Showing papers on "Pervious concrete published in 1992"

Influence of curing methods on the strength and permeability of GGBFS concrete in a simulated arid climate

Abstract: Problems are frequently encountered in producing good-quality concrete in hot climates. Inadequate curing results in early cracking or porous and permeable concrete, or both; these effects, in turn, make structures prone to reinforcement corrosion and other processes of degradation. This research compares the development of strength and permeability of ordinary Portland cement (OPC) and ground granulated blast furnace slag (GGBFS)-modified concretes which were cured in a simulated arid climate. This was achieved with an environmental room in which temperature and humidity were cycled to imitate a typical Algerian Sahara climate. Four curing regimes were investigated to encompass the range of practical methods encountered on site. Specimens were placed in the hot environment immediately after casting and conditioned for up to 28 days. The strength of the GGBFS concretes was higher than that of the OPC control concrete at all test ages (7, 14 and 28 days) when good curing was provided. Partial cement replacement with GGBFS therefore offers the potential to produce stronger and more durable concrete in hot climates. The disadvantage of GGBFS concretes is that they proved to be more sensitive to poor curing than OPC concrete. In this case, both their strength and permeability, and hence their durability, were seriously impaired. Therefore, special care must be taken when using this type of concrete, especially on site, where the working conditions and the application of curing are not as easy to control as in the laboratory.

Effect of field and laboratory curing on the durability characteristics of plain and pozzolan concretes

Abstract: The environmental conditions in the Arabian Gulf countries are classified as aggressive and severely corrosive. Field and laboratory studies have shown that concrete in this region should be designed not only for strength but also for durability. Utmost emphasis should be given to produce dense and impermeable concrete, to extend the service life of structures. In this study, concrete samples were prepared using various types of cements and fly ashes at various mix designs. The samples were cured in the field and in laboratory conditions. The permeability was determined by volume of permeable voids and absorption tests. The results showed that continuous water curing is necessary to obtain the least permeable concrete for both plain and pozzolan concretes. Irrespective of curing procedure followed, the fly ash concrete exhibited lower permeability than plain concrete for an initial test period of 7 days during curing. The fly ash concrete samples cured in the laboratory exhibited lower initial surface absorption than control concretes after 90 days of curing for all fly ash additions (10–40%) and cement factors (275–450 kg/m3) used.

Performance of slag concrete in hot climates

Abstract: GGBS (Ground Granulated Blast Furnace Slag) concrete (with 30%, 50% and 70% cement replacement) and an ordinary Portland cement (OPC) control concrete, all designed for equal workability and 28 day water-cured strength, were found to have a wide range of strength and permeability when cured under one of four regimes in a simulated arid climate. The effect of curing method and cement replacement level on compressive strength, ultrasonic pulse velocity, water absorption and permeability are reported. The tests show that a GGBS concrete can have a superior performance to an equivalent all OPC concrete in a hot climate, provided that proper curing is provided. However, without proper curing, the GGBS concrete suffered more than the OPC, resulting in a highly permeable concrete whose strength reduces with increasing replacement level. Of the replacement levels studied the 50% mix produced the best performance. For the covering abstract of the conference see IRRD 853062.

Biological gas cleaning device esp. for exhaust air - comprises microorganism supported on fixed filter bed made up of mixt. of nutrient material and particles of porous concrete

Abstract: The gas is passed upwards through a fixed bed of nutrient mateiral contg. microorganisms in which a certain moisture content is maintained. The fixed bed (5,8) consists of a mixt. of nutrient and porous granular concrete having a grain size of 2 to 25 mm. The mixt. ratio 1:5-5:1 by vol., ore pref. 1:2-2:1. The grain size of most of the concrete particles should pref. = 4-8mm. Broken particles of concrete should be used, and the porous concrete is formed by mixing the wet concrete with a humus substrate and subsequently treating it with steam. The porous concrete may be impregnated with nutrient for the microorganisms. The pH value of the concrete is below 9, and pref = 7-8. USE/ADVANTAGE - In the cleaning of gases, and especially exhaust air. The proposed filter has an extended service life and maintains its cleaning capacity and low resistance to air flow over long periods of operation.

Water-permeable concrete

Abstract: PURPOSE:To improve water permeability and bending strength by containing an aggregate having a specific grain diameter and cement as principal components. CONSTITUTION:Water-permeable concrete is obtained by mixing an aggregate composed of >=20% aggregate having 2-3mm grain diameter, >=20% aggregate having 7-8mm grain diameter and the remainder of an aggregate having 3-7mm grain diameter with cement, slaked lime in an amount of 3-6% based on the cement, water and a water-reducing agent.

Permeable square concrete brick

Abstract: The utility model discloses a permeable concrete square brick, which is used in engineering construction and ground paving. The concrete square brick material which can be permeated by water solves the previous problem that the water or rain can not permeate quickly after ground paving. The permeable concrete square brick is mainly characterized in that permeable channels which are through from above to below are arranged in a square brick, and the permeable channels can ensure water or rain permeate the square brick and enter ground surface. The water loss can be reduced by adopting the permeable concrete square bricks to pave ground, and the permeable concrete square brick not only is beneficial to the growing of plant but also has the function to adjust the air humidity and temperature in a certain extent, and furthermore, the utility model brings a great convenience to passerby because the ground seeper after rain is reduced.

Foundation for vegetation

Abstract: PURPOSE:To provide a vegetation foundation suitable for growing of plant by mixing tree-planting aggregate including a water absorptive expansion mate rial with a granular aggregate for concrete, sprinkling a binder for consolidation over the mixture, and coupling and solidifying in the form of porous concrete CONSTITUTION:A soil base for vegetation, a water absorptive expansion mate rial which expands when absorbing water, and a water soluble binder are mixed together, and this mixture is molded and solidified in the form of grains, and thus tree-planting aggregate 4 is fabricated This aggregate 4 is mixed with a granular aggregate 3 for concrete, and thereover an inter-aggregate consolidating binder is sprinkled, and thereby they are coupled and solidified in the form of porous concrete while continued voids are left inside Thus, a vegetation foundation 1 is prepared After this preparation, the voids in the porous concrete are filed with the constituents of the tree-planting aggregate 4 in association with water absorption and expansion of the water absorptive expansion material, which provides a three-phase distribution suitable for grow ing of plant as a whole

Porous concrete surfacing for roads

Abstract: Surfacing roads with a durable porous wearing course has the potential for providing two major benefits. A free-draining suface can reduce the spray and splash generated by vehicles in wet conditions, thus contributing to safety by removing water which acts as a lubricant at the tyre/road interface and helping to maintain road capacity. In addition, an open surface texture provides the capacity to absorb tyre noise and reduce that which arises from the pumping of air between tyres and the road surface. Trials with porous asphalt have been conducted on a number of sites in the United Kingdom since 1967, including the A38 Burton By-pass and the M6, and have demonstrated its suitabilty for use on major roads. This report describes the results of a study to establish mix design criteria for porous concrete suitable for such applications. In order to establish some of the factors which govern the properties of porous concrete, a series of laboratory tests were undertaken, all based on a single-size, crushed granite coarse aggregate. A broad band of voids content was investigated using both cement paste and cement mortar as the matrix material, with and without air- entraining and superplasticizing admixtures. Over a more limited range of voids content (20-30 percent), the effect of sand content, sand grading and the use of polymer additions were studied and from the data collected, four mixes were selected for strength, fatigue, freeze-thaw resistance, sound absorption and abrasion testing.