Dry-mixed Mortar Research Articles

Research on the Preparation of Dry Mixed Mortar Using Waste Incineration Fly Ash

This study investigated the effect of water-washed municipal solid waste incineration fly ash (MSWI FA) as an admixture on the performance of dry mixed mortar and used X-ray diffraction (XRD) and scanning electron microscope (SEM) detection methods to conduct microscopic analysis. The experiment investigated the effects of the amount and water content of washed municipal solid waste incineration fly ash, cement, additives, sand and gravel, and curing time on the compressive flexural strength of dry mixed mortar at 28 days. The results show that when the content of water-washed MSWI FA is 9.80%, the content of sand and gravel is 73.50%, the content of ordinary Portland cement (PO42.5) is 16.66%, the content of water-reducing agent is 1.47‰, the content of cellulose is 0.03‰, the content of the expansion agent is 0.49‰, the addition of water is 130–160 mL/kg, the consistency of the sample can reach 91.8 mm, and the water retention rate can reach 93.6%. The flexural strength of the sample at 28 days can reach 7.5 MPa, and the compressive strength at 28 days can reach 28.30 MPa. Metal ions, such as Pb2+ and Gd2+ in MSWI FA, under the combined action of silicate cement in dry mixed mortar and fibers in cellulose, crisscross and form a solidified material, which will not be leached out. This quality meets the requirements of dry mixed mortar for ordinary plastering and masonry mortar (GB-T 25181-2019), and the leaching toxicity of the sample meets the “Identification Standard for Hazardous Waste” (GB5085.3-2007). This work provides a meaningful exploration of the resource utilization of water-washed MSWI FA.

DEVELOPMENT OF DRY MIX MORTARS FOR FLOOR ELEMENTS

Dry mix mortars are widely used in construction projects for the implementation of construction works in new construction, reconstruction, and repair. The improvement of properties of dry mix mortars for the installation of floor screeds is relevant. The purpose of such mortars is to equalize the differences in the thickness of the floor surface, to create an intermediate layer characterized by the necessary strength, durability, and even surface with the possibility of decoration with various types of flooring. A step-by-step design of the composition of dry mix mortar for the installation of floor screeds was carried out. The ratio of fine aggregates and limestone filler was optimized according to the maximum packing density criterion, the required amount of plasticizer was selected according to the consistency index of the fresh mortar, and the minimum amount of Portland cement was selected to ensure the required strength.

Development and standardization of sustainable dry mix mortars with supplementary cementitious materials

Development and standardization of sustainable dry mix mortars with supplementary cementitious materials

Methodological approach based on life cycle assessment for upcycling leftover concrete into dry industrial mortars

This study examines the integration of Life Cycle Assessment (LCA) as a crucial decision-making tool in by-product recovery studies within the construction sector. Unlike conventional methods that often delay LCA until after thecnical studies, our approach places LCA at the forefront of decision-making, ensuring that environmental considerations guide material design.This study investigates the valorization of concrete return fines in dry-mix mortars, starting with an initial LCA to validate environmental benefits of substituting natural sand by recycled sand before testing various formulations with different substitution rate.Our findings reveal significant reduction mainly in natural resource depletion, particularly evident at a 55% substitution rate, suggesting complete independence from natural resources. Additionally, the ecological profitability threshold is established at 200 km, indicating the radius within which the recycled sand can be used without compromising environmental gains.Economically, Life Cycle Costing (LCC) analysis demonstrate the cost-effectiveness of using recycled sand, even when its price exceeds that of natural sand. This economic resilience allows for flexibility in setting the selling price of recycled sand, thereby enhancing its valuation.In conclusion, our approach represents a paradigm shift in ecological decision-making by priotirizing LCA to emphasize the balance between environmental benefits and economic viability. This study paves the way for an eco-friendly application with significant potential for adoption within the construction industry.

The influence of hydroxyalkyl methylcellulose on early skin formation in cement‐based tile adhesive

AbstractThe effect of cellulose ethers (CE) with same water retention (WR) level but different molecular weight on the early skin formation of cement adhesive mortars was studied. In drymix mortars CE provide WR higher molecular weight and dosage of CE both improve WR. In this study all CE concentrations were adjusted to provide same WR independently from molecular weight of CE. Adjusted concentrations were obtained from zero‐shear viscosities measured in aqueous CE solutions.Measurements with cement‐based mortars identified the interstitial pore solution viscosity to determine WR level. Data show comparable WR for equal interstitial pore solutions, independently from the molecular weight of the CE if its concentration was adjusted accordingly. However, for cement adhesive mortars formulated with CE having different molecular weight which all provide equal WR, early skin formation was found to vary notably. Higher dosed low molecular weight CE outperforms CE with lower dosage but high molecular weight. This effect can be explained through the formation of a CE containing layer upon evaporation of water from the water‐air interface of the mortar.

Integrated evaluation of the performance of phosphogypsum recycling technologies in China

The Chinese government is implementing policies, such as the “Guidance on comprehensive utilization of bulk solid waste for the 14th Five-Year Plan period”, to stimulate phosphogypsum (PG) reduction and recycling. Thus, the comprehensive evaluation of PG recycling technologies for sustainable development is crucial. This study proposes a novel multi-criteria decision analysis (MCDA) method that considers the criteria of resources, environment, economy, and society and risk attitudes of decision-makers and integrates game theory (GT) and utility theory for criteria weighting and ranking to assess industrial-scale PG recycling technologies in China. The results demonstrate that GT provides more reasonable criteria weights than individual weighting methods. PG-based lightweight plaster is the top performer in the resource and environmental dimensions owing to its exceptional resource and energy efficiency. PG utilized for dry-mix mortar and organic fertilizer production exhibited the best utility performance of 0.74 and 0.73, respectively. Measures, such as subsidies and product publicity, should be implemented to promote these technologies. However, technologies with poor performance, such as PG used for the co-production of sulfuric acid and fertilizer or cement, may require optimization or substitution for the sustainable recycling of PG. The proposed MCDA method is robust and can serve as a reliable decision-making tool for other waste-recycling technologies. However, caution must be exercised when determining risk attitude using the MCDA method as it may vary with the number of technologies and affect the final rankings.

Enhancing dry mix mortar strength with natural fillers and polymers

Dry mix mortars are becoming more and more popular in the world’s building materials market. Therefore, the issue of increasing the technological and mechanical properties of stucco mixes is relevant. The aim of the paper is modification of lightweight dry stucco mixes with fine limestone and perlite as well as with hydroxyethyl methyl cellulose and dispersible polymer. In order to investigate the different mixes, an 18-point experiment was designed. Density, compressive strengths and crack resistance of dry plaster mixes were studied using requirements of standard. Mathematical models were obtained for the compositions as a result of processing the experimental data. The regularities of the fillers’ and additives’ influence on the properties of the mixes were established, depending on their amount and combination. It was observed that methyl hydroxyethyl cellulose improves the crack resistance and compression strength, and contributes to a slight decrease in density. The crack resistance of plaster mortars changes more than 1.5 times, the most crack-resistant compositions have an average amount of porous fillers.

Hydration characteristics of tailing mud–42.5 OPC composite cementitious system and its application to dry-mixed mortar

This study investigated the influence of the raw material ratio on the product quality of tailing mud with type-I 42.5 ordinary Portland cement (OPC) in a binary cementitious system. In particular, this research aimed to expand the applicability of tailing mud and tailing waste rock while minimizing the production cost of dry-mixed mortar. The results demonstrated a synergistic reaction between the tailing mud and 42.5 OPC, which was beneficial for enhancing hydration and gelation, increasing the production of calcium silicate hydrate (C–S–H) and calcium hydroxide (C–H), promoting more free magnesium oxide (MgO) in the cement to participate in the hydration reaction, and improving the structure of the composite gelation system. When the concentration of tailing mud in 42.5 OPC was 20%, the cementitious block attained a 28-day compressive strength of 44.85 MPa. To manufacture the dry-mixed mortar product, 80% mud and 20% 42.5 OPC were mixed with equal amounts of tailing mud and waste rock aggregate. For the dry-mixed mortar, the 28-day compressive strength was 7.32 MPa, 2-h consistency-loss rate was 12.4%, and water retention rate was 99.2%. To further explore the synergistic reaction mechanism between the tailing mud and 42.5 OPC, the energy calculations, geometric optimization, and dynamic modeling of the tailing mud–42.5 OPC cementitious system were performed using the Forcite module in Materials Studio software. Overall, the results indicated that including tailing mud improved the mechanical strength of 42.5 OPC.

Experimental Study on Preparation of Dry-Mixed Mortar from Coal Gangue

In this experiment, the influence of coal gangue as the admixture on the performance of dry-mixed mortar was studied, and the results were analyzed by XRD and SEM. The effects of different ways of crushing, particle size distribution, coal gangue, cement, admixture, and water content on the water retention, consistency, and 7 d compressive strength of dry-mixed mortar were investigated. The results show that the optimum content of hammer crushing of coal gangue through 3 mm sieve and cement is 83% and 17% of the total mass (W/W), respectively, the admixture content of 1# compound is 0.2 g/kg, and the amount of water is in the range of 194~200 mL/kg. At this time, the consistency can reach 91.5 mm, the water retention rate can reach 92.11%, and the 7 d compressive strength can reach 10.6 MPa, which meets the requirements of dry-mixed mortar for ordinary plastering and masonry mortar (GB-T 25181-2019).

Composition mapping of highly substituted cellulose-ether monomers by liquid chromatography–mass spectrometry and probability-based data deconvolution

Cellulose ethers (CEs) are semi-synthetic polymers produced by derivatization of natural cellulose, yielding highly substituted products such as ethyl hydroxyethyl cellulose (EHEC) or methyl ethyl hydroxyethyl cellulose (MEHEC). CEs are commonly applied as pharmaceutical excipients and thickening agents in paints and drymix mortars. CE properties, such as high viscosity in solution, solubility, and bio-stability are of high interest to achieve required product qualities, which may be strongly affected by the substitution pattern obtained after derivatization. The average and molar degree of substitution often cannot explain functional differences observed among CE batches, and more in-depth analysis is needed. In this work, a new method was developed for the comprehensive mapping of the substitution degree and composition of β-glucose monomers of CE samples. To this end, CEs were acid-hydrolyzed and then analyzed by gradient reversed-phase liquid chromatography-mass spectrometry (LC-MS) using an acid-stable LC column and time-of-flight (TOF) mass spectrometer. LC-MS provided monomer resolution based on ethylene oxide, hydroxyl, and terminating methyl/ethyl content, allowing the assignment of detailed compositional distributions. An essential further distinction of constitutional isomer distributions was achieved using an in-house developed probability-based deconvolution algorithm. Aided by differential heat maps for visualization and straightforward interpretation of the measured LC-MS data, compositional variation between bio-stable and non-bio-stable CEs could be identified using this new approach. Moreover, it disclosed unexpected methylations in EHEC samples. Overall, the obtained molecular information on relevant CE samples demonstrated the method's potential for the study of CE structure-property relationships.

Effect of Cellulose Ether and Starch Ether on Hydration of Cement Processes and Fresh-State Properties of Cement Mortars.

The production of factory-made mortars is a multicomponent system. Viscosity-modifying admixtures (VMAs) are an inherent ingredient of these materials. The correct choice of the amount and type of these admixtures is important from the practical and scientific points of view. In this article, the use of cellulose ether (CE) and starch ether (SE) in cement pastes and mortars is studied. This research focuses on the hydration process and fresh-state properties of mortars because this subject determines the correct choice of the amount and type of admixture used, and the results determine the application and properties of hardened mortars. Polymers were added in the range from 0.056% to 0.22% in relation to the dry ingredients of the mortar. The research showed that cellulose ether had the greatest impact on the consistency, air content, bulk density, and water retention of ordinary dry-mix mortars. On the other hand, starch ether affected the hydration process, delaying the setting and hardening processes much more than cellulose ether. The action of these admixtures rose with the increase in the amount of polymer used in different ways (depending on the type of ether).

Solid waste-based dry-mix mortar using fly ash, carbide slag, and flue gas desulfurization gypsum

The hydration characteristics, performance, and economic feasibility of inorganic cementitious materials prepared using circulating fluidized bed fly ash (FA), carbide slag (CS), and flue-gas-desulfurization gypsum (FGDG) are investigated, focusing particularly on FA-CS binary and FA-CS-FGDG ternary cementitious systems. Experimental results show that the compressive strength of the binary system is less than that of the ternary one. The ternary cementitious material exhibits strong synergistic effects, as the 28 days compressive strength of the ternary system can reach 6.35 MPa, suggesting that it has good prospects for practical application. A dry-mixed mortar using the material has been manufactured and tested in a pilot project; it meets Chinese government quality standards and reduces cost and carbon emissions relative to traditional mortar. The 28 days compressive strength of dry mix mortar can reach 13.1 MPa, the production cost of solid waste-based dry-mixed mortar was reduced by approximately 48.8%, and the carbon dioxide emission reduction ratio was 82.9%.

Investigations on Flexural and Compressive Strengths of Mortar Dedicated to Clinker Units—Influence of Mixing Water Content and Curing Time

The article presents laboratory tests on the impact of the mixing water content used in the preparation of fresh mortar on the flexural and compressive strength of one of the dry-mix mortars produced by a leading European producer and dedicated to bricklaying with clinker elements. The development of these parameters in relation to curing time was also analyzed. The mortar samples were prepared from a factory-made mortar mix using 4.0 L (the value recommended by the mortar manufacturer), 4.5 L, and 5 L of water per 25 kg bag of ready-made, pre-mixed dry mortar mix. All samples were tested in five series after 5, 9, 14, 21, and 28 days of sample curing. The results of these tests showed that the use of 6 and 18% more mixing water than recommended by the manufacturer (4.5 and 5 L per bag) adversely affected the basic mechanical parameters of the tested mortar. Moreover, it was found that the highest compressive strength values were obtained after 21 days of curing and not after 28 days as usual. It was also found that hardening time and higher than recommended water content adversely affected the bending strength of the mortar.

The Key Application Technology of Desulfurized Gypsum in Dry-Mixed Mortar

In this paper, in view of the problem of low early and late strength of dry-mixed mortar prepared by cement-fly ash-slag powder composite cementing system, the ratio of mixing fly ash and slag powder to replace cement is 70%. To study the effect of desulfurization gypsum (FGD) on improving the activity of the system. The results show that adding desulfurized gypsum, which accounts for 6% to 8% of the total mass of the cementitious material, has no adverse effect on the workability and can significantly improve the compressive resistance of the slurry. Strength and tensile bonding strength, shrinkage rate is reduced by more than 10%, and the ability to resist carbonization is improved to make the mortar volume more stable.

Mechanical strengths, drying shrinkage and pore structure of cement mortars with hydroxyethyl methyl cellulose

This paper aims at investigating the long-term mechanical strengths and drying shrinkage, as well as pore structure of cement mortars with hydroxyethyl methyl cellulose (HEMC). The results show that the 3-d flexural strength and compressive strength of cement mortars tend to decrease with the HEMC content increasing. At 28 d to 360 d, the strengths keep decreasing with the HEMC content increasing at 0–1%, and then increase from the minimum value with the HEMC content increasing at 1–3%, still being much lower than those of the control (0% HEMC). Throughout the curing age, both the tensile bond strength and the drying shrinkage value gradually increase with the HEMC content, to be nearly twice at 3% HEMC than those of the control. HEMC significantly delays the 3-d hydration of cement pastes, but has negligible retardation effect on the hydration after 28 d, to bring the similar late hydration degree of cement pastes with HEMC or not. With the HEMC content increasing in the range of 0–1%, incorporating HEMC brings the sharp increase of macro pores, large capillary pores and porosity, and decreases the interconnected pores to bring many more closed pores. Further increasing the HEMC content to 3%, macro pores and porosity decrease, large capillary pores slightly increase and interconnected pores have a negligible change. Obviously, the understanding on the performance development of cement mortars with HEMC is conducive to the better application of HEMC in dry-mix mortars to meet different requirements.

Study of the Properties of Full Component Recycled Dry-Mixed Masonry Mortar and Concrete Prepared from Construction Solid Waste

Solutions are needed to solve the problem of a large amount of construction solid waste and a shortage of natural aggregate (coarse and fine aggregates). In this paper, simple-crushed coarse aggregate (SCRCA) and simple-crushed fine aggregate (SCRFA) were obtained by simple-crushing of construction solid waste. On this basis, SCRCA and SCRFA were treated with particle-shaping to obtain particle-shaping coarse aggregate (PSRCA) and particle-shaping fine aggregate (PSRFA), and the recycled powder (RP) produced in the process of particle-shaping was collected. Under the condition of a 1:4 cement-sand ratio, RP was used to replace cement with four substitution rates of 0, 10%, 20%, and 30%, and dry-mixed masonry mortar was prepared with 100% SCRFA, PSRFA, and river sand (RS). The basic and mechanical properties and microstructure of hydration products of dry-mixed mortar were analyzed, and the maximum substitution rate of RP was determined. Under the condition that the amount of cementitious material is 400 kg/m3 and the RP is at the maximum replacement rate, three different aggregate combinations to prepare concrete are the 100% use of SCRCA and SCRFA, PSRCA and PSRFA, and RS and natural aggregate (NCA); the workability, mechanical properties, and aggregate interface transition zone of the prepared concrete were analyzed. The results show that when the replacement rate of RP is less than 20%, it has little effect on the properties of products. The performance of PSRCA and PSRFA after treatment is better than that of SCRCA and SCRFA. Under different RP substitution rates, the performance of dry-mixed mortar prepared with PSRFA is very close to that prepared with RS. The performance of recycled concrete prepared with PSRCA and PSRFA is also very close to that of products prepared with NCA and RS. The failure morphology of PSRCA and RSRFA concrete is also similar to that of NCA and RS concrete.

Investigation on the performance of hydroxyethyl methyl cellulose modified cement mortars with Portland cement-calcium sulfoaluminate cement binders

Dry-mix mortars with Portland cement and calcium sulfoaluminate cement (PC-CSA) binders are gradually applied in many fields due to their various excellent properties. Hydroxyethyl methyl cellulose (HEMC) is commonly used as an agent in the dry-mix mortars to further improve performance. Herein, the purpose of this study is to investigate the performance of HEMC-modified cement mortars with PC-CSA binders. The results show that HEMC has great effects on the properties and hydration of the cement mortars with PC-CSA binders. HEMC improves the water retention ability, decreases the consistency and fluidity to bring the flowability reduction, and increases the air content consequently to decrease the bulk density. Meanwhile, HEMC somewhat extends the setting time. With the HEMC content increasing, HEMC obviously decreases the flexural and compressive strengths. However, HEMC can improve the tensile bond strength, especially at the high HEMC content. HEMC decreases the drying shrinkage, regardless of its content. HEMC retards the hydration process of the PC-CSA binders, and affects the formation of ettringite (AFt) and calcium hydroxide (CH). HEMC delays the transformation of AFt to monosulfoaluminate (AFm) and decreases the consumption of CH at later age, and the preferred orientation growth of CH is also declined. Moreover, HEMC increases the macro-capillary pores and macro pores, but decreases the meso-capillary pores.

Experimental Study on the Effect of Fine Powder in Iron Tailings on the Durability of Ordinary Dry Mixed Mortar

This paper mainly discusses the application of fine powder in iron tailings in ordinary dry mixed mortar. The effect of fine powder in iron tailings on the durability (frost resistance, impermeability and shrinkage) of common dry mixed mortar after replacing river sand or machined sand with iron tailings was studied. The microcosmic analysis was carried out by SEM. Under the condition of satisfying the mobility and strength of ordinary dry mixed mortar, iron tailings can replace river sand or mechanized sand in different proportion, and the micro powder in iron tailings can improve the durability of dry mixed mortar. Through the study of the influence of fine powder in iron tailings on the properties of ordinary mortar, it can be found that it is feasible to use iron tailings to produce ordinary dry mixed mortar, and can meet the requirements of current engineering, national or industry standards.

Comparison and analysis of dry mixed mortar and traditional shotcrete and equipment development scheme

In order to study the advantages and disadvantages of dry mixed mortar and traditional shotcreting in underground shotcreting operation, and improve the mechanization level of underground shotcreting operation. This paper makes a statistical analysis on the use of dry mixed mortar shotcreting machines in 10 pairs of mines, such as Fucun and Tianchen of Zaokuang group. It is found that the dust content in the feeding point and the shotcreting point is higher, and the rebound is also higher. Six pairs of coal mines, such as Fucun and Tianchen, were selected to compare and analyze the shotcreting efficiency, rebound rate, dust rate and economic and technical indicators between dry mixed mortar and traditional mortar. The results showed that compared with traditional mortar, the shotcreting efficiency of dry mixed mortar was increased by 55.1%, the work efficiency was increased by 97.9%, and the rebound rate was reduced by 4.8%. Based on the above problems existing in dry mixed mortar shotcreting operation, the joint scientific research institute of Zao mining group put forward the schemes of bag feeding of finished dry mixed mortar and centralized feeding of finished dry mixed mortar, as well as the new shotcreting machine JSPB-8LX which can automatically adjust the water cement ratio, laying a foundation for the comprehensive promotion and application of dry mixed mortar under the mine.

Assessment of the Constancy of Performance of Cementitious Adhesives for Ceramic Tiles: Analysis of the Test Results Commissioned by Polish Market Surveillance Authorities

Assessment and verification of constancy of performance (AVCP) is a complex process. Without it, the manufacturer cannot mark the product with the Conformitè Europëenne (CE) marking and place it on the EU market. The verification of the correctness of the AVCP is carried out by market surveillance. In Poland, supervision authorities regularly check manufacturers by collecting construction products that exist on the market for inspection. Among the dry-mix mortars, adhesives for ceramic tiles (CTA) constitute an essential group. The requirements for CTAs are specified in EN 12004. According to the standard, the basic characteristics of cementitious CTAs are tensile adhesion strength and open time. The adhesion measurements are performed after various laboratory conditions tests. The study analyzes the results obtained for 129 samples of cementitious CTAs, collected between the years 2016 and 2019 from the market, and tested in notified laboratories at the request of Polish construction supervision authorities. Many tested products did not meet the threshold values, which resulted in removing them from the market. The paper discusses the complexity of the tensile adhesion strength measurement. The obtained test results are considered in various dimensions, including using the simple acceptance rule method when evaluating the results, which does not consider the measurement uncertainty.