Mortar Aggregate Research Articles

Study of mechanical, acoustic, and microstructure properties of lightweight mortars produced with expanded clay

The inclusion of alternative materials in concrete production is very efficient, having a sustainable bias and improving the main properties of concrete. Expanded clay has been used to produce mortar and concrete, partially replacing the aggregate with the main purpose of reduces specific mass and the weight of the structure, also improves acoustic and thermal characteristics. This study proposes the use of expanded clay to a lightweight laying and coating mortar compared to conventional mortars. It was investigated the influence of expanded clay as a substitute for conventional fine aggregate in mortars in ratios of (5, 10, 15, and 20) %. Tests were carried out in the fresh (consistency index, mass density, incorporated air, and water retention) and hardened states (flexion tensile strength, axial compression, apparent mass density, and potential tensile adhesion strength) based on the Brazilian Technical Standards Association (ABNT). The microstructure was also investigated using a scanning electron microscope (SEM). The results show that the replacements improved the strength of the mortars, being 20% higher than expected by the standard. Expanded clay is a sustainable alternative and adds new properties (thermal and acoustic) to mortars.

Performance evaluation of treated recycled fine aggregate on mortar properties

The utilization of Construction and demolition (CDW) of building material has proven to be a sustainable option. However, the inferior properties of CDW limit its utility as construction material, especially the finer portion of demolition waste. Therefore, this research study aims to investigate the influence of Treated recycled fine aggregate (TRFA) on the flow and strength property of mortar over untreated recycled fine aggregate (URFA). Two types of mortar mix with cement-to-aggregate proportions of 1:3 and 1:4 at 0%, 25%, 50%, 75% and 100% replacement of River sand by two types of RFA- untreated (URFA) and treated (TRFA) were prepared. Results show that untreated recycled aggregate mortars present poorer behavior, whereas improved results are obtained in the case of treated aggregate mortar which is even better than the reference sample prepared with natural sand. Therefore, the study concluded that there is the possibility of enhancement in the properties of mortar by using TRFA. Further, the finding reveals the valid potential of RFA (after treatment) as a replacement for river sand in mortars.

Experimental Study of High-Temperature Resistance of Alkali-Activated Slag Crushed Aggregate Mortar

Experimental Study of High-Temperature Resistance of Alkali-Activated Slag Crushed Aggregate Mortar

Effect of basalt and polypropylene fibers on crumb rubber mortar with Portland cement and calcium aluminate cement binders: Strength and artificial neural network prediction model

This paper aims to study the influence of basalt fiber (BF) and polypropylene fiber (PPF) in crumb rubber (CR) mortar made of two different types of cement, including ordinary Portland cement (OPC) and calcium aluminate cement (CAC). CR was used to partially (5%, 10%, 15%, and 20% by volume) replace the fine aggregate in OPC and CAC mortars. BF and PPF were added (0.1%, 0.3%, and 0.5% by total volume) in the CR mortars. The consistency, density, compressive, and flexural strength of cement mortars were investigated. The use of CAC cement slightly increased the consistency; however, the results showed that the CR replacement and the addition of both fiber types tend to reduce the consistency in OPC and CAC mortars. Significant reduction in the density of fiber-added CR mortar was found with increasing CR content, whereas the influence of both PPF and BF was minimal. The fiber-added CR mortar made of both binder and fiber types in general exhibited a reducing trend in the 28 days compressive strength when increasing CR and fiber contents. Nevertheless, an enhancement in the compressive strength of CAC mortar with 20% CR was found with the addition of 0.1% of both fibers. The use of CR and addition of the fibers generally decreased the flexural strength of mortar made of both binder types; however, the addition of 0.3% BF in mortars containing 15–20% CR positively affected the flexural performance. Finally, the artificial neural network (ANN) approach demonstrated the ability to predict the compressive strength of fiber-added CR mortars. The model showed a considerably insignificant mean square error (MSE) of 1.4–1.5 and high plot regression (R) results of 0.97–0.98.

Alkali-silica reaction of sanitary ware ceramic wastes utilized as aggregate in ordinary and high-performance mortars

Waste management has been the foremost concern in the last decades. Utilizing sanitary ware ceramic (SWC) wastes in concrete has been found to be beneficial in terms of sustainability and cost in previous studies; however, deleterious alkali-silica reaction (ASR) potential of this waste aggregate, albeit it’s high SiO2 content, has not been taken into account. This study aims to examine ASR potential of SWC wastes as well as the effects of permeability, w/c ratio, and reactive powder content of mixtures on the ASR-induced expansions in detail. Accelerated mortar bar, total and capillary water absorptions, and chloride ion penetration tests were conducted for %20, %40, %60, %80, and %100 replacement ratios at the first part of the study. The SWC aggregate showed ASR-induced expansions in “pessimum proportions”. With a 9-day delay, similar patterns (trends) of ASR expansions were observed in the mixtures with a w/c ratio of 0.3 as compared with those of 0.5 w/c ratio. While the ASR expansions had meaningful relations with the water absorption tests and w/c ratio, there was no noteworthy correlation with the rapid chloride ion penetration test results, since the SWC aggregate effected the properties of pore solution. The effect of the finer grains of the SWC aggregate on ASR was investigated in the second part of the study. For this purpose, the SWC aggregate finer than 250 µm was replaced with same sized limestone aggregate. The results revealed that the finer grains of SWC aggregate were responsible for the reductions observed in the first part of the study not due to “pessimum effect” phenomenon but rather to the pozzolanic activity of the finer grains.

Multifield coupling study on random aggregate concrete under microwave irradiation

Microwave-assisted concrete aggregate recycling is a new green technology with minute pollution and low energy generation during the heating process. In this study, a random aggregate concrete model is established based on a real industrial microwave heating system. The secondary development of a MATLAB and COMSOL Multiphysics interface is applied to realize a multifield coupled numerical analysis of the electromagnetic field, heat transfer field, and mechanical field of concrete under microwave irradiation. The model is validated by experimental tests. The results show that the dielectric loss is the main factor that influences the concrete temperature variation. Tensile stress and shear stress are generated at the mortar–aggregate interfaces. A high microwave energy input leads to significant temperature and stress gradients between the aggregates and the mortar. Compared to the aggregates, the mortar suffers a larger deformation in a microwave field, finally leadings to its damage. Thus, the investigation of the thermal responses of aggregates and mortars under microwave irradiation will provide reference for the further development of microwave-assisted concrete recycling technology.

Experimental Investigation on the Effect of Converter Slag Aggregate for Blended Mortar Based on CT Scanning

This study investigated the air aging converter (Basic Oxygen Furnace, BOF) slag aggregate mortar with pulverized fly ash (PFA) and ferronickel slag (FNS). The chemical composition and mineralogical constituents of BOF incorporated mortar were analyzed. Setting time, flowability, compressive strength, and length change were measured to evaluate the fundamental properties of BOF mortar. The X-ray CT analysis was employed to observe the effect of converter slag in the cement matrix visually. The results showed that the hydration of BOF generated a pore at the vicinity of the aggregate, which decreased the compressive strength and increased the length change of mortar. However, the PFA or FNS incorporation of PFA or FNS can decrease the alkalinity of pore solution and subsequently reduce the reactivity of BOF aggregate. Thus, the incorporation of PFA and FNS can be a way to eliminate the disadvantage of BOF, such as volume expansion.

An investigation on the performance of lightweight mortar-based geopolymer containing high-volume LECA aggregate against high temperatures.

The influence of lightweight expanded clay aggregate (LECA) on the physico-mechanical properties and microstructure of geopolymer mortar containing slag binder alkali-activated with sodium silicate solution before and after exposure to thermal loads was investigated. In the current procedure, siliceous sand was partially substituted with LECA fine aggregate at levels of 0%, 25%, 50%, 75%, and 100%, by volume. The effect of LECA on the performance before exposure was evaluated by measuring flowability, water absorption, bulk density, thermal conductivity, and compressive strength. To monitor the behavior after exposure, a batch of specimens having the same composition was subjected to high temperatures in the range of 400-1000°C for 2h with a heating rate of 5°C/min. In a similar fashion, mass loss and residual compressive strength were determined. New phase-based geopolymers were examined using Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The findings indicated that the incorporation of LECA up to 100% as an alternative to siliceous sand aggregate in geopolymer mortar has an adverse effect on compressive strength and water absorption, but has a positive effect on workability, thermal conductivity, and relative strength after exposure to elevated temperatures.

Effect of magnesium phosphate cement on the mechanical properties and microstructure of recycled aggregate and recycled aggregate concrete

This paper aims to investigate the effects of magnesium phosphate cement (MPC) on the mechanical properties and microstructure of recycled aggregates (RA) and recycled aggregate concrete (RAC). Two surface modification methods, namely, the MPC wet and dry mix methods, were designed and applied to improve physical properties of RA, respectively. Further, the mechanical properties of the RAC mixes with modified RA (MRA) were assessed in terms of compressive, splitting tensile strength, and elastic modulus. In addition, X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), and Energy Dispersive Spectroscopy (EDS) were carried out to illustrate the effects of surface modification methods on the microstructure of RAC. The results indicated that the MPC dry mix method shows more appropriate on the quality enhancement of RA compared to MPC wet mix method, improving the apparent density, specific gravity, water absorption, and the crushing value of RA by 3.6%, 7.4%, 26.7%, and 3.0%, respectively. Meanwhile, the corresponding mechanical properties of the concrete are enhanced, particularly the compressive strength getting increased by up to 41.5%, due to the new hydration reactions. Based on the microstructural analyses, the coarse surface of RA is changed more homogeneous and denser when modified by MPC, and the MPC is observed at both interfacial sides of recycled aggregate mortar and fresh concrete mortar for the reinforcement of the interfacial strength between the new and old mortar.

Potential use of clay brick waste powder and ceramic waste aggregate in mortar

This study investigates the potential use of clay brick waste powder (CBP) and ceramic waste aggregate (CWA) in mortar. Cement was replaced by CBP in the mortar mixtures at four ratios (10, 20, 30 and 40 wt%). Meanwhile, CWA was used as a substitute for river sand in the mortar at two levels (50 and 100 wt%). The results demonstrated that the flow spread of the mortars made of CBP and CWA declined sharply owing to the rough and multi-angle texture of their surface. The compressive strength of the mortars decreased slightly at early ages but noticeably improved long term.

Use of Wood Waste as Aggregate in Mortars: An Experimental Study

The construction sector is one of the largest and most active in the world economy, being responsible for consumption of huge amounts of natural resources. Natural sand and gravel are the most important resources in construction, they are mainly used as aggregates, and its extraction often causes environmental damages. Bearing these considerations in mind, the wood waste has been used as partial replacement of natural sand in concrete and mortars to reduce the environmental burden of natural sand extraction. The aim of this paper is to characterize the physical and mechanical properties of natural hydraulic lime-based mortars proportioned with different percentages of wood wastes (0% to 30%) as replacement of natural sand. Thus, several specimens of mortar proportioned with wood wastes have been subjected to different experimental procedures, such as: workability, mechanical strength, water absorption and thermal conductivity. Results obtained showed that the incorporation of wood waste causes a reduction of mechanical resistance mostly due to the increase in open porosity, but on the other hand the thermal conductivity presents an improvement up to 83%. The results obtained are quite acceptable and encouraging for the follow-up studies using wood wastes as fine aggregate in mortars and, simultaneously, to improve the energy efficiency of buildings since this waste material contributes to obtain mortars with improved thermal performance.

Research on the effect of carbon nanotubes on cracking and impact properties of rubber aggregate mortar

Carbon nanotubes (CNTs) were added into rubber aggregate mortar (RM) as fillers. Three CNT gradients of 0.05%, 0.1%, and 0.2% were set to study the effects of different CNT contents on the fluidity, mechanical strength, cracking resistance , and impact performance of RM. The strain and displacement of the specimen's critical path during the impact process were analyzed by data simulation. As a result, CNT can reduce the fluidity of RM to a certain extent. The effect on mechanical strength, cracking property, and impact property of RM increases first and then decreases. When the content of CNT was 0.1%, the performance of RM was optimal, the flexural strength and compressive strength of 3d, 7d, and 28d are 6.3 MPa, 7.5 MPa, 8.7 MPa, and 30.3 MPa, 43.8 MPa, 52.1 MPa, respectively, increased by 46.5%, 38.9%, 29.9% and 43.6%, 53.7%, 40.1%, according to the control group. And the cracking time was 52.33 h, 16.1% longer than the control group. The first crack and failure impact times were 61 and 66, respectively, were greatly improved. Numerical simulation of impact tests found that the displacement of the specimen reached its peak value at 30°, 90°, and 150° along the circumference, which is consistent with the location of tensile damage. • The strength loss caused by rubber particles was compensated by the addition of CNT. • Carbon nanotubes can effectively slow down the cracking of rubber aggregate mortar and improve its impact resistance. • The stress state of U-shaped specimen under impact load is analyzed in detail by calculation.

New system for vibrating and orientation of steel fibers in masonry mortars

The incorporation of reinforcing fibers during the kneading process has become an efficient method to improve the flexural strength of building binder materials. In this work, a new system for the vibration and orientation of metallic fibers has been developed. This allows the fibers to be positioned perpendicular to the direction of the flexural stress. This vibrating system for construction mortars in a fresh state improves the performance of mortars made with recycled aggregate, increasing their mechanical resistance and their application within the building sector. Testswere carried out with mortars made with two types of recycled aggregates and two different percentages of reinforcing fibers. The results show thatby applying the vibrating system implemented, it is possible to increase the mechanical resistance of mortars made with recycled aggregate by more than 15%. • A new vibrating device to orientate fibers was developed. • A comparison between concrete and ceramic aggregate mortars was performed. • It was possible to orient more than 50% of the steel fibers content in all the samples made. • The orientation of fibers transversely to the load increases the flexural strength of mortars made with recycled aggregate.

Recycling of WEEE Plastics Waste in Mortar: The Effects on Mechanical Properties

This work focused on the recycling of WEEE plastic waste as a partial substitute for aggregate in light mortars. The plastic mix, provided by the IREN group, was used as a replacement of aggregate in 15, 30, 45, 60, 75, and 90%vol in mortars. Worsening of the mechanical performance of around 50% was detected already at only 15%vol of mineral aggregate substituted with plastic waste. The explanation of this phenomenon was found in both the scarce mechanical properties of the used plastic and in the poor adhesion between matrix and plastics that resulted in extra-porosity formation, as also demonstrated by comparing the results with several models in the literature. However, the use of plastic waste as a partial replacement of natural aggregate contributes to the preservation of natural resources and, in any case, does not limit the application of these materials in non-structural applications.

Preliminary Study of Recycled Aggregate Mortar for Electric Arc Furnace Dust Encapsulation

This article shows the preliminary results of a study carried out to determine the technical feasibility of encapsulating a high percentage of EAFD in cement-based mortars manufactured with the fine fraction of recycled concrete aggregates (RCA). Two families of mortars, with natural aggregate as a reference and with RCA, were studied. An incorporation rate by weight of two parts mortar to one part EAFD was tested. The mechanical strengths (compressive strength and tensile strength) before and after immersion in water, the rate of delitescence and the leaching behavior were studied. Mortars made with RCA showed similar mechanical strengths to the reference mortars made with natural aggregates; however, the incorporation of EAFD decreased the mechanical strengths. Encapsulation considerably reduced the leaching of heavy metals, although the Pb concentration remained above the hazardous waste limit. With this preliminary study, two wastes are managed together, and the results have shown that the use of RCA instead of natural aggregate is a viable alternative since it does not significantly impair the mechanical or leaching properties of the cement-based matrices used to encapsulate EAFD.

Performance and Fracture Analysis of Composite Interfaces for Semi-Flexible Pavement

Semi-flexible pavement is widely used in pavement engineering due to its excellent rutting resistance; however, it mainly fails due to cracking. Therefore, it is important to understand the properties of the aggregate–mortar–asphalt interfacial transition zone, to better understand the cracking mechanism of the semi-flexible pavement. In this work, we used pull-off tests and digital image analysis technology to compare and analyze the interfacial tensile strength and granite–bitumen–mortar interactions in three types of asphalt (70# matrix asphalt, PG76-22 modified asphalt and S-HV modified asphalt) at different curing ages. The analysis results showed that, for the three different bitumen materials, with settled mortar, the peak interfacial tensile strength values all occurred at approximately 14 d of curing. In addition, the order of the tensile strength followed the order of asphalt penetration degree; the order of the interfacial water damage resistance from weak to strong was 70# asphalt cementation specimen, PG76-22 modified asphalt cementation specimen, and S-HV modified asphalt cementation specimen. The results of this analysis highlight the original contributions of the optimum curing time for the composite interface of semi-flexible pavement materials prepared with different asphalts to reach optimum crack resistance.

Properties of Mortar Composites from Plastic Waste

ABSTRACT An application of plastic waste blended with the sand aggregate in mortar helps to improve some properties of the mortar as well as reducing environmental pollution while solving the problem of a shortage of natural sand. In this study, polystyrene (PS) and high density polyethylene (HDPE) wastes were examined as partial replacements for sand in mortar. The water absorption, bulk dry density, flow value and compressive strength of mortar containing these plastic wastes were analyzed. In addition, the thermal conductivity of wall models plastered with mortar containing plastic waste was investigated. The main results were as follows. The plastic waste and the sand had comparable particle sizes. The properties of mortar with PS were found to be better than that of the mortar with HDPE. The water absorption of mortar with PS was comparable with the reference mortar but lower than that of mortar with HDPE. The compressive strength of the mortar with PS was significantly higher than that with HDPE. The thermal conductivity of a wall plastered by mortar containing PS decreased as the PS content was increased, whereas the thermal conductivity of a wall plastered by mortar containing HDPE increased as the HDPE content was increased. The results indicated that 10.0% PS could be used as a partial replacement for sand in mortar with an improvement in some of the properties of the mortar.

Micro Destructive Analysis for the Characterization of Ancient Mortars: A Case Study from the Little Roman Bath of Nora (Sardinia, Italy)

In this work, a protocol of a partially invasive sampling for the archaeometric characterization of ancient mortars from the little Roman Bath of Nora (Sardinia, Italy) is presented. Optical microscopy and different analytical techniques such as X-ray diffraction, X-ray fluorescence, thermo-gravimetric analysis, and physical/mechanical tests have been carried out on the mortars. These analyses were performed to investigate the chemical composition, alteration products, and binder pozzolanic activity. An innovative method of image analysis has been tested to obtain information about the size and shape of both the mortar aggregates and the binder/aggregate ratio. This new particle-size analysis has two different advantages: (i) it saves a huge volume of material compared to a classic granulometric classification through its use of a sieve and (ii) is eco-friendly in respect to the environment by saving a large volume of liquid waste derived from the acid attack for the separation of the insoluble aggregate from the soluble binder, as would be done for a common sieving. Results show a local provenance of the aggregates. The use of two different limestones for the mortars’ binder production was detected and probably this raw material belongs to the nearby Roman town of Karales (current day Cagliari).

Unexpected Findings in 16th Century Wall Paintings: Identification of Aragonite and Unusual Pigments

Sixteenth century wall paintings were analyzed from a church in an advanced state of decay in the Apennines of central Italy, now a remote area but once located along the salt routes from the Po Valley to the Ligurian Sea. Infrared spectroscopy (FTIR-ATR), X-ray diffraction (XRD) and scanning electron microscopy (SEM) with a microprobe were used to identify the painting materials, as input for possible future restoration. Together with the pigments traditionally used for wall painting, such as ochre, ultramarine blue, bianco di Sangiovanni, cinnabar/vermilion, azurite, some colors were also found to have only been used since the 18th century. This thus suggests that a series of decorative cycles occurred after the church was built, confirmed by the multilayer stratigraphy of the fragments. Some of these colors were also unusual, such as clinochlore, Brunswick green, and ultramarine yellow. The most notable result of the analytical campaign however, was the ubiquitous determination of aragonite, the mineralogical form of calcium carbonate, mainly of biogenic origin. Sources report its use in Roman times as an aggregate in mortars, and in the literature it has only been shown in Roman wall paintings. Its use in 16th century wall paintings is thus surprising.

Effect of Fly Ash on Properties of Mixed Aggregate Plastering Mortar

The effect of fly ash content on the properties (fluidity, apparent density, water retention, strength, and bonding strength) of mixed aggregate plastering mortar is mainly studied in this paper. The results show that with the increase of the fly ash content, the flow degree of the mortar is gradually increased and then decreased; the apparent density, water retention, and compressive strength of the mortar are gradually reduced; the bonding strength of the iron-tail mineral sand and the artificial sand mixed aggregate mortar is gradually reduced, and the bonding strength of the iron-tail mineral sand and the sand-sand mixed aggregate mortar firstly increases and then falls.