Reinhart Verschoore

Influence of the cement type on the resistance of concrete to feed acids

Abstract Concrete in animal houses is subject to aggressive substances from feed and manure. Chemical attack by the most important feed acids, lactic and acetic acid and abrasion caused by animals and cleaning, were simulated and studied using accelerated corrosion tests. The resistance of concrete prisms with different cement types and approximately constant water-to-cement ratio, to simulation liquids with different pH-values, was investigated. The decrease of volume in terms of percentage and the mass loss per unit area were measured, as well as the pH-change and calcium content of the liquids. It appeared that the cement type had an important influence on concrete resistance in the highly to very highly aggressive simulation liquids. Four groups with decreasing vulnerability to the attack were distinguished: portland cement without C3A, ordinary portland cement, cement containing fly ashes, blastfurnace slag cement. The percentage of slag in the slag cement and the cement content of the pozzolanic cement had no significant influence.

RESISTANCE OF CONCRETE WITH LIMESTONE SAND OR POLYMER ADDITIONS TO FEED ACIDS

By using limestone sand or polymer additions in the concrete mix, it was attempted to reduce the deterioration of concrete floors in pig houses by lactic and acetic acid. To simulate in a standardized and automated way chemical attack by those acids and abrasion caused by animals and cleaning, a testing apparatus for accelerated degradation tests was developed. Concrete cylinders mounted on rotating axles were turning through containers with simulation liquid. After each attack cycle the concrete was brushed with rotary brushes. Concrete degradation was measured with laser sensors connected to a computer and the average attack depth and the Ra-value, which is a measure of surface roughness, were calculated. Results of previous experiments, showing that concrete with blast furnace slag cement was much more resistant than the reference concrete with ordinary portland cement, were confirmed. The use of limestone sand and possibly limestone aggregates led to a quicker neutralization of the aggressive liquid, but was insufficient to reduce the average attack depth. When limestone sand and limestone aggregates were used, the increase in concrete roughness was smaller than for concrete with limestone sand and gravel aggregates. Addition of 10% polymers to the concrete mix increased the resistance significantly, when care was taken that the polymer cement concrete (PCC) didn’t contain too much air voids. The most resistant PCC, containing a styrol acrylic acid ester showed after six cycles an average attack depth 12 times smaller than the reference concrete. Furthermore the potential benefit of the polymers was probably underestimated, as an investigation with the scanning electron microscope showed that the emulsified polymer had not completely formed a film.

IMPACT OF WATER DROPS ON THE VISIBLE RADIATION TRANSMITTANCE OF GLAZINGS UNDER OUTSIDE RADIANT CONDITIONS

Abstract Experimentally determined directional-hemispherical transmittances for visible radiation were used to calculate the effect of condensate on the hemispherical–hemispherical transmittance values under diffuse radiant conditions for single glass and polyethylene. The hemispherical–hemispherical transmittances were determined in the horizontal plane for different inclinations of both glazing materials assuming a completely overcast sky and a clear sky. In all cases, condensate was found to reduce the transmittance. Under an overcast sky, the transmittance of single glass was reduced by the presence of condensate from 8 up to 13% (on a relative scale) for increasing inclination angles of the glass plate, while for the polyethylene film, the transmittance reduction due to condensate decreased from 20 down to 13%. Under a clear sky, depending on date, time, and orientation of the glazing material, the transmittances of single glass and polyethylene were reduced by between 6 and 15% and by between 8 and 21%, respectively, due to the presence of condensate. These results revealed that the impact of the presence of condensate on the transmittance of a glazing cannot be omitted from design and performance calculations of solar energy systems.

Simulation of the influence of differential control on tractor work rate

This paper deals with numerical simulation tests carried out on agricultural tractor drive lines, to analyse the influence of differential locking and tire deflection on the work rate. In most cases the highest travel speed, and hence the maximum work rate, can be reached with a locked differential. With a controlled differential, a more effective power distribution can be reached only when the tyres are non-rigid. The increase in efficiency, however, is very small. When the tractor is turning, the controlled differential gives the highest work rate; the improvement, however, looks only to be of interest when the turning radius is less than 10 m. The controlled differential gives the best manoeuvrability and the smallest ground deterioration.

Measurements and simulation on the comfort of forklifts

Abstract In order to determine the influence of some parameters of a forklift such as the road profile, the tyre characteristics, the riding comfort, etc., measurements carried out on a forklift with different tyres and seats were evaluated using different standards and methods. In addition, a simulation model was developed and used to investigate the influence of these parameters. Simulations and test run results showed good agreement. The comparison of the results obtained with several methods of comfort evaluation and a series of tests showed that they nearly all resulted in the same classification. However, the results obtained with different methods could not always be compared among themselves. Solid tyres were found to be more comfortable than pneumatic ones because of their high damping. The negative influence of higher stiffness was smaller than the positive influence of higher damping. The simulations pointed out that for a global general investigation about comfort, the influence of the horizontal tyre stiffness and damping can be neglected. Also the seat characteristics could be linearized. When the stability of the forklift has to be investigated, the horizontal forces must also be considered.

Angular dependence of forward scattering induced by condensate on greenhouse cladding materials

The forward scattering properties of four cladding materials, namely low-density polyethylene (LDPE), anti-drop condensation polyethylene (ADCPE), diffusive polyethylene (DPE), and single glass (SG) were measured in the dry state and when covered with condensate at three different incidence angles, namely 0, 15, and 30°. In the dry state, single glass behaved as a quasi non-diffusive material in contrast to the three plastic films which scattered the radiation due to their surface roughness, bulk heterogeneities or the addition of diffusive agents. With the exception of the anti-drop condensation polyethylene, the forward scattering of the materials was broadened by the presence of condensate. For these materials, the scattering pattern shifted towards the normal to the cladding with increasing incidence angle. This meant that less radiation was scattered to the opposite side of the directly transmitted, unscattered beam. At an incidence angle of 30°, a distinct shoulder in the scattering pattern, situated between the direct beam and the normal, was found on wet single glass in contrast to the plastic films.

Quality assessment of antishock systems for potatoes

SummaryLoading trailers and trucks includes a high risk for mechanical damage to potatoes, particularly when no anti-shock system is used. Manufacturers offer anti-shock equipment to reduce mechanical damage. A selection of anti-shock systems was compared.Firstly, the effect of protecting the product layer at the bottom of the trailer was investigated by dropping tubers in the empty trailer and analysing tissue discolouration and cracks. The combination of a shock absorber and a mattress yielded the highest bruise protection. Secondly, to investigate the bruising profile in the trailer and the damage reduction effect of each anti-shock system a bulk mass of potatoes was dumped into the trailer. Five hundred test potatoes were mixed into the bulk mass. Test potatoes were visually analysed for bruising and compared with controls (anti-shock systems absent). The results allowed the introduction of a mathematical relationship between drop height and tissue discolouration. Using an anti-shock system bruising was reduced by 10–90%, depending on the system and the bulk layer.On-field experiments were carried out to validate laboratory results. However site-specific harvest conditions and variable commodity properties made comparisons difficult.