Polyvinyl alcohol solution(PVA) proveded potential enhancement of the properties of cement mortar composite. This work investigated the effect of (w/c) and polymer-cement ratios (p/c) on the flexural strength of type I Portland cement mortar. A sand-cement ratio (s/c) of 1.25 and 0.5 by mass was used, and PVA powder was dispersed in water at (0.7%, 1%, 2%, and 3%) by weight of cement. The p/c solution was adjusted at five different values of 0.008, 0.012, 0.016, 0.020 and 30% covering relatively low and high values. Two types of curing were used; wet and dry curing. The study results demonstrated that flexural strength and significant water absorption properties of Portland cement mortar, as well as workability can be basically enhanced by the addition of PVA. Composite was prepared with optimum (p/c) 1.6% at concentration of 1% by mass under dry curing. The highest flexural strength was above twice the flexural strength of unmodified mortar. Also modified mortar samples illustrated that increasing of (p/c) causes reducing water absorption due to the packing effect caused by PVA, while mortar prepared at 0.1 and 0.3 w/c and (p/c) respectively, exhibited an increase in flexural strength which was more than the strength of unmodified mortar.
This paper presents an experimental investigation on the flexural behavior of reinforced concrete beams made from a combination of two types of concrete as a (built-up or composite) member. The experimental program consists of casting and testing of eleven rectangular cross-sections of simply supported reinforced concrete beams. Distribution of the specimens was three beams used as a reference which were fully poured from conventional concrete (CC) and reactive powder concrete (RPC). The remaining were eight (built-up) beams made by incorporation of two types of concrete as an element, about those beams, the RPC is poured as layers different in depth and the effective regions (compression and tension), where they are compatible with CC to complete the beam depth. Experimental results show that a stiffer behavior of load-deflection appears, especially when the RPC is in tension region (the bottom of the beam) with respect to increase of the layer depth and the volumetric ratio of steel fibers (vf). The load-carrying capacity of (built-up) beams increase when the RPC is used in the compression region affected by the increase of the layer depth and the volumetric ratio of steel fibers, with less stiffer behavior compared to the beams where the RPC used in the tension regions. The results can be summarized that RPC utilizing in compression regions is more influential than utilizing it in tension regions.
Finite element modeling is used for tracking the flexural response of built-up reinforced concrete beams under the influence of dominant flexural loading. ABAQUS finite element analysis program was used toward this goal, due to its superior capability to represent the mechanical properties of concrete including compressive and tensile strength in strain hardening and softening behaviors; and the features related to steel reinforcement rebar. This study is based on the comparison between the theoretical analysis by the finite element method and the experimental results. The experimental program consists of casting and testing six rectangular cross-sections of simply supported reinforced concrete beams. Two beams are cast as a reference which fully Conventional Concrete (CC) and Reactive Powder Concrete (RPC), the rest four were built-up beams made by the combination of two types of concrete in one element. The study deals with, the load which caused a first crack, ultimate carrying capacity, load and deflection behavior at mid-span of beams, cracks patterns, and damage index of the examined beams. Good agreement was gained with the available experimental results that show the effectiveness of the finite element method for simulating the flexural performance of beams.
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