Practical Mix Preparation

Overview

Lesson 18 of 30 in Infrastructure Skills Development. Students prepare small concrete batches using different aggregates, apply a specified mix ratio, and evaluate workability and consistency. The session builds on prior learning about materials, measurement, tools, workshop safety, and interpreting specifications.

Learning intentions

Students will:

• calculate and measure aggregate, cement and water quantities for a specified mix.
• select suitable aggregates and explain how aggregate size affects the mix.
• safely prepare, combine and test a small concrete batch.
• record results and use quality-control feedback to recommend adjustments.

Success criteria

• I can convert a specified mix ratio into measured quantities.
• I can use tools, materials and PPE safely and accurately.
• I can describe the workability and consistency of my mix using evidence.
• I can identify whether my batch meets the specification and suggest a justified improvement.

Curriculum links

• Undertake development and implementation of an effective manufacturing process: establish specifications and tolerances, organise resources, select processes and use quality-control feedback.
• Implement advanced procedures using resistant materials to make a specified product with special features: select techniques, undertake testing, and comply with relevant health and safety requirements.
• Demonstrate understanding of advanced concepts used to make products: explain how tools, techniques, materials and accepted conventions support construction.
• Select and use planning tools to manage the development of an outcome: set achievable goals, identify resources, and review progress at critical points.

Lesson structure (120 minutes)

1. 0–10 min · Hook and goals. Teacher displays two concrete samples—one likely too wet and one too dry—and opens the hook and learning-intention slides. Students predict which sample would be stronger or easier to place, then explain what evidence they would collect.

2. 10–25 min · Demonstration and safety briefing. Teacher uses the ratio, process and safety slides to model reading the specification, weighing materials, dry mixing, adding water gradually, and carrying out a slump/workability check; explicitly demonstrate PPE, dust control, safe lifting, mixing-tool use, spill response and handwashing. Students annotate the concrete mix planning and testing sheet, identify hazards and answer the teacher’s ratio-check questions.

3. 25–40 min · Planning and calculations. Teacher allocates groups of four or five and provides each group with a target ratio, such as 1:2:3 cement:sand:coarse aggregate, plus a fixed total dry mass and water limit. Students calculate required quantities, nominate roles—materials manager, measurer, mixer, tester and recorder—and complete their resource list, predicted outcome and control points on the concrete mix planning and testing sheet. Teacher checks calculations and signs off each group’s plan before practical work begins.

4. 40–75 min · Batch preparation. Teacher stations materials and monitors groups as they weigh, combine and mix; return to the practical procedure and timing slides for staged prompts. Students wear PPE, measure accurately, dry-mix aggregates and cement, add water in controlled amounts, and record actual quantities, observations and any deviations. The teacher questions students about why water is added gradually and checks that no group proceeds with an unsafe method.

5. 75–95 min · Testing and comparison. Teacher demonstrates the agreed workability test and quality-control recording method, then facilitates a comparison between aggregate choices. Students test their batch, complete visual and workability checks, compare results with the specification, retain a labelled sample where appropriate, and photograph or sketch the result on the concrete mix planning and testing sheet. Groups compare their findings with another group and identify one variable that may have influenced performance.

6. 95–110 min · Review and improvement decision. Teacher uses the review and discussion slides to lead a critical review point: “Would you change the ratio, aggregate grading, water quantity, or mixing sequence?” Students analyse their evidence, distinguish observation from assumption, and write a justified improvement to the process. Each group gives a brief report covering accuracy, workability, safety and resource use.

7. 110–120 min · Clean-down and exit check. Teacher displays the plenary and exit-question slide, checks benches, tools and waste disposal, and collects completed worksheets. Students clean the workspace safely, then answer: “Which measurement or process decision most affected your result, and what evidence supports your view?”

Resources

• the practical mix preparation slide deck
• the concrete mix planning and testing sheet
• Cement, fine aggregate/sand and selected coarse aggregates
• Digital scales, measuring containers, buckets and mixing trays
• Trowels, mixing hoes or other approved mixing tools
• Water containers and graduated measuring vessels
• PPE: safety glasses, gloves, dust masks and protective footwear
• Slump/workability testing equipment or the department’s approved consistency test
• Labels, marker pens, phones or cameras for evidence
• Cleaning equipment, waste containers and first-aid supplies

Assessment

• Formative questioning during the demonstration checks students’ understanding of ratios, aggregate choice, hazards and process sequence.
• Teacher approval of each group’s calculations and observations assesses planning, resource identification, safe practice and accuracy.
• The completed worksheet and exit response provide evidence of testing, quality-control review, specification checking and a justified process improvement.

Differentiation

• Provide a worked ratio example, calculation prompts, a visual process sequence and a prepared conversion table for students who need mathematical or literacy support.
• Pair students strategically and allocate practical roles, while allowing students to record observations using labelled diagrams, measurements or sentence starters.
• EAL learners may use illustrated equipment labels and rehearse explanations with a partner before reporting; explicitly teach terms such as aggregate, workability, consistency, ratio and tolerance.
• Extend confident students by asking them to compare aggregate grading or water content, quantify the impact of any deviation, and justify how their revised process could reduce waste or improve repeatability.
• Students with sensory, mobility or health needs should be assigned a safe, meaningful role away from dust or heavy lifting, with teacher-approved PPE and an alternative testing or recording task where necessary.