Crushed Brick Research Articles

Thermal and mechanical properties of demolition wastes in geothermal pavements by experimental and machine learning techniques

Despite the growing interest in using construction and demolition (C&D) waste materials in geotechnical engineering projects, there is limited knowledge of their thermo-mechanical properties, which is essential for the design of energy geostructures, such as geothermal pavements. The pavement unbound layers can be integrated with heat exchangers to form a novel pavement concept, namely geothermal pavements. This study focuses on recycled concrete aggregate (RCA), crushed brick (CB), waste rock (WR), and reclaimed asphalt pavement (RAP), and aims to investigate the thermal conductivity of these C&D materials as well as their response to combined dynamic loads and temperature. Thermal conductivity was measured using a prototype divided bar equipment. Temperature-controlled repeated loading triaxial (RLT) tests were undertaken to evaluate the effect of temperature on deformation properties of the C&D materials. RLT tests were conducted at 5 °C, 20 °C, 35 °C, and 50 °C. Deformation behavior of the C&D materials at different temperatures was characterized using the shakedown concept. Thermal conductivity measurements indicated that CB and RCA had higher thermal conductivity compared to WR and RAP. RLT results showed that RCA exhibited plastic shakedown (Range A) behavior in all temperatures, while CB and WR demonstrated plastic creep (Range B) behavior. RAP exhibited plastic creep behavior at 20 °C and 5 °C, and incremental collapse (Range C) behavior at 35 °C and 50 °C. An artificial neural network (ANN) model was developed considering the physical properties and test variables as input parameters. Sensitivity analysis was then performed on the proposed ANN model. Results of the ANN modeling provided new insight into the deformation behavior of C&D materials at different temperatures and agreed with the experimental results.

Permanent Deformation and Rutting Resistance of Demolition Waste Triple Blends in Unbound Pavement Applications.

Virgin quarried materials are becoming increasingly scarce in our environment, and these materials are no longer a viable or economical solution for the construction industry. The construction industry is constantly seeking new markets for recycled waste in civil engineering applications. This research’s primary focus is the optimization of the usage of recycled materials such as recycled glass (RG), crushed brick (CB), and crushed concrete (CC), in pavement base/sub-base applications. Various percentages of RG, up to 40%, were blended with two types of CC in this research. The CC and CB, which were used as triple blends in this research, were utilized for the upper (100% CC) and lower sub-bases (up to 50% CB). This study sought to establish the maximum amount of RG that could be incorporated in the triple blends with CB and CC whilst maintaining an acceptable performance. Thus, a comprehensive series of fundamental and advanced geotechnical laboratory tests, including repeated load triaxial (RLT) and wheel-tracker (WT) tests, were performed to assess the engineering properties and permanent deformation characteristics of these triple blends. The particle-size distribution curve and California Bearing Ratio (CBR) values of all the blends met the minimum requirements. Results of RLT tests confirmed that all the nominated blends were found to provide the resilient modulus value required to be used as pavement materials. The WT results on the triple blend with 15% RG showed that the specimen performed exceptionally well during the test and comfortably met the requirements to be used in pavement applications. Based on the engineering properties and permanent deformation results, up to 15% RG can be suggested for incorporation as an accompanying material in unbound roadwork applications. Subject to the outcomes of future field testing, there might be potential to increase the percentage of RG added in the blends up to 30%.

Compacted Anthropogenic Materials as Backfill for Buried Pipes.

Buried pipe design requires knowledge about the fill to design the backfill structure. The interaction between the backfill envelope and the pipe impacts the structural performance of the buried pipe. The backfill material and compaction level respond to the backfill’s overall strength and, therefore, for pipe-soil interaction. The strength of backfill material is described in terms of modulus of soil reaction E’ and constrained modulus Eode. As the E’ is an empirical parameter, the Eode can be measured in the laboratory by performing the oedometer tests. In this study, we have performed extensive oedometric tests on five types of anthropogenic materials (AM). Three of them are construction and demolition materials (C–D materials) namely, recycled concrete aggregate (RCA), crushed brick (CB), and recycled asphalt pavement (RAP). Two of them are industrial solid wastes (ISW) namely, fly ash and bottom slag mix (FA + BS) and blast furnace slag (BFS). The results of the tests revealed that AM behaves differently from natural aggregates (NA). In general, the Eode value for AM is lower than for NA with the same gradation. Despite that, some of AM may be used as NA substitute directly (RCA or BFS), some with special treatment like CB and some with extra compaction efforts like RAP or FA + BS.

Utilisation of Dune Sand and Clay Brick Waste in the Production of Sustainable Concrete

The massive growth of the construction sector has increased demand for sustainable concrete that meets the requirements of modern eco-friendly policies; this in turn has made it necessary to reuse abundant and recycled materials to achieve this end. In this study, crushed clay brick (CCB) as a coarse aggregate and dune sand (DS) as a fine aggregate were used to produce a sustainable concrete. An experimental programme was accomplished by performing partial replacement by DS of conventional sand (CS) at various percentages (25%, 35%, and 50%), with a similar procedure used for crushed clay brick (CCB) and conventional coarse aggregate (CA). The impact of this dual aggregate replacement on workability, density, tensile splitting, and compressive strength was then studied, and the experimental results showed that the density decreased by 12.3% as the dual replacement of aggregates increased to 50%. The workability of the sustainable concrete was within the standard limits, while the results of the slump tests ranged between 120 mm for control concrete and 80 mm as the dual replacement of aggregates increased to 50%. Both the splitting and compressive strengths of the produced concretes were systematically decreased as the dual replacement of aggregates increased under 7- and 28-days curing. The produced concrete was thus deemed to be generally affordable though suitable only for general small works or non-structural uses.

Impact behaviour of crushed-brick lightweight RC sandwich slabs

In recent construction practice, sandwich panels have been increasingly adopted due to the fact that they are lightweight, energy efficient, aesthetically attractive, and easy to handle and erect. This study examines the impact behaviour of lightweight reinforced concrete (RC) sandwich slabs produced from local lightweight coarse aggregate. The experimental program included testing two slabs produced with normal coarse aggregate (solid slab + sandwich slab) and six concrete sandwich slabs (CSSs) produced using crushed clay bricks as lightweight coarse aggregate with various shear connecter configurations and types and steel fibre volume fractions (VF%). The impact load was applied at the midpoint of each slab using an 8 kg drop-weight from a height of 2 m. The test results showed CSS behaviour variation with different VF% and the optimum layout and location of shear connectors.

Performance of asphaltic concrete modified with recycled crushed bricks

The pavement industry relies greatly on this conventional material in constructing the road. However, the shortage of the mined material has led to the need of finding alternative with local materials to partially substitute the asphalt components. The conventional pavement industry also contributed to thermal and greenhouse emission resulting from the mining activities. In addition, throughout the year, the amount of construction and demolition (C&D) waste generated from civil construction activities particularly in Malaysia is increasing in alarming rate. Recycling the C&D waste specifically in bricks is viewed as reasonable potential as aggregate modifier in the impulse for greener and sustainable asphalt pavement production. In this paper, recycled crushed bricks (RCB) is introduced to bituminous wearing course as partial replacement for coarse aggregates. The coarse aggregate is partially replaced with RCB in proportions of 0%, 10%, 20%, 30% and 40% by weight. This study summarizes the results of laboratory evaluation of Los Angeles Abrasion Value, Aggregate Crushing Value and Marshall Test. Results show that asphaltic concrete modified with 10% RCB has the lowest abrasion and crushing values which were 20.2% and 30% respectively. Similarly, the mix has the highest Marshall Stability and lowest flow which 15.61 kN and 3.37 mm respectively. Thus, partial replacement of coarse aggregates with 10% RCB in bituminous mix is suitable to be used in wearing course and can be used as alternative material in bituminous mix to reduce the dependency on natural aggregates and utilize the C&D waste efficiently.

Cyclic behavior of semi-rigid recovered plastic blends in railway track substructure

Plastic deformation of granular layers in railway tracks under cyclic loading is a key factor controlling the substructure’s stability. In particular, the granular subballast capping layer placed between the ballast and subgrade can undergo permanent deformations due to the moving wheel load of trains. This study was conducted to evaluate the cyclic behavior of recovered plastic (RP) blended at different percentages with construction and demolition (C&D) aggregates as railway subballast capping layer. Recycled concrete aggregate (RCA) and crushed brick (CB) were used as the parent C&D aggregates. Multistage triaxial compression tests were initially undertaken to determine the shear strength and the effect of RP inclusion on strength characteristics. The results of multistage triaxial compression tests were also used to find a link between static shear strength and cyclic deformation of the granular recycled materials. The plastic deformability of the RP + C&D blends was also assessed through multistage cyclic triaxial tests at three confining pressures and incremental deviator stress at each confinement. The shakedown theory was employed to characterize the changes in permanent axial and radial deformations, resilient axial strain, and permanent axial strain rate. Inclusion of RP in the RP + C&D blends was found to increase the sample’s deformability particularly in the secondary phase of deformation, reduced the stiffness, and most importantly increased the rate of permanent strain accumulation.

Shear behavior of exploiting recycled brick waste and steel slag as an alternative aggregate for concrete production

This research is mainly studied the effect of treated waste crushed brick and steel slag on the shear behavior of reinforced concrete beams. For that purpose, eight concrete beams with 1000 mm length, 150 mm height, and 125 mm width, and the transverse reinforcement spaces are constantly equal. The obtained crushed brick from building demolition wastes are incorporated in the concrete mixes at these percentages 0%, 13%, 26%, 39% and 52% as a replacement by the weight of coarse aggregate. Furthermore, the steel slag was merged in the beams at 0%, 11%, 22% and 33% as a replacement of fine aggregate to improve the strength characteristics. Samples underwent at four points bending test. In this test, the diagonal cracking load, ultimate shear strength have been evaluated to check the behavior of beam concrete with the two waste materials, and maximum deflection occurred at the mid-span of the beam. The determination of the influence of crushed brick and steel slag on the mechanical properties and the reinforced concrete beams was the target of this investigation. In addition, the outcome of this experiment has shown that at the first substitution (13%) of fine aggregate with treated crushed brick does not have a negative impact. The results show steel slag improved the samples in terms of mechanical properties and improved the shear behavior of crushed brick concrete beams comparable to control samples. The results show that the optimal ratio to be utilized for steel slag is 22% and in terms of crushed brick even after treatment still there is a reduction as compared to the control mixture.

Impact strength and shrinkage of sustainable fiber reinforced crushed brick aggregate concrete

In the presented work, sustainable High-Performance Lightweight Aggregate Concretes (HPLWACs) containing crushed clay bricks from the demolition and construction wastes as coarse lightweight aggregates (LWA) reinforced with the mono fiber, double, and triple fibers in many aspect ratios (l/d), and types have been created. Six prepared HPLWAC mixes were studied. Generally, the fibers’ inclusions in HPLWAC greate enhancing the ultimate failure and first crack impact resistance compared to plain specimens for hybrid and mono fiber specimens. Impact energy is increased at the failure related to concrete specimens, reinforced with the mono steel fiber was 1283%, 1042 %t, 984, and 892%. In contrast, the increment in single plastic reinforced specimens was 917%, 908%, 766, and 753% at 7, 28, 60, and 90, compared to the plain specimen. The concrete specimens that are reinforced via double hybrid fibers show an insignificant decrease in first crack impact resistance and overall failure compared to the mono steel fiber specimen. Triple hybrid fiber reinforced concrete specimens show the largest number of blows at the ultimate failure and first crack. Concrete specimens reinforced with mono steel and plastic fibers have decreased in drying shrinkage relative to plain concrete specimens. Double-hybrid concrete specimens reinforced have a slight improvement. In comparison, concrete specimens reinforced triple hybrid fiber show a reduction in drying shrinkage than plain concrete specimens.

Crushed bricks as aggregate in cement based binder

The work deals with the impact of crushed brick on properties of Portland cement binder. The source of brick recycled materials is not only the demolition waste, but also the waste from brick production. One way to reduce the amount of this recyclate is to use it in cement-based composite. The advantages of using bricks as aggregate are their lower bulk density compared to conventional aggregates. Economic and ecological benefits are also important, because less natural sources need to be mined. First, the phase composition of used brick aggregate, its particle size and morphology were analysed. Test specimens with different content of brick recyclate were prepared and tested for the mechanical properties. Subsequently, the microstructure of prepared samples was examined using a scanning electron microscope. The phase composition of samples was analysed by X-ray diffraction analysis.

Effect of Steel Fibers on Properties of Modified Reactive Powder Concrete

This paper provides the result of an investigation to use of crushed brick as aggregates which was collected from the demolition waste of buildings from different sites then crushed with (maximum size 10 mm) in producing modified reactive concrete MRPC, which was presented by replacement the cementation binder (cement +silica fume) of original reactive powder concrete by 25% of crushed brick aggregates. The objective of this work is to study the effect of different type of steel fibers added in ratio 1% on the flowability and mechanical properties of reactive powder concrete and modified reactive powder concrete, which was micro steel fiber and hooked end steel fiber. The mechanical properties are examined by the tests of compressive strength, split tensile strength and flexural strength. The results showed that the compressive strength at 28 days of ORPC was 126.46 MPa, 120 MPa for the two types of steel fibers micro, hooked respectively. For the mix MRPC with micro, hooked the compressive strength at 28 days decreased by 1.53% and 1.15%, compared with those of the RPC made with micro, hooked steel fibers. And observed from the experimental results that two mixtures (RPC and MRPC) with micro steel fiber gave higher mechanical properties compared with the hook end.

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.

Hydrological Behaviour of Extensive Green Roofs with Native Plants in the Humid Subtropical Climate Context

Different mitigation measures with vegetation have been proposed to sustainably manage rainwater, among which green roofs have demonstrated to be a valid solution in urbanized areas. Green roofs have gained interest also in Italy, but their spreading is generally based on application of ready-to-use packages, poorly tested in the specific climate conditions. A study was carried out to evaluate the green roof solution most suitable in the humid, subtropical climate context of Veneto Plain (north-eastern Italy) to reduce outflow volumes from building roofs into the urban drainage systems. Twelve different microcosm combinations of extensive green roof (three plant mixtures × two substrates × two storage/drainage layers) were tested and compared with gravel (considered as a conventional flat roof with gravel ballast). The tested drainage/storage layers were a preformed layer in recycled HDPE (PL) and an expanded perlite mineral layer (ML), and the growth medium layers were recycled brick substrate (RS) and volcanic substrate (VS). Three different mixtures of native plant species were transplanted: Sedum (SE), herbaceous perennial (HE), and suffruticose (SF). Results showed that all the green roof systems have a good ability to manage rainwater, with a retention ranging on average from 46.2% (SE-RS-PL microcosms) to 62.9% (SF-RS-ML microcosms) of the precipitation in the two-year period (September 2014–August 2016), against 15.4%, retained by gravel. Over the two-year period, the retained rainfall volumes were about 100% for all the light rainy events (<10 mm) and varied within a range of 48–95% for medium rainy events (≥10 and <25 mm) and 20–88% for heavy rainy events (≥25 mm), depending on rainfall depth and the antecedent weather period. The layer that gave the highest relative contribution to the stormwater retention was the vegetation layer, followed by the drainage/storage layers and then the substrate layer. In particular, SF plants decreased the outflows by 15.2% on average compared to SE, and ML layer retained more than 10% of precipitation compared to PL layer. At last, the analysis of variance showed that, within each layer, the more effective in water retention, able to generate less outflow volumes, was similarly suffruticose and herbaceous mixtures, the crushed bricks substrate, and the mineral drainage/storage layer.

Mechanical Properties of Normal Strength Concrete Containing Different Types of Waste Material as Coarse Aggregate Replacement

In this study, the effect of different types of waste materials on the mechanical properties of normal strength concrete was investigated. Three types of waste material crumbed rubber, granular plastic, and crushed brick with different percentage up to 15% ( by weight of coarse aggregate) were used. The effect of waste material on the compressive strength, splitting tensile strength, and static elastic modulus of hardened concrete for 28 days of curing with constant w/c= 0.45 were studied. The maximum loss in concrete compressive strength was recorded to be 54.95%, 50.31%, and 20.41% for concrete mix with 15% crumbed rubber and plastic aggregate and 5% crushed brick particles. Maximum reduction in splitting tensile strength noticed to be 65%, 43.15%, and 13.59% for 15% replacement of crumbed rubber, granular plastic, and crushed brick respectively. The maximum loss in static elastic modulus was found to be 48.29%, 27.14, and 11.23% for concrete mix with 15% crumbed rubber, granular plastic, and 5% crushed brick. From test results it is concluded that up to 15% waste material can be safely used to produce this type of recycled concrete.

Shakedown analysis of PET blends with demolition waste as pavement base/subbase materials using experimental and neural network methods

Recycling and reusing construction and demolition (C&D) wastes for civil engineering construction activities has been identified as an energy-saving and sustainable solution. The purpose of this study is to evaluate the deformation behavior of two types of C&D waste materials, namely recycled concrete aggregate (RCA) and crushed brick (CB) when mixed with polyethylene terephthalate (PET) plastic waste. RCA and CB were mixed with 1%, 3%, 5%, and 7% of PET, and the permanent deformation behavior of the blends was evaluated using repeated load triaxial (RLT) test. The shakedown criterion was utilized for identifying the deformation behavior of blends. Most of the PET/RCA and PET/CB blends exhibited Range B (plastic creep) and Range C (incremental collapse) response, respectively, in the investigated stress levels. Shakedown analysis of the test results indicated that up to 3% PET could be mixed with RCA for base/subbase applications, while CB should be mixed with 1% PET, in the subbase layer. Artificial neural network (ANN) method was next used to simulate the permanent strain and shakedown behavior of the blends with consideration of the physical properties and stress states. The ANN model was found to be highly efficient for simulating the permanent strain graph and identifying the shakedown behavior of the blends. A sensitivity analysis was subsequently performed to investigate the impact of input variables on the permanent deformation behavior and the results indicated that number of cycles and confining stress were the most important factors.

Mechanical, Thermal, and Moisture Buffering Properties of Novel Insulating Hemp-Lime Composite Building Materials.

Hempcrete is a sustainable biocomposite that can reduce buildings’ embodied energy while improving energy performance and indoor environmental quality. This research aims to develop novel insulating hemp-lime composites using innovative binder mixes made of recycled and low-embodied energy pozzolans. The characterization of composites’ mechanical and hygrothermal properties includes measuring compressive strength, splitting tensile strength, thermal conductivity, specific heat capacity, and moisture buffer capacities. This study also investigates the impact of sample densities and water content on compressive strength at different ages. The findings suggest that mixes with a 1:1 binder to hemp ratio and 300−400 kg/m3 density have hygrothermal and mechanical properties suitable for insulating infill wall applications. Hence, compressive strengths, thermal conductivity, and specific heat capacity values range from 0.09 to 0.57 MPa, 0.087 to 0.10 W/m K, and 1250 to 1557 J/kg K, respectively. The average moisture buffer value for all hempcrete samples of 2.78 (gm/m2 RH%) indicates excellent moisture buffering capacity. Recycled crushed brick pozzolan can enhance the hygrothermal performance of the hemp-lime composites. Thus, samples with 10% crushed brick have the lowest thermal conductivity considering their density and the highest moisture buffer capacity. The new formulas of hydrated lime and crushed brick have mechanical properties comparable to metakaolin and hydraulic lime formulas.

Effect of Waste Burnt Bricks as Coarse Aggregate on the Compressive Strength of Ligth Weight Re-Vibrated Concrete

The paper presents an experimental study on the compressive strength of re-vibrated concrete cubes using waste burnt bricks as coarse aggregate. Using 1:2:4 as concrete mix ratio and 0.6 water-cement ratio to cast 48 cubes specimens and cured for 7 and 28 days; 24 cubes for control (granite as coarse aggregate); and another 24 cubes for waste burnt bricks as coarse aggregate. Each of these categories were re-vibrated at an interval of 10 minutes each, for 60 minutes after the initial vibration. The compressive strength of the cured concrete cubes specimen were determined. The results obtained showed a maximum strength of 24.96N/mm2 at 60th minutes re-vibration for 28 days curing and a maximum strength of 18.64N/mm2 at 60th minutes re-vibration for 28 days curing for the control (granite as coarse aggregate) and waste burnt bricks (WBB) as coarse aggregates respectively. It was concluded that crushed waste burnt bricks can be used to replace granite in the production of lightweight re-vibrated concrete.

Effect of Cement on Strength Properties of Recycled Construction and Demolition Materials

Evaluation of innovative ways is necessary to use a huge amount of recycled construction and demolition materials generated in Bangladesh and require satisfaction considering environmental, economic and engineering perspectives. In that sense, this study evaluates the outcomes when stabilized with locally available ordinary Portland cement. Furthermore, this study evaluates the research laboratory characterization of physical, geotechnical, and strength properties of unbound construction and demolition materials, for example, reclaimed asphalt from the pavement (RAP), recycled crushed concrete (RCA) and crushed brick (CB). The results advocated that cement can be a feasible alternative for the stabilization of unbound construction and demolition materials. Based on the test outcomes, RAP, CB, and RCA were found to require 2% of cement to meet the requirements for stabilization with a curing duration of 7 days.
 Journal of Engineering Science 11(1), 2020, 09-17

Determination of thermal conductivity of backfill

Shallow foundations with thermal insulation can be used in the construction of low-rise buildings. Thermal insulation prevents freezing of soils under the foundation. The article presents the results of determining the thermal conductivity of sand with the addition of crushed brick and concrete rubble. The research was carried out in a specially designed unit, which consists of two climatic chambers connected to each other. The soil sample is maintained into the special cell. Heat flow and temperature sensors are placed in the soil sample. Before soil testing a numerical simulation of laboratory test was implemented in GeoStudio. Due to numerical modelling optimal dimensions of testing cell was defined. Results of laboratory testing of sand with a known thermal conductivity with using designed parameters of cell has a good agreement with calculated value. The test procedure was extended to soils with construction waste. The addition of 20% crushed brick to the sand reduces its thermal conductivity coefficient by 20.6% in the frozen state and by 10.1% in the thawed state. At the same time sand with concrete rubble showed a decrease in the thermal conductivity coefficient in the frozen state by 6.4% and an increase by 13.4% in thaw. The effect is occurred because of the addition of particles of different mineralogical composition with different thermal conductivity. The results of testing can be used in making forecast of the thermal regime of soil stratum when designing shallow foundations.

The triaxial test of construction and demolition (C&D) materials with different particle sizes and sand contents

Recycled construction and demolition (C&D) materials are widely used in engineering fills to reduce the pressure on the environment. This study intended to investigate the effect of particle sizes and sand contents on mechanical behavior of recycled C&D materials using triaxial tests. The results demonstrated that the water absorption rate of crushed bricks (CB) was much higher than that of recycled concrete aggregate (RCA), and crushing value of recycled C&D materials was slightly lower than that of natural aggregate (NA). An appropriate amount of sand can effectively improve the particle gradation and maximum dry density of C&D materials. Results from the triaxial test showed that C&D materials with particle sizes smaller than 40 mm have higher porosity and lower strength than that of C&D materials with particle sizes smaller than 20 mm. At low porosity and confining pressure, the stress–strain curve followed a strain-softening trend. Under high confining pressure, the curve exhibited a strain hardening trend. After mixed with a suitable amount of sand, the soil changes from skeleton-void structure to suspended-dense structure, and the overall strength of specimens also increases. Finally, the modified power-law model was found to adequately describe the constitutive behavior of recycled C&D materials.