furthermore, the filler effect of trass reduced the total intruded volume and total porosity by 11.7% and 9.2%, respectively. In the case of mechanical performance, the blended sample showed higher compressive strengths, whereas slightly lower flexural ones in comparison to its plain counterpart, which could be owing to the changes in phase composition and microstructure induced by blending cement with trass. Lastly, it was revealed that the nitric acid attack, by progressively decalcifying the exposed samples, gradually transformed them into soft, cracked, and highly porous materials with new microstructural morphology and mineralogical composition. This way, substantial losses in their performance and integrity happened over immersion time. [ABSTRACT FROM AUTHOR]

Tuffs which are known as a trass are used as the additive material in the manufacture of the portland composed cement. Zeolitic tuffs (ZT) are porous, natural volcanic tuffs that contain zeolite mineral. The most important feature of zeolite mineral is the ability of changing ion. In the first stage of this study, zeolitic tuff sample was taken from rock mass and grinded alone in order to be used as additive material to portland cement of 42,5. The usability of zeolitic tuff sample as trass was investigated and chemical, physical, mechanical properties were also determined and were inspected in accordance with TS 25 standard. In subsequent stage of this study, ZT were used in the ratio % 0, % 10, % 20, % 30 and % 40 instead of Portland cement of 42,5. Tap water and sea water were used in two different ways as mixture water and mature water to produce cement paste and 40x40x160 mm mortar prisms: In the first group production tap water was used as mixture water, used tap water was used as mature water (TT), in the second group production was used sea water as mixture water, used tap water as a mature water (ST). The use of sea water as mixing water and the addition ratio of ZT into the cement effect on setting time, volume expansion of cement paste and compressive and flexural strength for 7, 28, 90 days were tested. After control samples, the highest compressive and flexural strength value of % 10 were obtained ZT additive cement mortars. [ABSTRACT FROM AUTHOR]

The specific rate of breakage (Si) in the widely accepted first-order expression of grinding rate is one of the important factors required to evaluate a grinding process, particularly for the initial grinding stage in various mill types.In this study, the effects of ball diameter and feed size on the specific rate of breakage were investigated on limestone, trass and clinker samples at batch grinding conditions based on a kinetic model. Eight different monosize fractions were prepared between 1.7 and 0.106 mm, using a √2 sieve series. The specific rates of breakage (Si) were determined from the size distributions at different grinding times, and the specific rates of breakage were compared for three different ball diameters (41, 25.4 and 9.5 mm).The results indicated that the variation of the specific rate of breakage with feed size of cement materials could be expressed. For the specific rate of breakage of each material, empirical equations were developed to express it as a function of feed size and ball diameter. [Copyright &y& Elsevier]

The influence of four naturally occurring mineral additives (zeolite, diatomite, trass and bentonite) on the hydration and properties of cement pastes and mortars was investigated. The materials change the phase composition, heat of hydration (determined by calorimetry) and mechanical properties of composites. After 28 days, the amount of Ca(OH)2 was reduced by up to 23% and up to 35% more C-S-H was formed, as proved by TG measurements. Differences were observed in the kinetics of heat release, especially for 25% of the addition. In the calorimetric curves, an additional exothermic effect is observed, related to the alteration in the hydration of C3A in cement. From the point of view of beneficial influence on mechanical properties of mortars, the additives could be ranked as follows: bentonite < diatomite, zeolite < trass after 2 days and bentonite < diatomite < trass < zeolite after 28 days of curing. The highest compressive strength (58.5 MPa) was observed for the sample with a 10% addition of zeolite. Zeolite, trass, bentonite and diatomite are all pozzolanic materials; however, their activity varies to an extent due to the differences in their specific surface area and the content of the amorphous phase, responsible for the pozzolanic reaction. [ABSTRACT FROM AUTHOR]