Abstract
Pervious concrete is increasingly being utilised in the construction of driveways, parking lots, and pavement in many industrialised nations. Testing must be done to assess the performance of this new kind of high-performance concrete in order to establish material specifications for pervious concrete. Additionally, the manufacturing of Portland cement produces significant carbon dioxide emissions, contributing to global warming and unfavourable climate change. To mitigate these environmental impacts, it is necessary to substitute industrial by-products like fly ash, silica fume, and ground-granulated blast furnace slag for a portion of the cement. These materials have all been used successfully as supplementary cementitious materials in structural concrete mixes.This study is divided into two parts:
1- Production of Pervious Concrete using Conventional Cementitious Materials
The pervious concrete is produced using conventional cementitious materials, including cement, sand, water, and aggregate. The mixing ratios of these components have been modified to achieve high strength concrete and water permeability. The combination of pervious concrete was tested for compressive strength, water permeability, and density. The optimal results obtained are for a mixture consisting of the following proportions (1:1:6:0.45) cement, sand, aggregate and water. The compressive strength of this mix was measured at 29.33MPa, while the water permeability was determined to be 7.37 cm/s. Combination of pervious concrete is tested in density and water permeability. The density was approximately 2500 kg/m3 .
2- Production of Pervious Concrete using Supplementary Cementitious Materials
The pervious concrete is produced using supplementary cementitious material such as silica fume, fly ash, and ground-granulated blast furnace slag (GGBS) to partially replace Portland cement in the pervious concrete mixes, with a substitution rate of up to 50% by weight. Environmentally friendly concrete mixes may be created by using these cementitious components extensively. The best results obtained are for a mixture consisting of the following portions: 0.5 parts cement, 0.5 parts (GGBS), 1 part sand, 6 parts aggregate and 0.45 parts water (0.5:0.5:1:6:0.45). This combination underwent testing for the same properties as the conventional mix. The result for the compressive strength for this mix was 42 MPa. This is a desirable result for pervious concrete, which is highly permeable. The density remained around 2500 kg/m3 , while the water permeability was 7.95 cm/s. Further investigation on the development of this system is recommended to have adequate water permeability, strength and durability.
Properties pertaining to the durability of pervious concrete were also investigated after the physical and mechanical properties of the pervious concrete mixtures had been determined. A freeze and thaw investigation were carried out to evaluate the potential of the pervious concrete mixtures to resist damage when subjected to successive freeze and thaw cycles. Sulphate resistance tests were conducted on concrete systems by immersing test specimens in a saline solution and comparing their degradation rates to specimens immersed in fresh tap water. The chosen saline solution, rich in chloride (Cl⁻) and sulphate (SO₄²⁻) ions, was selected for two primary reasons. First, it provides an environment that may influence the long-term durability of concrete mixtures. Second, this choice serves as a benchmark for evaluating the performance of hydrated mixtures in practical applications, especially in systems engineered to meet the required physical and mechanical characteristics, including Permissible chloride concentrations.
| Date of Award | 2024 |
|---|---|
| Original language | English |
| Supervisor | John Kinuthia (Supervisor) & Jonathan Oti (Supervisor) |