This paper presents the use of blend of Portland cement with rice husk-bark ash in producing self-compacting concrete (SCC). CT was partially replaced with ground rice husk-bark ash (GRHBA) at the dosage levels of 0%–40% by weight of binder. Compressive strength, porosity, chloride penetration, and corrosion of SCC were determined. Test results reveal that the resistance to chloride penetration of concrete improves substantially with partial replacement of CT with a blend of GRHBA and the improvement increases with an increase in the replacement level. The corrosion resistances of SCC were better than the CT concrete. In addition, test results indicated that the reduction in porosity was associated with the increase in compressive strength. The porosity is a significant factor as it affects directly the durability of the SCC. This work is suggested that the GHRBA is effective for producing SCC with 30% of GHRBA replacement level.
Self-compacting concrete (SCC) is featured in its fresh state by high workability and rheological stability. SCC has excellent applicability for elements with complicated shapes and congested reinforcement [
In Thailand, rice husk-bark ash is a residue obtained from the burning of rice husk-bark as fuel source in the small power generation plants (Thai Power Supply Company Ltd., in Chachoengsao Province). Two portions of rice husk and one portion of eucalyptus bark are the normal composition and it is burnt at 800–900°C [
Portland cement type I (CT) and rice husk-bark ash (from Thai Power Supply Company Ltd., in Chachoengsao Province, Thailand) and Superplasticizer (Viscocrete by SIKA; SP) were the materials used for this study. Local crushed limestone was used as coarse aggregate. Graded river sand was used as fine aggregate. Rice husk-bark ash (GRHBA) was ground by a ball mill until 5% weight retained on a sieve number 325. The increase in fineness of pozzolanic materials increased the surface area and the reaction [
The mechanical properties of cement and pozzolanic materials.
Physical properties | CT | GRHBA |
---|---|---|
Median particle size ( |
25.0 | 20 |
Retained on a sieve number 325 (%) | N/A | 5 |
Specific gravity | 3.14 | 2.23 |
Blaine fineness (cm2/gm) | 3.600 | 11.000 |
The chemical composition of CT and GRHBA is shown in Table
Chemical components of CT and pozzolanic materials [
Oxides (%) | CT | GRHBA |
---|---|---|
CaO (%) | 54.9 | 5.5 |
Si |
25.0 | 76.0 |
|
5.5 | 1.5 |
|
5.5 | 1.5 |
MgO (%) | 3.0 | 0 |
|
0.5 | 3.9 |
S |
4.5 | 0.9 |
LOI (%) | 0.9 | 8.2 |
Si |
— | 79.0 |
Portland cement type I (CT) was partially replaced with GRHBA at the dosages of 0%, 20%, 30%, and 40%. CT was partially replaced with pozzolans in order to produce self-compacting concrete (SCC) with compressive strength at 28 days higher than 20.0 MPa (design at the age of 28 days). The content of cementitious materials (B) was maintained at 650 kg/m3. All concrete mixtures had constant water to binder ratio (W/B) of 0.46. A slump flow ranking from 650 to 800 mm is considered as the slump flow required for self-compacting concrete [
The cast specimens were covered with polyurethane sheet and damped cloth and placed in 23 ± 2°C chamber for one day. After that, they were demoulded and were cured in water at 23 ± 2°C until the test age. The self-compacting concrete (SCC) mix proportions are given in Table
Self-compacting concrete mixture proportions.
Mix | *W/B or *W/C | Mix proportions (kg/m3) | SP | Flow (mm) | ||||
---|---|---|---|---|---|---|---|---|
Cement | GRHBA | Fine aggregate | Coarse aggregate | Water | ||||
CT | 0.46 | 650 | 0 | 780 | 975 | 299 | 3 | 720 |
20 GRHBA | 0.46 | 520 | 130 | 780 | 975 | 299 | 5 | 740 |
30 GRHBA | 0.46 | 455 | 195 | 780 | 975 | 299 | 6 | 750 |
40 GRHBA | 0.46 | 390 | 260 | 780 | 975 | 299 | 7 | 745 |
The 100 mm diameter and 200 mm height cylindrical specimens were used for compressive strength testing. The compressive strength test was carried out as per ASTM C39 [
For porosity test, SCC were cut into 50 mm thick slices and the 50 mm ends were discarded. They were dried at 100 ± 5°C until the weight was constant. They were then placed in desiccators under vacuum for 3 hours. The setup was finally filled with deaired and distilled water in order to measure the effective porosity of concrete at the ages of 7, 28, and 90 days. The porosity was calculated by using [
The 100 mm × 200 mm cylinders were prepared in accordance with ASTM C39 [
The RCPT test setup with ASTM C1202 [
This test was successfully used on the previous research work on the corrosion of mortar and concrete containing pozzolans [
Concrete prism for accelerated corrosion test.
The accelerated corrosion test setup.
The results of the required SP of SCC are given in Table
The results of compressive strengths and the normalized compressive strengths are presented in Figures
Compressive strength of SCC.
Normalized compressive strength of SCC.
Relationship between compressive strength and % of GRHBA replacement.
The results of porosity of SCC concrete are given in Figure
Porosity of SCC.
Relationship between compressive strength and porosity of SCC.
The results of the chloride resistance test of the self-compacting concrete (SCC) at 7, 28, and 90 days are presented in Figure
Chloride penetration of SCC with RCPT [
The test result is presented in Figure
Time of first crack (h) of SCC.
At the age of 90 days, the time of first crack of self-compacting concrete control (CT) was 110 hours, whereas the time of first crack of self-compacting concretes containing GHRBA was longer at 120 to 145 hours. The time of first crack of SCC increased continuously. This confirms the results of the time of first crack that incorporation of GHRBA improves the resistance to corrosion of self-compacting concretes. The pozzolanic materials increased the reaction products and reduced the volume of the cavities in the paste [
Sample of time of first crack.
From the tests, it can be concluded that GHRBA containing fine irregular-shaped particles increases the amount of SP required. The use of the blend of pozzolans of fine GHRBA also effectively improves the self-compacting concretes (SCC) in terms of corrosion and resistance to chloride penetration. The results indicate that the incorporation of 30% of GRHBA decreases the corrosion, chloride penetration of self-compacting concrete. This is due to the fact that the fine particles of GHRBA could fill the void and also caused the nucleation sites for the acceleration of the hydration reaction in the cement paste.
The authors declare that there is no conflict of interests regarding the publication of this paper.
This work was supported by the Thailand Research Fund (TRF) under the TRF Research Grant for New Scholar no. MRG5580120; Office of the Higher Education Commission (OHEC); Rajamangala University of Technology Phra Nakhon (RMUTP).