2. Background

The durability of concrete it is understood so far as the resistance of cement components to various destructive influences of physical, physic-chemical and chemical within the specified time.

During the last decades, found that although compliance with existing standards and regulations, structures, concrete did not meet established requirements for durability. This mainly elements and concrete structures subject to the influence of the environment with different levels of aggressiveness. This condition was caused by poor diagnosis of the impact of various factors and destructive processes taking place at a certain time in concrete structures. Although in recent years knowledge in this field has developed significantly, the problem of real-life and not standardized is far from being solved.

Causes damage to and destruction of concrete can be divided into the following groups (Neville, 2000) [1]:

1 Physical causes, include. The effects of high temperatures and effects related to the different coefficients of thermal expansion of the aggregate and the hardened cement paste; important cause damage to the concrete is also cyclical freezing and thawing; the water contained in the pores of the capillary freezes and exerts pressure on the surrounding wall of the pores, which may lead to micro cracking

2- Causes chemical include aggressive ions, soft water, acids and salt water.

3- Mechanical causes, which could include for example: Stroke, overload, abrasion, vibration;

The process of degradation of concrete due to freezing and thawing explains Richardson (2002) [2], and finds that occurs due to the extension of the pores of the cement paste frozen in the ice.

 Richardson (2002) [2] indicates the expansion of the water ice is about 8%, and Micah Hale et al. (2008) [3] state that is about 9% creates hydraulic pressure inside the concrete when there is no space to extend the ice.

Shang et al. (2009, p5) [4] determines the size of the hydraulic pressure depends on the permeability grout, degree of saturation and the rate of freezing.

Richardson (2002) [2] found that the resulting network of pores and micro-cracks magnification allows passage of a greater quantity of water during the thawing step leads to a further accumulation of ice, and thus the cumulative effect of degradation in the concrete. The extension of the ice in capillary pores mainly responsible for the degradation of the concrete is also caused by the osmotic pressure.

Richardson (2002) [2] states that the freeze-thaw degradation manifests itself in three forms:

1- The internal cracking.

2- D-line cracking.

3- pop-out and scaling.

D-line cracks are small cracks parallel to the edge and due to the expansion of large particles at the depth of the pop-out caused by the expansion of the coarse aggregate, but this time near the surface which could cause them to fracture.

Frost resistance may be shaped by application: aeration grout, reduce capillary pores by reducing the water-cement ratio, respectively, selected aggregates and cement and mineral additives (Rusin, 2002) [5]. The concrete used in construction and the like on the road in addition to the resistance to freezing and thawing cycles must also be resistant to the effects of de-icing. This resistance is significantly dependent on the type of cement. Cement that would ensure durability of concrete should be characterized by:

– Increased resistance to aggressive chemical agents;

– A low or moderate heat of hydration;

– Constancy of volume;

– Prolonged bonding time

Cement that meets these requirements, among others cement with the addition of ground slag.

With the addition of slag cement differs from Portland cement CEM-I: the heat of hydration, resistance to corrosion, bonding time, speed strength development and the impact on workability. These properties have contributed to the widespread use of cement in the industry massive construction, hydro-technical, bridge, road, works of foundation, precast and self-compacting concrete SCC and concrete high strength (Giergiczny and Pużak, 2004) [6].

Blast furnace cement can be produced by a joint milling of the Portland cement clinker with dry GGBS-granulated blast furnace slag, or by dry mixing Portland cement and slag.

GGBS – Granulated blast furnace slag, according to PN-EN 206-1 [7], is an addition to the concrete type II (next fly ash and silica fume).

As we know from cement and concrete technology [1,8,9], granulated blast furnace slag is among the materials with undisclosed properties of hydraulic (hydraulic additive), which why it is an essential component of Portland cements, multiple cement CEM II, cements CEM III and composite cements CEM V [10, 11, 12].

PN-EN 197-1: 2002 [10] identifies five types of cement depending on the content of granulated blast furnace slag. Sulphate- blast furnace cement HSR found mainly used in environmental exposure classes XA1, XA2 and XA3. Not found in the literature inconclusive regarding the behaviour of cement concrete with steel in exposure classes XF1 ÷ XF4. Table (1). Polish construction practice commonly used methods to determine the frost resistance of concrete should be the method described in PN-88 / B-06250 “Concrete ordinary” (The usual method) [13, 14].

According to the guidelines, standards, evaluating the resistance of concrete to frost as a condition, it is assumed that:

1- The loss in mass of the samples before frozen in relation to mass of the same samples after frozen may not exceed 5%.

2- The decrease in compressive strength of the samples frozen in relation to the strength of the samples not frozen (witnesses) may not exceed 20%.

Procedure for the study determines that a sample-witness stored in water at 18 +/- 2 ° C, for the same period of time in which the test samples are subjected to freeze-thaw cycles [13]. The result is a continuous increase in the strength of witnesses, while in samples frozen the process is slowed down [5].

Rating frost resistance of concrete through the appointment decrease the strength of frozen samples may be controversial for concrete made with cement with slag additives. This is because the concretes are characterized by high increases in strength over long periods of ripening (56, 90, 120 or more). Therefore, the strength-witness samples made of cement with the additives of the slag (GGBS) is much higher than the strength concretes Portland cements CEM-II.

Table 1 – the National Annex to I.S. EN 206-1:2002 and provides minimum strength classes, maximum water cement ratios, minimum air content and minimum cement content for 20 mm max aggregate size for each of the four XF exposure classes.

			and min. cement
Exposure Class	Min Strength Class	Max W/C Ratio	content for 20mm	Min. Air content
XF1	C25/30	0.60	300	3.5
	C28/35	0.60	300	_
XF2	C30/37	0.55	320	3.5
	C35/45	0.50	360	_
XF3	C30/37	0.55	320	3.5
	C40/50	0.45	400	_
XF4	C32/40	0.50	340	3.5
	C40/50	0.45	400	_

Professor Pawel Lukowski. Head of the Department of Building Materials Engineering. Warsaw University of Technology

Dr. Eng. Joanna Julia Sokolowska. Department of Building Materials Engineering. Warsaw University of Technology

MSc. Eng. Ali Salih Technical and Quality Manager – Casey Concrete, Gorey Co. Wexford

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Part I – DURABILITY OF CONCRETE CONTAINING GGBS IN EXPOSED TO FREEZING AND THAWING CONDITIONS

1- Abstract 2. Background 3. Prisms analysis of cement samples (MORTARS) 4. Test results of the Prisms 5. Test on Without Air Entrained concrete samples: 6. Strength test results 7. Durability Test

Part II – DURABILITY OF CONCRETE CONTAINING GGBS IN EXPOSED TO FREEZING AND THAWING CONDITIONS

8. Air Entrained Concrete 9. Strength test results of the air entrained concrete samples maturated in tank water 10. Durability Test 11. Conclusions of the study/a> 12. Literature