Partial Replacement of Cement with Basalt Rock Powder on the Effects of Concrete

Project Overview

This study examined concrete where basalt rock powder (BRP) replaced 0%, 10%, 15%, 20%, 25% and 30% of cement. Basalt sourced from Kibaale District was crushed into powder, then evaluated with conventional concrete materials to identify the replacement level that delivers the strongest, most workable concrete.

RESEARCH PROBLEM

Concrete needs lower-carbon binders without sacrificing performance.

Cement production is resource- and energy-intensive and produces substantial carbon dioxide emissions. Basalt rock powder is abundant and contains reactive mineral compounds, but the most effective proportion for replacing cement must be established to protect fresh and hardened concrete performance.

OBJECTIVES

Research Objectives

Main Objective

Determine the effect of basalt rock powder on the physical and mechanical properties of concrete.

Composition

Determine the chemical properties and composition of the basalt rock powder.

Fresh Concrete

Assess workability and setting behaviour across the BRP proportions.

Optimum Strength

Identify the best cement-replacement percentage in hardened concrete.

MATERIALS

Materials Used

Portland Cement

The primary binder, partly replaced with basalt rock powder.

Basalt Rock Powder

Crushed basalt from Kibaale District, characterised for its chemical and physical properties.

Natural Aggregates

Fine sand and crushed coarse aggregate tested for grading, density and strength.

Clean Water

Mixing water used in the controlled concrete mix design.

METHODOLOGY

Research Methodology

Laboratory tests at Energo Laboratory, Kawanda, compared fresh and hardened concrete performance across six BRP replacement levels.

Source & Process Basalt

Basalt was collected from Zirobwe Quarry and crushed into powder.

Characterise Materials

Aggregate quality and BRP chemistry were assessed, including X-ray fluorescence testing.

Mix Proportions

Six mixes contained 0%, 10%, 15%, 20%, 25% and 30% BRP in place of cement.

Cast Specimens

150 mm concrete cubes were prepared for every mixture.

Cure & Test

Cubes were cured and assessed at 7, 14 and 28 days.

Compare Performance

Slump, setting time and compressive strength identified the optimum mix.

KEY FINDINGS

Research Results

Strength increased as BRP rose to 15%, then decreased at higher replacement levels.

15%

Optimum basalt rock powder replacement of cement

25.6 MPa

28-day compressive strength at 15% BRP

24.8 MPa

28-day control concrete strength

19.5 MPa

28-day strength at 30% BRP replacement

52 mm

Workability measured for the optimum 15% mix

7.0 hrs

Setting time recorded at the optimum replacement level

CONCLUSIONS

Major Findings

Suitable Mineral Composition

Dominant silica, iron oxide and calcium oxide supported BRP's pozzolanic potential.

Improved Strength at 15%

The 15% mix exceeded the control strength and the 25 MPa target.

Balanced Optimum Mix

15% BRP provided the best balance of strength, workability and setting time.

RECOMMENDATIONS

Next Steps

Use 15% basalt rock powder as a partial cement replacement for normal concrete.

Study higher BRP proportions with mix adjustments that can retain strength and durability.

Assess compatibility between BRP and other concrete admixtures.

Investigate carbonation resistance and long-term durability.