Brick Aggregate Research Articles

Acoustic emission characteristics of recycled brick-concrete aggregate concrete under freeze-thaw-load coupling action and damage constitutive model

Replacing natural aggregate with construction waste to prepare concrete is an effective way of its resource utilization, which is in line with China 's " carbon peaking and carbon neutrality " strategy and the green development needs of the construction industry. Due to the existing technology is difficult to completely separate waste bricks and waste concrete, this paper mixes recycled brick aggregate and recycled concrete aggregate in a ratio of 1:1 into a mixture, and replaces the natural aggregate with a replacement rate of 30% to prepare Recycled Brick-Concrete Aggregate Concrete (RB-CAC). Concrete in northern China is often subjected to freeze-thaw and load coupling, which accelerates the damage degradation of RB-CAC. Therefore, it is necessary to study its damage constitutive model. In this paper, the effects of different stress levels (0%, 20%, 40%, 60% of flexural strength) and freeze-thaw cycles (0 times, 40 times, 80 times, 120 times, 160 times) on the apparent morphology, mass loss, relative dynamic elastic modulus and acoustic emission characteristics of RB-CAC were analyzed by freeze-thaw-load coupling test, constitutive relation test under uniaxial compression and acoustic emission characteristic test. The dynamic evolution of its frost resistance and damage process was analyzed and evaluated. Finally, combined with the knowledge of damage mechanics, the elastic modulus is defined as the damage variable generated by the freeze-thaw-load coupling effect. Based on the mesoscopic damage theory, the ratio of the number of failure interfaces to the total number of interfaces is defined as the damage variable generated by uniaxial pressure. The damage evolution equation of RB-CAC and the damage constitutive model of freeze-thaw times and stress level are established.

Experimental Study on The Effect of Size, Type, and Replacement Ratio of Recycled Aggregate on The Mechanical Properties of Reactive Powder Concrete

This paper presents an experimental investigation of the mechanical characteristics of Reactive Powder Concrete (RPC) and Recycled Aggregate Reactive Powder Concrete (RPC-RA), utilizing two types of recycled aggregate (RA), recycled concrete aggregate (RCA), and recycled concrete brick aggregate (RCBA) as alternative aggregates. A series of sixteen RPC and RPC-RA mixes were prepared and tested. A reference RPC mix without RA was tested to determine the maximum compressive strength of 128.17 MPa, the tensile strength of 15.56 MPa, and the flexural strength of 25.90 MPa. Then, the study examines twelve different mixes of RPC-RA, each with RCA with maximum particle sizes of 0.6, 1.18, 2.36, and 4.75 mm and replacement ratios of 20%, 40%, and 60%, to study the effects of varying replacement ratios of the RCA and various maximum particle sizes. Additionally, three mixes of RPC-RA are investigated using RCBA with a maximum particle size of 0.6 mm and replacement ratios of 20%, 40%, and 60%. The use of RA resulted in various percentages of reduction in compressive, splitting, and flexural strength, as shown in the results of the study.

Experimental Torsional Capacity of Plain Concrete Beams Made from Crushed Clay Brick and Recycled Brick Concrete as Coarse Aggregate

Concrete was made with four different types of coarse aggregate, i.e., natural stone aggregate concrete (NSAC), crushed virgin clay brick aggregate concrete (VBAC), crushed recycled brick concrete aggregate concrete (RBAC), and crushed recycled stone concrete aggregate concrete (RSAC). Beam specimens prepared from these four types of concrete were subjected to pure torsional moment up to failure. From this experimental procedure, ultimate torque at failure along with twisting angle were observed. From the torque vs. twisting angle curves, torsional stiffness and torsional toughness were also evaluated for these four types of concrete. It was observed that ultimate torque of VBAC and RBAC was 95% and 90% of that of NSAC, respectively. The torsional toughness of VBAC was found to be 68%–72% of that of NSAC. In addition, experimental torques were compared with predictions of torsional strength as per five commonly used models. For VBAC, the ultimate torque prediction made by skew bending theory was found to be the closest to the experimental findings.

Fresh and Hardened Properties of Brick Aggregate Concrete with Maximum Aggregate Sizes of 10 mm to 75 mm

The fresh and mechanical properties of concrete made with brick aggregates of eight different maximum aggregate sizes (MAS), i.e., 10 mm, 12.5 mm, 19 mm, 25 mm, 37.5 mm, 50 mm, 63 mm, and 75 mm, were investigated. The other parameters studied were sand-to-aggregate volume ratio (s/a) (0.40 and 0.45), W/C (0.45, 0.50, and 0.55), and cement content (375 kg/m3 and 400 kg/m3). In total, 80 different concrete mixes were studied; the perimeter of the interfacial transition zone (ITZ) along the brick aggregates was quantified with an image-analysis software and the microstructure along the ITZ was investigated using a scanning-electron microscope (SEM) to corroborate the hardened properties of the concrete. Although larger MAS leads to greater slump in concrete, its effect on hardened properties is linked to other design parameters. For a cement content of 375 kg/m3 and W/C of 0.45 and 0.50, the compressive strength of concrete increases (by up to 5%–15%) with increases in MAS of up to 37.5 mm irrespective of s/a (0.40 and 0.45) and then reduces gradually. For all other cases, the compressive strength of concrete is reduced with increases in MAS. The SEM imaging confirmed the presence of weak and porous ITZ and the deposition of ettringite in the voids left by entrapped bleed water under large aggregates. The compressive strength also increased with increases in s/a from 0.40 to 0.45, predominantly for smaller MAS. Correlations between mechanical properties of concrete and stress–strain curves are proposed for different MAS.

Mechanical properties and frost resistance of recycled brick aggregate concrete modified by nano-SiO2

Abstract In this work, brick aggregates were immersed in nano-SiO2 solution for 2 days, and the effects of nano-SiO2 on the brick aggregate properties, mechanical properties (compressive strength, flexural strength, and splitting tensile strength), frost resistance (apparent phenomenon, mass loss, relative dynamic modulus of elasticity, and compressive strength) of recycled brick aggregate concrete and the microstructure of recycled brick aggregate concrete were investigated. The results show that nano-SiO2 can effectively improve the performance of recycled brick aggregate and the mechanical properties of recycled brick aggregate concrete, mainly by reducing the water absorption and crushing index and improving the compressive strength, flexural strength, and splitting tensile strength. With increasing nano-SiO2 solution concentration, the compressive strength, flexural strength, and splitting tensile strength of recycled brick aggregate concrete first increase and then decrease. The frost resistance of recycled brick aggregate concrete is superior to that of ordinary aggregate concrete, while the frost resistance of nano-SiO2-modified recycled brick aggregate concrete is inferior to that of recycled brick aggregate concrete. In addition, the freeze‒thaw damage mechanism of recycled brick aggregate concrete is analyzed, and a freeze‒thaw damage life prediction model of nano-SiO2-modified recycled brick aggregate concrete based on the Weibull distribution is proposed.

Validated simulation of thermal performance of phase change material infused recycled brick aggregate in 3D printed concrete

Passive design solutions are important in reducing the amount of heating and cooling energy required to maintain thermal comfort inside a building, without adding to the problem of climate change. Phase change materials (PCMs) are a thermal energy storage passive design solution, with the ability to change phase and store heat at chosen temperatures. PCMs can be added to concrete to create PCM-concrete, a composite material with sensible and latent heat storage ability. The purpose of this research is to create an accurate 2D model which can be used to determine the heat transfer through 3D printed concrete (3DPC) building façades containing PCM. Two building façade wall sections are simulated in ABAQUS and validated by thermal tests – a reference 3DPC façade section, in which 64% of the natural aggregate is replaced with recycled brick aggregate (RBA-3DPC), and a PCM-3DPC façade section, containing the same replacement level of RBA but with PCM vacuum impregnated into the RBA. With the validated model, computational simulations of the thermal performance of the PCM-3DPC façade section with varying PCM melting temperatures and different façade surface colours are tested. Subsequently, a PCM-3DPC façade section with 100% replacement of natural aggregate with RBA, infused with PCM of two melting temperatures (such as 18 °C for activation in winter and 28 °C for activation in summer) is proposed for climates with large seasonal temperature changes. In addition, contrary to most studies, an iterative approach was used for modelling cavity convection and internal ambient temperature, and this approach is found to be necessary, so as not to over constrain the model with set façade and internal temperatures.

An analytical model for determining realistic tensile strength and fracture toughness of fired clay bricks

The crack resistance of fired clay bricks is crucial for the safety design of brick masonry structures and needs to be evaluated reasonably. However, the realistic fracture parameters are extremely difficult to predict owing to the porous and defective characteristics of bricks. Thus, this paper aims to determine the tensile strength (ft) and fracture toughness (KIC) independent of size for fired clay bricks, which are rarely reported in previous studies. The fracture mechanisms of the bricks were elucidated using the fracture tests on brick specimens having varied sizes and notch lengths. Considering the material heterogeneity and discontinuity, the maximum fracture load (Fmax) correlates linearly with ft and KIC according to boundary effect model. ft and KIC can be predicted directly once only Fmax is determined from the test. The results showed that the predicted ft and KIC were generally independent of notch length and specimen size. Using statistical analysis, the means and upper and lower limits of ft and KIC were determined. Moreover, the predicted ft and KIC of bricks proved to be suitable for recycled brick aggregates with particle sizes of 5–40 mm. Thus, the crack resistance of the brick aggregates was clarified based on the proposed analytical model.

Simulation-Based Analysis of Micro-Damage to Recycled Concrete-Containing Brick Coarse Aggregates

To achieve sustainable development during urbanization, construction waste is recycled for use as an aggregate in recycled concrete (RC). To determine the influence of the brick content in coarse recycled aggregates on the damage sustained by the resultant RC, the RC was first divided into seven phases: natural crushed stone, old gravel inside waste concrete, bricks, new mortar, old mortar on waste concrete surfaces, and new and old interface transition zones. The Monte Carlo method was then applied to establish a two-dimensional random aggregate model of the RC made with coarse brick aggregates. The ABAQUS software package was used to simulate a uniaxial compression test, the results of which were combined with those of a macro-test to determine the internal damage change rule of brick-containing RC. The stress–strain curves obtained from the simulation coincided well with that of the macroscopic tests. As the brick content increased, the damage zone inside the specimen and the number of microcracks increased. The stress concentration area decreased, as indicated by a lower compressive strength in the macro-test. The results indicate that higher brick contents in RC yield more initial damage inside the concrete and a lower compressive strength.

Study on the compressive mechanical properties of mixed recycled aggregate concrete with silane modified

This study used a 10% silane solution to strengthen recycled brick aggregates (RBA). Subsequently, mixed recycled aggregate concrete (MRAC) was prepared by using recycled concrete aggregate (RCA) and RBA modified with silane (Si-RBA). The properties of RBA and RCA were compared. The effects of the Si-RBA/RCA ratio on the failure modes, compressive strengths, and characteristics of the compressive stress strain curves under monotonic loading and cyclic loading were tested. The microstructures of the RBA, Si-RBA, and MRAC were analyzed by scanning electron microscopy (SEM). The test results showed that RBA modified with silane reduced water absorption by 51.61% and improved the crushing index by 14% compared to RBA. When the Si-RBA/RCA ratio changed from 0:10 to 10:0, the failure mode of MRAC transformed from interfacial transition zone (ITZ) failure to aggregated failure, while the compressive strength decreased. The MRAC specimens exhibited similar failure phenomena, regardless of monotonic or cyclic loading. The peak stress and elastic modulus decreased as the Si-RBA/RCA ratio increased, whereas the peak strain showed a fluctuating growth trend, and the plastic strain increased. In addition, SEM images showed that the reaction products of silane filled the pores of the RBA, and the silane solution made the ITZs of the RBA much denser. Based on the test data, a constitutive model for MRAC under monotonic and cyclic loadings was proposed, which showed good accuracy in predicting the response of MRAC under a compressive load.

Using recycled bricks to improve the compressive strength of concrete and produce lightweight concrete

This research presents the aim of using sustainable materials like crushed bricks from the demolition of old buildings as additives to preserve the environment, reduce energy consumption, reduce the cost of concrete, improve the properties of concrete, and obtain lightweight concrete for high buildings with more fluidity for narrow places. Also, it discusses the best replacement ratios because the knowledge about them is still lake. Three mixes of concrete were used and tested. Mix-1was the standard, where the replacement of coarse aggregate with crushed brick aggregate has been used in mix-2, the mix-3 was to study the replacement of fine aggregate by powder brick. In this analysis, only two factors were taken into account: the percentage of coarse aggregate replaced by brick aggregate (from 0 to 50%) and the percentage of fine aggregate replaced by brick aggregate (from 0 to 75%). Compressive strength was tested after curing at ages (7, and 28) days. The results showed that concrete with crushed brick aggregate reduces unit weight and increases of compressive strength of concrete. Using mix-2 increased the compressive strength by about 9.7%, and 7% at ages (7, 28) days respectively, and reduced the weight by 11%. Also, using mix-3 increased the compressive strength with high percentages of about 59%, and 61% at ages (7, and 28) days respectively, with a little percentage of reducing the weight by 2%.

Effects of Nanomaterials Reinforced Aggregate on Mechanical Properties and Microstructure of Recycled Brick Aggregate Concrete

In this paper, the effects of nano-SiO2 and nano-Al2O3 on the brick aggregate properties, compressive strength of brick aggregate concrete at different ages, and microstructure of brick aggregate concrete are investigated. The results show that the water absorption of recycled brick aggregate decreases with the increase of nanomaterials solution concentrations, and the crush index of recycled brick aggregate decreases. Nano-SiO2 and nano-Al2O3 improve the compressive strength of recycled brick aggregate concrete at different ages, and the effect of nanomaterials on the early strength of concrete are more obvious. With the increase of nano-solution concentration, the compressive strength of nano-SiO2 reinforced brick aggregate concrete increases first and then decreases, while that of nano-Al2O3 reinforced brick aggregate concrete increases. The internal structure of nanomaterials reinforced brick aggregate is denser, micro cracks and pores are filled with hydration products, and the interfacial transition zone is more compact.

Alkali-Activated Brick Aggregates as Industrial Valorized Wastes: Synthesis and Properties

In recent works, many industrial by-products were employed as solid precursors for the synthesis of alkali-activated binders and as alternatives to Portland cement for the immobilization of hazardous, toxic and nuclear wastes. Among industrial wastes, alkali-activated brick was found to be an interesting porous composite for removing very toxic heavy metals (Pb2+, Cd2+, Co2+) and radio-nuclides (Sr2+, Cs+, Rb+) from aqueous solutions. The starting material is very attractive due to the presence of metakaolinite as a geo-polymer precursor and silica for increasing material permeability and facilitating water filtration. The alkaline reaction gave rise to geo-polymerization followed by partial zeolitization. Elemental surface micro-analysis was performed by Scanning Electron Microscopy (SEM) equipped with an Energy-Dispersive X-ray Spectrometer (EDS). The formation of crystalline phases was corroborated by X-ray diffraction (XRD) analysis. Information about 29Si, 27Al and 1H nuclei environments in crystallized and amorphous aluminosilicates was obtained by 29Si, 27Al and 1H MAS NMR. 27Al–1H dipolar-mediated correlations were investigated by employing dipolar hetero-nuclear multiple quantum coherence (D-HMQC) NMR, highlighting Al–O–H bonds in bridging hydroxyl groups (Si–OH–Al) that are at the origin of adsorptive properties. Aqueous structural stability and cationic immobilization characteristics before and after material calcination were investigated from acid-leaching experiments.

Effects of mono and binary recycled aggregates on the rheological properties of geopolymer mortars synthesized with construction and demolition waste-based binders

This study comprehensively investigated the effect of different types of fine construction and demolition waste (CDW)-based aggregates, including recycled concrete aggregate (RCA), recycled ceramic tile aggregate (RTA) and recycled brick aggregate (RBA) on the fresh rheological properties of geopolymer mortars (GPMs) derived from CDW-based aluminosilicate binders. The results were compared to those of silica sand (SSA) and natural sand (NSA) with equivalent particle size distribution. In addition, the binary inclusion of RCA, RTA and RBA with 50% SSA or NSA fine aggregates was also considered in an attempt to reach rheological behavior closer to that of SSA and NSA-based GPMs. All mortars were blended with a CDW-binder composed of a ternary mixture of brick (RBP), ceramic (RTP) and concrete waste (RCP) powders optimized at pre-targeted chemical parameters of SiO2/Al2O3 and Na2O/SiO2 of 5.7 and 0.18, respectively. The geometrical shape parameters and packing densities of RCA, RTA, RBA, SSA and NSA aggregate skeletons and geopolymer mortar systems were also evaluated to examine their relationship with the rheological parameters of static and dynamic yield stresses, apparent and plastic viscosities, shear stresses and strains and thixotropy of GPMs. Although the incorporation of CDW-based aggregates resulted in enhanced rheological parameters, they exhibited shear-thinning or pseudoplastic behavior similar to SSA and NSA-GPMs. Yet the addition of RCA with a lower consumption of suspending fluids and reduced non-colloidal interactions than RBA and RTA resulted in overall rheological properties closer to those of SSA and NSA-GPMs, which further improved when combined with SSA or NSA in binary-aggregate-based GPM systems.

Feasibility Study of Brick Aggregate as a Partial Replacement of Natural Stones in Dry Lean Concrete Mix

This study aims to use two types of brick aggregates as partial replacements for natural stone and checks their feasibility as road aggregates in dry lean concrete (DLC) mixes. Laboratory studies were performed by partially replacing natural stones with both types of brick aggregates, and the optimum contents were evaluated. The paper describes a detailed analysis of DLC mixes with several percentages of bricks including a number of laboratory tests such as the moisture density, strength parameters, ultrasonic pulse velocity, and resistance to acid attack. For the replacement of stone with brick aggregate, the prime focus was paid to the usage of cement content and the aggregate to cement (A/C) ratio. An A/C ratio of 10:1 is found to be suitable for 100% replacement of natural stone aggregate (NSA) with first-class brick aggregate (FCBA), whereas an A/C ratio of 11:1 may be suitable for the use of 100% overburnt brick aggregate (OBBA). However, high contents of the A/C ratio can also be used if NSA is partially replaced by OBBA or FCBA. The strength parameters of DLC mixes such as flexural strength or split tensile strength showed a reduction of about 20%–22% when replaced by 50% OBBA and FCBA, while the compressive strength was within the limit (i.e., 7 MPa after 7 days of curing). Finally, the cost analysis showed that the production cost of DLC mixes can be reduced by about 15.6%–16.2% and 29%–32%, if the stone aggregates are partially (50% by volume) or fully replaced by FCBA and OBBA, respectively. Thus, the paper indicates that not only the scarcity of stone aggregates can be minimized but the cost can also be reduced by partially or fully replacing NSA with FCBA and OBBA.

Effect of Waste Clay Bricks on the Performance of Cemented Tailings Backfill and Its Damage Constitutive Model

In this study, two types of cemented tailings backfill (CTB) were prepared by breaking up the waste clay bricks (WCB) from dismantled buildings and replacing part of the cement with brick powder and part of the tailings with brick aggregate. The mechanical properties of the modified CTB were investigated. The results showed that the strength of CTB with 10% brick powder content increased by 16.24% at the curing age of 28 days, while the content of 20% brick powder only decreased by 0.11%. The strength of the brick aggregate with less than 20% content can be increased at each curing age, and the strength of the 15% brick aggregate at the curing age of 7 d and 28 d is increased by 65.54 and 58.8%. The failure strain of the CTB-containing brick powder decreases with the extension of the curing time, and the failure strain of the CTB-containing brick aggregate decreases significantly at the curing age of 7 days. In addition, a three-stage damage constitutive model was established based on the results obtained in the present study, and the laboratory test results of CTB under uniaxial compression were effectively described with high confidence.

Mechanical Properties of Polypropylene Fiber Recycled Brick Aggregate Concrete and Its Influencing Factors by Gray Correlation Analysis

Making construction waste into raw materials for recycled concrete is beneficial for resource conservation and environmental protection. This paper investigated the effects of different recycled brick aggregate (RBA) replacement rates (30%, 50%, 70%, and 100%) and different contents of polypropylene fibers (PPFs) (0.08%, 0.10%, 0.12%, 0.16%, and 0.2%) on the mechanical properties of recycled brick concrete. Gray correlation was also used to analyze the degree of effect factors on the mechanical properties of concrete. The results showed that the mechanical properties decreased when the natural coarse aggregate (NCA) was replaced with RBA, while PPFs could better improve the mechanical properties of RBA concrete. The improvement of compressive and flexural properties was optimal when the PPF content was 0.12%; the improvement of tensile properties was optimal when the PPF content was 0.2%. In addition, PPFs significantly improved the toughness of RBA concrete. The gray correlation degrees between compressive strength (tensile strength, flexural strength) and NCA, RBA, and PPFs were 0.8964 (0.8691, 0.8935), 0.7301 (0.6530, 0.7074), and 0.5873 (0.5870, 0.5840), respectively.

Influence of natural fiber rope wrapping techniques on the compressive response of recycled aggregate concrete circular columns

The utilization of recycled waste in the production of new concrete raises significant concerns regarding the quality of the resulting concrete. One prominent drawback of recycled aggregate concrete (RAC) is its inferior mechanical properties compared to natural aggregate concrete. In this study, we examine the impact of hemp fiber rope (HFR) confinement on improving the compressive stress-strain behavior of RAC, specifically using recycled brick aggregates from fired-clay solid bricks (RAC-FCSB) as a partial substitute for natural coarse aggregates. Furthermore, we explore and compare the effectiveness of HFR confinement in the form of strips versus fully wrapped confinement. To conduct the experiments, a comprehensive framework was developed, involving a total of 32 cylindrical specimens. The parameters of interest included the configuration of HFR confinement (strips or full wrapping), the number of HFR layers, and the inherent strength of the concrete. The results indicate that HFR strips can significantly enhance the compressive stress-strain response. However, their performance falls short when compared to the fully wrapped HFR confinement. Nonetheless, HFR strips were able to enhance the peak compressive stress and strain of RAC-FCSB up to 204% and 190%, respectively. The second part of the study investigated the performance of existing models of HFR confinement in predicting the peak compressive stress and strain of RAC-FCSB. The deficiencies in existing models were highlighted, and new models based on non-linear regression analysis were proposed to accurately predict the peak compressive stress and strain of HFR-confined RAC-FCSB.

Impacts of biomimetic self-healing of Lysinibacillus boronitolerans immobilized through recycled fine and coarse brick aggregates in concrete

Recycling waste bricks for concrete is cost-effective and eco-friendly but may impact strength and durability. A promising solution is biomimetic self-healing concrete that uses bacteria to repair cracks. The efficacy of this approach is contingent upon the bacterial strain, carrier medium, medium size, and immobilization utilized. Nevertheless, it remains uncertain how carrier size affects biomimetic self-healing concrete when the same carrier substance and immobilization technique are used. This study explored using Lysinibacillus boronitolerans (LBBT) to develop biomimetic self-healing concrete using recycled fine brick aggregate (RFBA) as a carrier medium. Recycled coarse brick aggregate (RCBA) was also employed for the relative evaluation of the impact of carrier size in biocrete. Results revealed that adding LBBT to concrete through RFBA resulted in significant improvements in strength and toughness. Compressive, split tensile, and flexural strength increased by 16.2%, 17.6%, and 22.0% respectively, while compressive and flexural toughness improved by 51.0% and 27.6%. The abundant RFBA particles ensured the even distribution of LBBT throughout the mixture. RCBA immobilization facilitated self-healing, achieving 0.6 mm of crack healing with 89.7% compression strength recovery and a 26.0% healing potential. The achievement can be attributed to the macro-voids and the stiffened structure of RCBA. Additionally, forensic investigations confirm the presence of microbial induced carbonate precipitation. Thus, RFBA is a promising immobilizer for LLBT, exhibiting a greater impact on mechanical performance due to its smaller particle size. In contrast, RCBA facilitates self-healing by entrapping the biomimetic agent, despite its lower abundance.

Effects of compaction on the properties of pervious concrete made with local aggregates

The global shortage of regular construction materials has encouraged researchers to discover alternatives; crushed over-burnt brick aggregate (Cobba) has been found to be a suitable option. In this study, Cobba was used in pervious concrete (PC) and the effect of compaction on the properties of the PC was examined. PC needs to have a sufficient amount of voids, but is also expected to have some strength. This study particularly focused on this bi-functional aspect through several experimental tests. Compaction was carried out with a standard Proctor hammer by varying the number of blows. For larger aggregates, PC made with 40 compaction blows showed a compressive strength (CS) and porosity of about 12 MPa and 15%, respectively, whereas, for smaller aggregates, PC made with only 25 blows showed a CS of around 16 MPa and a porosity of about 18%. Based on porosity, permeability and CS, the optimum number of compaction blows is also identified for various sizes of coarse aggregates. Finally, statistical analysis is carried out and some equations are proposed to estimate the pore parameters and strength of the PC mix made with Cobba with an accuracy of about 97–98%.

Application of rice husk ash in brick aggregate concrete to improve the permeability and resistance against acid and sulfate attack

AbstractBrick‐aggregate‐concrete with a greater permeability is susceptible to decay at a faster rate under the action of acid and sulfate. This study tries to improve the durability of brick aggregate concrete by the addition of rice husk ash, which has been termed brick‐ash concrete in this paper. The permeability and sorptivity of stone‐aggregate‐concrete, brick‐aggregate concrete, and brick‐ash concrete samples with different percentages of rice husk ash and different water‐to‐binder ratios were investigated. The concrete samples were also exposed to 1.5 % hydrochloric acid and 5 % sodium sulfate along with periodic drying and wetting cycle and periodic observations in terms of compressive strength, weight loss, and ultrasonic pulse velocity test for 360 days. 5 % to 10 % rice husk ash can significantly improve the permeability and resistance to the harsh environment of brick aggregate concrete. Additionally, this study also presents the equations to predict the actual strength from ultrasonic pulse velocity values for the brick ash concrete specimen exposed to acid and sulfate environments.