Air Void Spacing Factor Research Articles

Frost resistance of OPC-CSF mortars investigated by means of repeated cycle- and one cycle-freezing test

Mortars of ordinary portland cement containing 0, 5 and 10 per cent of condensed silica fume (CSF), and with water/binder ratio of 0.6 and 0.44, each non-aerated and aerated, were subjected to frost resistance investigation at 50 days age. This was done by repeated cycle freezing test (up to 150 cycles) and by one cycle freezing test method. The air void spacing factor was determined as well. The results obtained by both methods confirmed that silica fume presence improves the mortars frost resistance but the results also indicated the necessity of air entrainment if high freeze-thaw resistance of csf-containing mortars is requested or if such composites are supposed to be exposed to severe freezing conditions. Useful data (“B-point” of freezing, R W-value), as a feed-back information of the composites pore structure, are obtained after evaluation of the one cycle freezing curves.

Freeze-thaw durability and deicer salt scaling resistance of a 0,25 water-cement ratio concrete

Specimens of 0,25 water-cement ratio concrete with various air void spacing factors were tested for freezethaw durability in accordance with ASTM Standard C 666 (procedure A) and for deicer salt scaling resistance in accordance with ASTM Standard C 672. All specimens were moist cured 14 days. Few specimens showed signs of deterioration after 300 and 800 cycles of freezing and thawing and a critical air void spacing factor of approximately 750 μm was determined. All specimens that underwent scaling tests showed a very good resistance to deicer salts and, even after 150 cycles, a maximum of only 0.6 kg/m 2 of scaled off particles was measured.

Critical air-void spacing factors for low water-cement ratio concretes with and without condensed silica fume

Normal Portland cement concretes with a water-cement ratio of 0,3 and concretes containing 9% condensed silica fume (CSF) at a water-cementitious material ratio of 0,3 were submitted to freeze-thaw cycles in water in accordance with ASTM Standard C 666. The CSF concretes were also submitted to freeze-thaw cycles in air at 100% relative humidity. For both types of concrete and both types of test, the values of the critical air void spacing factor were found to range between 300 μm and 500 μm. Air entrainment was thus needed to protect these concretes from frost damage.

The effect of superplasticizers on the entrained air-void system in concrete

This paper deals with the effect of two different superplasticizers (Mighty and Melment) on the air-void system parameters produced by two different air-entraining agents (NVR and Darex), when the superplasticizer is added some 40 minutes after the concrete has been batched and mixed. A significant drop in air content was observed with corresponding reductions in total air-void surface areas and increases in air-void spacing factors.

Freeze-Thaw Durability of Concrete With and Without Silica Fume in ASTM C 666 (Procedure A) Test Method: Internal Cracking Versus Scaling

Abstract The freeze-thaw durability of concrete with and without silica fume was investigated in accordance with the requirements of ASTM Test Method for Resistance of Concrete to Rapid Freezing and Thawing (C 666 Procedure A). The water-cement ratio of all mixes was 0.5, and the silica-cement ratio of the silica fume mixes 0.1. The test results show that the critical value of the air-void spacing factor in these ASTM C 666 tests is significantly lower for the silica fume concretes. These concretes are therefore more susceptible to internal cracking caused by rapid freeze-thaw cycles in water, even though the use of silica fume decreased the surface scaling of the test specimens. This confirms that scaling and internal cracking are two different forms of frost damage caused by rapid freeze-thaw cycles in water. The use of silica fume also decreased the internal cracking of the nonair-entrained mixes damaged during the tests.

Critical Air Void Spacing Factors for Concretes Submitted to Slow Freeze-Thaw Cycles

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