Mortar Aggregate Research Articles

Barium carbonate and supplementary cementitious materials to counteract thaumasite sulfate attack in mortars: Effect of aggregate composition

Abstract Supplementary cementitious materials (SCMs) have been shown to have a beneficial impact on carbonate-bearing mortar and concrete resistance to sulfates in general and thaumasite sulfate attack (TSA) in particular, although the effect is limited in some cases. In pursuit of improved sulfate-resistance formulations that inhibit thaumasite formation, this study added barium carbonate, both as mineral addition and as aggregate, to cements blended with SCMs. The aim was to immobilise sulfates via conversion to barite, a practically insoluble form of barium sulfate. The study was conducted on standardised mortars prepared with CEM I 52.5 N-SR 5 (reference, Ref) cement, laboratory-blended CEM III/C-SR (with slag) or CEM IV/B-SR (fly ash-bearing) cements. Mixes were also prepared with the latter two cements in which the slag or fly ash filler was partially replaced with barium carbonate. Barium or calcium carbonate sands were used as aggregate in the respective mortars, all of which were soaked in a Na2SO4 solution at 8 °C for 6 months and monitored for variations in mass, compressive strength, ultrasonic velocity, soundness (expansion) and mineralogy. The findings showed that at such low temperatures the amount of Ba2+ solubilised did not suffice to effectively immobilise the external sulfates in the blends containing SCMs. The fly ash-bearing samples, particularly where the addition was partially replaced with barium carbonate, deteriorated severely or very severely (substantial expansion and mass loss) because thaumasite precipitated even in the presence of the barite formed. The low cement content, slag-bearing blends exhibited greatest sulfate resistance, irrespective of the presence of barium carbonate as addition or aggregate. In mortars made with commercial, low C3A content (Ref.) sulfate-resistant cement, barium carbonate sand inhibited gypsum and ettringite formation, whereas both products precipitated in analogous and less porous mixes bearing limestone aggregate.

Acoustic and thermal insulation properties of recycled aggregate mortar

This study focuses on the design of a lightweight cement mortar with recycled fine aggregates of wood, plastic, and glass. The normal fine aggregate (sand) was replaced with 20%, 40%, and 60% by weight of sand of recycled aggregates, prepared by cleaning wood sawdust, broken plastic, and broken glass with mechanical milling and then using a mill to obtain a similar gradation to that of the sand. The main goal of this paper was to study the effects of using these recycled aggregates on acoustic and thermal properties as compared with those of the reference cement mortar. Acoustic insulation tests were thus carried out on samples with dimensions of 23 × 23 × 0.8 cm prepared for this purpose at the age of 28 days, with three models for each replacement ratio. The acoustic isolation results showed that cement mortar with sawdust at replacement ratios 20%, 40%, and 60% showed better acoustic isolation properties than cement mortar with plastic and glass with the same replacement percentages or ordinary cement mortar. The thermal insulation of the samples was tested in samples with dimensions of 10 × 5 × 2 cm at 28 days. The results for thermal conductivity coefficients were 0.2353 W.m-1K-1, 0.1981 W.m- 1K-1, and 0.1609 W.m-1K-1 for the replacement ratios 20%, 40%, and 60%, respectively. These results show that the cement mortar with sawdust offered less thermal insulation than cement mortar with plastic debris, while cement mortar with crushed glass was even less thermally isolated.

The Workability and Crack Resistance of Natural and Recycled Aggregate Mortar Based on Expansion Agent through an Environmental Study

Greenhouse gas emission has been a serious problem for decades. Due to the high energy consumption of traditional construction and building materials, recycled aggregate and other environmentally-friendly materials or recycled materials have been researched and applied. The treatment and reuse of construction and demolition waste (CDW) is a good way to reasonably distribute the renewable resources in the urban city. The recycled aggregate can be used in road engineering, geotechnical engineering and structural engineering. The combined use of natural aggregate and recycled aggregate may possess better performance in real constructions. This paper investigates the mechanical performance, micro-mechanism and CO2 footprint assessment of NAM (natural aggregate mortar) and RAM (recycled aggregate mortar). Compressive strength test, flexural strength test, XRD and SEM, and CO2 emission evaluation were conducted and analyzed. The results indicate that NAM depicts better compressive strength performance and RAM has higher flexural strength. The XRD and SEM patterns illustrate that the ettringite and C-S-H are the most important role in shrinkage-compensating mechanism, which is more obvious in RAM specimens. The proportion of CaO and MgO hydrated into Ca(OH)2 and Mg(OH)2 is also a key point of the volume expansion through the curing period. Finally, the CO2 emission of NA is higher than RA per unit. This indicates that utilizing recycled aggregate over other conventional resources will reduce the energy consumption, and hit the mark to be environmental-friendly.

Artificial Intelligence Approach in Predicting the Effect of Elevated Temperature on the Mechanical Properties of PET Aggregate Mortars: An Experimental Study

In this study, the effect of high temperature on the flexural and compressive strength of mortars containing waste PET aggregates was investigated experimentally. The mortar samples prepared in 5 different concentrations with a total of 2.5%, 5%, 10%, 20% and 30% PET aggregate substitution were heated up to 100, 150, 200, 250, 300 and 400 °C. After waiting for 1, 2 and 3 h at these temperatures, flexural and compressive strength tests were performed. It was observed that flexural strength and compressive strength values decreased with increasing temperature and PET aggregate amounts in all mixtures. An artificial neural network was designed to estimate flexural and compressive strength values using experimental data. It has been observed that the developed artificial neural network can predict flexural and compressive strengths with an average error of − 0.51%.

Partial Replacement of Fine Aggregates in Cement Mortar by using Pond Ash and Development of Low Cost Tiles

Pond ash is squanders and waste product of Thermal force plant, have been acquainted into Indian solid industry with save common assets of elements of cement. In India, a large portion of the Thermal force plants embrace wet technique for debris removal. Lake debris is gathered from Thermal force plant at the base, in that it contains critical measure of generally coarser particles (crossing from 150 microns to 2.36 mm). Lake debris usage assists with diminishing the utilization of normal assets. Additionally it is help to take care of the issue of removal of Pond debris since it contains enormous measure of substance mixes, for example, SiO2, Al2O3 and so on. These synthetic mixes (SiO2, Al2O3) are assumes a significant job in hydration response and assists with delivering bond between two nearby particles. Utilization of Pond Ash in concrete is a significant eco productivity drive. It is important to locate the specific appropriate rates of lake debris so it is chosen to use in differing rate as 0%, 5% 10%, 15%, 20%, 25%, 30%. Also, to check the properties of new concrete and solidified cement, for example, droop and compressive quality, rigidity, flexural quality individually. Likewise solid assumes a significant job in long life time of structure so it is additionally critical to check impact on strength by utilizing sulfate assault, chloride particle entrance, drying shrinkage. Study shows the essential properties of Pond ash. It likewise contrasts these properties and characteristic sand. Fractional substitution doesn't bring on any unfavorable impact on properties of new concrete. The outcome shows that solid invigorating great with fractional substitution of fine total. Just as Pond debris is the acceptable whenever utilized as filler material in concrete. Subsequently, it is appropriate to utilize lake debris as fine total or halfway supplanting with normal sand.

Waste Incineration Bottom Ash as a Fine Aggregate in Green Mortar: An Assessment of Engineering Properties, Durability, and Microstructure

Waste Incineration Bottom Ash as a Fine Aggregate in Green Mortar: An Assessment of Engineering Properties, Durability, and Microstructure

Avaliação da substituição total de areia natural por RCC em argamassa de assentamento

A alta geração de resíduos da construção civil (RCC) e os problemas causado pela destinação incorreta deste resíduo assim como a escassez dos recursos naturais faz crescer o número de estudos para reaproveitar o RCC em matrizes cimentícias. Contudo, poucos estudos são efetuados nos agregados reciclados finos (menor que 4,75mm) não beneficiado. O objetivo deste trabalho é avaliar a utilização da parte fina do RCC como substituição total da areia natural em argamassas de assentamento realizando a caracterização dos agregados e das propriedades argamassas no estado fresco e endurecido e verificando a influência temporal do resíduo durante um período de seis meses. Foi confeccionado 7 argamassas, uma com o agregado natural, e outras seis, para cada mês de coleta do resíduo, com a substituição total do agregado natural pelo agregado reciclado. O traço utilizado nas argamassas foi de 1:1:6 (cimento: cal: agregado), em massa. Os resultados mostram que as argamassas com agregado reciclado tiveram resultados inferiores para a densidade, retenção de água, resistência à tração e à compressão e superiores para absorção de água por capilaridade quando comparado com a argamassa com agregado natural. Em geral, os agregados reciclados se mantiveram constantes ao longo do tempo analisado. Contudo, os agregados reciclados atingiram limites superiores ao mínimo permitido por normas brasileiras, sendo uma alternativa viável a sua utilização em argamassas de assentamento.

Recycling of crushed waste clay brick as aggregates in cement mortars: An approach from macro- and micro-scale investigation

The waste clay brick (WCB) was crushed and used as the fine aggregates to produce recycled mortars with sufficient workability (i.e. high water-cement ratio of 0.6). Two curing conditions (air and standard) and two statuses of WCB (dry and pre-soaking) were considered in this study. It was found that the recycled mortars with the dry WCB had relatively higher mechanical properties and lower water absorption but a converse tendency for pre-soaking WCB mortars, regardless of the curing conditions. Although the internal curing effect of WCB was more pronounced under the air condition, the overall performance of recycled mortars cured in the standard condition was better. Microstructural changes were then investigated through X-ray diffraction (XRD), thermogravimetric-differential scanning calorimetry (TG-DSC), scanning electron microscopy (SEM), and mercury intrusion porosimetry (MIP) to support the macro property changes of recycled mortars. As evaluated by TG-DSC, the hydration degree of cement in the recycled mortar with dry WCB were greater than that of reference group without WCB, and the hydration degree further increased when the natural aggregates were replaced by the pre-soaking WCB. Regardless of the curing conditions, the WCB aggregate were tightly bonded by cement paste in the recycled mortar with dry WCB, and the interfacial transition zone (ITZ) between them was more compact. Conversely, the interval between pre-soaking WCB and cement matrix was observed. The incorporation of dry or pre-soaking WCB increased the porosity of recycled mortars. The recycled WCB mortars could be used for producing the cleaner building materials.

Radiation Shielding Properties Prediction of Barite used as Small Aggregate in Mortar

Construction materials used in the nuclear industry used to be mainly heavy materials, including lead plates, radiation-resistant heavy concrete, etc. However, these materials are either toxic after a long time of use (lead) or difficult to construct (radiation-resistant heavy concrete) and their cost is rather high. Therefore, there is a need for the manufacturing of a new kind of material with good radiation resistance, which is light, easy to use, and costs less. Barium is less toxic and more cost-effective than lead. Due to the importance of barium compounds in radiation shielding, the study of gamma radiation interactions within these compounds becomes essential, so the most important part of such a study is the experimental one, which shows the effect of the barite powder in the radiation resistance of the mortar. The research results show that the higher the thickness and percentage of barite powder, the higher is the radiation resistance.

Efficacy of expanded polystyrene as fine aggregate in cement mortars modified with latex paint as an alternative to polymer admixture

Abstract In this present study, the effectiveness of expanded polystyrene (EPS) waste used as 20, 40 and 60% fine sand replacement in development of lightweight cement composite was evaluated. The cement mortar was strengthened by 10% low cost latex paint emulsion as an alternative to the more expensive polymer admixtures. Six different mix designs were produced and tested for compressive and split tensile strength according to BS EN standards. Scanning electron microscope (SEM) analysis was also conducted to analysis the micrograph of the samples. It was observed that as the EPS content, latex paint polymer admixture and curing days were increased, marginal increment in compressive strength was obtained. However, EPS fines were most effective in improving the split strength while latex paint admixture had comparatively less part to play in the strength development. The micrograph images showed that the EPS fines were uniformly distributed within the microstructure and the latex paint developed polymer films. These mechanisms coupled with the cement hydrate products were responsible for the enhanced strength observed in the samples.

Enhancing the Performance of Recycled Aggregate Mortars Using Alkali-Activated Fly Ash

The aim of this paper is to advance the research on the use of alkali-activated fly ash in recycled concrete aggregate (RCA) bearing mortar (RAM) to achieve low carbon footprint and sustainability in construction. To this end, the present paper explores the advantages in terms of improved properties of RAM by incorporating fly ash with an alkali-silicate activator. Results of testing reveal that compressive strength of RAM is improved by more than 30% by using 20% fly ash with 3–6% silicate-activator. RAM with activated-fly ash showed significant improvement in resistance against water absorption, chloride penetration, and acid attack. The durability parameters are fairly correlated with the compressive strength: improvement in durability performance is noticed with increasing compressive strength, indicating that microstructural developments that yield high mechanical strength also contribute to improvement in durability.

Study on the effect of selected parameters on the alkali-silica reaction of aggregate in ground glass fiber and fly ash-based geopolymer mortars

In this study, the effect of selected parameters on the alkali-silica reaction (ASR) of aggregate in ground glass fiber (GGF) and fly ash-based geopolymer mortar was investigated. This work focuses on three main objectives: 1) to study the effect of the binder composition, 2) to study the effect of the ASR accelerating environment, and 3) to study the effect of the chemical/mineralogical composition of aggregate, on the ASR behavior of geopolymer mixtures. To study the effect of paste composition on the ASR behavior of GGF-based geopolymer mortars were compared to a fly ash-based geopolymer mixture and an ordinary Portland cement mixture. To investigate the effect of curing condition, mortar bars were cured in two ASR accelerating environments; mortar bars were either immersed in a high alkali solution or exposed to a high relative humidity environment. To evaluate the effect of the chemical composition of aggregate, two types of ASR-reactive aggregate, one mainly composed of glassy silica and one mainly composed of limestone with chert impurities were used for the ASR study, and the results were compared to a mixture with non-reactive limestone aggregate. To evaluate the ASR behavior of geopolymer mixtures, length expansion, and the change in dynamic modulus of elasticity (DME) of mortar bars that were exposed to either of the ASR accelerating conditions were monitored for ten weeks. Based on the results obtained from this study, both geopolymer mixtures showed lower levels of expansion in comparison to the OPC mixture. However, despite the lower expansion level, a significant loss in DME was observed for fly ash-based geopolymer specimens made with siliceous aggregate and cured in a high alkali environment. Finally, curing the specimens in a high relative humidity environment did not seem to be an effective procedure in the evaluation of the ASR behavior of aggregate, as this method failed to discriminate the ASR-reactive aggregate used in this study.

Feasibility of using treated corn cob aggregates in cement mortars

In this research, a method of cement paste treatment for corn cob aggregates was applied to improve the compatibility with the cement matrix, and the possibility of utilizing the treated corn cob aggregates (TCCAs) as an economical and sustainable alternative to river sand was investigated. The mix proportions of the treatment were determined by water absorption. Microstructural investigations using XRD and SEM were carried out to evaluate the cement hydration products. The effects of the volume replacement of sand by TCCAs and the size of the TCCAs on the physical, mechanical, and thermal resistance properties of the mortars were studied. The results demonstrate that, after treatment, the corn cob aggregates had a lower water absorption and almost no inhibitory effects on the cement hydration products. A high content of TCCAs was even found to accelerate the cement hydration. The use of TCCAs was found to decrease the workability and strength while improving the ductility and thermal insulation properties of the mortars. The increase in the size of TCCAs was found to have no effects on the density and thermal conductivity, whereas it decreased the workability and mechanical properties of the mortar. Moreover, the substitution of sand with TCCAs did not significantly change the residual strength until the temperature reached 200 °C. Mortars constructed with TCCAs therefore have promising applications as lightweight structural concrete.

Utilization and assessment of recycled polyethylene terephthalate strapping bands as lightweight aggregates in Eco-efficient composite mortars

In this work, we explored the possibility of using aggregates of shredded polyethylene terephthalate strapping bands (SPETSB) in mortar. A survey was carried out to assess the feasibility of recycling this plastic waste to be used in the manufacture of environmentally-friendly lightweight mortars through partial replacement of silica-calcareous sand with lighter SPETSB aggregates, by volume at 0, 15, 30, 45 and 60 %. A scanning electron microscopy analysis along with a study of the alkali – silica reaction was conducted; the density, mechanical and thermal properties were assessed for evaluating the properties of lightweight mortar containing SPETSB aggregates (LWMSB). Laboratory tests revealed encouraging results and confirmed the feasibility of manufacturing lightweight aggregate mortar with a density between 1620 and 1944 Kg/m3, a compressive strength equal to 28.8 MPa and thermal conductivity of 0.75 W/m.K, at 28 days, for 60% of SPETSB. The flexural strength, ultrasonic pulse velocity (UPV) and dynamic elastic modulus (Ed) were lower by 46%, 25% and 56%, respectively, compared to the values of normal weight mortar (NWM). This study also allowed deducing that the expansion due to the alkali–silica reaction decreases for all LWMSB types, when the substitution rate of SPETSB increases; this makes it possible to obtain a non-reactive mortar. Therefore, these findings suggest that using LWMSB composite mortars in building applications is possible.

Leaching behavior of copper and chromium in the mortar containing artificial fine aggregate prepared by contaminated soil

The feasibility of recycling contaminated soil by preparing artificial fine aggregate (AFA) and applying in artificial fine aggregate mortars (AFAM) was investigated systematically. Properties and heavy metal immobilization status of AFA, compressive strength and heavy metal leaching behavior of AFAM were tested. Results showed that Cu reduced the melting and crystallization temperatures of AFA, whereas Cr improved that. Heavy metal addition had a negative impact on the compressive strength of AFAM, but the toxicity characteristic leaching procedure (TCLP) test indicated that the AFAM system was is suitable for solidification of heavy metals. Moreover, it was observed that Cu leaching almost disappeared in the initial periods, while it tended to dissolve in the terminal periods. The leaching mechanism of AFAM with Cr at the initial periods conformed to Fick's law of diffusion, and it tended to deplete in the terminal periods. These results are practically instructive the recycling of heavy metal contaminated solid waste in the field of construction materials.

Resource-saving potential of brick scrap from demolition of buildings

The composition and properties of crushing products of brick scrap of different sizes were studied. It is shown that a large (5–40 mm) and small (0.16–5.0 mm) fraction of brick scrap crushing products may be of interest for replacing natural aggregates, while a pulverized (0–0.16 mm) fraction has pozzolanic activity. The presence of cement masonry mortar in the composition of products for crushing scrap brick walls of buildings is the main obstacle to their use as a large aggregate for light concrete: the average density of crushed brick grains in this case was 890 kg/m3, while for crushed cement grains – at least 1350 kg/m3. With an increase in the degree of crushing of these wastes, their material composition and physical properties are averaged and therefore more suitable for reuse in construction, including as a fine aggregate for mortars. The chemical and mineral composition of brick scrap, studied on the example of a dusty fraction, allows us to predict its good prospects for replacing natural mineral raw materials in the production of firing materials, for example, Portland cement.

Impact of Mixing Approaches on Properties of Recycled Aggregate Mortar

Impact of Mixing Approaches on Properties of Recycled Aggregate Mortar

An Experimental and Environmental Evaluation of Mortars with Recycled Demolition Waste from a Hospital Implosion in Rio de Janeiro

Construction and demolition waste generation have increased significantly over the century, many times, as a result of obsolete buildings that lead the effort toward demolition. This paper investigates the environmental performance of mortars developed with recycled concrete from the partial building demolition of the Clementino Fraga Filho University Hospital in Rio de Janeiro, Brazil. Life Cycle Assessment is associated with experimental data to validate the application of the residue as an alternative to cement-based mortars. Natural river sand and recycled concrete aggregates, both at a micrometer scale, are employed in the production of four different mortars of compressive strength ranging 50 MPa. The aggregates’ replacement rates defined are 15, 25, and 50% in volume. The recycled microparticles’ mineralogical composition was determined by SEM images and XRD analysis. In addition, the attached cement paste surrounding the original aggregate particle was quantified by chemical attack. Rheological and mechanical properties of the resulting mortars were assessed by the Vane spindle rheometer and uniaxial compressive strength experiments, respectively. The approach to mortars’ environmental performance considered a cradle-to-gate scope using different sensitivity analysis parameters. We demonstrated the feasibility of developing an eco-efficient mortar taking advantage of rarely applied recycled particles. Compressive strength and environmental performance (particularly, the ozone layer depletion potential and abiotic resource depletion potential categories) increased with the aggregate replacement rate. In addition, the rheological results provided relevant data, still insufficient to recycled aggregate mortars, presenting an exponential increase of yield stress with effective water to cement ratio.

High-pressure behaviour and phase stability of Ca2B6O6(OH)10·2(H2O) (meyerhofferite)

The high-pressure behaviour of meyerhofferite [ideally Ca2B6O6(OH)10·2(H2O), with a ~ 6.63 Å, b ~ 8.34 Å, c ~ 6.47 Å, α = 90.8°, β = 102°, γ = 86.8°, Sp. Gr. P\(\overline{1}\)], a B-bearing raw material (with B2O3 ≈ 46 wt%) and a potential B-rich aggregate, has been studied by single-crystal synchrotron X-ray diffraction up to 9 GPa, under hydrostatic conditions. Meyerhofferite undergoes a first-order phase transition to meyerhofferite-II, likely iso-symmetric, bracketed between 3.05 and 3.48 GPa, with a spectacular unit-cell volume discontinuity (i.e., ΔV ~ 30 Å3). The isothermal bulk modulus (KV0 = β−1P0,T0, where βP0,T0 is the volume compressibility coefficient) of meyerhofferite, was found to be KV0 = 31.6(5) GPa, and a marked anisotropic compressional pattern, with K(a)0: K(b)0: K(c)0 ~ 1.5:1:3, was observed. The bulk modulus of meyerhofferite-II increases to 55(2) GPa and, differently to the majority of the borates studied at high pressure so far, the anisotropic compressional pattern of meyerhofferite decreases markedly in the high-pressure form. The P-induced deformation mechanisms controlling, at the atomic scale, the bulk compression of meyerhofferite are here described. Considerations about the use of meyerhofferite as a potential B-based aggregate in concretes, mortars or resins, are provided.

Effect of bed roughness on flow field around spur dyke in a rigid bed meandering channel

ABSTRACT Effect of bed roughness on flow field and turbulence characteristics due to spur dyke in rigid bed meandering channel is presented in this study. This is an extension of authors’ earlier work. In the experiments, cement mortar, sand particles on cement mortar and small aggregates on the cement mortar surfaces are used to generate different bed roughness. 3-D velocity measurements are obtained with Acoustic Doppler Velocimeter (ADV). In a rigid bed meandering channel without spur dyke, flow concentrates near the convex bank up to inflection point in the downstream of Apex. Inflection point moves towards the upstream with increase in the roughness of the channel. The water surface slope along the center line increases with increase in bed roughness. In presence of spur dyke, the maximum velocity in the channel decreases with increase in bed roughness. When the spur dyke is located on the convex bank of Apex, the length and width of separation zone decrease with increase in bed roughness. The magnitude of turbulence intensities decreases with increase in roughness.