Study was designed to assess the merits of polymer addition to superplasticized cement paste, mortar, and concrete. Three superplasticizers--a sulfonated melamine formaldehyde, a sulfonated naphthalene formaldehyde, and a commercial superplasticizer--were used in combination with experimental polymers. Polymer and superplasticizer dosages ranged from 0 to 15 percent and 0 to 0.3 percent, respectively. The effect of binary admixture systems (superplasticizer and polymer) on the physicomechanical properties of the cementitious systems was determined. Properties investigated included slump, slump retention, setting time, compressive strength, flexural strength, surface area, porosity, and density. Compatibility of the polymers with the superplasticizer was assessed with respect to the influence of the individual admixtures on the properties of the various systems. Synergistic effects were observed for one polymer, the results of which are discussed in detail.

Eight samples of sodium salts of naphthalenesulfonic acid-formaldehyde condensates with different molecular weight have been synthesized by stopping the polymerization process at different reaction times between zero (monomer) and 14 hr at 112 C using a molar H2SO4/naphthalene ratio of 1.07 and a molar HCHO/naphthalene ratio of 1.20. The longer the reaction time, the higher the molecular weight. The condensates have been analyzed by Gel Permeation Chromatography to determine the chemical composition and average molecular weight. The condensates have been used as superplasticizers (0.4 percent of dry product by weight of cement) for cement paste (water/cement ratio = 0.35) and the fluidifying effect has been determined by the mini slump test. It was found that the fluidifying effect increased by reducing the content of monomer and increasing the molecular weight of the condensate. To confirm that the fluidifying effect of the condensate substantially depends only on the content of the higher molecular weight fraction, two samples of the condensate, with different reaction times and then with a different condensation degree have been subjected to an ultrafiltration process. This technique allows removal of the monomer and the lower molecular weight fraction. The two samples of the condensate, which had different fluidifying effects before the ultrafiltration process, behaved similarly as superplasticizers after the ultrafiltration process.

Results of tests on modified cement mortars admixed with naphthalenesulfonate and acrylic latex used for repairs are presented. Theological and mechanical properties as well as durability have been measured. The combined use of polymer latex and naphthale

Structural lightweight concrete is becoming more and more important in building practice as such material can provide mechanical and durability performances like normal weight concrete with higher strength-density ratio. A special superplasticizing admixture able to improve the lightweight concrete workability at very low water-cement ratio, avoiding the segregation problems, has been developed. The considerable advantages of this admixture, in comparison with traditional superplasticizers (ASTM C 494, Type F), are emphasized with workability and mechanical tests on standard mortars made with artificial lightweight fines obtained from sintered fly ash particles or natural sand, two types of cement (blast furnace cement or a mix of portland cement and fly ash), and different silica fume percentages. Water permeability and vacuum water absorption tests on lightweight mortars have also been performed. Finally, the properties of total lightweight concretes made incorporating the new admixture, blast-furnace cement in varying amounts, and silica fume and sintered fly ash lightweight aggregates have been evaluated.

Describes the construction of San Marco dry dock in Italy. Approximately 82,000 m3 of superplasticized concrete with a slump of 250 mm was placed, of which 40,000 m3 were underwater at a depth of 16 m using a tremie system. The concrete was mixed at a central plant and transported to the site where it was pumped for 250 m from a fixed station to the hopper of the tremie located on a floating barge. The presence of heavy reinforcement (steel trestles) made the positioning of the tremie pipe and inspection by divers very difficult. To limit the number of shiftings of the tremie pipe, concrete had to have a very high workability and had to be very cohesive to prevent washing by seawater. Moreover, the specification required an impermeable, sulfate-resistant concrete with a strength of 25 MPa. In the first stage, a slab of 4 m thickness was created by placing overlapping "pizzas" of 45 m3 volume and 15 m diameter. If the concrete was not superplasticized, then the size of the "pizzas" would have been much smaller (approximately 20 m3 volume and 3 to 4 m diameter). After dewatering, the slab was completed with a second pour of self-levelling concrete of 1 m thickness. The use of a superplasticizer helped the contractor complete the job 3 months ahead of schedule.