The development and use of geopolymers (GP) considerably increased in the construction industry. This paper assesses the suitability of metakaolin-based GP mortars for masonry plastering works, including their comparison to masonry cement (MC) mortars and compliance to relevant EN 413-1 and ASTM C91 specifications. Three classes of GP mortars prepared with different metakaolin-to-limestone ratios are tested; the sodium hydroxide and sodium silicate activators contained air-entraining molecules to secure approximately 10% ±2% air content. Test results showed that GP mortars exhibited excellent water retention and increased rheological properties, which was related to higher viscosity of alkaline solution that increases stickiness and overall cohesiveness. For given limestone concentration, the mechanical properties of GP mortars including the pulloff bond strength and sorptivity were remarkably better than MC mixtures. Almost 90% of ultimate compressive strength was achieved after 7 days for GP mortars cured at ambient temperature, while this varied from 55 to 80% for MC mixtures cured in moist conditions. This can be particularly advantageous in masonry applications to speed up construction operations while, at the same time, eliminate the hassle of moist curing normally required with cement-based plasters.

Gypsum plaster is widely used in buildings for different purposes, but the low strength and weak water resistance of gypsum limit its application. To improve the properties of gypsum plaster, the effects of carbide slag (which is a waste material) and CO2 curing on the physical properties of gypsum plaster were investigated. The compressive strength and softening coefficient (or water resistance) of different samples were tested. The related mechanisms, mineral characterization, and microstructure were studied through differential thermal analysis-thermogravimetry (DTA-TG), X-ray diffraction (XRD), and scanning electron microscope (SEM) tests. The gypsum powder, carbide slag, and water were mixed together and then pressed into a disc sample under a compression pressure of 3 MPa in a cylinder mold. The disc samples were then cured in a CO2 chamber with 70% relative humidity under 25 ± 2°C for 24 hours. The results show that the replacement of 30 to 50% gypsum with carbide slag can increase the compressive strength of gypsum plaster by more than 100%, and at the same time, the softening coefficient or water resistance could be improved by more than 400%. The results from DTA-TG, XRD, and SEM show that the main minerals in the blended gypsum plaster are CaSO4·2H2O and CaCO3. The reaction between the carbide slag and the CO2 formed CaCO3, which increased the compactness, compressive strength, and the water resistance of the blended gypsum plaster. Except for the improved physical properties, the use of carbide slag can reduce the environmental impact by fixing CO2.

The sulfate activation of basic oxygen slag waste (BOS) using plasterboard gypsum waste (PG) and cement by-pass dust (BPD) was investigated to produce a novel composite binder without using portland cement. The interactions between these three waste-derived materials were analyzed in terms of strength development of binary and ternary paste mixtures to establish the optimum mixture proportions corresponding to the highest compressive strength. The results show that crushed plasterboard gypsum waste can be used as a source of sulfate to form a novel sulfate activated pozzolan binder. It was observed that the optimum percentage of BOS and PG is affected not only by the type and characteristics of materials used, but also the order of optimization with which binary and ternary mixtures were made. It was found that BPD content has a great influence on compressive strength of binary and ternary combinations of BPD, PG, and BOS pastes.

This paper presents an experimental study on the impact response of protective reinforced concrete structural elements that are coated with plaster on their interior faces. Even when a structural element’s perforation is prevented, impact conditions may initiate rear face scabbing due to high-intensity reflected tensile stress waves at the element’s rear face. Israeli standards for civil defense shelter design forbid any interior wall coating, such as plaster or wall tiles, as they may be easily detached upon impact and produce scabbing fragments. Following the Gulf War, a new Israeli civil defense policy became effective, where the protective spaces have been included within the dwelling units. Although plaster coating is the common finish work of the entire interior of a dwelling unit, it seems to a priori contradict the above requirements of scabbing prevention. Further study of the problem and investigation under impact conditions are therefore required to better understand the behavior of the concrete-plaster composite under local hard projectile impact. An experimental program was conducted at the laboratory and included response studies of reinforced concrete specimens to hard projectile impact. The specimens with plastered rear faces were impacted at the center of their front faces. The results showed different responses of various types of plaster coating and demonstrated the importance of parameters that affect the specimens’ performance under impact loads, which are mainly the plaster-background adhesion strength, the plaster density and stiffness, and the improved toughness of the plaster layer. The latter is obtained by reinforcing the plaster with a fiberglass mesh.

For economically and effectively solving the widely existing rehabilitation problem of marine reinforced concrete superstructures due to reinforcing steel corrosion damage in China, a kind of secondary anode (patented AS conductive mortar overlay) and a CN-1-type conductive plastic wire anode have been developed. One system consists of linear CN-1-type anode embedded in AS mortar overlay, and another one consists of a netlike CN-1-type anode embedded in OPC mortar overlay. These two new systems have been applied as anode systems on the bottom parts of some marine reinforced concrete superstructures, and impressed current cathodic protection was applied in sites normally for 3 years. Paper presents and discusses the results and the techniques in practice. It verifies that both anode systems of cathodic protection are highly effective for such structures, and the systems could also be applied economically and easily on a side or soffit surface by a plasterer.