In this study, the clogging mechanism of pervious concrete was evaluated using three different cloggers such as, Sand (S), Clay (C), and combination of sand and clay (S &C). The clogging mechanism was performed through falling head permeability apparatus, using clogger sediment load at the rate of 50, 150, and 200 grams in repetitive clogging cycles. It was observed from the results that combined (S & C) clogger shows overall critical results of clogging as 80% of the clogging was seen in 3 to 4 cycles. Moreover, it was observed from the results that pervious concrete mix made with R- type of aggregate gradation shows optimum compressive strength of the order of 8.6, 15.9, and 17 MPa at 7, 28 and 56 days of curing. Furthermore, the visual inspection test shows that clogging by clay clogger shows an even distribution of sediment on the whole length of the sample.
En este estudio se evaluó el mecanismo de obstrucción del hormigón permeable utilizando tres obturadores diferentes: arena (S), arcilla (C) y una combinación de arena y arcilla (S & C). El mecanismo de taponamiento se realizó a través de un aparato de permeabilidad de cabeza descendente, utilizando una carga de sedimento del obturador a razón de 50, 150 y 200 gramos en ciclos de taponamiento repetitivos. A partir de los resultados se observó que el obturador combinado (S & C) muestra resultados críticos generales de obstrucción, ya que el 80% de la obstrucción se observó de 3 a 4 ciclos. Además, se detectó que la mezcla de hormigón permeable hecha con gradación de áridos tipo R presenta una resistencia a la compresión óptima del orden de 8.6, 15.9 y 17 MPa a los 7, 28 y 56 días de curado. Finalmente, la prueba de inspección visual muestra que la obstrucción por arcilla muestra una distribución uniforme de sedimentos en toda la longitud de la muestra.
According to ACI, Pervious Concrete is a highly porous concrete that can be used combinedly as a pavement and drainage system. In recent times, pervious concrete has been the most significant development in concrete technology and had a profound environmental benefit. It is a special type of concrete made with or without the inclusion of fine aggregate content than a normal conventional type of concrete. It is widely used in pedestrian footpaths, car parks, sidewalks, car washing areas, efficient sanitization systems, and slope stability in hilly areas and other low-traffic areas (
Moreover, the porosity of pervious concrete ranges between 15% to 30% (
Some authors have investigated surface cleaning with pressurized water and air-blowing techniques and suggested that the air-blowing technique is the best practice to de-clog the choking (
Based on the literature survey presented in the preceding section indicates that a lot of research has been done to examine the strength and hydraulic properties of pervious concrete made with single grade proportion of aggregates. However, the information on clogging potential for pervious concrete made with different aggregate grade proportions is scanty. Therefore, an investigation has been developed on the effect of grade aggregate proportions on the clogging phenomenon of pervious concrete. In this study, three grades proportion of aggregates (P, Q, and R) were prepared from four aggregates proportions (A: B: C: D) such as 2.36 mm, 4.75 mm, 6.3 mm, and 10 mm. Moreover, to stimulate the actual sediment load conditions and to calculate actual load percentages, sieve and hydrometer analyses have also been done. Furthermore, other properties such as porosity, permeability, and compressive strength have been evaluated at 28 and 56 days of curing. Additionally, a visual inspection test through the half-cut method, dry cut method, and slicing method is performed to check the flow and depth of clogging sediment.
The experimental program in this study was divided into two general findings. The first aim involves the determination of porosity, water permeability, and compressive strength. secondly, the clogging performance of pervious concrete was evaluated using three different sediment cloggers.
The different materials utilized in this experimental study have been discussed in the following sub-sections.
Ordinary Portland Cement (OPC) 43 grade, according to IS: 8112 (
The three different grades (P, Q, and R) of Natural Coarse Aggregates (NCA) and Natural Fine Aggregates (NFA) have a size of 12-10 mm, 10-6.3 mm, 6.3-4.75 mm, and 4.75-2.36 mm were used in the ratio of A:B:C:D. The different grades were used in the ratios of, 0:40:40:20, (i,e 0% of 2.36 mm, 40% of 4.75 mm, 40% of 6.3 mm, and 20% of 10 mm) for P, 10:40:40:10 (i,e 10% of 2.36 mm, 40% of 4.75 mm, 40% of 6.3 mm, and 10% of 10 mm) for Q, and 20:40:40:0 (i,e 20% of 2.36 mm, 40% of 4.75 mm, 40% of 6.3 mm, and 0% of 10 mm) for R, respectively. Natural Fine Aggregates, 2.36 mm was obtained locally and was utilized in the ratios of 0%, 10%, and 20% as per IS 383 guidelines (
Aggregate properties | 2.36 mm (NFA) | 4.75 mm (NCA) | 6.3 mm (NCA) | 10 mm (NCA) | Testing standards |
---|---|---|---|---|---|
Impact value (%) | - | 13.36 | 13.10 | 13.00 | IS:2386-Part-IV ( |
Abrasion value (%) | - | 20.86 | 19.00 | 18.03 | ASTM C 131 ( |
Water absorption (%) | 2.10 | 0.56 | 0.57 | 0.98 | ASTM C127 ( |
Soundness (%) | - | 5.70 | 5.68 | 5.30 | IS:2386-Part-V ( |
Apparent density (kg/m^{3}) | 2490 | 2445 | 2420 | 2410 | ASTM C127 - 15 ( |
Bulk density (kg/m^{3}) | 1795 | 1780 | 1765 | 1750 | ASTM C29/C29M ( |
Sediment load for clogging was selected from the actual road dust sample and the particle size distribution is shown in
The mix proportions of the different pervious concrete mixes are presented in
Mix Notation | Aggregate proportion (AP) | AP Notation | W/C ratio | P/A ratio | 2.36 mm (A) | 4.75 mm (B) | 6.3 mm (C) | 10 mm (D) | OPC Kg/m^{3} | Water Kg/m^{3} |
---|---|---|---|---|---|---|---|---|---|---|
P-A0 | 0%A+40%B+40%C+20%D | P | 0.35 | 1:5 | 0 | 640 | 640 | 320 | 320 | 112 |
P-A10 | 10%A+40%B+40%C+10%D | Q | 0.35 | 1:5 | 160 | 640 | 640 | 160 | 320 | 112 |
P-A20 | 20%A+40%B+40%C+0%D | R | 0.35 | 1:5 | 320 | 640 | 640 | 0 | 320 | 112 |
After 24 hours of casting, the specimen was demoulded and placed in a curing tank for 7, 28, and 56 days at room temperature conditions (20 ± 1°C while as humidity was maintained over 95%. All the testing procedures are discussed in the following sub-sections.
ASTM C1754 (2012) was used to evaluate the porosity of the pervious concrete (
Where P is the porosity of cylindrical sample, %; W_{1} is the mass of sample in dry condition, g; W_{2} is the mass of sample in submerged condition, g; V represents volume specimen, cm^{3}; and ρw represents the density of water, g/cm^{3}.
A falling head permeability apparatus as shown in
Where K is permeability, A_{1} is the area of the head pipe, A_{2} is the specimen area, L is specimen length and ‘t’ is the time required for water to drop from the preliminary head h_{1} to bottom head h_{2}.
A compressive strength test on pervious concrete was performed according to IS 516 (1959), (
The falling head permeability apparatus used for measurement of permeability was used to evaluate the outcome of artificial clogging in pervious concrete. Three cloggers (S, C, and S&C) were used to produce artificial runoff and permeability reductions are calculated using Darcy’s Equation [
To know whether the blockage in the pore channel was at the top, bottom, or center, a visual inspection is necessary to perform. In this study visual inspection was performed through three techniques. a) Half-cut method: In this method, the clogged samples of pervious concrete are cut into two halves as shown in
With the help of a high-resolution micro-focus X-ray computed tomography (X-CT) system and filter 7 image processing software, the exact presence of sediment was predicted with clear visuals. Moreover, the clogging of clogged sample was predicted through X-CT at three sections, top, mid, and bottom respectively.
Two rejuvenation techniques are used to un-clog the clogged samples of pervious concrete are:
Vacuum rejuvenation
Pressure washing
Eureka Forbes vacuum cleaner having a suction capacity of 2300 mm of WC (0.022 MPa) was used for vacuum treatment of clogging. Both the nozzles, floor cum carpet, and crevice nozzle were used to remove the sediment particles from cylindrical samples. Whereas, a car service pressure washer having 20.7 MPa (3,000 psi) pressure of water was used pressure washing treatment of clogging. Both the rejuvenation methods are intended to wash out the ingressed materials and regain the hydraulic functionality of clogged pervious concrete samples.
The porosity of all the mixes of pervious concrete made with different grade aggregate proportions is presented in
Furthermore, it was also observed from
The water permeability tests on pervious concrete were performed at 7 and 28 days of curing age and are presented in
Furthermore, a relationship was developed between permeability and porosity of all the mixes as shown in
The compressive strength results of the pervious concrete mixes made with three aggregate grade proportions are presented in
Furthermore, the development of compressive strength in pervious concrete shows optimum results at 28 days of curing for each mix as compared to the compressive strength of pervious concrete at 7 and 56 days. A prominent development of 43% in compressive strength was seen for the control mix, at 28 days as compared to 7 days strength. Nevertheless, the increase in strength for the same control mix, P-A0 at 56 days was only 17% as compared to compressive strength at 28 days. Moreover, the same increment in compressive strength for pervious concrete was seen for mix P-A10 and P-A20, in which aggregate grade proportion of Q and R type was used having 10% and 20% of NFA respectively. An increment of 45% and 46% was observed for mix P-A10 and P-A20 at 28 days as compared to compressive strength at 7 days. However, a marginal development of 9% and 6% in compressive strength was seen for the same mixes of P-A10 and P-A20 at 56 days as compared to compressive strength at 28 days. This shows that on increasing the curing period from 7 to 28 days, maximum hydration of pervious concrete mix occurs at 28 days because of higher creation of C-S-H which contributes to more compressive strength. The increase in strength was also attributed to the more pozzolanic and filler effect of pervious concrete by incorporating more NFA which increases the overall density of pervious concrete. For pervious concrete mix in the varied graded proportion of aggregates.
The falling head permeability apparatus used for measurement of permeability was used to evaluate the outcome of artificial clogging in pervious concrete as shown in
From
It can be seen from
It was also analyzed from the slicing method of visual inspection that the clay clogger was evenly distributed over the whole length of the sample. However, peripheral sand sediment was seen at the outer periphery of cylindrical samples clogged with sand only as shown in
The image processing techniques such as X-CT tomography and filter 7 image processing were used and are shown in
Vacuuming as shown in
Moreover, pressure washing as shown in
The present study was designed to determine the influence of different aggregate grade proportions on the clogging potential of pervious concrete. Based on the results obtained, a few conclusions are drawn.
Relative to the control mix, made with P-type of aggregate gradation, the 28-day compressive strength increased significantly by 10% and 24% for mixes P-A10 and P-A20 in which Q and R type aggregate grade proportion was used respectively. Therefore, the inclusion of NFA up to 20% in pervious concrete increases the compressive strength significantly at 28 days of curing age due to increasing the overall density of concrete matrix.
Clogging done by combined sand and clay clogger shows an 80% loss in permeability in 4 to 5 cycles for all three mixes. However, clogging through clay alone take highest number of cycles (
All the visual observations supported by image processing shows that clogging due to clay alone could show critical results of clogging as the sediment of clay was evenly distributed over the whole depth of sample. Whereas, clogging due to combined sediment shows least clogging due to formation of mud lid on the top of sample.
Rejuvenation treatment shows that a maximum 80% recovery of permeability was observed for sand clogged samples against vacuuming treatment. Whereas, a maximum recovery of 50% in permeability was seen for combined clogged samples against pressure washing. However, in general it was observed that pervious concrete mix made with R-type of aggregate gradation shows optimum results of recovery against both the rejuvenation techniques.
The authors are highly thankful to the Department of Civil Engineering, Dr B R Ambedkar National Institute of Technology Jalandhar for proving the necessary equipment for conducting this investigation.
The first author received financial support from the Ministry of Human Resource Development (MHRD), Government of India.
Conceptualization: K. Kapoor, S.P. Singh. Data curation: K. Kapoor, M. Nazeer. Formal analysis: K. Kapoor, S.P. Singh, M. Nazeer. Investigation: K. Kapoor, M. Nazeer. Methodology: K. Kapoor, S.P. Singh, M. Nazeer. Project administration: K. Kapoor, S.P. Singh. Resources: K. Kapoor, S.P. Singh. Supervision: K. Kapoor, S.P. Singh. Validation: K. Kapoor, S.P. Singh, M. Nazeer. Visualization: K. Kapoor, S.P. Singh, M. Nazeer. Writing, original draft: M. Nazeer. Writing, review & editing: K. Kapoor, S.P. Singh.