Compressive Strength Of Mortar Research Articles

Change of Mechanical Properties of Repair Mortars after Frost Resistance Rests.

The use of repair mortars for concrete structures repair with no or limited resistance to the impact caused by freeze and thaw cycles is often the primary repair failure cause. This is particularly important in Poland. Due to the geographical location of the country, there is a large temperature difference between summer and winter. The number of passes through the threshold temperature of 0 °C throughout the year in the winter season exceeds 100. The article presents a comparison of the frost resistance results of tests of repair mortars. The first method was performed according to the Polish Guidelines (without the use of de-icing salts) and the second method according to PN-EN 1504-3 (with the use of de-icing salts). The results obtained were inconsistent in many areas. In particular, significant differences in the results for the change in compressive strength and the change in bending strength were observed. In the case of the frost resistance testing without the use of de-icing salts, a decrease in compressive strength was usually accompanied by a decrease in bending strength. In the case of frost resistance tests with the use of de-icing salts, an increase in the bending strength of mortars was observed (even by a dozen or so percent) with a decrease in the compressive strength of mortars (even by several dozen percent).

Experimental Study on the Effect of Compound Activator on the Mechanical Properties of Steel Slag Cement Mortar

In this study, activator, metakaolin, and silica fume were used as a compound activator to improve the activity of steel slag powder. The influence of activator, steel slag powder, metakaolin, and silica fume on the resulting strength of steel slag cement mortar was investigated by orthogonal experiments. For four weight fractions of steel slag powder (10%, 20%, 30%, 40%), the experimental results indicate that the compressive strength of mortar can reach up to more than 85% of the control group while the flexural strength can reach up to more than 90% of the flexural strength of the control group. Through orthogonal analysis, it is determined that the activator is the primary factor influencing the mortar strength. According to the result of orthogonal analysis, the optimal dosages of activator, steel slag powder, metakaolin, and silica fume are suggested. The GM (0, N) prediction model of compressive strength and flexural strength was established, and the compressive strength and flexural strength of mortar with the optimal dosage combinations were predicted. The prediction results show that by using the optimal dosage combination, the mortar strength can reach the level of P·O·42.5 cement. Considering the different strength and cost requirements of cementitious materials in practical engineering, the economic benefits of replacing cement with steel slag powder activated by compound activator in various proportions and equal amounts were presented. The results show that the method proposed in this study can reduce the cost of cementitious materials.

Experimental characterization of quaternary blended mortar exposed to marine environment using mechanical strength, corrosion resistance and chemical composition

The durability of concrete is significantly influenced by its binder composition, especially in the presence of aggressive chemical environment. This paper represents a study on the strength, durability, and corrosion resistance of quaternary blended mortar made with Portland pozzolana cement (PPC), ground granulated blast furnace slag (GGBS) and rice husk ash (RHA) exposed to marine environment. Binary blended concrete mix using GGBS and RHA as partial replacement for cement is already well established. Previous research reports several shortcomings in using binary blended and ternary mix including low initial strength and increasing shrinkage strains with increasing percentages of GGBS, silica fume and RHA as partial substitutes for cement. Hence, this study is focused on overcoming the limitations of binary and ternary blended mixes by implementing a quaternary blended mix using GGBS and RHA to partially replace cement. This quaternary blended cementitious system is optimized based on its mortar compressive strength, determined by varying the percentages of GGBS and RHA as substitute for cement. These optimized quaternary mortar specimens are moist-cured for 28 days and then exposed to an artificially prepared marine environment for 180 days. The optimized quaternary blended mortar specimens show improved mechanical strengths, both compressive and flexural. These specimens also exhibit enhanced resistance to chloride penetration, corrosion, and water absorption compared to the control mix after 28 days of water curing. A quaternary blended mortar mix prepared with 70% PPC, 20% GGBS, and 10% RHA exhibits the maximum mechanical strength, resistance to chloride penetration, and corrosion, mass loss and water absorption upon exposure to marine environment up to a period of 180 days. Mineralogical analyses using X-ray diffraction (XRD), chemical bond analyses using Fourier Transform Infra-Red (FTIR) spectroscopy, and microanalyses using scanning electron microscopy (SEM) in conjunction with energy dispersive X-ray spectroscopy (EDS) are implemented to determine the effects of marine environment exposure on the different mixes. The findings are then used to corroborate the observations from the specimen scale mechanical and chemical characterizations.

Experimental and Modelling of Alkali-Activated Mortar Compressive Strength Using Hybrid Support Vector Regression and Genetic Algorithm.

This paper presents the outcome of work conducted to develop models for the prediction of compressive strength (CS) of alkali-activated limestone powder and natural pozzolan mortar (AALNM) using hybrid genetic algorithm (GA) and support vector regression (SVR) algorithm, for the first time. The developed hybrid GA-SVR-CS1, GA-SVR-CS3, and GA-SVR-CS14 models are capable of estimating the one-day, three-day, and 14-day compressive strength, respectively, of AALNM up to 96.64%, 90.84%, and 93.40% degree of accuracy as measured on the basis of correlation coefficient between the measured and estimated values for a set of data that is excluded from training and testing phase of the model development. The developed hybrid GA-SVR-CS28E model estimates the 28-days compressive strength of AALNM using the 14-days strength, it performs better than hybrid GA-SVR-CS28C model, hybrid GA-SVR-CS28B model, hybrid GA-SVR-CS28A model, and hybrid GA-SVR-CS28D model that respectively estimates the 28-day compressive strength using three-day strength, one day-strength, all the descriptors and seven day-strength with performance improvement of 103.51%, 124.47%, 149.94%, and 262.08% on the basis of root mean square error. The outcome of this work will promote the use of environment-friendly concrete with excellent strength and provide effective as well as efficient ways of modeling the compressive strength of concrete.

Influence of liquid accelerators combined with mineral admixtures on early hydration of cement pastes

The main purpose of this paper was to investigate the influence of different liquid accelerators (AR, liquid accelerator based on sodium aluminate; AS, liquid accelerator based on aluminum sulfate; AF, liquid accelerator based on fluoroaluminate) and mineral admixtures (fly ash, slag and silica fume) on the setting time of cement pastes and compressive strength of mortar. In addition, the early hydration process of cement pastes with different mineral admixtures in the presence of AR, AS and AF was explored by isothermal calorimetry, and the crystals composition and micro morphology of hydration products were analyzed by XRD and SEM. The results indicated that in the presence of 7.0% AF, the initial and final setting time of cement pastes with 10% and 5% silica fume are 0.67 min and 1.47 min, respectively. In the presence of 4.0% AR, the mortar with 10% silica fume reaches the highest value of 16.8 MPa. In addition, when the dosages of AF and silica fume are 7.0% and 10%, the first exothermic peak value of paste is 87.79 mW/g. Furthermore, in the presence of liquid accelerators, different mineral admixtures also have great influence on the morphology and crystals composition of hydration products.

Experimental Study on High-Strength Concrete, Ultrahigh-Strength Concrete and Corresponding Mortar Under Triaxial Compression

Based on uniaxial and triaxial compression tests, the present study investigates the mechanical properties of high-strength concrete (HSC), ultrahigh-strength concrete (UHSC) and the corresponding mortars with the same mix proportions of the matrixes of two types of concretes. The tests recorded the mechanical responses including peak stress, axial strain at peak point and failure modes of HSC, UHSC and mortars specimens. The test results show that the compressive strength and deformation capacity of concretes and mortars gradually grow higher with the increasing of confining pressure, and the enhancement of confining pressure on the compressive strength of mortar is significantly lower than that of concrete. For HSC and UHSC, the enhancement on compressive strength has a negative relationship with the uniaxial compressive strength and similar relationship is also found between the two types of mortars. Compared with the mortar, the increase in confining pressure can, to some extent, better enhance the deformation capacity of concrete. There are three failure modes of concretes and mortars under the confining pressure: vertical splitting failure, oblique shear failure and extrusion flow failure. Confining pressure has very little effects on the initial tangent modulus, the initial tangent modulus of the two types of concretes is larger than that of corresponding mortars, and the addition of coarse aggregate can improve the tangent modulus of HSC more significantly than UHSC. Failure surfaces for concretes and mortars under triaxial stress were identified by using the four-parameter failure criterion.

Effect of K2O content on properties of sugar cane bagasse ash-cement-based systems

The influence of potassium oxide contamination of sugar cane bagasse ash (SCBA) on the hydration of cement-based pastes and the compressive strength of mortars was investigated. Three SCBAs with different potassium oxide contents (2.7–12.6%) were used. The SCBA samples were initially characterised by their particle size distribution, BET specific surface area (SSA), pore volume, mineralogy and pozzolanic activity based on the Chapelle method. The hydration of cement-based pastes containing 20 wt% of SCBA was investigated using isothermal calorimetry and chemical shrinkage. The compressive strength of the mortars was evaluated at 3, 7, 28 and 90 days. The pozzolanic activity of SCBA was found to increase with decreasing potassium oxide content due to the higher silicon dioxide content and SSA of the SCBA dosed with a low potassium oxide content in comparison with other samples. The potassium oxide dosage had a limited influence on the paste hydration, except for a slight increase in the induction period observed by calorimetry. Cement replacement with SCBA with a high potassium oxide dosage led to maintenance of the compressive strength in relation to the reference up to 90 days. The mortars with low and medium potassium oxide contents showed good performance in terms of compressive strength, with significant increases compared with the reference after 90 days of curing.

Application of bagging ensemble model for predicting compressive strength of hollow concrete masonry prism

In the current research, a newly developed ensemble intelligent predictive model called Bagging Regression (BGR) is proposed to predict the compressive strength of a hollow concrete masonry prism ( f p ). A matrix of input combinations is constructed based on several predictive variables, including mortar compressive strength ( f m ), concrete block compressive strength ( f b ), and height to thickness ratio ( h/t ). Three modeling scenarios based on the different data divisions (i.e., 80–20%, 75–25%, and 70–30%) for training-testing phases are evaluated. The proposed model is validated against classical support vector regression (SVR) and decision tree regression (DTR) models using statistical indicators and graphical presentations. Results indicate the superiority of the BGR over the other models. In quantitative terms, BGR attains minimum root mean square error (RMSE = 1.51 MPa) using the data division scenario of 80–20% in the testing phase, while DTR and standalone SVR models offer RMSE = 2.55 and 2.33 MPa, respectively.

Effect of sugar on Compressive Strength, Drying Shrinkage and Carbonation of Mortar

Mortar is one of the most common construction materials, used in bind building blocks such as stones, bricks, and concrete masonry units. This paper presents the experimental investigation on the effect of sugar on setting time of cement and compressive strength, drying shrinkage, and carbonation of mortar using composite cement. Different percentages of sugar varying from 0 to 0.08 % by weight of cement was selected as retarder. It was found that the initial and final setting time of composite cement paste increased, with the increase of sugar dosage. The maximum initial and final setting time occurred when sugar content is 0.08 %, where it increased the initial time from 100 minutes to 550 minutes and increased final setting time from 135 minutes to 610 minutes. The compressive strength, drying shrinkage and carbonation specimens were tested at 7, 28, 56, 90, and 150 days. The compressive strength of mortar containing 0.06% sugar increased by 9.25 % at age 150 days compared to control specimens, while the drying shrinkage of mortar was less affected by sugar. The carbonation depth test shows that all specimens are almost the same, with a slight increase in specimens that contain sugar.

Study on the particle size distribution characteristics and cementitious activity of different fineness components in cement

In order to obtain the change law of the cementitious activity of the different fineness components in the Portland cement, the cement was classified by the air classifier and six components with different fineness were obtained. The particle size distributions of the six components were measured and their cementitious activities were evaluated. The results show that the cement powder obtained by classification basically conforms to the distribution model of Rosin-Rammler-Bennet equation. The fluidity of the mortar of different fineness components in cement does not change significantly with the change of fineness. The greater the fineness of each component is, the higher the early strength of their mortar test will be, but as the curing age increases, the strength increase is not obvious. The sample obtained by mixing three finer-grained components has the highest mortar compressive strength in the early age, and the strength increase in the later age is stable.

Impact of polycarboxylate superplasticizers (PCEs) with novel molecular structures on fluidity, rheological behavior and adsorption properties of cement mortar

Polyether macromonomers have shown diversified structures recently. In this work, a series of polycarboxylate superplasticizers (PCEs) were synthesized via copolymerization using a novel macromonomer, ethylene–glycol monovinyl polyethylene glycol (EPEG). The molecular structures were modified by varying the side chain length, carboxylate density and integrating sulfonic group. The synthesis reaction of PCEs with high reaction conversion ratio was achieved through rapid reaction(20–30 min) at low temperature (5-20℃). The fluidity of PCEs, the rheological parameters and the compressive strength of mortar were measured. The adsorption behavior and zeta potential of the cement particles were also measured. Results have shown that PCEs with short side chain and high carboxylate density had high adsorption ability, high dispersion capacity in mortar. In addition, PCEs with sulfonic group had increased adsorption amount on the cement surface. These results could allow further progress in the application of EPEG macromonomer.

The influence of fine aggregates on Portland cement mortar compressive strength

The studies regarding the influence of stone-extracted materials on the mechanical properties of Portland cement mortars, has a growing interest in Mexico due to its geological diversity. This is of great relevance since, according to the mechanical properties, a suitable use of mortars can be proposed to satisfy specific requirements of regional construction systems. For this reason, the main goal of this research is to relate the composition of three types of aggregates commonly used in construction practices in two geologically different regions in Mexico with the mortar's compressive strength. Composition is analyzed by mineral crystalline phase identification. The analytical techniques employed were: Petrography, Qualitative X-ray Powder Diffraction, Scanning Electron Microscopy Energy-dispersive X-ray spectroscopy (EDS). The results obtained showed that sands with same origin sands (igneous sands) can provide very different compressive strength values; while aggregates from different origin (igneous and sedimentary) can have similar behavior regarding compressive strength. The amorphous fraction of the pink sand aggregate was attributed as the main factor regarding the change in mechanical properties. The gray igneous sand is adequate for a type N mortar, while the pink igneous sand and the rock limestone powder provide type M mortars.

Prediction of cement-based mortars compressive strength using machine learning techniques

The application of artificial neural networks in mapping the mechanical characteristics of the cement-based materials is underlined in previous investigations. However, this machine learning technique includes several major deficiencies highlighted in the literature, such as the overfitting problem and the inability to explain the decisions. Hence, the present study investigates the applicability of other common machine learning techniques, i.e., support vector machine, random forest (RF), decision tree, AdaBoost and k-nearest neighbors in mapping the behavior of the compressive strength (CS) of cement-based mortars. To this end, a big experimental database has been compiled based on experimental data available in the literature considering, namely the cement grade, which is an important parameter for the modeling of mortar’s CS. Other important parameters are namely the age, the water-to-binder ratio, the particle size distribution of the sand and the amount of plasticizer. Many models based on the influential factors affecting machine learning techniques have been developed, and their prediction capacities have been assessed using performance indexes. The present research highlights the potential of AdaBoost and RF models as useful tools which can assist in mortar design and/or optimization. In addition, mapping the development of mortar characteristics can assist in revealing the influence of the different mortar mix parameters on the compressive strength.

Influence of different design parameters on the seismic performance of partially grouted masonry shear walls

In recent earthquakes in Chile (e.g., Maule’s 2010 earthquake), buildings built with bed-joint partially grouted reinforced masonry (BJ-PG-RM) shear walls made of multi-perforated clay bricks (MPCB) have not collapsed, although significant damages have been reported. Additionally, experimental data on the influence of the different design parameters that control its seismic behavior is scarce, and the available expressions for estimating their lateral resistance are inaccurate. To address these issues, nine full-scale BJ-PG-RM walls made of MPCB were tested under axial pre-compression and cyclic lateral loads. The study addressed the influence of the aspect (height-to-length) ratio, axial pre-compression, mortar compressive strength, mortar joints’ thickness, bricks’ height, and horizontal and vertical reinforcement ratio. The results were analyzed in terms of hysteretic response, damage evolution, seismic performance parameters (shear strength, equivalent viscous damping ratio, ductility, and lateral stiffness degradation). All designed walls failed in a diagonal tension failure mode. Besides, all studied variables influenced the stresses and crack patterns. Also, the shear strength increases when: (i) lower aspect ratio or joint thickness are used; and (ii) higher axial load ratio, horizontal reinforcement ratio, vertical reinforcement ratio, or mortar compressive strength are used. Moreover, when damage progresses, the lateral secant stiffness decays faster as a result of: (i) larger joint thickness or vertical reinforcement ratio; (ii) lower mortar compressive strength. Most walls exhibited an equivalent viscous damping ratio between 5% and 10% for an intermediate state of damage. However, the evaluated design parameters did not considerably affect the development of the viscous damping ratio as a function of the drift ratio. The displacement ductility of the walls ranged from 1.5 to 2.5, where the height of bricks and the vertical reinforcement ratio had positive effects, and the joint thickness, the mortar compressive strength, and the horizontal reinforcement ratio a negative effect. The lateral resistance of tested walls was also estimated with six expressions, but none of them provided accurate results.

Evaluation of corn straw ash as supplementary cementitious material: Effect of acid leaching on its pozzolanic activity

The use of biomass ash is an environmentally friendly practice in the search for sustainable construction materials. This study aimed to produce pozzolanic ash from corn straw with a high amorphous silica content, low carbon content, and high specific surface area via controlled acid leaching, two-step burning, and grinding. The effect of pretreating corn straw on the properties of the material was assessed by comparative analysis with corn straw and rice husk ashes produced without acid pretreatment. To this end, characterization data, hydration heat, chemically bound water, and portlandite consumption in pastes, and mortar compressive strength were used to evaluate the pozzolanicity of the ashes. The results indicated that all the ashes exhibited pozzolanic behavior and that the leaching process significantly improved the physical and chemical properties of corn straw ash, with reduction in portlandite content. The calorimetric results showed a change in hydration kinetics with an increase in ash in the cement mixes. Moreover, the compressive strength of leached corn straw ash-based mortars was greater than that of the other mortars, primarily for high levels of cement replacement (20 and 30% by mass).

Evaluation of the Pozzolanic Activity of Uncontrolled-Combusted Sewage Sludge Ash

Waste management is a crucial issue facing modern society. The generation of sewage sludge is increasing annually due to the urbanization and improvement of sanitation systems of cities. The construction sector has emerged as a solution for the elimination of waste due to the enormous volume of materials that this sector can absorb. This paper evaluates the pozzolanic activity of sewage sludge ash (USSA) obtained following an uncontrolled-combustion process, a simple and economic procedure. Compressive strength of Portland cement/USSA mortars with 5%–25% by weight USSA were evaluated. Calcium hydroxide/USSA and Portland cement/USSA pastes were chemically and physically characterized through thermogravimetric/differential-thermogravimetric (TG/DTG), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM) analyses. The increase in the replacement of Portland cement by USSA is associated with an increase in the compressive strength of mortars. These values for USSA containing mortars cured for 90 days were in the range of 49.6–55.4 MPa, higher than the one reached by the reference mortar. According to the microstructural analysis, the increment on the compressive strength can be attributed to the formation of hydrated products (C─ S─ H, C─ A─ S─ H, and C─ A─ H) by the pozzolanic reaction of USSA.

Hydration behaviour of limestone-calcined clay and limestone-slag blends in ternary cement

The effect of kaolinitic calcined clay and slag on the hydration of limestone-containing ternary blended cements was investigated. The effect of alumina from different sources of SCMs was considered to activate the formation of carboaluminates. Ternary blends with 50% ordinary portland cement clinker, 45% blends of limestone calcined clay (LC2) in 1:2 blend and slag limestone blend (SLS) in 2:1 mix proportion with 5% of gypsum were studied. The hydration behaviour was analysed based on cement mortar compressive strength, heat of hydration using an isothermal calorimeter and bound water measured using thermal gravimetric analysis (TGA). In addition, the degree of hydration of clinker phases and the composition of calcium - alumino - silicate - hydrate (C-A-S-H) gels forming in two different systems were compared on 90 days hydrated samples analysed using X-Ray diffractometry (XRD) and scanning electron microscopy - energy dispersive X-ray spectroscopy (SEM-EDX) respectively. The results show a rapid early strength development in limestone calcined clay cement blend (LC3) but a lower clinker hydration in comparison with slag limestone cement blend (SLSC) at later ages. In both the cement blends the formation of hemicarboaluminate (Hc) and monocarboaluminate (Mc) was confirmed at 90 days, but the conversion of Hc to Mc was higher in SLSC. Results further confirmed a lower degree of hydration and higher alumina incorporation in the C-A-S-H gel in the LC3 comparison to SLSC. The presence of calcium hydroxide was also confirmed in the SLSC blend due to the hydraulic nature of slag that supported the later age conversion of Hc to Mc as not seen in LC3.

Setting Time and Compressive Strength of Mortar Containing Cockle Shell Powder as Partial Cement Replacement

Environmental degradation caused by deforestation activities for harvesting of limestone from the hills and its calcination process at cement factory along with disposal of cockle shell waste from fisheries industries is in need of resolution. In view of sustainable green environment, approach of utilizing cockle shell waste as partial cement replacement in cement production would reduce pollution caused by both industries. Thus, this research investigates the effect of cockle shell powder as partial cement replacement on setting time and compressive strength of mortar. A total of five types of mortar mixes consisting different percentage of cockle shell powder as partial cement replacement from 0%, 10%, 20%, 30%, and 40% by weight of cement were prepared. Setting time test were conducted on fresh paste. All specimens were subjected to water curing until the testing age. Compressive strength test were conducted on hardened mortar cubes at 3, 7 and 28 days. Finding shows that integration of cockle shell powder as partial cement replacement influences the setting time and compressive strength of mortar. Suitable combination of 10% cockle shell powder successfully enhances the compressive strength of mortar. Conclusively, success in transforming the cockle shell waste to be used as partial cement replacement in mortar production able to reduce cement consumption, save landfill usage for trash dumping and promote cleaner environment for healthier lifestyle of community nearby.

Evaluation of mortars produced with Baosteel slag short flow (BSSF) steel slag as fine aggregate

The objective was to evaluate the influence of Baosteel slag short flow (BSSF) steel slag, a byproduct of a Brazilian steel mill, as a fine aggregate on the properties of fresh state and on the compressive strength of mortars. The experimental work was to characterize the BSSF steel slag and to produce simple mortars (only cement) and mixed mortars (cement and lime), replacing the natural sand with the slag aggregate in 20%, 40%, and 60% by volume. The fresh state tests were specific mass, incorporated air, water retention, and squeeze-flow, while in the hardened state, compressive strength at 28 days was investigated. It was verified that mortars with higher slag contents required greater amounts of water to obtain the spread (consistency) on the flow table, which was fixed at 260±5 mm. The mortars with slag presented higher specific mass since the slag had a higher density than natural sand and less water retention in the case of simple mortars. In addition, it was verified that the mortars with BSSF steel slag presented lower values of maximum displacement in the squeeze-flow test, which negatively affected its workability in the fresh state, besides the properties of mortar adherence. In addition, it was verified through the analysis of variance that the substitution of natural sand by BBSF steel slag did not significantly influence the compression strength of mortars.

Effect of Superplasticizer Dosage on Compressive Strength and Microstructure of High Volume Basic-Oxygen Slag Mortar Exposed to Sea Water Attacks

The influence of superplasticizer addition on durability reinforcement of cement mortars made with basic-oxygen blast-furnace slag fine aggregate (BOF) as completely substitute for natural sand after being exposed to sea water solution for 6 months was evaluated by determining physico-mechanical characteristics in terms of water absorption and compressive strength in addition to microstructure analysis. In this procedure, all studied mixtures were doped with 1% and 2% superplasticizer. After the initial curing of samples in tap water for 28 days, they were subjected to sea water solution for 6 months using water to binder ratios of 0.35 and 0.45. The new hydration phases and microstructure of hardened specimens were identified by X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The results showed that cement mortars with slag fine aggregate blended with 2% SP offered better water absorption, compressive strength and microstructure than their counterparts with natural sand against sea water attacks. Therefore, they can be used in offshore structure applications.