🧱 Cement Compressive and Flexural Strength

Construction PN-EN 196-1

Overview

Cement compressive strength is the main classification parameter for common cements per PN-EN 197-1. Testing involves preparing standard mortar prisms (cement : CEN standard sand : water = 1 : 3 : 0.5), curing in water, and testing flexural strength (3-point) and compressive strength on prism halves.

Cement strength classes after 28 days: 32.5 (≥32.5 MPa), 42.5 (≥42.5 MPa), 52.5 (≥52.5 MPa). Sub-classes R (rapid) and N (normal) distinguish early strength (2 days).

Standard PN-EN 196-1 is fundamental for cement quality control — every plant performs this test routinely. Results form the basis of Declaration of Performance (DoP) and CE marking of cement.

Method principle

Standard mortar: 450 g cement + 1350 g CEN standard sand (Normensand) + 225 g water, mixed in standard mixer (90 s slow + 30 s pause + 60 s fast). Molding in 3-gang molds 40×40×160 mm on jolting table (60 jolts). Curing: mold 24 h at RH ≥90%, then in water 20±1°C until testing.

Flexural testing: 3-point loading, support spacing 100 mm, rate 50±10 N/s → flexural force Rf. Compression testing: prism halves compressed on 40×40 mm platens, rate 2400±200 N/s → force Rc.

Applications

• Quality control of cement production (factory production control)
• Type certification of cement (type testing per PN-EN 197-1)
• Qualification of cement batches on construction sites
• Early (2 days) and late (28, 90 days) strength testing
• Comparative testing of cements from different producers
• Control of cement for special concretes (precast, HSC)

Key parameters

Standard

Standard number

PN-EN 196-1:2016

Title (PL)

Metody badania cementu — Część 1: Oznaczanie wytrzymałości

Title (EN)

Methods of testing cement — Part 1: Determination of strength

Step-by-step procedure

1. Weighing ingredients

   Weigh 450±2 g cement, 1350±5 g CEN standard sand, and 225±1 g water (W/C = 0.50).

   ⏱ Time: 5 min

2. Mortar mixing

   Cement + water → mix 30 s slow (140 rpm). Add sand within 30 s. Mix 30 s slow. Pause 90 s (scrape mortar). Mix 60 s fast (285 rpm).

   ⏱ Time: 4 min

3. Molding

   Fill 3-gang mold in 2 layers. Compact each layer on jolting table (60 jolts). Level surface with trowel.

   ⏱ Time: 5 min

4. Curing I (mold)

   Place mold in humidity chamber (RH ≥90%, T=20±1°C) for 24±1 h. Cover with glass plate.

   ⏱ Time: 24 h • 🌡 Temperature: 20°C

5. Demolding

   After 24 h demold prisms. Mark with date and number. Place in water 20±1°C.

   ⏱ Time: 10 min

6. Curing II (water)

   Store in water 20±1°C until test day. Water must cover specimens min. 5 mm.

   ⏱ Time: 2–28 days • 🌡 Temperature: 20°C

7. Flexural testing

   Place prism on supports (spacing 100 mm). Load centrally at rate 50±10 N/s until fracture. Record force Ff.

   ⏱ Time: 1 min

8. Compression testing

   Place prism halves between compression platens 40×40 mm. Load at rate 2400±200 N/s until failure. Record Fc.

   ⏱ Time: 1 min

9. Calculations

   Rf = 1.5×Ff×l / b³ [MPa]. Rc = Fc / 1600 [MPa]. Average of 6 compression results (reject outliers >±10%).

   ⏱ Time: 10 min

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• Cement — strongly alkaline (pH >12), irritates skin and eyes, gloves mandatory
• Cement dust — use FFP2 mask, work with ventilation
• Press — crushing hazard, do not insert hands in testing zone
• Jolting table — noise >85 dB, hearing protection

Frequently asked questions