Hydration, strength, and durability of cementitious materials
incorporating untreated corn cob ash
The researchers found when they replaced 3% and 20% of cement with
untreated corn cob ash (CCA) in their concrete mixtures
3% Replacement (CCA replaces 3% of cement)
• Slight acceleration in hydration- The cement reacted a bit faster due to high
potassium in the ash.
• Reduced compressive strength- Concrete became weaker than the control mix.
• Lower durability- Lower bulk resistivity, Lower formation factor and Higher
chloride ion permeability.
20% Replacement (CCA replaces 20% of cement)
• Faster hydration – Even more pronounced than at 3%
• Significantly reduced strength – Concrete lost a lot of its compressive strength.
• Durability greatly reduced: Very low resistivity, Very high chloride ion permeability
and Poor resistance to chemical attack
The researcher conducted a comprehensive set of tests to evaluate the
effects of replacing Ordinary Portland Cement (OPC) with untreated corn cob
ash (CCA)
• Isothermal Calorimetry- Accelerated early hydration
• Compressive Strength- Replacements led to significantly lower
compressive strengths
• Bulk Electrical Resistivity- The untreated CCA mix exhibited lower
resistivity values
• Strength Activity Index (SAI)- The low SAI values suggested that untreated
CCA lacks significant pozzolanic properties.
RESULT
High potassium content in CCA speeds up early cement hydration.
• Both 3% and 20% CCA mixes showed lower compressive strength than the
control.
• CCA replacements resulted in Lower bulk resistivity, Lower formation
factor and Higher chloride ion permeability
• CCA behaved like an inert filler, not an active pozzolan (based on SAI and
R3 tests).
• Most significant reductions in mechanical and durability properties.
Enhancing the usability of electronic waste fibers in high-performance self-
compacting mortar incorporating corn cob ash and silica fume: Fresh and
hardened properties
The researchers explored the incorporation of corn cob ash (CCA) as a partial
replacement for cement in self-compacting mortar
-Corn Cob Ash (CCA) Replacement in the Research
• Corn Cob Ash (CCA) replaced 10% of the cement by weight
• Silica Fume (SF) was also added at 10% as a supplementary material
• The aim was to partially substitute cement with CCA to improve
sustainability and performance.
-Purpose of Replacement:
• To reduce cement usage (lower CO₂ emissions).
• To improve microstructure and enhance durability.
• To increase sustainability by using agricultural waste
The researchers conducted a comprehensive set of tests to evaluate both the
fresh and hardened properties of the developed self-compacting mortar.
Fresh Properties Tests-
• Slump Flow Test – To measure the flowability and workability of the fresh mortar
without external compaction
• V-Funnel Test - To determine the viscosity and flow time, indicating the ease with
which the mortar flows.
• L-Box Test –To evaluate the passing ability of the mortar through
reinforcement bars, ensuring that it can flow easily in the presence of
obstacles .
• Hardened Properties Tests
• Compressive Strength Test –To assess the load-bearing capacity of the mortar
under compression, which is a key indicator of its strength.
• Flexural Strength Test – To evaluate the ability of the mortar to resist bending and
the development of cracks under load.
RESULT
The findings suggest that incorporating electronic waste fibers, corn cob ash,
and silica fume into self-compacting mortar can produce high-performance,
durable, and sustainable construction materials.
• The inclusion of corn cob ash (CCA) and silica fume (SF) enhanced the
compressive and flexural strengths of the self-compacting mortar.
• The modified mortar demonstrated better resistance to water absorption
and chloride ion penetration, indicating improved durability.
• The study successfully utilized electronic waste fibers and agricultural by-
products like CCA, addressing waste management issues and reducing the
environmental footprint of construction materials.
Development of corn cob ash blended cement
In this research, Corn Cob Ash (CCA) was used to replace Ordinary Portland
Cement (OPC).
The CCA Replacement Percentages Tested are 0%, 2%, 4%, 6%, 8%, 10%, 15%,
20% and 25%.
Important:-
• The best performance for strength and standards compliance was seen at
8% replacement.
• Up to 15% CCA replacement was still acceptable under standards (NIS
439:2000 and ASTM C150).
• Above 15%, strength started decreasing significantly.
The researchers conducted several tests to evaluate the suitability of corn cob
ash (CCA) as a partial replacement for Ordinary Portland Cement (OPC).
• Chemical Composition Analysis
➔To determine the chemical constituents of CCA, ensuring it meets the
required standards for use as a pozzolan.
• Setting Time Determination
➔ To evaluate the effect of CCA on the setting time of cement, ensuring it
falls within acceptable limits.
• Pozzolanic Activity Test
➔To assess the pozzolanic reactivity of CCA, indicating its ability to react with
lime to form additional cementitious compounds..
RESULT
The research supports the use of CCA as a sustainable and effective partial
replacement for OPC in cement production, particularly at lower substitution
levels, contributing to waste utilization and environmental conservation.
• Corn Cob Ash (CCA) is rich in pozzolanic materials
• Blended cement with up to 15% CCA meets Nigerian (NIS 439:2000) and
ASTM C150 standards.
• Optimal replacement level is 8% CCA for good strength in structural
concrete.
• Higher CCA content (>15%) reduces strength significantly.
• CCA utilization promotes environmental sustainability and waste recycling.
• Blended cement is cost-effective compared to pure Ordinary Portland
Cement (OPC).
A study of the workability and compressive strength characteristics
of corn cob ash blended cement concrete
Corn Cob Ash (CCA) was used to replace Ordinary Portland Cement (OPC) at
the following percentages 0%, 2%, 4%, 6%, 8%, 10%, 15%, 20%, and 25%.
After performing tests, it was found that 8% CCA replacement produced the
best balance of strength and workability.
Above 15% CCA replacement led to a decline in compressive strength, which
is why 8% was identified as the optimal replacement level.
The optimal replacement level for both workability and compressive strength
was found to be 8% CCA. Replacing more than 15% CCA resulted in a
reduction in concrete strength
The researchers conducted several tests to evaluate the properties of
concrete incorporating Corn Cob Ash (CCA) as a partial replacement for
Ordinary Portland Cement.
• Workability: As the percentage of CCA increased, both the slump and
compacting factor of the concrete decreased, indicating reduced
workability.
• Compressive Strength: At early curing ages (3 to 28 days), concrete with
CCA showed lower compressive strength compared to the control mix.
However, at later ages (120 and 180 days), the compressive strength of
CCA-blended concrete surpassed that of the control mix.
• Optimal Replacement Level: The study identified that replacing OPC with
up to 8% CCA is optimal for structural concrete applications, as higher
percentages could adversely affect strength development.
RESULT
These findings highlight the potential of CCA as a supplementary
cementitious material, offering benefits such as enhanced long-term strength
and sustainability in concrete production.
• Workability:
• As the percentage of Corn Cob Ash (CCA) increased, workability decreased.
• Concrete became stiffer, making it harder to handle and compact.
• Compressive Strength:
• At early curing stages (3-28 days), the compressive strength was lower in CCA-
blended concrete compared to the control
• At later stages (120-180 days), concrete with CCA showed higher compressive
strength than the control.
• Optimal CCA Replacement:
• 8% CCA replacement produced the best balance of strength and workability.
A study of the permeability and acid attack of corn cob ash
blended cements
In the study, Corn Cob Ash (CCA) was used as a partial replacement for
Ordinary Portland Cement (OPC).
- 10–15% CCA replacement was optimal, giving:
• Lower water absorption (better against moisture damage).
• Reduced permeability (better durability).
• Improved acid resistance (less weight loss when attacked by HCl and
H₂SO₄).
- At 20% CCA replacement, performance started to decline slightly, suggesting
that too much CCA can weaken the concrete.
The researchers performed 3 main types of tests in the study:
-Water Absorption Test:
• The use of CCA blended cement reduced the water absorption of concrete
specimens. Optimal reduction occurred at 10% CCA replacement for
1:1½:3 and 1:2:4 mix proportions and at 15% CCA replacement for the
1:3:6 mix proportion.
• Mix Proportions: 1:1½:3, 1:2:4, and 1:3:6.
-Chemical Attack Test:
• The addition of CCA up to a 15% replacement level improved resistance to
chemical attack, leading to a decrease in permeability and reduced weight
loss due to reactions with HCl and H₂SO₄ acid solutions.
• Mix Proportions:1:1, 1:2, and 1:3.
RESULT
The researchers investigated the durability of concrete made with Corn Cob Ash
(CCA) blended cement, focusing on permeability and resistance to acid attacks.
Water Absorption Reduction:-
• The incorporation of CCA into cement reduced the water absorption of
concrete specimens.
• Optimal reduction occurred at 10% CCA replacement for mix proportions of
1:1½:3 and 1:2:4, and at 15% CCA replacement for the 1:3:6 mix proportion.
Improved Resistance to Acid Attack:-
• The addition of CCA up to a 15% replacement level enhanced the concrete's
resistance to chemical attacks.
• This was evidenced by a decrease in permeability and a reduction in weight
loss when specimens were exposed to HCl and H₂SO₄ acid solutions.
Machine learning algorithms in the environmental
corrosion evaluation of reinforced concrete structures - A
review
• Cement and Concrete Composites in August 2022, does not involve
the execution of physical tests. Instead, it provides a comprehensive
overview of various machine learning (ML) algorithms applied to
assess the corrosion of reinforced concrete structures.
• The authors discuss the application of these algorithms in
evaluating corrosion caused by factors such as chloride, sulfate, and
carbonation.
• The review highlights the significance of ML methods in
corrosion evaluation, particularly in environments where
traditional methods may be less effective. It emphasizes the
growing importance of ML techniques in assessing the
environmental corrosion of reinforced concrete structures.
RESULT
The study highlights the significance of ML methods in evaluating corrosion
caused by factors such as chloride, sulfate, and carbonation.
• The review emphasizes the growing importance of ML techniques in
corrosion evaluation, particularly in environments where traditional
methods may be less effective.
• Various ML algorithms have been applied to predict and assess corrosion
in RC structures. These include Artificial Neural Networks (ANNs), Support
Vector Machines (SVMs), Decision Trees (DTs), Random Forests (RFs), and
Extreme Gradient Boosting (XGBoost).
• The review discusses the effectiveness of these ML models in predicting
corrosion, highlighting their potential to outperform traditional methods
in certain scenarios.
