Recycled Clay Brick Aggregate Research Articles

Improvement of stress-strain behavior of brick-waste aggregate concrete using low-cost FCSM composites

Reusing the waste materials generated from demolishing existing infrastructures can play a vital role in minimizing their detrimental environmental impacts. A substantial portion of the total construction waste comprises brick wastes (B-waste). It has already been established that recycled aggregate concrete (RAC) fabricated using recycled clay brick aggregates (CBA) lacks adequate compressive strength and corresponding strain. This limits the application of RAC-CBA to mainly non-load-bearing works. External strengthening of RAC using fiber reinforced polymer (FRP) sheets has been found beneficial in terms of the improvement in ultimate compressive strength and ultimate strain. With massive costs associated with synthetic FRP sheets, this study proposes the use of Fiberglass Chopped Strand Mat (FCSM) sheets as a low-cost alternative to synthetic FRP sheets to improve compressive strength and behavior of RAC-CBA. To accomplish this, RAC was constructed with three different waste brick aggregates, mainly hollow-clay, solid-clay, and hydraulic cement-clay interlocking bricks. Typical cylinders of size 150 mm in diameter × 300 mm in height were cast and strengthened using 2, 4, and 6 layers of FCSM sheets. It was found that FCSM sheets successfully enhanced the ultimate compressive strength and strain of RAC-CBA irrespective of the type of constituting brick aggregates. Further, a correlation in the improvement of axial compressive behavior was found with the number of external FCSM sheets. The accuracy of existing ultimate strength-strain models was assessed in predicting the experimental ultimate stress and strain. In general, none of the existing models exhibited a consistent trend in predicting the axial behavior of RAC-CBA. Hence, the ultimate stress–strain models were proposed.

Study on Mix Proportion Design Based on Strength and Sulfate Resistance of 100% Recycled Aggregate Concrete

This paper presents the mechanical properties of 100% recycled aggregate concrete (RAC), and the results and analysis of the dry–wet cycle accelerated sulfate attack test. The results show that recycled concrete aggregate (RCA) can replace the coarse and fine aggregate. The recycled clay brick aggregate (RCBA) is not suitable for use as a coarse aggregate because the water absorption exceeds the standard. RCA replaces the coarse aggregate; and RCBA returns the fine aggregate to prepare 100% recycled concrete aggregate (RAC). The water–cement ratio is the most significant factor affecting the compressive strength of 100% RAC. The results of the mechanical properties analysis show that the compressive strength of RAC is less than that of NAC, and the difference in compressive strength between 100% RAC and NAC decreases with age. The splitting tensile strength of 100% RAC was slightly higher than that of NAC except for 7 d. The results of the dry–wet cycle accelerated sulfate attack test showed that the performance of 100% RAC was lower than that of NAC under the dry–wet process and sulfate attack coupling. Still, the loss rate was less than 5%, which met the standard resistance to the dry–wet cycle accelerating the sulfate attack.

Influence of recycled clay brick aggregate on the mechanical properties of concrete

Abstract This article presents the experimental results of the compressive strength, the splitting tensile strength, the macro destruction mode, and the microstructure of recycled clay brick aggregate concrete (RBC) with different recycled clay brick aggregate (RBA) replacement rates. The results show that the compressive strength and the splitting tensile strength of RBC are lower than those of natural aggregate concrete (NAC), but the effect of RBA on the splitting tensile strength of concrete is not significant. The effect of the water–cement ratio (w/c) on the splitting tensile strength of RBC is smaller than that on the splitting tensile strength of NAC. The compressive strength of concrete shows a trend of first decreasing and then increasing with the increase in RBA replacement rates. The effect of RBA replacement rates on the compressive strength gradually decreases with the increase in the w/c. The AFt in NAC is thicker than that in RBC, and the C–S–H of RBC is in the form of agglomerated networks with large and uniform pores and less filler.

Workability, strength, and microstructure of high strength sustainable concrete incorporating recycled clay brick aggregate and calcined clay

Abstract This study examines the workability, strength, and microstructure of high strength eco-concrete incorporating recycled clay brick aggregate and calcined clay. The study adopted a design mixes proportioning of 1:1:2 by weight at a constant water/binder ratio of 0.25. The waste bricks were crushed, then used to partially substitute sand at levels of 0, 10, 20, 30, 40, and 50%, while calcined clay was used as a pozzolanic supplement was blended with cement at a constant replacement dosage of 10%. The workability was determined using the slump apparatus. The compressive, split tensile and flexural strengths of the hardened samples were evaluated using cubes, cylinders and beams of dimension 100 mm3, 100 × 200 mm and 100 x 100 × 550 mm, respectively. Scanning electron microscopy (SEM) coupled with energy dispersive x-ray (EDX) was conducted on selected samples. Results from the tests indicated a decreasing trend in the workability as the recycled clay brick content increases. Results on the mechanical properties show some levels of improvement in the strength performance and microstructure of the hardened samples containing recycled clay brick aggregate, not beyond 30% at constant calcined clay content. Concrete mix with 10% recycled clay brick aggregate and 10% calcined clay achieved a higher strength compared to the control. This implies that recycled clay brick aggregate can be utilize in the production of structural concrete.

Mechanical properties of recycled aggregate concrete modified by nano-particles

In this study, different nano-particles were used to modify recycled aggregates concrete (RAC) containing recycled clay brick aggregates (RCBAs) to improve the RAC properties. Two stages of experimental works were performed. In the first stage, various nano-particle mixtures produced by different mixing methods, i.e. the use of surfactant and ultrasonication, were examined by optical microscope to evaluate the dispersion of the nano-particles in water liquid. The nano-particles modified cement mortar specimens were further evaluated by flexural tensile test to check how these mixing methods affect the properties of the nano-particle modified cement mortar. In the second experimental stage, the effects of four replacement ratios of recycled aggregates, three type of nano-particles, two mixing methods of RAC, additional surfactant and ultrasonication process used in the mix of nano-particle liquid, and the dosages of the nano-particles on the workability, compressive and split tensile properties of the nano-particle modified RAC were investigated.

Reuse of Clay Brick Waste in Mortar and Concrete

The application of recycled clay brick can not only solve the disposal problem of demolished solid waste but also reduce ecological environment damage caused by the excessive development of resources. Clay brick powder (CBP) exhibits pozzolanic activity and can be used as cement replacement. Recycled clay brick aggregate (RBA) can be used to substitute natural coarse aggregate. Recycled clay brick aggregate concrete (RBAC) can attain suitable strength and be used in the production of medium‐ and low‐strength concrete. Clay brick waste as potential partial cement and aggregate replacement material is reviewed herein. Performances in terms of mechanical and durability‐related properties of mortar and concrete are discussed. Understanding the properties of clay bricks is crucial to further research and applications.

Internal Curing Effect and Compressive Strength Calculation of Recycled Clay Brick Aggregate Concrete.

In order to investigate the internal curing effect of recycled brick aggregate (RBA) in recycled aggregate concrete (RAC) and calculate its contribution to the final compressive strength, two RAC groups with different recycled aggregates and 6 replacement ratios (r) under 4 curing ages were tested. Results show that the compressive strengths of RACI and RACII decrease steadily with the increase of r when below 40%, and that there is a significant drop once the r is higher than 60%. The internal curing effect for RAC with a low RBA ratio is mainly reflected during the curing age of 14–21 days, while for RAC with a high RBA ratio, this internal curing effect appears earlier, during 7–14 days, and becomes very obvious after 14 days. In addition, the actual tested compressive strength of RAC replaced by 100% RBA exceeds around 40% of the expected compressive strength at the age of 28 days. When the age of RAC entirely with RBA is 28 days, the compressive strength caused by the internal curing effect accounts for around 28% of the actual tested compressive strength. The most appropriate r of RBA for RAC production is between 40% to 60%. Finally, the equations for calculating the compressive strength of RAC are presented considering the curing ages, the replacement ratios and the internal curing effect of RBA. Further, a unified equation is suggested for convenience in calculation.

The impact of aggregates from recycling, discharge time and mixing technique on the consistency of concrete

Concretes prepared by the application of the triple mixing approach and by the use of both recycled concrete aggregate (RCA) and recycled clay brick aggregate (RBA) were tested in terms of loss of consistency. Fly ash was used to improve the performance of recycled aggregates during mixing – this is a specific aspect of the triple-mixing method. The slump test was performed immediately after mixing, as well as after next 90 minutes. The results were evaluated from the point of view of prolonged discharge time. Concrete consistency changes with time, having the impact on technological processes at construction site. Over the discharge time, the RBA-based concrete achieved the worst result – by 87% slump loss. Discharge time influenced the slump loss more favourably in the case of normal mixing and in the case of using natural aggregate (NA). The substitution of NA with both the RCA and RBA caused the slump loss turned worse, while RCA provided better results than RBA. However, the substitution of NA with both RCA and RBA resulted in more favourable change in the slump loss when concrete was mixed by 3M method.

Mechanical properties of recycled concrete with demolished waste concrete aggregate and clay brick aggregate

Abstract This paper presents an experimental investigation on the effect of the replacement of natural coarse aggregate (NCA) with either recycled concrete aggregate (RCA) or recycled clay brick aggregate (RBA) on the compressive strengths of the hardened concrete. Two grades (C25 and C50) of concrete were investigated, which were achieved by using different water-to-cement ratios. In each grade concrete five different replacement rates, 0%, 25%, 50%, 75% and 100% were considered. In order to improve the performance of the recycled aggregates in the concrete mixes, the RCA and RBA were carefully sieved by using the optimal degradation. In this way the largest reduction in the 28-day compressive strength was found to be only 7.2% and 9.6% for C25 and C50 recycled concrete when the NCA was replaced 100% by RCA, and 11% and 13% for C25 and C50 recycled concrete when the NCA was replaced 100% by RBA. In general, the concrete with RCA has better performance than the concrete with RBA. The comparison of the present experimental results with those reported in literature for hardened concrete with either RCA or RBA demonstrates the effectiveness in improving the compressive strength by using the optimal gradation of recycled aggregates.

Behavior of polyester FRP tube encased recycled aggregate concrete with recycled clay brick aggregate: Size and slenderness ratio effects

Compared with normal aggregate concrete, recycled aggregate concrete (RAC) containing recycled clay brick coarse aggregates (termed as RAC-RCBA) shows very lower compressive strength and larger variation in compressive strength, which hinder the application of RAC-RCBA as structural concrete. This study used polyester FRP (PFRP) as confining material of RAC-RCBA cylinders to improve the strength of RAC-RCBA. The axial compressive behavior of 42 PFRP tube encased RAC-RCBA cylinders (termed as PFRP confined RAC-RCBA) and 24 unconfined RAC-RCBA cylinders were investigated. Compared with conventional glass/carbon FRP (G/CFRP) materials, the main advantages to use PFRP are its much lower material cost and much larger tensile strain capacity. In this study, the experimental parameters considered were: (1) strength, (2) size, and (3) slenderness ratio of RAC-RCBA cylindrical specimens. Statistical analysis was also conducted to investigate the size effect and the slenderness ratio effect. The experimental results indicated that compared with conventional G/CFRP composites, the PFRP had a significantly lower tensile strength and modulus, but a much larger tensile strain at failure. The PFRP tube enhanced the ductility of the RAC-RCBA cylinders remarkably, while the enhancement on the compressive strength of RAC-RCBA by PFRP was not so pronounced as that by carbon/CFRP tubes. It was also found that the size and the slenderness ratio influenced the compressive strength of the RAC cylinders at the transitional point (fct) remarkably, and the fct decreased with the increase in size and slenderness ratio for middle, large and tall sized cylinders. In addition, a size-dependent model for fct was proposed and the predictions fitted well with the experimental results, the applicability of the proposed model for other weakly confined RAC-RCBA was also verified through the comparison with the experimental results of flax FRP tube confined RAC-RCBA.

Behavior of glass and carbon FRP tube encased recycled aggregate concrete with recycled clay brick aggregate

In literature, there are few studies which investigated compressive behavior of fibre reinforced polymer (FRP) tube confined recycled aggregate concrete (RAC) where the recycled aggregates (RAs) mainly came from demolished old concrete components. Study which considered FRP tube confined RAC using recycled clay brick aggregates (RCBA) originating from demolished brick masonry components is rare. Thus, this paper reports a systematic study on axial compressive behavior of FRP tube encased RAC containing RCBA (termed as FRP-confined RAC-RCBA). The experimental variables considered are, i.e., replacement ratio of RCBA (r=0, 50, 70 and 100%), FRP tube thickness (nf=2, 4 and 6 layers) and type of fibre material (GFRP and CFRP). This study shows that both GFRP and CFRP tubes enhanced strength and deformation of the confined RAC-RCBA specimens remarkably. The ultimate compressive stress of the confined specimens decreased with an increase of RCBA replacement ratio but their axial deformation kept approximately constant. Failure mode and the compressive stress-strain behavior of G/CFRP-confined RAC-RCBA were similar to these tube confined normal aggregate concrete (NAC) and the ultimate compressive strength of G/CFRP tube confined RAC-RCBA specimens enhanced with an increase in FRP tube thickness. The CFRP-confined specimens showed higher ultimate strength but lower ultimate axial strain than those of GFRP-confined specimens. The applicability of eight widely used confinement models, i.e., 5 design-oriented and 2 analysis-oriented models, for FRP-confined NAC to FRP-confined RAC-RCBA was also evaluated.

Properties of New and Recycled Clay Brick Aggregates for Use in Concrete

The testing described in this paper was performed to establish the physical and mechanical properties of new and recycled crushed clay brick aggregates for use in portland cement concrete (PCC). Various physical and mechanical properties of eight different types of aggregates were determined and compared with the limits set out in the British Standards for aggregate from natural sources used in concrete. The results were also compared with granite aggregate that has been proved to be a good natural aggregate for producing PCC. The results showed that most of the crushed clay-brick aggregates tested can be used in producing PCC for low-level civil engineering applications and that some kinds of brick aggregate possess good physical and mechanical properties that qualify them for producing high-quality concrete.