Concrete Quality Research Articles

THE EMERGENCE AND DEVELOPMENT OF A CRACK IN THE CONCRETE OF THE ABUTMENT OF THE LOWER HEAD OF LOCK № 2 OF THE VOLGA-BALTIC WATERWAY

An analysis of the concrete structures state of the lower head of lock № 2 of the Belousovsky hydroelectric complex of the Volga-Baltic waterway is presented. In 1985, a crack was discovered in the concrete of the left abutment of the lock lower head. Observations for the dynamics of its development have showed that the crack size increases with time. To explain the causes of the crack occurrence and development, an analysis of concrete quality of the lower head structures is made according to the data of previous studies. Taking into account the technology of concreting during the construction process, as well as studies carried out during operation, the low quality of concrete and its heterogeneous structure have been stated. The analysis of the soils structure at the base of the lower head is carried out; the filtration regime of groundwater movement is considered. It is noted that the base soils are represented by fine-grained sands with an interlayer of loams. The presence of several aquifers in the basement soils, as well as the formation of the pressure front of the hydroelectric complex, led to significant gradients of the filtration flow. This contributed to the development of suffusion processes in the soils of the lower head base, which led to the formation of a decompacted layer in the roof of the rocks of the lower head base. The data of modern surveys of soil characteristics confirm that suffusion processes continue at the present time. This led to the occurrence of multidirectional settlement of the right and left abutments of the lower head, which, in turn, led to the development of the crack in the concrete mass. The measures taken to eliminate or stabilize the development of the crack, namely, pumping a cement-sand mixture into the soil, grouting the abutment concrete, anchoring the structure, injecting the concrete mass with a two-component synthetic resin, have not stopped the crack opening, because the main reasons such as the poor quality of concrete and the weak bearing capacity of the underlying soils of the base had not been eliminated.

Recycling of Glass Waste on the Concrete Properties as a Partial Binding Material Substitute

Concrete is a significant construction material that is utilized extensively worldwide. A research study on the properties of concrete was conducted using Glass Waste (GW), which was readily available locally. As broken glass is difficult to sort, it is possible to positively utilize this waste particulate matter to reduce its detrimental impacts on both human health and the environment. Besides crushing or grinding, glass can transform into a natural pozzolan which enhances the fresh and hardened properties of concrete. This study also intends to reduce the amount of binding material used in the manufacturing of concrete blocks by making the best use of cement with Glass Waste. Therefore, an attempt has been made by using GW from 5-20% by weight as cement replacement for concrete blocks. When 5% crushed glass waste was added to the concrete mix (1:2:4), maximum compressive strength was 25.90 N/mm2, as opposed to Ordinary Cement Concrete's 21.09 N/mm2 strength, according to workability and laboratory testing. The 5% Glass Waste Mixed Cube and 5% Glass Waste Mixed Cylinder had the lowest water absorption test values at 2.22% and 3.58% respectively. In comparison to Ordinary Cement Concrete, Glass Waste Concrete has higher tensile strength. The maximum splitting tensile strength for 5% crushed Glass Waste Concrete was 2.115 N/mm2, compared to 1.815 N/mm2 for an Ordinary Cement Concrete Cylinder. The concrete with 20% glass waste content had the highest density, which was 2380.4 kg/m3 that defines good quality concrete.

Effect of Alum Sludge (AS) and Palm Kernel Ash (PKA) with Coconut Shell as Partial Replacement of Aggregates

At present, there is a high demand for concretes with varying properties. Generally, concrete with high durability can be produced by considering the constituents of the concrete, such as cement, sand, aggregates, and water. The quality of concrete is also dependent on the mix design and production method, such as transporting and pouring of concrete. In recent years, the developed countries have been focusing on the issue of sustainability in construction to create a healthier environment and reduce the environmental impact of a building throughout its lifetime while optimizing its economic viability and ensuring the comfort and safety of the occupants. One way to achieve sustainability is using agricultural waste material such as palm oil fuel ash, rice husk, fly ash slag, sludge, and coconut shell in concrete production. This study performs a series of tests to investigate the effect of using alum sludge (AS) and palm kernel ash (PKA) with coconut shells as a partial replacement of aggregates. The concrete samples were subjected to compressive strength, flexural strength, rebound hammer, ultrasonic pulse velocity, water permeability, water absorption, carbonation, alkali-silica reaction, SEM, and shrinkage tests.

Properties of pavement quality concrete prepared with coarse RAP containing different percentages of asphalt

ABSTRACT The present study was carried out to establish the proportion of Coarse Reclaimed Asphalt Pavement (C-RAP) containing varying percentages of asphalt for preparing Pavement Quality Concrete (PQC) mixes. RAP was collected from the 5-year-old pavement and separated into coarse RAP (C-RAP) and fine RAP (F-RAP) aggregates using a 4.75 mm sieve. Asphalt content in the C-RAP and F-RAP was found to be 4.12% and 4.33%, respectively. The C-RAP was immersed in the toluene solvent for a different predetermined time and asphalt content was reduced to 3.05%, 2.12%, and 1.24%. Using this exercise, C-RAP containing four different percentages of asphalt (4.12, 3.05, 2.12, and 1.24%) was produced. Then, the cement concrete mixes were prepared in the laboratory by replacing Natural Coarse Aggregate (NCA) with C-RAP varying from 25% to 100% with an increment of 25% in each type. Manufactured Sand (M-Sand)/Crushed Stone Sand (CSS) was used as a fine aggregate. Altogether, 17 concrete mixes (one control and 16 mixes containing C-RAP) were produced while keeping the water–cement ratio unchanged in all the mixes and evaluated their fresh and hardened concrete properties. As the asphalt presence in the RAP is sensitive to the temperature, the strength of concrete containing RAP at different temperatures was also examined. The current study showed that the amount of NCA substituted by C-RAP and the quantity of asphalt present in the C-RAP influenced the properties of concrete. The study also established that NCA up to 100% could be replaced with the C-RAP containing low asphalt content. Using test results, empirical models were developed to estimate the properties of hardened concrete by considering the percentage of C-RAP, percentage of asphalt in C-RAP, and compressive strength of concrete as predictor variables. The developed models were found statistically significant, supported by .

PERENCANAAN STRUKTUR ATAS GEDUNG DEKANAT UNIVERSITAS MUHAMMADIYAH SUMATERA BARAT KAMPUS IV PAYAKUMBUH

This building is one of the dean's buildings of the University of Muhammadiyah West Sumatra campus IV located in the Payakumbuh area which aims to improve educational facilities and infrastructure. To realize a safe development, careful planning is needed, so that when the building is completed and ready for the building it is safe and comfortable to use. The results obtained that the material used is steel fy = 420 MPa and concrete quality fc' = 24.9 MPa. For the reinforcement of floor slabs, reinforcement is used for the direction of x = 10 – 150, while the direction of y = 10 – 150. The planning of the columns for the 1st and 2nd floors uses steel quality fy = 420 MPa and concrete quality fc' = 24.9 MPa with K1 size 45cm x 45cm, and the 3rd floor column uses steel quality fy = 420 MPa and concrete quality fc' = 20.75 MPa with K2 size 30cm x 30cm. While planning for beam 1 with a size of 35cm x 55cm using steel quality fy = 420 MPa and concrete quality fc' = 24.9 MPa, beam 2 with a size of 25cm x 45cm using steel quality fy = 420 MPa and concrete quality fc' = 20.75 MPa, and a beam with a size of 25cm x 40cm using steel quality fy = 420 MPa and concrete quality fc' = 20.75 MPa. Keywords: Building Structure, Education, Reinforcement.

PERENCANAAN STRUKTUR ATAS GEDUNG PASAR SURANTIH KABUPATEN PESISIR SELATAN

Surantih Market is one of the trade locations on a large scale, this market is a central trading center in the South Coast which has great potential in increasing the economy, especially the local community. So that the Surantih market plays an important role in improving the economy. To realize these things, it requires physical facilities and facilities such as access to traffic, offices and market buildings. The goal that the writer wants to achieve in this thesis is the planning of the Pasar Surantih building with the ductile principle in order to create a building that is safe and resistant to earthquakes. This is one of the bases for planners to plan the Pasar Surantih building. . The results obtained that the material used is steel fy = 420 Mpa and concrete quality fc' = K-300 (24.9 Mpa). For floor slab reinforcement, reinforcement is used for the x = 10 – 150 direction, while the y direction = 10 – 150. Column planning uses steel fy = 420 Mpa and concrete quality fc' = 24.9 MPa with a column size of 1 55 cm x 55 cm, for column 2 50cm x 50cm, and for column 3 40cm x 40cm. While the design of the beam using steel quality fy = 300 Mpa and concrete quality fc' = K-300 (24.9 Mpa) Mpa with sizes for the main beam 70cm x 45cm, child beam 50cm x 30cm.Keywords : Upper Structure, Multi-storey Building, Moment, Shear Force

Seismic Behavior of Assembly Joint with CFST Column and H-shaped Steel Beam

Existing concrete-filled steel tubular (CFST) structures are mostly based on cast-in-situ concrete construction technology. The beam-column joint emphasizes the horizontal connection, while the vertical connection of columns is mostly based on a steel tube connection instead of a precast CFST column connection; this is detrimental to the control of the concrete pouring quality and the full assembly of the structure. Thus, the investigation of an assembly joint that enables the full connection between the beam and CFST column is the key to the improvement of the construction quality and the promotion of the development of the assembled structure. This work proposes an assembly joint between an H-shaped steel beam and a CFST column, and the seismic behavior of the joint was investigated by low-cycle loading experiment. The finite element model of the joint was then established by the numerical analysis method. After verifying the rationality of the finite element model, the influences of both the endplate thickness and the bolt diameter on the energy dissipation performance of the joint were investigated via parametric analysis. The results reveal that with the increase of the endplate thickness and the bolt diameter within a certain range, both the bearing capacity and energy dissipation capacity of the joint will be improved. Moreover, the cooperative bearing mechanism of the column connector and concrete can be fully exerted. Thus, these conclusions indicate the feasibility of the use of the proposed assembly joint in practical engineering applications. Finally, the mechanical mechanism of the assembly joint was studied, and the calculation formula of the joint bending capacity was proposed.

Optimization of Red Sand Particle Size and Composition in Mixture with Ordinary Sand to Enhance Concrete Quality

Abstract In this study we determined the effect of variations in composition and particle size of Red Sand (RS) grains on the quality of concrete. Concrete was prepared as cubes of 15 cm3 with a composition of cement, sand and gravel in a ratio 1:2:3 and water to cement ratio of 0.5. Variations of RS (fine aggregate) composition are 0 %, 5 %, 10 %, 15 %, 20 % of the weight and red sand grain particle size were prepared as 80 mesh, 100 mesh, 120 mesh. Mechanical properties of the maximum concrete pressure strength test at a composition of 5 % along with a decrease in the size of the red sand grain size of 100 mesh and 120 mesh RS 100-5 and RS 120-5 with pressure forces of 35.4 MPa, and 35.5 MPa, respectively. On the other hand, the red sand with 80 mesh grain size have maximum pressure force in a composition 10 % RS 80-10 is 34.6 MPa. It is considered the addition of red sand fine aggregate has an impact on improving the quality of concrete.

Assessing printing synergism in a dual 3D printing system for ultra-high performance concrete in-process reinforced cementitious composite

3D printed ultra-high performance concrete (3DP-UHPC) acting as the reinforcement to in-process reinforce 3D printed concrete (3DP-C) can significantly improve the load-bearing capacity of 3DP-C. This method (3DP-UIRC) is achieved via a dual 3D printing procedure in which 3DP-UHPC as inner core is wrapped by 3DP-C and extruded together. However, lack of printing synergism between 3DP-C and 3DP-UHPC in deposition parameters, such as deposition layer height, printing speed and deposition rate, may result in heterogeneity of composite materials, and thus negates the overall mechanical strength of the structure. Therefore, parameters of nominal proceeding error (NPE) and co-printing factor (CF) are suggested to characterize the simultaneous manufacturing precision of 3DP-UIRC. The two suggested indicators are practically geometrical parameters to reflect the 3D concrete printing quality. Correspondingly, the printing precision error e and area ratio r are defined based on the experimentally measured values for comparison with NPE and CF, respectively. The printing precision error e and the area ratio r are calculated to be 0.37 and 0.163 by evaluating the practical syncing printing results with different layer height and extrusion volumetric flow rates of 3DP-C and 3DP-UHPC. They are approximately equal to NPE of 0.4 and CF of 0.16 with deviations of 7.5% and 2.5%, respectively. This study provides a new concept and quality assessment method for simultaneous printing of 3DP-UIRC. It also provides ideas and scientific references for promoting the application of 3DP-UIRC in 3D printing structured applications.

The Strength of Reinforced Concrete Slabs of 30% Candlenut Shell Variation Using Destructive Testing Methods

The compressive strength of concrete is one of the parameters used to control the quality of concrete. Concrete compressive strength testing method which is considered the highest level of reliability is a destructive testing method using a compression testing equipment. Based on the case, a testing tool is needed to measure or determine the compressive strength of concrete known as the Universal Testing Machine (UTM). Experimental research is conducted with a scientific approach using several of variables. The purpose of this research is to get the compressive strength value of concrete slabs variation of 30% candlenut shells. From the test results using a UTM so that it can be obtained the quality of reinforced concrete. The research variable are the 28 days age of concrete and the curing methods (wet curing and dry curing). The number of specimens of reinforced concrete slabs is 4 pieces measuring 50cm x 25cm x 12cm. The results of the study are the compressive strength of concrete slabs 30% variation of candlenut shells using UTM shows that the strength of reinforced concrete slabs reaches 75 MPa in wet curing and 59 MPa in dry curing or equivalent to the quality of K400 to K500 concrete at 28 days. The results also show the compressive strength of concrete in wet curing is higher than in dry curing.

Planning of Development Upper Structure of the Rorotan Labor Intensive Flats North Jakarta

The planning for this 16-storey building is a re-planning of the construction project for the Padat Karya Flats located in Rorotan, North Jakarta. This building planning is carried out based on the procedure for calculating concrete structures for buildings (SNI 2847:2019). The data for this building plan was obtained from the architect planning the construction of the Rorotan Solid Work Flats. The design of the superstructure includes the planning of slab, beam and column elements; The scope of the discussion includes calculation of loading, calculation of initial dimensions, ETABS analysis, control of analysis results, final dimension design and reinforcement, design drawings. The material used is reinforced concrete with a concrete quality of fc'35 Mpa fc’40 Mpa and fy 420 Mpa. The basics of planning refer to SNI 2847:2019 Procedures for Planning Concrete Structures for Buildings. And SNI 1726:2019 Earthquake Resistance Planning for Building Structures. Structural analysis using ETABS program with dynamic analysis of Response Spectrum.The keyword Multi-storey building, planning, superstructure, slab, column, beam.

Experimental and Analytical Investigation of R.C Beam with HPC Containing Nano Silica

Abstract: Concrete is the most widely used construction material in the world. It is a heterogeneous material composed of cement, fine aggregate, course aggregates and water. The proportion of these constituents affect the mechanical properties and durable properties of concrete. Also it is a versatile material due to the continuous demand. In recent years, lot of researches has been focused on improving the quality of concrete. This lead to the extension in the limitations to improve the performance of concrete with the addition of various admixtures super plasticizers subsidiary cementitious materials like silica fume, fly ash, blast furnace slag, metakaoiln, rice husk, etc. the properties like compressive strength, flexural strength, durability and workability of concrete enhances due to the addition of these materials. The concrete thus formed with high strength and durability compared to normal concrete are called High Performance Concrete. The compressive strength of HPC may be greater than 50Mpa. This HPC with compressive strength greater than 50Mpa can be used for structural members like beam, column, slab etc In this investigation the cement is replaced by 1%, 2% and 3% of Nano silica. Experimental and analytical investigation were done to investigating the flexural behaviour of conventional RC beam and R.C beam with HPC containing optimum percentage of Nano silica. Analytical investigation was done by ANSYS. This chapter discusses about the HPC, its mechanical strength properties like compressive strength, split tensile strength, flexural strength, effect of Nano materials like Nano Silica in HPC, determining the optimum percentage of Nano silica which gives maximum strength, investigating its durability property, investigating the strength development of RC beam with HPC containing optimum percentage of Nano silica, examining the load deflection behaviour of beam with HPC containing Nano silica and finally analysing the deflection of beam using Ansys. The key objective of this project is to investigate the importance of Nano silica as a replacement for cementitious materials in normal concrete and this paper presents strength and durable properties of HPC containing Nano silica.

Minimizing the negative impacts of rebar stored in the Persian Gulf on reinforced concrete corrosion

The study aims to ascertain the impact of improving concrete quality on decreasing the unfavorable impact of pre-rusted rebar on steel corrosion in reinforced concrete. Steel corrosion was assessed using half-cell potential and corrosion rate intensity tests, and concrete quality was assessed using electrical resistance measure and rapid chloride permeability test (RCPT). The efficiency of each element in influencing the steel corrosion in reinforced concrete was determined by the factors of the impact of rebar surface conditions and concrete quality on corrosion. The results showed that when using normal rebar, the effect of concrete quality index and rebar surface conditions on corrosion was 40.11% and 0.24%, and when using rebar with a corrosion index (CI)=11 was 1.25 % and 55.57%, respectively. Therefore, by increasing the pre-rusted rebar surface, the effect of concrete quality on corrosion reduces, and the effect of rebar surface conditions increases. In this study, until CI=7, the influence of the concrete quality index was more significant on corrosion than rebar surface conditions, followed by a reverse trend. Therefore, until CI=7, the concrete quality was the dominant factor in determining the corrosion rate intensity. By increasing the corrosion index, the steel corrosion rate intensity in reinforced concrete depends on the rebar surface conditions, and by increasing the concrete quality, these adverse effects cannot be reduced to a large extent.

Effect of cooling methods on the residual properties of concrete exposed to elevated temperature

One of the most damaging effects a building may suffer is a fire. Structures may be exposed to temperatures of more than 1000 °C while the fire is burning. In the course of and after the fire, structural concrete loses its rigidity and strength. The concrete's residual strength qualities may also be significantly influenced by the cooling phase's speed and cooling medium. In an attempt to compare the impact of various cooling regimes on concrete, an investigation has been made. The effects of adding polypropylene fibres and air entrainment admixtures were examined in addition to studies on traditional concrete. The water-cement ratio, cement mass and type, and aggregate type were all the same throughout the test. After cooling down from five distinct heat stages ranging from 150 to 900 °C, samples were compared to their unheated counterparts' results. Five distinct approaches, including slow cooling, forced air cooling, cooling with water mist, quenching, and the “normal” cooling under laboratory conditions, were used to study the cooling effects. The study aimed to examine integrated temperature endurance numbers, relative residual compressive strength values, and residual compressive strength values in addition to visual observation. Regulations were matched with the outcomes. The findings demonstrated that, up to 600 °C, there were no appreciable changes in the residual properties between the various cooling methods or between the different mediums with virtually the same cooling pace. The apparent disintegration of water-cooled samples was evident after cooling from 900 °C.

Using GA - BP Coupling Algorithm to Predict the High-performance Concrete Mechanical Property

As a cementitious composite, concrete's property depends on the matrix generated from cement hydration and the dispersed phases such as aggregates. Compression strength is an important mechanics performance index of concrete quality, especially the High-performance Concrete (HPC). However, owing to the expensive cost of test and the existence of high-dimensional nonlinear mapping between compression strength and basic materials, it is uneasiness to precisely forecast the compression strength value of HPC by general formula method. In this research, a novel machine learning system, Genetic Algorithm and BP Neural Network (GA-BPNN) coupling algorithm, is offered to predict the compression strength of HPC. GA-BPNN coupling algorithm model used 181 groups of HPC mixture data to determine 8 factors affecting its compression strength (i.e., Water, Portland Cement, Waterbinder Ratio, Fine Aggregate Ratio, Air-entraining Agent, Fly Ash, Silica Fume, and Superplasticizer) as the input variables of the model, while compression strength was set as the output variable. In addition, 166 sets of training set data were segmented into training, validation and test set again, and BP neural network (BPNN) was compared with GA-BPNN to verify the generalization capacity of the model in this research. By forecasting the compression strength of 15 test sets, the average relative error is only 0.902%. Finally, the sensitivity of input variables of GA-BPNN model was analyzed by using Gray Relational analysis (GRA) method. Six models were established to research the impact of sensitivity and quantity of input variables on model performance by ignoring individual input variable. The research is shown that GA-BPNN model not only has the powerful nonlinear mapping ability of BPNN, but also has the global search optimization ability of GA, and showed stronger robustness and prediction potential in the assessment of compression strength value of HPC. The sensitivity analysis shows that, to compression strength of HPC, Cement, Water and Water-binder ratio has a sensitivity score of 0.8166, 0.70122, 0.66772, respectively while Fly Ash has the lowest sensitivity.

The Use of Polymer Admixtures for Concrete Quality 45 Mpa Using the Combination of Bangkalan and Pandan Aggregate

Madura Island has natural resource potential, one of which is the result of mining excavations, including class C. Bangkalan Regency has aggregates that could be used in concrete mixtures, including fine aggregate (sand) and coarse aggregate (gravel). The compressive strength of concrete using Bangkalan aggregate, on the other hand, is just 20 MPa, or the regular concrete category. High-quality concrete is one of the most frequently utilized building materials nowadays. Admixture is required to build high-strength concrete, particularly in Bangkalan Regency. In this research, a polymer admixture was used.The goal of this study was to determine the proportion of polymer additives used in the concrete mixture when fine aggregate from Lumajang, coarse aggregate 10/20 from Bangkalan, and coarse aggregate 5/10 from Pandaan were used to achieve a concrete compressive strength of 45 MPa.Based on the findings of research on the usage of polymer-type additives in concrete mixtures using fine aggregate from Lumajang, 10/20 coarse aggregate from Bangkalan, and 5/10 coarse aggregate from Pandaan, a concrete compressive strength of 0.95% Fc '45 Mpa was obtained from cement weight. At the design concrete quality of Fc '45 Mpa, the average compressive strength of concrete aged 28 days is 45.54 Mpa.

Experimental Investigation on Bond, Microstructure and Durability of Expired Hardened Cement Blended with Ground Granulated Blast Furnace Slag as Partial Replacement of Cement in High-Strength Concrete

The current study aimed to investigate the influence of the expired hardened cement blended with ground granulated blast furnace slag on the bond, microstructure, and durability of high-strength concrete (HSC). Five concrete mixes are prepared; the first mix is taken as a control, and the remaining four mixes are used as experimental blends. HSC characteristics are evaluated by compressive, flexural, splitting tensile, bond, and durability tests. Furthermore, the ultrasonic pulse velocity and microstructural characteristics tests are carried out to check concrete quality. The synergistic action of blends (expired harden cement with GGBS) on the strength test results was found to increase with an increase in blends up to 20%. The durability result reveals that HSC was found to be impermeable under aggressive conditions. The microstructural characteristics achieved in the current investigation explain the above strength, bond, and durability performance of these mixes. The whole performance of blends in HSC is adequate for industrial use.

The Application of Two-Dimensional Continuous Wavelet Transform Based on Active Infrared Thermography for Subsurface Defect Detection in Concrete Structures

The early condition-based assessment of civil infrastructures plays an essential role in extending their service life, preventing undesirable sudden failures, and reducing maintenance and rehabilitation costs. One of the most commonly used and fastest nondestructive testing (NDT) techniques is infrared thermography (IRT), which has emerged as a powerful method for assessing general concrete quality and detecting subsurface damage in structural members. Nevertheless, the accurate detection and classification of localized defects is still a challenging task to achieve. The contribution made by enhancing defect detection using two-dimensional (2D) wavelet transformation (WT) as a post-processing method, however, has received little attention within the field of active IR thermography. In this study, we explored the use of continuous wavelet transform (CWT) to visualize how the wavelet function at different frequencies could enhance the damage features of thermal images. A concrete slab under an applied heat flux was tested experimentally by an IR camera with well-controlled excitation sources. The qualitative visualization of thermograms was translated into quantitative results by extracting, processing, and post-processing the values assigned to the pixels in the thermal images. With the assumption of there being no oriented damage features, an isotropic (non-directional) Mexican hat wavelet was utilized as the mother wavelet. The experimental results showed that the 2D-CWT method achieved strong detection performance in extracting discriminatory features (defective areas) from the acquired thermal images. Compared with raw thermograms, the resultant CWT-transformed images were less affected by the non-uniform heating effect, and the boundaries of the defects contrasted more strongly. The 2D-CWT method demonstrates good sensitivity when an appropriate wavelet type and scale factor are chosen. Due to the desire to detect localized defects, adjusting the scale factor of the wavelet is important to improve the efficiency of detection as lower scale factors provide the finer details of thermal images, whereas higher scale factors provide the general outline of internal defects. The findings of this study represent a further step toward improving thermographic data for more precise defect-detection imaging, and principally for large concrete structures, that can be verified easily using other NDT surveys.

Compactness prediction of asphalt concrete using Ground-Penetrating Radar: A comparative study

The compactness is an important indicator of quality control during the construction of the asphalt concrete pavement. The construction quality of asphalt concrete can be continuously, quickly, and non-destructively tested by establishing the correlation between dielectric constant and compactness through ground-penetrating radar. In this study, five compactness prediction models were established based on the relationship between volume parameters and the dielectric constant of each component of asphalt concrete. 18 samples of Sup20 asphalt concrete (Superior Performing Asphalt Pavement with the nominal aggregate size of 19 mm) were used to verify the established compactness prediction models. The results showed that the average relative error, maximum error, and root mean square error of the CP_Rayleigh model (compactness prediction model of Rayleigh.) were minimum, and thus the CP_Rayleigh model was selected for the following-up research in this study. The shapes of scatterers (aggregates and pores) were not spherical, and a shape factor u of 0.033 was introduced to modify the CP_Rayleigh model. The prediction accuracy of compactness can be effectively improved by the modified CP_Rayleigh model. Combined with field engineering verification, it was shown that the modified CP_Rayleigh model can be used to predict the compactness of asphalt concrete in the field.

Systematic Evaluation of Permeability of Concrete Incorporating Coconut Shell as Replacement of Fine Aggregate.

The concern about coconut shell disposal and natural fine aggregate depletion has prompted researchers to utilize coconut shell as aggregate in recent years. However, the majority of the present literature has focused on utilizing coconut shell as a coarse aggregate replacement in concrete via the traditional method. In this study, concrete incorporating coconut shell as a fine aggregate replacement (10-100%) was evaluated using permeability and water absorption tests in a systematic way. The response surface methodology (RSM) was first used to design the experimental works. In addition, an artificial neural network (ANN) and genetic expression programming (GEP) were also taken into account to mathematically predict the permeability and water absorption. Based on both experimental and theoretical modeling, three scenarios were observed. In the first scenario, high quality concrete was achieved when the replacement percentage of sand by coconut shell ranged from 0% to 10%. This is because both the permeability and water absorption were less than 1.5 × 10-11 m and 5%, respectively. In the second scenario, an acceptable and reasonable low permeability (less than 2.7 × 10-11 m/s) and water absorption (less than 6.7%) were also obtained when the replacement percentage increased up to 60%. In contrast, the high content coconut shell, such as 90% and 100%, developed concrete with a high permeability and water absorption and was defined in the third scenario. It was also inferred that both the experimental and mathematical models (ANN, GEP, and RSM) have consistent and accurate results. The correlation statistics indicators (R2) were greater than 0.94 and the error was less than 0.3, indicating a strong correlation and minimum error. In conclusion, coconut shell could act as a good alternative material to produce cleaner concrete with an optimum value of 50% as a fine aggregate replacement.