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The present study aimed to investigate the effect of an expandable additive on the compressive strength and linear expansion of geopolymer cement, which is an alternative to ordinary Portland cement, for oil-well cementing. Fly-ash-based geopolymer cement samples, with the addition of slag cement as a strength enhancer, were prepared by using an elastomeric expandable additive (R-additive), which consists of styrene–butadiene rubber with a specific gravity of 0.945, at concentrations of 10%, 15%, 20% and 25% by weight of the solid blend, and cured in a water bath at 60 °C and atmospheric pressure, and a curing chamber at 90 °C and 3000 psi, or approximately 20.68 MPa. Mixability, amount of free water and slurry density were studied, and the effects of the concentration of R-additive on the compressive strength (F) and linear expansion (∆l/l0) of the samples were analyzed. When cured at 60 °C and atmospheric pressure, the highest F of 15.01 MPa was obtained when the concentration of R-additive was 10%, while the highest ∆l/l0 of 0.9985% was obtained when the concentration of R-additive was 25%. An increase in the curing temperature and pressure to 90 °C and 3000 psi (≈20.68 MPa) resulted in the reduction of F from 15.01 to 14.62 MPa and from 10.33 to 9.61 MPa, and the increase in ∆l/l0 from 0.52% to 0.63%, and from 0.99% to 1.32%, when the concentrations of R-additive were 10% and 25%, respectively. The findings suggest that the formulations adopted, which contain R-additive at concentrations ranging from 10% to 25%, fulfilled the requirements of the oil and gas industry.

This experimental study investigated the effects of polyvinyl alcohol (PVA) and copper-coated steel (CCS) on the mechanical properties and the post cracking behavior of fiber reinforced concrete (FRC). In designing high-performance concrete mixes, cement replacement materials are the essential ingredients. Therefore, the research objective was to investigate PVA and CCS fiber’s post-cracking performance in 100% cement concrete and concrete with 80% cement and 20% fly ash. The fiber content was fixed as a 0.3% volumetric fraction. CSS fibers required 15% more superplasticizer to achieve the desired slump of fresh concrete than the PVA fibers. Simultaneously, CCS fibers showed a 10% higher compressive strength than the concrete made of PVA fibers. Both fibers exhibited a similar effect in developing tensile and flexural strength. PVA fibers showed a value of 47 Gpa of secant modulus, and CCS fibers resulted in 37 Gpa in 100% cement concrete. In post-cracking behavior, CCS fibers showed better performance than the PVA fibers. The reason for this is that CCS showed 2.3 times the tensile strength of the PVA fibers. In comparing the two concretes, fly ash concrete showed about 10% higher compressive strength at 56 days and about 6% higher tensile and flexural strength. Similarly, fly ash concrete showed more than 15% first crack strength and flexural toughness than the 100% cement concrete in post-cracking behavior. Fiber-reinforced concrete containing PVA or CCS fibers showed enhanced post-cracking characteristics and its use could be preferred in structural applications.