Surface Dressing Research Articles

The performance of aggregates in a single surface dressing, subjected to wear by studded tyres

In Sweden, studded tyres cause considerable wear on road surfacings. The properties of aggregates are known to be of importance, but lack of experience with road conditions has prevented relevant specifications.The performance of nine aggregates—in a single surface dressing—has been studied by means of small test surfacings in road E4. The flakiness of two of the aggregates was varied, too. The change of the texture depth was determined with the aid of a laser profilometer and sand-patch measurements. The former is considered to give more reliable results. After two years in service, the test surfaces have been rated by an expert panel and aggregate samples have been removed from the road after heating the binder. The changes in grading and flakiness have been analyzed.The macrosurface depths after two years and the changes of that property, not considering the first summers change, because of particle orientation and embedment going on, correlates well with the Swedish aggregate abrasion value. Also, the flakiness of the worn aggregates and reduction of that property in the road, due to traffic wear, correlate. The aggregate impact value does not correlate. However, a fair relationship exists with the aggregate crushing in the road. Obviously, most of these particles, that have been crushed by traffic stresses, can go on functioning in the surface dressing. The condition is, however, that a proper aggregate-binder adhesion exists. The aggregate flakiness is also of importance mainly as it determines the “particle layer height” of the road surfacing. A lack in the abrasion property of an aggregate can partly be compensated by improving the flakiness.

Colloid chemical studies on bitumen-in-water emulsions part IV. On the seiting mechanisms of cationic emulsions in contact with mineral aggregate

A modification of the Wet Track Abrasion Test of McCoy and Coyne for assessing road surfaces was developed for the characterization of the performance of surface dressings. The tent was applied to emulsion-based systems during their curing period. Parameters influencing setting rates are extensively discussed on the basis of information obtained with this test in combination with emulsion breaking, emulsifier titration and light microscopy experiments. The most important factors Include water evaporation, chemical interactions between emulsifier solution/mineral aggregate (for instance carbonate), bitumen grade and application conditions such an temperature and rolling.

Some properties of crushed stone for road surfaces

On wet roads a sufficiently rough surface texture on the macroscale is necessary to ensure rapid removal of water from the contact zone between the tire and road surface, especially at high speeds. For this surface texture on the macroscale, beside the particle size of the aggregate also the resistance to crushing and abrasion is rather important. The macroroughness is likely to decrease rapidly in case of insufficient resistance to crushing which will cause destruction of stones at the surface. It decreases too, if the resistance to abrasion of stones, which protrude from the road surface, is poor. The texture depth, which is a measure of the roughness on the macroscale, can easily be determined. A satisfactory surface texture on the microscale is required as well, because this texture is at least largely determinant of the level of skid resistance. It is not yet possible to express the surface texture on the microscale in a number. The resistance to polishing of aggregates can, however, be expressed as the polished stone value which is determined in the laboratory using an apparatus for accelerated polishing. The correlation between the polished-stone value and the skid resistance, i.e. the similarity with practice, appears to be good in cases in which the surface consists of a continuous mosaic of coarse aggregate such as in surface dressings. Finally also the shape of the stone particles may be important for the skid resistance (unfractured faces in crushed gravel) and for the resistance to crushing (thin pieces).

Sprinkler irrigation on clay soils in southern Finland IV. The effect of repeated applications of water and nitrogen fertilization on spring cereals

In 1967 and 1968, in the month of June, irrigation of silty clay soil in southern Finland by a single sprinkling, which involved the application of 30 mm of water, increased the yields of spring wheat by an average of between 880 and 970 kg per ha, or 37—51 %, and the yields of barley by 1140—1340 kg per ha, or 37—42 %. Repeating the irrigation after about one week further increased the wheat yields on the average by from 670 to 800 kg per ha and the barley yields between 810 and 860 kg per ha. The effect of the irrigation on the size of the yields was virtually of the same magnitude both years in spite of the fact that in 1967 both June and July were extremely dry months, whereas in 1968 the dry June was followed by a rainy July. The sprinkling affected the ripening of the grain, on the other hand, differently each year: slightly retarding the ripening in 1967 but considerably hastening it in 1968. In the latter year, the irrigation prevented detrimental late tillering and thereby augmented the hectoliter weight and 1000-grain weight of the crops. In response to the one-time sprinkling, the protein content of the grains decreased in the case of the wheat by an average of 1.0—1.3 and of the barley by 0.1—0.7 %-units. The effect of two sprinklings was corresponding decreases of 1.9—3.1 and 0.8—1.0 %-units. The application to the seedlings as surface dressing immediately before irrigation of calcium nitrate containing 60 kg/ha of nitrogen increased the protein content of the wheat on the average by 1.6 and of the barley by 1.9 %-units. The nitrogen fertilization thus prevented excessive lowering of the protein content by irrigation and, furthermore, considerably intensified the salutary effect of the irrigation in augmenting the yield. A disadvantage of abundant nitrogen fertilization was a slight retardation of ripening. The placement of basal dressing with a fertilizer drill at a depth of 9 cm proved effective, particularly in 1967, when both the wheat and the barley yields increased 22 per cent in comparison with the effect of surface dressing. Use of the fertilizer drill, moreover, promoted the ripening process. Sprinkling did not appear to reduce the placement effect of the fertilizer; rather did these two methods form an exceedingly favorable combination.

Adhesion test for road surface dressing binders

AbstractA study has been made of the adhesion of chippings to a film of road tar, supported on a base plate, under conditions similar to those encountered in surface dressing, but without interlock of stone particles. Chippings are removed by inertial stresses set up in them when a carefully regulated blow is applied to the base plate.A critical adhesion temperature, above which chippings should be applied to road tar, has been shown to be about 32 deg. c below the equiviscous temperature (e.v.t.) for clean, dry basalt chippings; a lower value is shown to apply in the case of PVC‐modified tar.Results indicate that the unit reasonably simulates service conditions and its use is proposed for additional studies.

Influence of irrigation and placement of nitrogen fertilizers on the uptake of nitrogen by spring wheat

The effect of irrigation and fertilizer placement on the accumulation of nitrogen in the aerial parts of spring wheat was studied in the relatively dry summer 1969, on the basis of plant samples collected at various stages of development from a field trial on silty clay soil. In addition to 16 kg/ha of nitrogen in the basal dressing, 120 kg/ha of nitrogen was applied as ammonium nitrate limestone, as urea, or as Ureaform, either on the surface, or in rows at the depth of 8 cm. 60 mm of water was applied by sprinkler irrigation, one half about three, and the other half about four weeks after sprouting. Under the conditions of this trial, spring wheat only slightly responded to Ureaform. No significant difference in the effect of urea and ammonium nitrate limestone could be detected. Placement of these two fertilizers tended to increase both the amount of dry matter and its content of nitrogen; these effects were more significant without irrigation. Though irrigation, usually, markedly increased the total amount of nitrogen in the aerial parts of the plants, this was in the later stages of development due only to higher yields of dry matter, since in July the positive effect of irrigation on the percentage of nitrogen in plant dry matter changed to a negative effect. In the grain yields the apparent recovery of nitrogen in urea or ammonium nitrate limestone was estimated to be only about 30 per cent of the 120 kg N/ha applied as surface dressing. Irrigation increased this recovery to 54 per cent, placement of the fertilizer to 42 per cent, and both placement and irrigation resulted in an apparent recovery of 61 per cent. On the basis of plant samples collected two days before harvest, the apparent recovery of nitrogen in urea or ammonium nitrate limestone by the aerial parts of wheat was estimated to be, on the average, 36 per cent from the surface-dressing, and 60 per cent when the fertilizers were placed. Irrigation increased the apparent recovery in the first case to 76 per cent and in the latter case to 96 per cent. Thus, in the field experiment the uptake of fertilizer nitrogen by spring wheat was markedly increased by irrigation and to a lesser extent by fertilizer placement. Both treatments together are recommended.

Effect of the placement of fertilizer on the development of spring wheat

The placement of fertilizer was studied in the field trial on a clay soil in Southern Finland. The placement of fertilizer in the depth of 8 cm gave 28 per cent greater grain yield of spring wheat, and the placement in the depth of 12 cm 26 per cent greater grain yield than the surface dressing. The growth of shoots on the soil receiving placement was much better than on the soil receiving surface dressing. The results of shoot analyses showed that the placement caused a much greater uptake of nutrients than the surface dressing. The uptake of nitrogen was relatively most increased by the placement, somewhat less that of potassium and least that of phosphorus. The ripening of wheat was speeded up by the placement, which probably was due to the better early uptake of nitrogen and to the better uptake of phosphorus by means of the placing. The superiority of the placement to the surface dressing could be explained by the distribution of nutrients in the experimental soil during the dry early part of the growth season. A great deal of fertilizer nitrogen, phosphorus and potassium remained near the surface of the soil receiving surface dressing, and plants were not able to take up nutrients from the dry surface layer. On the contrary, the placed nutrients were deeper, in moister soil and better within the reach of wheat roots. Any movement of ammonium nitrogen was not found by the used methods. Nitrate nitrogen appeared to move to a greater extent particularly in the irrigated plots.

Observations on the reduction of soil temperature

In some of the vegetable growing areas of Israel the soil temperature during the day at sowing depth is above the average optimum for vegetable crop germination from the beginning of June until mid-September. During July the temperature equals the average maximum for germination. Surface dressings of a commercial grade of magnesium carbonate were applied in an attempt to reduce the temperatures. These maximum soil temperatures were reduced by some 10°C for approximately three weeks after treatment. Doubling the rate of application did not increase the effect, but it was maintained for a longer period. Measurements showed that the radiation balance on the treated surfaces was only one sixth of that on the control surface, mainly because the application of magnesium carbonate doubled the albedo of the soil surface. The treatment reduced the evaporative heat flux by one fifth and reversed the direction of the convective-heat flux. Except in the period immediately following application, the soil heat flux was not greatly affected by the surface treatment.

White‐line road‐markings and light‐coloured road surfacings

AbstractWhite‐line road‐markings and light‐coloured road surfaces are considered from the point of view of their visibility, durability and non‐skid properties. It includes a survey of the different types of material available, the visibility requirements for white lines and road surfaces under daylight and night conditions (including both street‐light and headlamp illumination), and the requirements for a good resistance to skidding in wet weather. The extent to which the different materials available meet these requirements is also discussed.The thermoplastic road‐marking material covered by B.S. 3262: 1960 is the most satisfactory vet developed for general use. It has good durability and good skidding‐resistance in wet weather. The night visibility under headlamp illumination is improved by the addition of ballotini.For light‐coloured bituminous surfacings, a light‐coloured aggregate is essential. For surface dressings, calcined flint‐gravel is most suitable: in premixed materials the very white calcined flint is better. The skid resistance of these aggregates is adequate for most purposes.

Surface‐active agents in bituminous road materials

AbstractThe application of cationic surfactants to surface dressing and coated materials is discussed and results are given of some recent full‐scale road experiments. It is shown that the application of cationic agents in surface dressing may now be extended successfully to bitumen macadam and other coated materials. The action of cationic agents in bituminous materials is to some extent specific and care is needed in their selection for a particular purpose. This specific action depends partly on the conditions of use and partly on the binder and stone to which the agents are applied.

The surface dressing of rolled products with shot

The surface dressing of rolled products with shot

A method for recovering small samples of bitumen from road mixtures and surface dressings

AbstractA method has been devised for recovering from surface dressings 30‐g. quantities of cutback or penetration‐grade bitumen. This gives sufficient material for a determination of the viscosity in a Couette viscometer. The method was developed to investigate the rate of hardening on the road of cutback bitumens used in surface dressing.

Fertilizer nitrogen in soil

The distribution of ammonium nitrogen and nitrate nitrogen in the soils of field trials was followed in two growing seasons. In these trials ammonium nitrate limestone and calcium nitrate were, at several rates, applied as surface dressing. It was found that not only the ammonium nitrogen but also the nitrate nitrogen applied to the surface of loam, silt, silt clay, and fine sand clay soils tended to remain in the top inch for a considerable period in the absence of heavy rainfalls or a longer wet period. The plants appeared rapidly to deplete the layers downwards from 1 inch, but even after six and eight weeks from the application of the fertilizers the ammonium nitrogen and nitrate nitrogen contents of the surface inch could be markedly higher in the treated plots than in the untreated ones. In the non-cropped soil, eight weeks after the application of the fertilizers, the mineral nitrogen content of the top inch corresponded to about 60 % of the nitrogen applied. On the basis of these results the working in or placement of nitrogen fertilizers seems to be profitable. Fixation of ammonium nitrogen in unexchangeable forms was observed in some of the trials. This, however, did not significantly impair the value of ammonium nitrate limestone as a nitrogen source in these trials.

Calcium nitrate and ammonium nitrate limestone as sources of nitrogen for oats and barley

Calcium nitrate and ammonium nitrate limestone (»Oulunsalpietari») were compared as the nitrogen fertilizer for oats in 15 field trials and for barley in one trial. The trials were carried out in summers 1959 and 1960 in various places in Finland. The split plot technique was employed in order to reduce the variation as much as possible. In 1959 the amounts of nitrogen applied as these two fertilizers to the corresponding halves of the plots were 25 and 50 kg/ha. In 1960 also higher applications were used: 75 and 100 kg/ha of N. In three trials these fertilizers were compared both as a surface dressing and worked in. Visual observations suggested about 5—6 weeks after sowing a darker green colour in the stands treated with calcium nitrate as compared with the other half treated with ammonium nitrate limestone. These differences later disappeared. In some trials a higher nitrogen content of the plants from the calcium nitrate stands could be demonstrated during this period. The uptake of nitrogen by plants was regularly followed throughout the growing period. Owing to the large variation, usually, no statistically significant difference between the effect of the fertilizers could be detected. In a few cases the superiority of calcium nitrate could be demonstrated. No differences in the ripening could be found. In most trials there was a fairly regular tendency to higher yields and higher nitrogen content in the grain and straw produced by calcium nitrate. Yet, only in a few cases were the differences statistically significant at the five per cent level. Thus, it was concluded that on the basis of the results of these trials ammonium nitrate limestone and calcium nitrate may be considered practically equal as nitrogen fertilizers for oats. There was no difference in the yields of barley produced by these two fertilizers, but the nitrogen content of grains was significantly lower with ammonium nitrate limestone than with calcium nitrate. This may be worth further study in connection with the production of malting barley.

The setting of road tar in surface dressing

AbstractTar has been recovered from a number of surface dressings at intervals during the first year of their life and the changes in viscosity determined. A method is described for determining the contributions of oxidation and loss of oils to the observed hardening, and the results for one pair of dressings are given. The hardening of the tar was mainly due to loss of oils, oxidation accounting for about one quarter of the effect. Tars derived from a high‐aromatic crude only have been examined; other tars are to be tested in a similar way.

CONSERVATION OF HUMUS IN TROPICAL SOILS

THE part played by humic manures in soil processes and in plant nutrition, both as a source of mineral elements and by improving the physical condition of the soil, is well known. The advantages of properly devised rotational systems of cropping in soil husbandry are also established by both practice and experience. It is therefore reasonable to expect results of great economic importance by a combination of rotational cropping with humic manuring. The permanent manurial small plots at the Institute of Plant Industry, Indore, afforded an opportunity of studying the relative importance of humic manures and crop rotation on the conservation of soil properties. These plots, sixteen in number, have, since 1933, been receiving annual surface dressings of farm compoat, farmyard manure and municipal compost, all at ten tons per acre, and have been under a four-year rotational cropping with (i) cotton, (ii) sann (Orotalaria juncea), ploughed in and followed by wheat, (iii) ground nut, and (iv) jowar (Andropogon sorghum) ; one set of four plots (including a control immanured plot) being under a particular crop during a season. The plots treated with the different humic manures, while yielding more or less alike from year to year with all the crops, had frequently given more than double the yields of the untreated plots.