2. Experimental procedure

### 2.1 Materials and methods

The novel H-Cement and CEM I/42.5 R as a reference were tested. Both are produced by the cement plant Považská cementáreň, a. s., Ladce in Slovakia;

Fundamental Properties of Industrial Hybrid Cement Important for Application in Concrete DOI: http://dx.doi.org/10.5772/intechopen.88060

H-Cement is according to internal standard. The cement was used in combination with river aggregates of 0/4, 4/8 and 8/16 mm fraction from Jelka (Slovakia). For the tests with steel slag, the river aggregate was completely replaced by the slag of the same fraction. All river aggregate properties met the requirements of STN EN 12620+A1 [14]. The compatibility of H-Cement was verified with seven types of plasticizers [15]. The concrete without admixture was examined as a reference. The shrinkage-reducing ability was confirmed on the concrete made from H-Cement, PC and selected blended systems [15]. The H-Cement suitability for mitigating alkali-silica reaction was verified on the cement mortars by the procedure reported in STN 721179 [16] (the related ASTM Standards: C289-03 for Chemical method; ASTM C1293-08b for length change of concrete). Resistance to sulphate and higher temperature/pressure attack was verified by own methodologies [10, 17].

### 2.2 Casting

low Portland clinker content [5]. In spite of the low clinker content, the hybrid binders can obtain useful early-age mechanical strengths [6]. Hybrid cements take advantage of the material properties of a cement and ordinary geopolymer with the resulting benefit on the acquired properties, so that hybrid cement can replace in large quantities energy-intensive PC [7]. The novel hybrid cement H-Cement is produced on the base of industrial by-products and wastes according to the patent application [8]. The content of clinker is always under 30 wt%. A typical feature for H-Cement binding phase formation is the combined effect of hydraulic properties of Portland clinker, pozzolanic properties of fly ashes, latent hydraulic properties of granulated blast furnace slag (GBFS) and geopolymeric properties coming from the alkaline inorganic polycondensing reactions of aluminosilicate materials. Such inorganic material is activated by addition of alkaline waste water separated from the caustic red mud ponds and Na2SO4 obtained from alkaline waste water neutralization by H2SO4. In the presence of these alkaline agents, the pH value of cement mixture is increased. This results in fly ash (FA) and GBFS dissolution leading to final geopolymerization effect. At the same time, Ca(OH)2 addition coming from Portland clinker hydration promotes the binding reactions of fly ash and GBFS. H-Cement is characterized by lower early strength and hydration heat but higher long-term strengths. H-Cement possesses high chemical resistance against aggressive action of sulphate, magnesium, chloride and acidic waters [9]. When autoclaving at an elevated temperature and pressure, H-Cement provided volume stability and strength increase in concrete with steel slag replacing a natural aggregate as opposed to PC concrete with steel slag which was disintegrated after the test [10]. The production of H-Cement does not require additional heat treatment. It is cured in the same way as traditional cements and owns the certificate of conformity [11] issued on the base of SK Technical Assessment [12]. H-Cement is a sustainable cement which, due to its material composition, does not meet the categorization of

This article shows that one possible solution for innovative binders with improved durability and decreased energy requirements is the production of hybrid

• H-Cement is suitable for production of ready-mixed concrete strength classes

• Shrinkage-reducing and alkali-silica reaction (ASR)-mitigating character of H-Cement is especially relevant because it prevents propagation of shrinkage or

• H-Cement is specified after 5-year impact of 5% wt. sodium sulphate solution by the same sulphate resistance with the sulphate-resistant CEM I 42.5 R-SR O

• H-Cement is suitable for making concrete with mostly landfilled steel slag

The novel H-Cement and CEM I/42.5 R as a reference were tested. Both are produced by the cement plant Považská cementáreň, a. s., Ladce in Slovakia;

expansive cracking during the service life of the concrete.

cements according to STN EN 197-1 [13].

when replacing a natural aggregate.

cement. It is demonstrated that:

Compressive Strength of Concrete

up to C30/37.

with C3A = 0.

2. Experimental procedure

2.1 Materials and methods

128

Specimens of ready-mixed concrete were made according to STN EN 12390-2 [18]. Fresh concrete was compacted on a vibration table (40 Hz) for 60 s and casted into 150 mm cubes or 100 100 400 mm prisms. Casting of the specimens for verification of specific properties of H-Cement is reported separately for each experiment, either shrinkage-reducing or ASR-mitigating property, sulphate resistance and volume stability of steel slag concrete.

#### 2.3 Curing

The moulds were stored at more than 95% relative humidity of air (abbreviated as RH) at (20 1)°C for the first 24 h, and then the concrete specimens were cured according to the test. A method of treating the specimens for special properties verification is given separately for each test.

#### 2.4 Testing procedures for cement

Both cements were tested for chemical composition by STN EN 196-2 [19]; the Bogue mineral composition was also determined. Standard consistency, initial and final setting, and soundness were verified by STN EN 196-3+A1 [20] and hydration heat by STN EN 196-8 [21]. After 2-, 28- or 90-day cure, flexural and compressive strengths of the mortars with cement-to-sand ratio 1:3 by weight were obtained according to STN EN 196-1 [22]. H-Cement is sensitive to excess of water; the PC and H-Cement mortars therefore differ in water-to-cement ratios.

#### 2.5 Testing procedure for fresh and hardened concrete

The consistency of fresh concrete was estimated by slump by STN EN 12350-2, volume density by STN EN 12350-6 and air content in the fresh mixture by STN EN 12350-7 [23–25]. Concrete specimens were tested for cube compressive strengths [26], compressive strengths of the edges of prisms of standard size [27] and dynamic elasticity modulus [28].

#### 2.6 Partially accelerated test of sulphate resistance

#### 2.6.1 Materials

Cement CEM I 42.5 R (PC) produced by Považská cementáreň, a. s., Ladce cement plant (PCLA) and C3A-free sulphate-resistant CEM I 42.5 R-SR O (SRC)

## Compressive Strength of Concrete

produced by Lafarge Zementwerke GmbH, Mannersdorf (Austria) according to STN EN 197-1, both as reference, were chosen for the investigation. H-Cement was tested as the verified sample.

• PC concrete contained 0/8 mm steel slag fraction as filler, 380 kg of CEM I 42,5 N, 241 kg of water and Sika superplasticizer in the amount of 0.5% of the

Fundamental Properties of Industrial Hybrid Cement Important for Application in Concrete

The production of the specimens used to test the properties of fresh and hardened concrete based on steel slag was carried out in two stages. The first stage involved the production of the specimens for testing cube strength after 3, 7, 14, 21, 28 and 90 days of age. The second stage involved the production of the specimens

The following properties of hardened concrete were tested: cube and prism concrete strengths. The durability of the concrete based on steel slag was tested in the conditions of a higher temperature and pressure. Determination of the volume changes of the concrete was carried out in a 540-l laboratory autoclave at the maximum saturated steam pressure of 1.2 MPa and a maximum temperature of 189° C. Cubes of 150 mm were used as the test specimens. The temperatures and pressures in the testing laboratory autoclave were set by this way to determine the volume changes of the concrete based on the steel slag as aggregate [10].

Chemical composition of main constituents of H-Cement (HC) and Portland cement (PC) clinker are listed in Tables 1 and 2. Table 3 confirms that H-Cement shows different chemical and mineral compositions compared to PC. Both hydrated cements differ in typical characteristic values as stated in Table 4. The results suggest that hybrid cement can be used prospectively in concrete for the same purposes as the blended cements of lower-strength classes, e.g., CEM III–V, probably CEM II/B-S according to STN EN 197-1, preferably in massive constructions due to low hydration heat and aggressively exposed media because of low Portland

H-Cement consists essentially in a blend of materials containing 20–30% wt. Portland clinker and 70–80% alkaline cement, in turn a combination of fly ash,

% wt. CaO SiO2 Al2O3 Fe2O3 MgO SO3 K2O Na2O L.O.I FA 3.36 51.42 26.93 7.27 2.10 0.87 3.28 0.17 1.84 GBFS 39.24 40.13 7.19 0.27 10.04 1.50 0.52 0.31 1.10

% wt. CaO SiO2 Al2O3 Fe2O3 MgO SO3 K2O Na2O P2O5 Clinker 64.4 20.80 4.80 3.08 1.45 0.47 1.05 0.28 0.49

> C3S C2S C3A C4AF Free CaO Arcanite Periclase 65.1 10.60 8.40 9.72 1.40 0.82 0.58

for the comparison of cube and prism strengths after 28 days of curing.

cement weight. No retardant admixture was used.

DOI: http://dx.doi.org/10.5772/intechopen.88060

3. Experimental results and discussion

3.1 Basic characterization of H-Cement

clinker (and therefore C3A) content.

Table 1.

Table 2.

131

granulated blast furnace slag and alkaline sulphates.

Abbreviations: FA, fly ash; GBFS, granulated blast furnace slag; LOI, loss on ignition.

Chemical composition of fly ash (FA) and blast furnace slag (GBFS).

Chemical and mineralogical composition of Portland clinker.
