Cement Testing Methods and Properties

Permeabilimeter

b = 0.9 in cements, V = 1902 ± 157 mm³. Three repetitions, three significant figures.

Loss on Ignition

15 min, 1000°C. Calcine the crucible first, then 1 gr in an oxidizing environment. Cool.

During calcination, previously absorbed CO₂ and water are released, along with the decomposition of carbonates and bicarbonates (allowing detection of cement adulteration with limestone filler).

Components oxidized during calcination: sulfides pass to sulfates (cement considered in iron and steel) and metals such as Fe, Mn... (negligible).

An assessment is made with S^2- + 2O₂ = SO₄^2- and titrated with BaCl₂, precipitated BaSO₄.

Weathering

Premature hydration and carbonation of cement (becomes lumpy and reduces its resistance capacity).

Hydration of clinker: SC_n + H₂O = SC_mH_p + SH + Ca(OH)₂.

Hydration of free lime: CaO + H₂O = Ca(OH)₂.

Hydration of calcium hydroxide: Ca(OH)₂ + CO₂ = CaCO₃ + H₂O.

Vicat Needle

Mold: 40 mm high, 80 mm and 90 mm diameter top and bottom respectively. Also allows one cylinder of 75 mm diameter and 40 mm in height.

3 needles: 10 mm in diameter (to determine normal consistency), another thin (1 mm²) for setting time measurement. Eventually, the central pivot of 1 mm² stands half mm from the circular annular rim around it.

Normal Consistency

20°C and RH above 50%. 500 g of cement, 125 g water, knead for 3 minutes. Weighted with 300 g probe, stopped after 30 sec. Normal if the needle is 4-8 mm from the base.

Setting Time Measurement

20°C and 90% RH. Mold submerged in water. Every 15 min with 10 mm separation, the needle sinks for 30 sec or until penetration stabilizes. Normal if penetration is 3-9 mm from the bottom (close to 3 mm, use 5-minute intervals). For setting time, use 30 min maximum intervals until penetration is less than 0.5 mm (modified needle can be used).

Normal Cement Mortar

Clean and inert sand (without fine or clayey material). Natural, not crushed, rounded. Siliceous nature (non-reactive silica content exceeding 98%). Particle size distribution within a specified zone (t_max less than 2 mm). Distilled or deionized water (reference material for verification or validation).

Manufacture

1350 ± 5 g standard sand, 225 ± 1 g water, 450 ± 2 g cement. 20°C and RH above 50%.

Procedure: Water and then cement in mixer (slow 30 s), sand (30 s), fast (30 s), rest (90 s). Clean walls (30 s), fast (60 s).

Mechanical Resistance

Prismatic cylinders 40 x 40 x 160 mm filled in 2 layers with compaction of 60 blows. Curing: wet, 20°C and 90% RH. Mold removed within 24-48 hours. Submerged in water at 20°C until the age of 3 days for breaking test. Never use the same mold at the same age.

Mortar Rupture

Bending

Load increases at 50 ± 10 N/s on 3 specimens, resulting in 6 pieces for compression test. R_f = 1.5 * P_max * L / (a * b²).

Compression

2400 ± 200 N/s. Results should be in the range R_mean * (1 ± 0.1), allowing discarding of up to 2 values.