Bitumen softening point

The principal characteristics of bitumen are its softening point and its needle penetrability. In France the latter has always been the basis for bitumen classification and class designation. Yet, the former is more representative of a bitumen s capacity to deform when the service temperature increases. The other properties have more or less importance depending on the application. 

Softening point for bitumen (ring and ball method) NF T 66-008 (future NF EN 1427) ASTM D 36 Temperature at which a ball passes through tin asphalt sample disk attached to a ring... 

Trinidad asphalt has a relatively uniform composition of 29% water and gas, 39% bitumen soluble in carbon disulfide, 27% mineral matter on ignition, and 5% bitumen that remains adsorbed on the mineral matter. Refining is essentially a process of dehydration by heating the cmde asphalt to ca 165°C. The refined product averages 36% mineral ash with a penetration at 25°C of about 2 (0.2 mm), a softening point (ring and ball method) of 99°C, a flash point (Cleveland open cup) of 254°C, a sulfur content of 3.3%, and a saponification value of 45 mg KOH/g. The mineral matter typically contains... 

Blends with styrenic block copolymers improve the flexibiUty of bitumens and asphalts. The block copolymer content of these blends is usually less than 20% even as Httie as 3% can make significant differences to the properties of asphalt (qv). The block copolymers make the products more flexible, especially at low temperatures, and increase their softening point. They generally decrease the penetration and reduce the tendency to flow at high service temperatures and they also increase the stiffness, tensile strength, ductility, and elastic recovery of the final products. Melt viscosities at processing temperatures remain relatively low so the materials are still easy to apply. As the polymer concentration is increased to about 5%, an interconnected polymer network is formed. At this point the nature of the mixture changes from an asphalt modified by a polymer to a polymer extended with an asphalt. 

Other properties such as calorific value, carbon residue, specific heat, softening point, flash point, molecular weight, and thermal conductivity are also used to determine the suitability of the bitumen for conversion options. 

The use of catalyst (FeCb) enabled the reaction time to be reduced nearly one-third by increasing rate constant nearly three to four times for bringing about some changes, in composition, softening point, and penetration of the bitumen. 

A novel application of mixed plastics is to toughen road surfaces. In 1986, the Ragusa Laboratories of ECP Enichem PoKmeri in Italy investigated the use of mixed plastics waste to reinforce bitumen. Sorted municipal waste with a polyethylene content of approximately 60% was mixed with bitumen in varying proportions up to 20%. The properties of the resultant bituminous concrete were improved in two important ways better wear resistance and raised softening point. Use of bitumen modified with mixed plastics waste of high polyethylene content as an experimental road surface under heavy trafiic has established its notable superiority over unmodified bitumen for road surfacing. 

The modification of bitumen with SBS copolymer powder was done using the mechanochemically devuicanized GRT (Zhu et al., 2009). The penetration index, softening point, 5°C ductility, aging behavior, and rheological properties of bitumens modified by 8,10, and 12 wt.% GRT/SBS mixtures were measured. In comparison with the bitumen modified by incorporation of 5.5 wt.% SBS alone, the majority of properties of the blends were improved, except their penetration. Rheological properties indicated that at high temperatures 10 wt.% GRT/SBS-modified bitumen was better than SBS-modifled bitumen. The SEM observation of the fractured surfaces showed that bitumens mixed with the GRT/SBS powder had a better interfacial adhesion with matrix than with SBS alone. 

The penetration grade, softening point, and ductility of the GRT-modified bitumens were studied as a function of rubber selection, temperature, rotational speed, shearing time, order of rubber, and oil addition (Li et al 2009). It was established that a shearing time of 40 min, a temperature of 180" C, a rotational speed of7000 rpm, and a rubber concentration below 25 wt.% with oil content below 4 wt.% were optimal for carrying out the technological process for preparation the GRT-modified asphalts. 

The consistency data (penetration and softening point), the analytical data, and the data from thermoanalysis have been investigated to discover whether there is any correlation between them. The aim is to find some simple means of characterization of the different bitumen types using thermogravimetry. 

The relation of the consistency data to the average relative pafficle mass M of the bitumens also reveals an increasing softening point with increasing M, whereas the penetration decreases. 

The index numbers T % and T5 % of the distillation bitumen can be correlated with the softening point (Fig. 4-42 T5% = f(S.P. R B). The curves of T1 % and T5 % versus S.P. R B have very steep slopes for the distillation bitumens. The values for the blown bitumens are scattered, away from these curves. The values for the laboratory blown product (sample I) and for the bitumen BIO (sample 16) lie between the curves of the... 

The maxima of the weight loss rate also rises rapidly against the softening point DTG = f(SP R B). The values of the samples 16 and I are again situated between the distillation and the blown bitumens (Fig. 4-44). 

The residue which may still be cracked, CR = 100 - (AG400 + R800), amounts to 25-70 wt% for the bitumens, 26-73 wt% for the dispersion medium, 24-62 wt% for the petroleum resins, and 38-54 wt% for the asphaltenes. A correlation of the CR with the consistency data may be seen for the bitumens and the dispersion medium the CR decreases with increasing penetration and rises with increasing softening point (Fig. 4-45 to Fig. 4-48). The petroleum resins only show a correlation of the CR with the softening point, whereas no correlation is seen for the asphaltenes. 

Crackable Residue CR of the Dispersion Medium versus Softening Point Ring Ball of Bitumen... 

Bitumen can only be used industrially in a limited range of temperatures. The upper limit is marked by the softening point R B (DIN 52 Oil, ASTM D 2398-68) and the lower hmit by the breaking point according to FraaB (DIN 52 013, IP 80 153). This range, also called the plasticity span, is limited towards lower temperatures by increasing brittleness and towards higher temperatures by plastic deformation under load. To extend this plasticity span, mixtures have been tested, with nearly every polymer, but only a few of these became commercial products. 

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