Mechanical Performance Of Mortars Research Articles

Hydrothermal and mechanical performance of mortars containing waste brick powder

It is widely recognised that green building, environmental sustainability, and technical performance have recently become requirements in the field of civil engineering. For this reason, the new trend in research is to focus on the recycling and recovery of materials, even if some of them such as industrial waste are still underexplored. In this perspective, the main objective of this work is to study the influence of brick powder on the thermophysical and mechanical properties of mortars containing this type of waste, in different environments, and within the temperature range between ambient temperature and 50 °C. To this end, a number of mortar mixtures, in which cement was replaced by brick powder in different proportions, were studied and characterised according to technical standards in order to define the optimal substitution percentage. Three batches of samples were examined at different ages, i.e., 3, 7, 28, and 90 days. The samples of the first batch were kept in water at a temperature of 20 ± 2 °C with a relative humidity RH = 100 %, while those of the second batch were immersed and stored in water at 50 °C in order to simulate a hot and humid climate. As for the samples of the third batch, they were kept in a dry oven at 50 °C in order to investigate the effect of the hot and dry climate. The results obtained revealed that the partial replacement of cement by brick powder makes it possible to improve the thermal insulation characteristics but reduce the mechanical strength of the mortar. In addition, it was shown that in a hot and dry environment, the mechanical characteristics of the different mortars decrease as the rate of weight substitution of cement by brick powder rises. However, in a hot and humid environment, a reverse trend is observed. The findings also suggested that the optimal recommended rate of substitution of cement by brick powder is 20 %.

Mechanical Performance of Mortars with Partial Replacement of Cement by Aluminum Dross: Inactivation and Particle Size

Although the use of primary aluminum dross as cement replacement has shown promising results in mortars and concretes, there is a knowledge gap between the effect of the secondary dross inactivation process and particle sizes on the mechanical properties and consistency. So, by using X-ray diffraction, laser granulometry, and scanning electron microscopy, this article describes first the inactivation process applied to a secondary aluminum dross. Second, this manuscript presents the fresh and hardened properties of mortar mixes containing 5, 10, and 20% inactivated secondary aluminum dross with three different particle sizes (i.e., fine, intermediate, and coarse). Mortar flow test results indicate that compressive and flexural strengths of mixes containing up to 20% fine and intermediate aluminum dross as cement replacement were satisfactory, respectively. These results have the potential to reduce the environmental and health impacts caused by cement production and secondary aluminum dross disposal, respectively. Moreover, the durability aspects of the mortar mixes, as well as the effectivity of the investigated inactivation process, are identified as future research topics.

Comprehensive Evaluation of the Performance and Benefits of SSA-GGBS Geopolymer Mortar.

The activity of sewage sludge ash (SSA) is not high; ground granulated blast slag (GGBS) has a high calcium oxide content that can accelerate polymerization rates and exhibit better mechanical performance. In order to improve the engineering application of SSA-GGBS geopolymer, it is necessary to conduct a comprehensive evaluation of its performance and benefits. In this study, the fresh properties, mechanical performance and benefits of geopolymer mortar with different SSA/GGBS, modulus and Na2O contents were studied. Taking the economic and environmental benefits, working performance and mechanical performance of mortar as evaluation indexes, the entropy weight TOPSIS (Technique for Order Performance by Similarity to Ideal Solution) comprehensive evaluation method is used to evaluate the geopolymer mortar with different proportions. The results show that as SSA/GGBS increases, the workability of mortar decreases, the setting time first increases and then decreases, and the compressive strength and flexural strength decrease. By appropriately increasing the modulus, the workability of the mortar decreases and more silicates are introduced, resulting in increased strength in the later stage. By appropriately increasing the Na2O content, the volcanic ash activity of SSA and GGBS is better stimulated, the polymerization reaction is accelerated, and the early strength increases. The highest Ic (integrated cost index, Ctfc28) of geopolymer mortar is 33.95 CNY/m3/MPa, and the lowest is 16.21 CNY/m3/MPa, which is at least 41.57% higher than that of ordinary Portland cement (OPC). The minimum Ie (embodied CO2 index, Ecfc28) is 6.24 kg/m3/MPa, rising up to 14.15 kg/m3/MPa, which is at least 21.39% lower than that of OPC. The optimal mix ratio is a water-cement ratio of 0.4, a cement-sand ratio of 1.0, SSA/GGBS of 2/8, a modulus content of 1.4, and an Na2O content of 10%.

Activated sugarcane bagasse ash as efficient admixture in cement-based mortars: Mechanical and durability improvements

Biomass ashes can be used in cementitious materials as cement or sand substitution. Nevertheless, ashes resulted from the combustion of biomass in generation plants present drawbacks that can reduce their potential use if they are not previously treated. In this research, industrial sugarcane bagasse ash (SCBA) was mechanically activated by grinding and its effects evaluated when used as mineral admixture in cementitious materials. Four different substitution rates (0%, 10%, 20% and 30%) where used to investigate the influence of the amount of ashes replaced on the durability and mechanical performance of mortars and identify the optimal substitution rate. To get a thorough comprehension, results were also compared to mortars containing untreated ashes. The combination of a performance-based testing campaign (compressive and flexural strength, open porosity, apparent density, water capillary absorption, surface electrical resistivity, rapid chloride migration coefficient) and a set of analytical techniques (XRD, FT-IR, SEM and TGA-DTA) enabled to characterise the mechanical and durability properties of mortars and identify the mechanisms behind the results. The research concluded that, at 28 days, the incorporation of ground SCBA enhances the compressive strength of mortars up to 62%, decreases the porosity of samples by 35%, highly improves the resistance to the diffusion of chlorides by 10 times and improve the interfacial transition zone by narrowing and closing the gap between aggregates and pastes.

Mechanical Performance of Mortar and Concrete Using Borneo Wood Sawdust as Replacement of Fine Aggregate

This study aims to analyze the utilization of wood sawdust from Borneo Island as a replacement for fine aggregate. For that purpose, two types of sawdust will be used, which are sawdust from ulin wood (Eusideroxylon Zwageri) and meranti wood (Shorea spp.). Subsequently, to test the effectiveness of replacing fine aggregate with sawdust, the compressive strength tests were carried out for mortar and concrete samples. Furthermore, the fine aggregate replacement ratio in all samples was set to 2.5% and 5% for both types of sawdust. Moreover, samples were also made by adding 0.5 kg/m3 and 1 kg/m3 of ulin and meranti sawdust to the concrete mixture. The compressive strength results of mortar samples show that sawdust from ulin wood has a better effect compared to meranti wood. In addition, the combination of sawdust from ulin and meranti gave a better effect in increasing the strength of the mortar samples. The same pattern could also be observed in the concrete samples, where ulin wood sawdust provides a good strength-enhancing effect, especially when used as an addition to the fine aggregate. Therefore, it is highly recommended to use sawdust, especially from ulin wood, as a material for making green concrete.

Effects of a Real Exposure Class XC4 Mediterranean Climate Environment in the Behavior of Mortars Made Using Ternary Binders with Addition of Slag, Fly Ash and Limestone.

For improving the contribution of the cement industry to mitigate global warming, many strategies have been put into practice, such as the use of eco-friendly cements with the incorporation of additions substituting clinker. Nevertheless, the use of ternary binders for the production of commercial cements is still reduced, particularly in Spain. The purpose of this research is to characterize the long-term influence produced by the exposure to a real in situ inland Mediterranean climate condition in the pore network, parameters related to durability and mechanical performance of mortars made with ternary binders, which incorporated limestone, fly ash, and ground granulated blast-furnace slag, in comparison with mortars without additions and binary blended mortars. The site verified the specifications of exposure class XC4 of Eurocode 2. The ternary and binary binders accomplished the prescriptions of cement type CEM II/B. The pore network was studied with mercury intrusion porosimetry and electrical resistivity. Water absorption, diffusion coefficient, carbonation depth, ultrasonic pulse velocity, compressive and flexural strengths have been determined. The exposure to the environment produced after 250 days an increase in porosity, a loss of pore refinement, a rise of the carbonation depths, and a reduction in the mechanical strengths, highlighting the better overall performance of ternary mortar with both fly ash and slag.

Microstructure, Durability and Mechanical Properties of Mortars Prepared Using Ternary Binders with Addition of Slag, Fly Ash and Limestone

In order to improve the contribution to sustainability of cement production, several strategies have been developed, such as the incorporation of additions as clinker replacement. Regarding the production of commercial cements with additions, those made with binary binders are mostly produced. However, the use of ternary binders for manufacturing commercial cements is still very low, at least in Spain, and they could also be an adequate solution for producing eco-friendly cements. The objective of this research is to study the effects in the long term produced by ternary binders which combine the additions of blast furnace slag, fly ash and limestone in the microstructure, durability and mechanical performance of mortars, compared to mortars without additions and mortars made with binary binders. The ternary and binary binders accomplished the prescriptions for a cement type CEM II/B. The microstructure was characterized using mercury intrusion porosimetry, electrical resistivity and differential thermal analysis. Absorption after immersion, diffusion coefficient, mechanical strengths and ultrasonic pulse velocity were studied. The best performance was noted for ternary binder with both slag and fly ash, probably produced by the synergetic effects of slag hydration and fly ash pozzolanic reactions. These effects were more noticeable regarding the compressive strength.

The effects of high temperature and cooling regimes on the mechanical and durability properties of basalt fiber reinforced mortars with silica fume

This study implemented an experimental program to evaluate performance of high strength mortars with basalt fibers (BF) and silica fume (SF) at ambient and elevated temperatures. The effects of ambient and elevated temperatures and curing regimes on the physical, mechanical and durability properties of BF reinforced SF blended mortars were investigated in this study. The effects of two types of cooling namely air cooling and water cooling after exposed elevated temperatures on the durability and mechanical performance of mortars was also assessed. In this study, all mortar mixtures were modified by replacing ordinary Portland cement (OPC) by 10% SF by weight and mortar mixtures were fabricated by the inclusion of BF at the rates of 0, 0.2, 0.4 and 0.6% by volume. The specimens were examined for compressive strength, flexural strength, porosity, ultrasonic pulse velocity, water absorption and unit weight and Scanning Electron Microscopy (SEM) analysis at ambient and elevated temperatures under air and water cooling after exposure to elevated temperatures. The effects of using different BF contents on the flowability of mortar mixtures were assessed by slump test. The results indicated that the flowability of mortar mixtures reduces with increasing fiber content. Test results also showed that with the inclusion of BF, the compressive strength enhances significantly and basalt fibers dosages of 0.2, 0.4, and 0.6% increased the compressive strength of mortar specimens by 19.46%, 21.77% and 31.40%, respectively, compared with that of reference mixture M1 at ambient temperature.

Mechanical and physical performance of natural hydraulic lime mortars

Natural hydraulic lime (NHL) is a material which has received increased interest in the past decade as a binder for the production of mortars. The renewed interest of researchers and builders in natural hydraulic lime is attributed to its enhanced compatibility with many traditional materials, as well as the fact that it is an environmentally friendly material, especially in relation to modern cement. In the present study, two different types of natural hydraulic lime mortars are studied, using NHL2 and NHL3.5 as binder (in accordance to the new classification EN 459-1:2010) and the same river sand, while the influence of different binder to aggregate ratios on mortar characteristics is also investigated. Fresh mortar characteristics are examined immediately after mixing, while hardened mortar characteristics are evaluated at different mortar ages. Specifically, the mechanical performance of the mortars is evaluated through flexural and compressive strength tests, as well as the dynamic modulus of elasticity, which is estimated through ultrasound pulse velocity measurements. Physical performance of the mortars is investigated through the examination of the pore network structure characteristics, via mercury intrusion porosimetry measurements, and through the examination of hygric characteristics, via water absorption tests. The binder to aggregate ratio seems to play an important role in the development of the mechanical and physical characteristics of the mortars, while it influences mortar properties differently according to the type of the binder.

Influence of treated bio-fibers on the mechanical and physical properties of cement mortars

Alfa plant (Stipatenacissima L.) and wheat straw fibers were investigated as reinforcement in cementitious matrix. The fibers were used separately in three states: raw, wet (by immersion in water) and alkali treated. A reference mortar without fibers and mortars with 1% and 1.5% by volume of the two different bio-fibers were used. The mechanical and physical properties of mortar specimens were studied as well as the morphological analysis was carried out after 28 days of curing. The results exhibit that both Alfa and Straw fibre addition changed the mechanical performance of mortars in comparison to the reference mortar. A higher porosity and water absorption were observed after the addition of raw and wetted fibers. The alkali treatment caused morphological changes that were proved more efficient. This treatment provided a good result in terms of mechanical and physical properties. Furthermore, the addition of 1% by volume of alkali treated fibers affords both mechanical and physical properties better than the control mortar. SEM micrographs confirmed the good fibers/matrix adhesion of the alkali treated fibers.

Experimental research on the effect of silicon powder on the performance of cement mortar

To study the effect of the mechanical properties of silicon powder on cement admixture, the experiment was carried out, to investigate the consistency of mortar fluidity, breaking strength and compression strength test of the cement mortar samples with different dosage of silicon powder. The experimental results show that when the content of silicon powder is 0-4%, the consistency and fluidity of mortar can be improved, and the working performance of cement mortar can be improved; when the content of silicon powder continues to increase to 12%, the working performance of mortar decreases, but it still has good performance; when the content of silicon powder is 0-8%, the mechanical performance of mortar can be improved, if the content is too large, the compression strength and bending strength of mortar will be reduced, but It still plays a positive role in the strength of mortar.

Hydration and strength development in blended cement with ultrafine granulated copper slag.

This study aims at evaluating the effect of ultrafine granulated copper slag (UGCS) on hydration development of blended cement and mechanical properties of mortars. The UGCS with the median particle size of 4.78 μm and BET surface area of 1.31 m2/g was used as a cement replacement to prepare blended cements. Hydration heat emission of blended cement and mechanical performance of mortars were investigated by using isothermal calorimetry and strength tests, respectively. X-ray diffraction (XRD), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM) were applied to the analysis of pozzolanic reaction and hydration products. The results illustrate that UGCS has influence on the hydration heat evolution of blended cement due to its filler effect and pozzolanic reaction. The cumulative hydration heat of blended cement is reduced by partial cement replacement with UGCS. The test mortar prepared by using blended cements with 30 wt. % UGCS shows a retardation of strength development with a low value at early ages (7 days) and a rapid growth at later ages (28 days). The 90-day compressive strength of test mortar is 45.0 MPa close to that of the control mortar (49.5 MPa). The obtained results from XRD and TGA analysis exhibit an increase in calcium hydroxide (CH) consumption and calcium silicate hydrates (C–S–H) formation in blended cement pastes with curing time. The cement replacement with UGCS induces changes in microstructure of blended cement paste and chemical composition of hydration products.

Mechanical strong and durable cement mortars reinforced by controlling the polymer phase size

The influence of polyvinyl alcohol phase size on the properties of cement mortars has been experimentally investigated. The compressive strength reduced sharply with the increase of polymer phase size. Based on Fourier transform infrared spectroscopy (FTIR) data, the existence of Al–O–H bonds indicates that there is a moderate crosslink between polyvinyl alcohol (PVA) and cement. Mechanical and durability-related properties were compared between PVA grain powder versus PVA solution combined with cementitious matrix. It was found that the mechanical performance of mortars with PVA solution was superior to those with PVA grain powder. Water absorption coefficient was improved with the incorporation of PVA. The water absorption coefficient of mortar with PVA grain powder was lower than that incorporating PVA solution. Finally, the introduction of PVA did not boost the chloride resistance of the material but provided significant enhancement to the freeze-thaw resistance compared to the control group.

Chemical, microstructural and mechanical properties of ceramic waste blended cementitious systems

There is an emerging need for a sustainable and cost-effective source of Supplementary Cementitious Material (SCM) to reduce clinker consumption, as well as an effective utilisation of the ceramic waste stream. This study explores the potential of two types of ceramic waste tiles as SCMs by examining the mineralogical properties and mechanical performance of mortar and paste samples prepared with 5%, 15% and 30%wt of the ceramics ground into powder form as cement replacement. Investigations were carried out over a 90-day curing period by using standard methods including the XRD, DTA/TGA and SEM analyses, as well as the compression test. The pozzolanic reactivity of both ceramics has been validated with the presence of the secondary hydration reaction. This study concludes that a mortar mix containing 15% White ceramic could achieve a compressive strength comparable to that of a standard Ordinary Portland Cement (OPC) mortar at 56 days after curing, and even exceeds the strength of the latter beyond this age.

Evaluation on the Surface Modification of Recycled Fine Aggregates in Aqueous H2SiF6 Solution

Recycled aggregates (RAs) production techniques are essential for the material circulation society because RAs from demolished concrete waste can sustainably be reused as a concrete material. However, RAs can bring about several performance decreases when they are used for recycled aggregate concrete (RAC) because of the low qualities (i.e., high water-absorption rate and low density) caused by the attached hydrated cement paste on the RA surface. Therefore, both the production of high-quality RAs and the surface modification of RAs are significantly important for the extension of RAC utilization. This paper focuses on the surface modification of RFA to reduce the water absorption rate and increase density. Hydrofluorosilicic acid (H2SiF6), which is one of the by-products in phosphoric acid manufacture, is used herein for the surface modification of the RFA. The physical properties and mechanical performance of mortar using RFA were evaluated after RFA modification. Consequently, the proposed method is effective in reducing water absorption rate and increasing density of RFA. The density of RFAs was slightly increased by 0.5–2.6% after modification. On the other hand, the water absorption rate decreased by 4–18% after modification. The compressive strengths of mortar at 28 days ages showed 18.1 MPa with modified RFA and 16.2 MPa with RFA.

The role of aggregate characteristics on the performance optimization of high hydraulicity restoration mortars

Performance characteristics of mortars are governed by the type of binder, type and grain size distribution of aggregates and their mix proportions. Aiming at parametric optimization of NHL restoration mortars, this study discusses the effect of physical and geometrical properties of aggregates on fresh and hardened mortars, tested after 28days of curing. Four different sands 0/2mm were studied and ten mixtures were prepared with natural hydraulic lime (NHL5). The effect of gradation, packing density and shape of aggregates was studied, versus the mechanical properties and porosity. The results highlight the crucial role of the morphological parameters of aggregates, especially of packing density, on the development of microstructure and the mechanical performance of mortars. The contribution of aggregates to tailoring and controlling the mechanical and microstructural properties of repair mortars is also demonstrated in this work. To this end, it was proved that the mechanical performance of mortars is controlled by the combination of both binder amount and packing density of the aggregates.

Impact of Air Entrainment on the Microstructure and Mechanical Performance of High Performance Mortar

High performance self-compacting mortar has the ability to push out air bubbles under its own weight. Consequently, the resistance against freeze-thaw cycles with or without deicing salts can decrease due to the total air content reduction. In order to assure the necessary expansion zones1,2 air entraining agents (AEA) are commonly used to increase the amount of stable air bubbles. Depending on the mixture, the workability and rheology decrease or increase by the entrained air bubbles3. This will depend on the ratio between the surface tension and the shear stress applied during the test. If the latter can overcome the first, the bubbles will deform and increase the fluidity of the mixture. Besides the influence on the durability and the fresh concrete, air entraining agents also alter the pore structure and the mechanical performance of the mortar. The effect of AEA on these properties is the subject of this paper. The pore structure is examined on two different levels. On the one hand, mercury intrusion porosimetry is used to investigate the capillary porosity, ranging from 10 nm to 10 μm. On the other hand air void analysis and fluorescence microscopy is performed to evaluate the larger air bubbles ranging from 0.1 mm to 1 mm4. Both techniques showed an overlap in their measuring range. Consequently it was possible to compare the techniques critically. Similar as in literature, mercury intrusion porosimetry underestimates the amount of larger air bubbles in mortar, due to its measuring principle5. Furthermore, the bubbles with a diameter of 80 μm increase significantly by the addition of AEA. This confirms the average air bubble size often used in literature to explain the influence of AEA on the workability and rheology3. The influence of air entraining agent on the mechanical performance was tested by the compressive and bending tensile strength. In conclusion, a good balance is necessary between the air content necessary for a proper freeze-thaw resistance without changing the mechanical performance drastically.

Rheological and mechanical properties of mortars prepared with natural and manufactured sands

The conventional assessment methods for fine aggregate used in Portland cement concrete are mostly based on round natural sand performance in spite of the increasing use of angular manufactured sands. Two natural and two manufactured sands were selected and tested at different water–cement ratios and fine aggregate-to-cement ratios for the same standard gradation to identify shape-related differences on the mechanical performance of mortars. Three tests were used in this study: flowability, stiffness and strength. Results showed that adequate flow and compressive strength were attained when the volume of paste exceeded the volume of voids in the loosely packed aggregate, i.e., just above the maximum void ratio e max of the fine aggregate. Given the dependence of e max on particle shape, mixture predesign can be facilitated by taking aggregate shape into consideration.