White Cement Mortars Research Articles

A Study of the Influence of Thermoactivated Natural Zeolite on the Hydration of White Cement Mortars.

One trend in the development of building materials is the partial or complete replacement of traditional materials that have a high carbon footprint with eco-friendly ecological raw materials and ingredients. In the present work, the influence of replacing cement with 10 wt% thermally activated natural zeolite on the structural and physical-mechanical characteristics of cured mortars based on white Portland cement and river sand was investigated. The phase compositions were determined by wavelength dispersive X-ray fluorescence (WD-XRF) analysis, X-ray powder diffraction (PXRD), diffuse reflectance infrared Fourier transformed spectroscopy (DRIFTS), and scanning electron microscopy (SEM), as well as thermogravimetric analysis simultaneously with differential scanning calorimetry (TG/DTG-DSC). The results show that the incorporation of zeolite increases the amount of pores accessible with mercury intrusion porosimetry by about 40%, but the measured strengths are also higher by over 13%. When these samples were aged in an aqueous environment from day 28 to day 120, the amount of pores decreased by about 10% and the compressive strength increased by nearly 15%, respectively. The microstructural analysis carried out proves that these results are due to hydration with a low content of crystal water and the realization of pozzolanic reactions that last over time. Replacing some of the white cement with thermally activated natural zeolite results in the formation of a greater variety of crystals, including new crystalline CSH and CSAH phases that allow better intergrowth and interlocking. The results of the investigations allow us to present a plausible reaction mechanism of pozzolanic reactions and of the formation of new crystal hydrate phases. This gives grounds to claim that the replacement of part of the cement with zeolite improves the corrosion resistance of the investigated building solutions against aggressive weathering.

Cost-effective microbial induced ZnO synthesis for building material: Antibacterial, photocatalytic and mechanical characteristics

Utilization of effective and economical nanoparticles/nanocomposite materials in civil engineering is still remaining a significant challenge in current research arena. In this study, microbial-induced precipitation was formulated for integration of white cement mortar to enhance efficiency and evaluate its potential applications in antibacterial and photocatalytic degradation of methylene blue. Hexagonal wurtzite structure of synthesized ZnO exhibited high crystallinity with significant contribution of hydration product after 28days analysis. Morphology of produced material showed less homogeneity with high densification and morphology altered from needles-like structure to tube with the integration of adsorbent ratio from ZnO-0 to 2.5, presented all the required chemical components in EDXS analysis. The water absorption rate in sample slurry of ZnO-2.5 exhibited significant reduction of 52.75 % compared to baseline water absorption rate of 12.71 % in commercial ZnO and contact angle was noted higher as 89.54°, which indicates hydrophilic character of material. The highest compressive strength of sample ZnO-2.5 was noted 508.89 kgf/cm2 in 28days of wet curing method, indicated the effective gel formation of calcium silicate in samples. Maximum methylene blue dye degradation recorded 79.95 % in case of using ZnO-2.5, which showed another influential character with excellent efficiency. In addition, prepared sample has shown almost complete bactericidal efficiency under simulated sunlight. Compared to commercial white cement mortar, biological white cement mortar can save NT$149,531 per cubic meter at industrial scale. Therefore, results indicate that microbial-induced zinc precipitation incorporated using hydrothermal preparation of biological white cement mortar improves the surface properties for applications and reduces its cost of study.

Characterizing connectivity and tortuosity of pore network based on LF-NMR method to assess the water permeability of white cement mortar

To better understand the macro transport properties and durability of cementitious materials, their microstructure should be characterised more accurately. This study investigated white cement mortars with different water-cement ratios, sand volume fractions, and curing ages. The water permeability was measured using a self-manufactured facility. The low-field nuclear magnetic resonance (LF-NMR) technique combined with the displacement method was used to test the pore size distributions (PSD) of total pores and connected regions. Two-dimensional mortar and pore-based matrix models were established to obtain the tortuosity of the transport path. The results show that the pore connectivity of the mortar ranges from 32 % to 52 %, and the tortuosity ranges from 1.428 to 1.542. The pore connectivity was spatially sensitive, and small pores were densely connected, linking large pores to form a pore network. Although capillary pores dominate the permeability, the role of gel pores cannot be ignored. Considering gel pores can improve the accuracy of the predicted water permeability by 80 %. The relative error of the modified model is [-23.76 %, 37.19 %], which shows a significant improvement.

Gamma Attenuation Features of White Cement Mortars Reinforced by Micro/Nano Bi2O3 Particles.

This study aims to explore the radiation protection properties of white mortars based on white cement as a binder and Bi2O3 micro and nanoparticles in proportions of 15 and 30% by weight as replacement sand. The average particle size of micro- and nano-Bi2O3 was measured using a transmission electron microscope (TEM). The cross-sectional morphology and distribution of Bi2O3 within the samples can be obtained by scanning electron microscopy (SEM), showing that nanoscale Bi2O3 particles have a more homogeneous distribution within the samples than microscale Bi2O3 particles. The shielding parameters of the proposed mortars were measured using the HPGe detector at various γ-ray energies emitted by standard radioactive point sources 241Am, 133Ba, 60Co, 137Cs, and 152Eu. The experimental values of the prepared mortars' mass attenuation coefficients (MAC) match well with those determined theoretically from the XCOM database. Other shielding parameters, including half value layer (HVL), tenth value layer (TVL), mean free path (MFP), effective electron density (Neff), effective atomic number (Zeff), equivalent atomic number (Zeq), and exposure buildup factor (EBF), were also determined at different photon energies to provide more shielding information about the penetration of gamma radiation into the selected mortars. The obtained results indicated that the sample containing 30% by weight of nano Bi2O3 has the largest attenuation coefficient value. Furthermore, the results show that the sample with a high concentration of Bi2O3 has the highest equivalent atomic numbers and the lowest HVL, TVL, MFP, and EBF values. Finally, it can be concluded that Bi2O3 nanoparticles have higher efficiency and protection compared to microparticles, especially at lower gamma-ray energies.

Effects of pure carbonation on pore structure and water permeability of white cement mortars

The effects of carbonation on cement-based materials have drawn much attention because of its profound influences on durability performance of concrete structures. Most accelerated carbonation in lab is conducted at RH 50%–70%, which also dries out cement-based materials. The introduced drying action changes pore structure significantly, making the effects of carbonation obscure. To clarify the effects of pure carbonation, water permeability and related micro-structural characteristics are measured on mature mortars, which have been carbonated at water-saturated state. It is found that after carbonation, the porosity of mortars decreases slightly, with finer overall pore structure and lower characteristic pore size. The water permeability also decreases by roughly 40% on average. Based on the pore size distribution curves obtained through the low-field proton nuclear magnetic resonance technique, water permeability is predicted by the Katz-Thompson and Kozeny-Carman theories with satisfactory accuracy. The decrease of water permeability after carbonation agrees well with the reduced characteristic pore length, which quantitatively verifies the observed refinement of nanoscale pore structure due to pure carbonation.

Dispersion of Multi-Walled Carbon Nanotubes into White Cement Mortars: The Effect of Concentration and Surfactants.

Multi-wall carbon nanotubes (MWCNTs) exhibit exceptional mechanical and electrical properties and can be used to improve the mechanical and piezoelectric properties of cement-based materials. In the present study, the effect of different MWCNT concentrations as well as different types of surfactants and a superplasticizer were examined to reinforce, at the nanoscale, a white cement mortar typically used for the restoration of monuments of cultural heritage. It was shown that sodium dodecylbenzenesulfonate (SDBS) and Triton X-100 surfactants slightly decreased the white cement mortars’ electrical resistivity (by an average of 10%), however, the mechanical properties were essentially decreased by an average of 60%. The most suitable dispersion agent for the MWCNTs proved to be the superplasticizer Ceresit CC198, and its optimal concentration was investigated for different MWCNT concentrations. Carboxylation of the MWCNT surface with nitric acid did not improve the mechanical performance of the white cement nanocomposites. The parametric experimental study showed that the optimum combination of 0.8 wt% of cement superplasticizer and 0.2 wt% of cement MWCNTs resulted in a 60% decrease in the electrical resistivity; additionally, the flexural and compressive strengths were both increased by approximately 25% and 10%, respectively.

The space image research base on the construction method of surface texture of the cement tiles

This study proposes a construction method that can produce cement tiles with cracked textures to achieve a richer performance through the surface texture of cement materials. During production tests, a step-by-step experimental method was used to determine the control variables that imitate natural cracks. The investigation showed that simulations of stone cracks, patched earth cracks, and cracked ice were the natural textures most preferred by the public; therefore, the study to make samples by color, surface layer thickness, drying time, and pressure level method as the control variables. A total of 12 samples were manufactured, and then applied to the display scene in a simulated space. The experimental results show that, for interviewees with design backgrounds, their preference scores improve when the space image shows “fashionable” and “calm” attributes. In contrast, for interviewees without design backgrounds, their preference scores improve when the space image shows “simple,” “non-oppressive,” and “hard” attributes. Using the quantification method of the first type, the results show the sample most preferred by the interviewees was the sample manufactured with the following method: pouring 30 g white cement mortar into the mold, letting it dry for an hour, and then filling the mold with gray-black cement mortar and pressuring it with the gentle slope of the pressure level setting. The preference of interviewees without design backgrounds or familiarity with the manufacturing process of cement tiles with cracked textures is affected by the color of cement tiles, and the preference of interviewees with design backgrounds and familiarity with the manufacturing process of cement tiles with cracked textures is affected by the pressure application method. It is hoped that the results of this study can provide a reference for the design and manufacturing process of cement mortar products, and further help the development of modularized cement mortar building materials.

IMPROVING THE VOLUMETRIC STABILITY OF WHITE CEMENT BY USING SOME ADDITIVES

Abstract: This study looked at the effects of three types of additives: limestone powder, Arabian gum AG, and polyvinyl alcohol (PVA), on White Cement Mortar's Physical and Mechanical Properties the mixing ratio for dry shrinkage was 1:2. (Cement: sand) while for other tests, it was 1:2.75 (cement: sand). The limestone powder proportions are (5%, 10%, and 15%) by weight of white cement, while the AG ratios are (0.2, 0.5, and 0.8) % by weight of white cement, the polyvinyl alcohol ratios are (2%, 4%, and 6%). This study was focused at the compressive and flexural strength of the modified mortar, as well as water absorption and drying shrinkage. According to the findings, utilizing of limestone powder as additive in white cement mortar is not advised. Since it had the negative affect on dry shrinkage of the mortar. Furthermore, polymer additives such as AG and PVA significantly increase the reduction of ability of forming crack in white cement mortar. Furthermore, the optimal additive percentages of AG and PVA are 0.5 percent and 6%, respectively.

Improvement of thermal efficiency in cement mortars by using synthetic feldspars

The use of white cements as a building material is widely employed due to its high whiteness and reflectance. However, building materials should adopt better thermal insulation characteristics to contribute for a significant urban heat-islands mitigation. In this work, synthetic feldspar has been evaluated as partial and total replacement of sand in white cement mortars. Thermal, mechanical, and optical properties of these new mortars are characterized by thermal conductivity, compression resistance test and reflectance-colorimetry, respectively. The replacement of sand by synthetic feldspar allows to obtain white mortars having ≈18% improvement in solar reflectance. Experiment under solar irradiance of mortars having synthetic feldspars reduce the surface heating of the mortar in 25% and the heating transmission to the rear of the mortar in >55%. Moreover, the high crystallinity of the synthetic feldspar reduces the mortar expansion due alkali-silica reactions (ASR). Improvement in reflectance and thermal conductivity resistance of white cement mortar having synthetic feldspar opens a wide range of building material applications.

Influence of sulphate ions on the crystal chemistry of white cement mortars with a high content of marble filler powder

Objects of this research are white cement mortars, characterized by both of high content of addition of marble powder and reduced water-cement ratio. The hardened cement mortars, formed after 28-and 120-day curing under standard conditions, are studied. The newly formed phases, containing [SO4]2-, [CO3]2-, [OH]-, etc., are identified using X-ray powder diffraction, infrared spectroscopy and thermal analysis (coupled with analysis of the outgoing gas mixture by mass spectrometry). Based on of the formed calcium silicate hydrates, calcium aluminate hydrates, the influence of sulphate ions is analysed and the mechanism of the thermal decomposition reaction at high temperatures in an oxidizing gas environment is studied. This allows us to establish that the hydration of Portland cement depends on the addition of marble powder (technically calcium carbonate CaCO3), as well as mono- and hemicarboaluminates are formed instead of monosulphoaluminates.

The effect of chemical aging on water permeability of white cement mortars in the context of sol–gel science

In the sol–gel science, the influence of chemical aging on the fundamental water permeability remains open regarding to the durability performance of cement-based material. To reveal the pure effect of chemical aging, the water permeability and related micro-structural characteristics are measured on water-saturated mature mortars, whose aging is accelerated through heat treatment under water. It is found that, the chemical aging increases the volumetric porosity and coarsens the pore structure to a notable extent, which enlarge water permeability by 2.6–4.9 times. Based on the pore structure obtained through the low-field proton NMR technique, the water permeability is predicted by the Katz–Thompson theory with satisfactory accuracy, quantitatively confirming the direct effects of chemical aging on water permeability. Physically, because of the polymerization and rearrangement of C–S–H gel, cement mortars undergo substantial changes with enlarging radii for both interlayer and gel pores, slightly decreasing interlayer space but remarkably enlarging gel pore space.

Photocatalytic Performance of White Cement Mortars Exposed in Urban Atmosphere

The objective of this study was evaluation of the photocatalytic performance of the addition of n-TiO2 in white cement mortars in terms of the light reflection (evaluated by CIE L*a*b* scale) and reflectance of the mortar surfaces exposed to solar radiation in an urban environment. Are produced specimens of 1.2m × 1.2m with n-TiO2 additions of 1%, 5%, and 10% concerning to the total dry powder mass.The performances of the specimens were then compared with two sets without n-TiO2,painted and unpainted, and these were used as references. To conduct an in-situ experiment, the mortars were mixed and applied by a mason. After 41 months of exposure and washing of the specimens, the painted mortars and the mortars with the addition of different n-TiO2 contents exhibited a statistically equivalent reflectance under exposure to solar radiation. All specimens exhibited color differences resulting from: (i)the accumulation of dirt on the surface; (ii) an increase in the surface roughness of the specimens; and (iii)a decrease in rainfall over the duration of exposure.

Enhancement of Some Mechanical Properties of White Cement Mortar by Adding Nanoparticles of Zirconium Oxide

This paper will study mortar compressive strength (fc) and flexural strength (fr) by cement replacement which is partial with the particles of Nano-Zr2O3. Zr2O3nanoparticles are used as well as using average diameter of 35 nm with four various contents by weight of cement (0.25%, 0.75%, 1.25% and 1.75%). The (fc) and (fr) tests were performed after the process of curing at the 28-days which is the standard age. The preparation of mortar of Nano-cement was done by using the ratio of cement-sand by weight which is 1:3 with the ratio of water-binder materials (w/b ratio) as 0.5. The results demonstrated that the (fc) and (fr) of the mortars of cement with Zr2O3were registered higher than cement mortar that is pure. The ultimate Nano-cement mortar strength was obtained at 1.25% of the replacement of cement. The improvement in (fc) and (fr) were 15.6 % and 18.4% in a respective way at 28 days.

Enhancement of Some Mechanical Properties of White Cement Mortar by Adding Nanoparticles of Zirconium Oxide

This paper will study mortar compressive strength (fc) and flexural strength (fr) by cement replacement which is partial with the particles of Nano-Zr2O3. Zr2O3nanoparticles are used as well as using average diameter of 35 nm with four various contents by weight of cement (0.25%, 0.75%, 1.25% and 1.75%). The (fc) and (fr) tests were performed after the process of curing at the 28-days which is the standard age. The preparation of mortar of Nano-cement was done by using the ratio of cement-sand by weight which is 1:3 with the ratio of water-binder materials (w/b ratio) as 0.5. The results demonstrated that the (fc) and (fr) of the mortars of cement with Zr2O3were registered higher than cement mortar that is pure. The ultimate Nano-cement mortar strength was obtained at 1.25% of the replacement of cement. The improvement in (fc) and (fr) were 15.6 % and 18.4% in a respective way at 28 days.

Compressive Strength of Cement Mortar with white cement and limestone

In this paper, the properties of cement mortar were studied after replacing part of the cement with other materials namely white cement, and limestone powder. The experimental test results were compared with normal cement mortar. Three kinds of mixtures were used. In the first type, cement was replaced with white cement only with different rates (5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, and 50%), the best ratio was determined, namely, the percentage that gave the highest value in the compression strength test, which is the compensatory ratio of 25%. In the second type of mixtures, a fraction of the cement was replaced with limestone powder only and with different rates (10%, 20%, 30%, 40%, and 50%). In the third type, cement was replaced by 25% white cement and different limestone powder ratio. Super-plasticizer (SP) was used with 1.5% rate. The compressive strength, absorption, the dry and wet density of all mixtures was measured. The results showed that the use of white cement instead of cement led to the production of cement mortar different in colors and better specifications, especially when the compensation rate was 25%. The results also showed that limestone powder gave a remarkable improvement in the properties of white cement mortar. Â

Pore-size resolved water vapor adsorption kinetics of white cement mortars as viewed from proton NMR relaxation

The dynamic pore structure of partially saturated cement-based material is rather essential to quantify its mass transport and many other properties. To clarify the influence of water removal and re-entry, the low-field nuclear magnetic resonance technique is employed to characterize the pore structure of two white cement mortars during isopropanol exchange and water vapor adsorption kinetics. It is found that, after isopropanol replacement the pore structures of mortars become remarkably coarsen due to the significant collapse of C-S-H interlayer pores, which are only partly reversible at water re-saturation. Consistently, water vapor adsorption is not a simple progressively filling process from finer to coarser pores, but accompanied by continuous expansion of C-S-H gel adsorbing water in priority. Furthermore, the irrecoverable contraction of C-S-H gel is the physical root of irreversible shrinkage. The smaller BET surface area using nitrogen than water is also attributed to the collapse of interlayer pores after drying.

Why permeability to water is anomalously lower than that to many other fluids for cement-based material?

The intrinsic permeability of porous medium is theoretically independent of percolating fluids. While concerning cementitious material, its water permeability is anomalously lower than that to many other fluids. To discover the responsible physical background, the permeability coefficients of two mature white cement mortars are measured using water, isopropanol and nitrogen gas. Their pore structures are also tested on specimens at various states through low-field NMR and MIP methods. It is found that the pore structures of water-saturated mortars are remarkably coarsen due to the contraction of C-S-H gel enforced by water removal through drying or isopropanol exchange. The coarsening of pore structure fundamentally increases the intrinsic permeability by 2–4 orders of magnitudes, which can be approximately quantified through the Katz-Thompson equation. The anomalous low water permeability is physically rooted in the swelling of C-S-H gel specific to water, which is intimately linked to the disjoining pressure of aqueous pore solution.

Structure of white cement mortars with high content of marble powder

In this study, three types of cementitious composites based on (i) white Portland cement and sand (cement-to-aggregate 1:3, and water-to-cement 0.50), (ii) white Portland cement and marble powder (cement-to-aggregate 1:2, and water-to-cement 0.60), and (iii) white Portland cement and marble powder with polycarboxylate-based admixture (HRWR) (cement-to-aggregate 1:2, and water-to-cement 0.40 + HRWR) were studied. Their states after 28 and 120 days of water curing were evaluated by measurement of physical–mechanical properties, such as density, compressive strength and porosity. Thermal analysis, X-ray diffraction analysis and scanning electron microscopy were used to identify the crystal phases and their morphology. The experimental data show that the white cement mortars with higher water content exhibit larder variety of newly formed phases, like hydration products of the C–S–H type. The structure of mortars with polycarboxylate-based admixture is so dense that there is no possibility of crystal hydrates development at late curing ages. The use of marble as filler leads to a partial inclusion of carbonate ions in the newly formed hydrated phases (carbo-aluminates).

Feasibility of using recycled glass in architectural cement mortars

► It is feasible to produce aesthetically-pleasing architectural mortar by using 100% recycled glass as decorative aggregate. ► It is possible to use self-compacting based approach to produce architectural mortar. ► Use of recycled glass has improved the fluidity, drying shrinkage , and resistance to acid attack. ► The flexural and compressive strength decreased with the increase in glass content. ► Metakaolin is found to be an effective suppressor to mitigate the ASR expansion of glass mortar. The feasibility of using 100% recycled glass (RG) as a fine aggregate replacement in architectural white cement mortar was investigated. All the cement mortar mixtures were proportioned with a fixed water to binder ratio of 0.40. The dosage of superplasticizer was varied to produce highly workable recycled glass self-compacting white cement mortar (RG-SCWM) mixtures. Metakaolin (MK) was used in the RG-SCWM mixtures to suppress alkali-silica reaction (ASR). The test results revealed that increased in the recycled glass (RG) content improved the performance of workability and drying shrinkage. However, there was a gradual reduction in flexural and compressive strengths as the content of RG increased. The incorporation of MK effectively mitigated the ASR expansion and also increasing the resistance towards acid attack. Overall results have proved that it is feasible to produce aesthetically-pleasing architectural cement mortar by using 100% recycled glass as the fine aggregate.

How sulfates and increased temperature affect delayed ettringite formation (DEF) in white cement mortars

In this study,white cement CEM I and white limestone cement CEM II-LL A and Β with 15%, 25% and 35% limestone substitution were studied. The way delayed ettringite is forming due to exposure to increased temperature (50 °C) and external sulfate attack was examined in mortar samples which were immersed for 90 days in three different solutions: (a) saturated solution Ca(OH) 2 at 50 °C, (b) saturated solution of Ca(OH) 2 at 20 °C and (c) 5% w/w Na 2SO 4 solution at 50 °C. During this period mortar samples were visually observed regularly while their expansion was estimated on a weekly basis by measuring the change of length with a micrometer. At the end of the 90-days period the compressive strength of the mortars was determined and the deterioration products were identified through means of X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and thermogravimetric analysis (DTG). The results of this study show that DEF occurred in two forms. Samples cured at increased temperature contained DEF type I, which caused mediocre expansion and damage. Samples cured at increased temperature in the presence of sulfates produced DEF type II, which caused significant damage on the surface and exhibited high expansion.