Control Mortar Research Articles

Effect of nano-TiO2 on the properties of cementitious composites under different exposure environments

This article presents the effect of 1%, 3% and 5% content of nano-TiO2 (NT) on the fresh, hardened, microstructural and corrosion resistance properties of cementitious composites under different exposure environments (tap water, saline water and acidic solution). Various investigations such as setting time, compressive strength, scanning electron microscope (SEM), energy dispersive x-ray (EDX), X-ray diffraction (XRD) and potentiodynamic polarization studies were carried out. The setting time test confirmed that the NT acts as an accelerator. The 28 days-compressive strength of mortar increased with the addition of NT. The results of SEM and XRD analyses indicate that NT improved the microstructure and increased the amounts of desirable hydration products. The 360 days-compressive strengths of NT admixed mortar exposed under tap water, saline water and acidic solution were found to be higher than control mortar. The corrosion inhibition efficiency of NT was observed to be increasing with the increase in the dosage, in all the exposure environments.

Influence of eggshell powder on the Portland cement mortar properties

Abstract This research presents an experimental investigation of eggshell powder (ESP) addition influence on the Portland cement mortar performance. Two different eggshell powders states were prepared. These include untreated eggshell powder (UESP) and treated eggshell powder (TESP). The TESP consists of heating the ESP to 750 °C for one hour in an electric furnace. Cement mortar of ordinary Portland cement with (1:3), (cement to sand) ratio, were mixed with each of two ESP states (UESP and TESP) at different percentages ranged from (0 to 20) wt% of the total weight of the cement mortar mixture. Water absorption, thermal conductivity, compressive strength, and hardness properties are measured for the mortar samples after curing for (28 days). The results generally showed that the addition of ESP to the cement mortar improved its properties. The addition of TESP to mortar mixture gave better properties as compared to the UESP addition at the same weight ratio. The water absorption percentages of the samples were decreased by about 30% at 15 wt% addition of TESP. The compressive strength of the mortar was increased by 29% over the control mortar at 15 wt% addition of TESP. The hardness values of mortar are slightly enhanced with increasing ESP ratio, which increased by about 2.5% at 20 wt% addition of TESP. The better thermal insulation of mortar samples was obtained from the addition of UESP, reaching the rate of reduction in the thermal conductivity to 40% than the control mortar.

Reuse of pulverized fired clay brick wastes as cement substitute in mortar for sustainable construction

Recently, there has been an increase on the use of waste materials for development of new materials for construction. This is due to the need for sustainable development which emphasizes on waste reduction, reduction of greenhouse gases (GHG), greener clean environment and conservation of raw resources. This study examines the appropriateness of clay brick waste in powder form as a suitable material for partial substitute of cement in mortar. The clay bricks were obtained as generated waste materials from a brick producing factory in Lagos metropolis and then subjected to grinding. Tests which include; specific gravity, particle size distribution, x-ray fluorescence and scanning electron microscopy were carried out on the pulverized clay brick material (CBP). Further, it is used to partially replace cement in mortar at replacement percentage of 0, 5, 10, 20, 25, 30, 40 and 50% using a mix ratio of 1: 2.75 at 0.45 water-cement ratio. Compressive strength and strength activity index tests were carried out on the cube specimens after days of curing. The obtained results clearly indicate that the pulverized clay brick is an amorphous material and contains similar chemical oxide compounds of a pozzolana. Furthermore, it was observed that the compressive strength of the mortar was further improve at an optimum value of 20% cement replacement with clay brick powder compared to the control mortar. Therefore it implies that generated clay brick wastes can be pulverized and used as pozzolanic admixture in mortar production instead of discriminate dumping in landfill.

Sulfuric Acid Resistance of Geopolymer Mortars from Co-combustion Residuals of Bamboo and Kaolin

This study presents an investigation of the durability and microstructure of geopolymer mortars from co-combustion residuals of bamboo and kaolin when exposed to 5% sulfuric acid solution for 2, 4, and 6 weeks, respectively. Geopolymer mortars sized 5 x 5 x 5 cm were prepared from co-combustion residuals of bamboo and kaolin with alkaline activators, i.e. mixture of 10 N potassium hydroxide solution and sodium silicate solution, and cured at 60 oC in oven for 8 hours and then at room temperature for 28 days. Mortars from ordinary Portland cement were also prepared as control mortars. The parameters studied were visual appearance changes, mass changes, compressive strength changes, and microstructure changes. Microstructure changes were examined using Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The results revealed that geopolymer mortars showed better sulfuric acid resistance compared to ordinary Portland cement mortars in terms of lower mass loss and lower compressive strength loss.

Investigation of ion chelator and mineral admixtures improving salt-frost resistance of cement-based materials

Ion chelator can improve the self-healing ability of cement-based materials. In this paper, the effects of the mixture of ion chelator and mineral admixture (slag or fly ash) on salt-frost resistance of cement-based materials were investigated. The internal structure and mechanical properties of the mortars with ion chelator and mineral admixture before and after salt-frost cycles as well as curing were studied. The results show that the pore structure, mechanical strength and salt-frost resistance of the mortar mixed with ion chelator and slag are better than those of mortar mixed with ion chelator and fly ash. Compared with the control mortar, the harmful pores (larger than 0.1 mm) ratio of the mortar with ion chealtor and slag declined by 44.5%, while the compressive strength increased by 40.7%. After 100 times salt-frost cycles, the mass loss ratio, harmful pores proportion and compressive strength loss ratio of the mortar with ion chelator and slag had declined by 42.5%, 24.7% and 35% respectively than the control mortar. Curing 28 days after salt-frost, the mortar mixed with ion chelator has good self-healing ability, the compressive strength recovery ratio and harmful pores reduction ratio are 21.18% and 27.04%, respectively. A large amount of needle-like repair products appear in the pores of the mortar mixed with ion chelator. The results of the energy-dispersive spectroscopy and X-ray diffraction tests proved that the main products in the pores and cracks of the mortar are CaCO3 and CaSiO3.

Evaluation of the eco-friendly crushed waste oyster shell mortars containing supplementary cementitious materials

The ever-increasing demand for natural aggregates in the concrete industry has resulted in substantial consumption of a dwindling supply of natural resources, leading to irreversible environmental damage. One solution to solve this problem is through the use of waste materials as alternatives to natural aggregates. In this study, 30% of natural river sand was replaced by crushed waste oyster shells (WOS). Full cement (control), different proportions (20%, 30%, and 40%) of cement replaced by fly ash (FA), and ground granulated blast-furnace slag (GGBS) were used. The hardened densities, mechanical properties, durability-related properties, microstructures, and sustainability of the WOS–Control, WOS–FA, and WOS–GGBS mortars were investigated. The test results indicated that, because of the low pozzolanic reaction activity, the inclusion of FA and GGBS decreased the hardened densities and mechanical properties of early-age crushed WOS mortars. Scanning electron microscopy with energy dispersive X-ray spectroscopy analyses indicated low hydration degrees of FA and GGBS in the early stage. These reductions decreased with increasing curing time. The secondary hydration products generated by supplementary cementitious materials considerably filled and compacted the microstructures of the WOS mortars in the later stage. The crushed WOS mortars with FA and GGBS had approximately identical hardened densities and mechanical behaviors to the control mortar. The chloride ion penetration of these blended samples decreased rapidly. The use of these waste materials would offset the demand for natural fine aggregate and cement, decreasing both CO2 emissions and associated costs. A greener mortar with adequate engineering properties could be produced by incorporating FA and GGBS and crushed WOS in limited quantities.

Waste polymers and gamma radiation on the mechanical improvement of polymer mortars: Experimental and calculated results

In this work, the effects of waste polymer particles and gamma radiation on the mechanical properties of polyester mortars were studied. Control mortar was elaborated with polyester resin (20%), and silica sand (80%). This last was partially substituted by each waste polymer (1, 2 and 3 wt. %), namely, i) PET from beverage water bottles, ii) Polycarbonate from computer monitors and displays, and iii) Waste tire rubber from automotive tires. A post-curing process was applied to polyester mortars by using gamma rays (at doses of 100 and 200 kGy). Analysis of the results were made according to irradiation dose and the particles concentration. We reminded that such polymer mortars are used in applications where high mechanical and chemical attacks resistance are required, moreover they are friendly to the environment. The results show, that the effect of the ionizing radiation was predominant, because higher percentages of improvement on the mechanical properties were obtained, up to 46% for irradiated mortars with PET particles, and up to 37% for those with polycarbonate particles, respect to that for control mortar. Respect to the waste particles concentration, a general behavior was obtained: mechanical properties decrease gradually with increase of particles concentration. Nevertheless, it was remarkable to use only 1% of waste particles concentration, for to obtain the highest values for both kind of mortars, non-irradiated and irradiated. The experimental results were simulated by Finite Element Method (FEM), both were in good accordance, having minimal difference between them. In addition, morphological modifications of each waste polymer after irradiating, were analyzed by scanning electron microscopy (SEM) and related to mechanical behavior of polyester mortars.The improvements in the mechanical properties of the composites, as well as the use of waste polymers, make these polymer mortar environmentally friendly construction materials that can be used in applications that require high mechanical resistance.

Utilization of waste from steel and iron industry as replacement of cement in mortars

The viability of combining waste slag produced from steel (Basic Oxygen furnace) and iron (Blast Furnace) industry as replacement of cement in cement mortars was investigated. The impacts on the normal consistency, setting times, soundness, compressive strength, microstructure, and durability of cement paste/mortar were studied. The results revealed that the water requirement and the setting time of cement paste increased by the addition of steel slag powder. The optimum content of steel slag and GGBS (ground granulated blast furnace slag) as a combined admixture was 40%. The 28 day compressive strength was comparable, whereas it exceeded the strength of control mortar after 90 days of curing. The microstructure of samples was studied using SEM micrographs, which indicated denser structures of ternary mortars. The durability tests of accelerated carbonation, sulphuric acid resistance, and electrical resistivity showed acceptable results. Life cycle assessment (LCA) of ternary mortar indicated visible decrease in environmental impacts in all categories. Response Surface Methodology (RSM) was adopted to find relation between partial replacement of cement by steel slag and GGBS in ternary blend and compressive strength. This research bestows a new understanding of how industrial wastes can be managed sustainably with imparting additional benefits to the concrete economically.

Strength characteristics and microstructural properties of cement mortars incorporating synthetic wollastonite produced with a new technique

In this study, synthetic wollastonite (SW) mineral was produced by using a new production method. This method which quartz and calcite minerals are used as raw materials, is 3-step wollastonite production method consisting of mechanochemical process, hydrothermal process and solid state reaction process. It was proved that the material (SW) produced with the help of this new method is wollastonite by using SEM, XRF and XRD analysis. The effect of SW on the mechanical and microstructural properties of cement mortar (CM) were experimentally investigated. The CMs were produced without SW as control mortar and by using SW with the ratios of 3%, 6%, 9%, 12% and 15% instead of cement. Compressive and flexural strength tests were conducted at 7 and 28 days. In addition, SEM/EDX, TGA/DTA and FTIR analysis were applied to mixtures incorporating SW in the ratios of 0%, 3%, 9% and 15% at 28 days. Test results indicate that mechanical performance of CMs improved up to 9% SW content. However, CMs with 12% and 15% SW had higher compressive and flexural strength than the control mortar. Microstructural analysis demonstrated that improvement in the strength characteristics of CMs incorporating SW can be explained with the acicular particle structure of SW. In addition, according to TGA/DTA and FTIR analysis, it is observed that CaCO3 in CMs decreased with the increase of SW.

Influence of slag powder in the cement mortar mixes on the characteristics of compactness and freeze –thaw strength

Worldwide, there is a clear imperativeness to reduce the consumption of non-renewable raw materials. The aim of the research is to obtain new ecological materials with applicability in the construction field, but also to efficiently manage these by-products by eliminating it completely and re-introducing it into the economic circuit. We envisaged the use of slag products as a material cementitious characteristics or as artificial aggregates, so that materials embedded in construction produce as little environmental impact as possible. After cooling, the blast furnace slag products was used in the new mortar mixes in two forms: in the form of a powder product milled from the granulated slag, and in the form of an aggregate made of non-granulated slag, sorted to the sized of 0/4 mm. Ground-granulated slag in the form of a powder below 63 μm was used as an addition to the cement mass, and the newly obtained artificial aggregate, sorted to 0/4 mm, was used in various percentages for replacing the natural aggregates in the control mix. The results show that the combined use of slag powder as an addition to the cement mass and artificial slag aggregates, regardless of the percentage of substitution of Natural aggregates in the mortar mortar mix, has led to the development of new mortar mixes with higher compaction than the control mortar. The higher filling rate due to the use of ground slag has influenced the increase of compressive strengths and freeze-thaw strengths from the repeated freeze-thaw action for new cement mortar mixes with blast furnace slag, as compared to the control mortar mix.

Combined use of waste concrete and glass as a replacement for mortar raw materials

The construction industry offers one of the most attractive options in the use of recycled materials due to its large consumption of raw materials and high construction work rates. Also, the debris from construction and demolition is responsible for a high participation rate in the generation of waste, with concrete being a major contributor in this category. Waste glass powder, on the other hand, is a material that offers an excellent alternative to replace cement due to its well-known pozzolanic properties. Hence, the combined behaviour of fine recycled concrete aggregates and glass powder of different particle sizes in mortars has been studied. Different mixtures are analyzed with the aim of minimizing losses in mechanical properties and durability in an attempt to maximize the amount of replaced materials. Due to the delayed pozzolanic reaction by the glass powder, the samples present highly satisfactory results at 90 days of curing, with values of their properties close to those of the control mortar. The results are encouraging when glass powder with a smaller particle size is used due to its filler effect combined with its pozzolanic activity, making it possible to replace up to 20% of glass powder with a maximum size of 38 µm, with up to 30% of fine recycled concrete aggregates. Finally, the evaluation of greenhouse gases showed that the simultaneous incorporation of both types of waste reduces the CO2 emissions associated with concrete by up to 19%.

Potential use of sugarcane bagasse and bamboo leaf ashes for elaboration of green cementitious materials

The paper presents the study of pozzolanic activity and hydration of cement pastes containing sugarcane bagasse (SCBA) and bamboo leaves ashes (BLA). Pozzolanic activity of binary and ternary mixtures of ashes was investigated using electrical conductivity measurements. A kinetic-diffusive model was used to quantify the pozzolanic reaction between ashes and calcium hydroxide solution. The influence of ashes on hydration of cementitious pastes was also investigated using thermogravimetry analysis, X-Ray diffraction, isothermal calorimetry and mechanical tests. The results showed that ternary mixtures of SCBA and BLA have a higher pozzolanic activity than the binary mixture of SCBA. Binary and ternary mortars have higher compressive strengths than the control mortar without mineral additives. Moreover, the replacement of cement by 10 wt% of SCBA and BLA leads to a decrease of the calcium hydroxide content and the heat of hydration. The results also showed that the production of 1 ton of binder with agro-industrial ashes needs lower energy than conventional cement. According to the results of the study, the use agro-industrial ashes in binary and ternary blend cements can bring economic, technical and environmental benefits for the industrial sector including fiber cement industry, precast plants and concrete producers.

Mechanical and microstructural properties of alkali-activated slag and slag + fly ash mortars exposed to high temperature

In this study, changes in the mechanical and microstructural properties of alkali-activated blast furnace slag (BFS) and BFS + fly ash (FA) blended mortars exposed to 25, 400, 600 and 800 °C temperatures are investigated. The alkali-activated mortars using the replacement ratios of 0, 25 and 50% FA by weight of BFS together with the activators are produced in addition to the control mortars produced by only cement. Three different optimum Ms (SiO2/Na2O ratio of activators) values of 0.50, 0.75 and 1.00 are determined for the alkali-activated mortars. The FA substitution by BFS increases the high temperature resistance of alkali-activated BFS mortars.

Strength development and acid resistance of geopolymer based on waste clay brick powder and phosphorous slag

AbstractThis study aims to investigate the strength development and durability of geopolymer mortars based on waste clay brick powder (WCBP) and phosphorus slag exposed to acid attack. WCBP was partially replaced with slag (8, 16, and 24 wt%) and resulting blends were activated by an aqueous solution of NaOH and sodium silicate with different SiO2/Na2O ratios (MS) and Na2O concentrations. The optimized geopolymer mortar specimens were also immersed in sulfuric and hydrochloric acid solutions of pH = 1 for 6 months to assess changes in their physical and structural properties. The results were compared with those of Portland cement and high alumina cement mortars as control specimens. The key durability parameters measured were the evaluation of mass change, compressive strength loss, and deteriorated depth. Complementary studies were also carried out using X‐ray diffractometry, Fourier transform infrared spectroscopy, and scanning electron microscopy in line with energy dispersive X‐ray techniques to quantify the compositional and microstructural changes. The results demonstrate a potential of value‐added reuse application for WCBP by adding a suitable amount of slag. The findings also showed that geopolymer mortars were less susceptible to acid attack than the control mortars; however, superior enhancement in durability properties was not achieved.

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.

Influence of treated mud on free shrinkage and cracking tendency of self-compacting concrete equivalent mortars

The present work aims at studying the formulation and characterization of self-compacting concrete equivalent mortars, using calcined mud from the dredged sediments brought from the dam (Western Algeria) and fly ash from the Central Thermal EDF (France). Three SCCEM samples were prepared; a control mortar sample and two mortar samples containing 22% of mineral additions, with a ratio W/B = 0.47. The analysis of the experimental results obtained indicates that mortars comprising calcined mud develop greater compressive strengths than those containing fly ash. Regarding free shrinkage, mortar with calcined mud is characterized by an autogenous shrinkage similar to those of control and fly ash mortars. However, it is more sensitive to total shrinkage and drying as compared to the other mortars. Under the conditions of restrained shrinkage, control and calcined mud mortars are more sensitive to early cracking than mortar based on fly ash.

Risk and performance assessment of cement made using municipal solid waste incinerator bottom ash as a cement kiln feed

To assess the feasibility of incorporating municipal solid waste incineration (MSWI) bottom ash (BA) as a replacement for traditional raw materials in cement kiln feed, an industrial-scale kiln trial was performed. Leach testing and chemical and physical characterization data from a cement product made at a replacement percentage of 2.8% by mass of kiln feed were comparable to results from ordinary portland cement. The concentrations of constituents of concern in leach tests were generally below risk-based screening levels or of similar or lower magnitude than leachate from control products. Ash-amended cement exhibited greater early age reactivity, and this was reflected in initial mortar compressive strength results; ultimate compressive strength results were higher in the control mortar. The ash-amended and control cements were similar in characteristic, but quantitative x-ray diffraction results reveal differences in alite and aluminate formation during the clinker formation process.

Influence of porosity on the tensile strength of fine grained mortar containing fly ash, palm oil fuel ash and rice husk ash

The study is to identify the influence of porosity on the tensile strength of fine grained mortar containing fly ash (FA), palm oil fuel ash (POFA) and rice husk ash (RHA). The aim of this study is to reduce the consumption of cement due to its negative impact on the environment. The cement-to-sand ratio used in the mix design of fine grained mortar is 1: 2. The maximum size of fine grained sand used in this study is 0.6 mm. There are four (4) mix designs of fine grained mortar which include control mortar (100% OPC), 80% OPC + 20% FA, 90% OPC + 10% POFA and 80% OPC + 20% RHA. The selection of the mix design for each type of fine grained mortar was based on the mix designs of previous studies which produced the highest compressive strength. The tensile strength test and the porosity test were carried out in this study. The tensile strength test was performed on cylinder specimens measuring 100 mm diameter and 200 mm height according to ASTM C496. On the other hand, the porosity test was conducted on prism specimens measuring 40 x 40 x 160 mm. The results showed that fine grained mortar containing FA achieved the highest tensile strength of 5.9 N/mm2 and a low porosity of 12.7%.

Production of bamboo leaf ash by auto-combustion for pozzolanic and sustainable use in cementitious matrices

In the context of world concern with the environment, this study aims to characterize an auto-combustion produced bamboo leaf ash (BLA) by its pozzolanic behaviour, reactivity and its influence in the total porosity, pore size distribution, tortuosity and mechanical behaviour of cementitious matrices. The chemical and physical characterization of the BLA was carried using X-ray fluorescence, determination of amorphous silica content, X-ray diffraction, Fourier Transform Infrared Spectrophotometry (FTIR), laser granulometry and field emission scanning electron microscopy (FESEM). The assessed BLA is a siliceous material (74.23%) with an amorphous nature due to the amorphous silica content, which represents 92.33% of the total silica. The BLA was classified as highly reactive by assessing its pH and conductivity in a saturated calcium hydroxide (CH) medium for different proportions and temperatures. Frattini analysis, the study of CH:BLA pastes (Thermogravimetric analysis and FTIR) and Portland cement (OPC)/pozzolan pastes (Thermogravimetric analysis and FESEM) are in agreement with this classification. The replacement of OPC by BLA improved the mechanical behaviour of the cementitious matrices, as well their durability. All the mortars containing BLA presented very similar compressive strength to a control mortar (100% OPC) after only 3 days of curing and at the following tested curing ages: 7, 28 and 90 days. In the mercury intrusion porosimetry analysis, the pastes with 20 and 30% BLA content presented higher tortuosity or fewer connected pores than the control paste. Thus, the auto-combustion method proved to be successful and BLA is a suitable alternative for sustainable high-performance matrices.

Study on the Properties and Mechanism of Mortars Modified by Super Absorbent Polymers

Abstract The article investigated the influence of Super Absorbent Polymers (SAPs) with absorption behaviors on the consistency, fluidity, water absorption, mechanical properties, early crack resistance, permeability resistance, and degree of hydration of cementitious construction materials. Mechanical strength was investigated using a flexural and compressive strength test machine. Nonevaporable water content was employed to assess the degree of hydration of the cement powders. The durability of mortar was characterized using early crack resistance and a permeability resistance test. Furthermore, the micromechanism of mortars modified by SAPs and control mortars was researched using a Scanning Electron Microscope (SEM). Experimental results showed that for the SAPs and mix designs used in this article, the incorporation of SAPs generally reduced the mechanical strength and increased the consistency, fluidity, water absorption, and degree of hydration of modified mortars compared with control mortars. The durability of mortars incorporating SAPs was greatly improved. The connection of the macroproperty and micromechanism of mortars was researched using an SEM.