scholarly journals Effect of locally sourced Nigerian gypsum on the strength and microstructure of Portland cement mortar

2021 ◽  
Vol 39 (4) ◽  
pp. 1001-1010
Author(s):  
A.D. Muhammad ◽  
Y.D. Amartey ◽  
J.M. Kaura ◽  
T.S. Ijimdiya ◽  
A. Lawan
Keyword(s):  
Compressive Strength ◽  
Portland Cement ◽  
Cement Mortar ◽  
Calcium Sulphate ◽  
Cement Clinker ◽  
Strength Increase ◽  
Sulphate Content ◽  
Curing Period ◽  
Gypsum Content ◽  
Cement Manufacture

The objective of this study was to investigate the suitability of Nigerian, sourced Gypsum for the manufacture of Portland cement. Gypsum samples were obtained from eighteen deposits across Nigeria. These were classified into five purity groups based on their calcium sulphate content.Foreign Gypsum, imported from Morocco, was used as control. Six cement samples where produced for each of the five Gypsum purity groups by grounding and blending cement clinker with 3%, 4%, 5%, 6% and 7% Gypsum content. The group 1 cement mix (having not more than 65% calcium sulphate content) has displayed flash set and could not be moulded and therefore not used for further analysis. Cement mortar prisms were produced for the groups 2, 3, 4 and 5 cement mixes, and subjected to flexural and compressive strength tests at 7, 14, 21 and 28 day curing periods. The cement mortar prisms were also subjected microstructure analysis at 7 and 28 days curing period. The spongy, gel and whitish colouration observed from the  microstructure of the specimens indicated silicates enriched regions which have proven the strength increase from 7 to 28 day curing period. The optimum gypsum content of 5.5% was recommended. The results show that all but the class one gypsum with less than 65% purity content are suitable for cement manufacture. Keywords: Gypsum, clinker, mortar, microstructure, compressive strength, flexural strength

scholarly journals Design and Development of Concretes for Special Rehabilitation Tasks

2018 ◽  
Vol 199 ◽  
pp. 07001
Author(s):  
Alexander Flohr ◽  
Andrea Osburg
Keyword(s):  
Portland Cement ◽  
Logical Consequence ◽  
Concrete Surface ◽  
Calcium Sulphate ◽  
Cement Clinker ◽  
Polymer Modification ◽  
Self Compacting Concrete ◽  
Engineering Structures ◽  
Sulphate Content ◽  
Repair Mortars

The requirements for concrete restoration are not only aspects of retrofitting or restoration of bearing capacity but also aspects of preservation of historic structures, such as industrial monuments or civil engineering structures and buildings of the 1960s [1]. Thereby the facsimile replication of the concrete surface is a particular challenge. For the manufacture of delicate and complex structures with restricted accessibility self-compacting concrete (SCC) is well suited [2]. A modification with polymers normally ensures the durability of repair mortars or concretes (PCC) [3]. The combination of PCC and SCC to the Polymer-modified Self-Compacting Concrete (PSCC) for the restoration of historic concrete constructions is the logical consequence, to combine the advantages of both materials and is therefore an interesting alternative to well established materials and methods. Historic concrete constructions are often manufactured of concretes with very stiff consistencies, the so called tamped concretes. So there is a need to develop materials and methods for the rehabilitation of structures made of tamped concrete. For this reason, first investigations have been performed to the recipe development and optimization of its composition, but also properties, furthermore to the design possibilities and how polymers influence the concrete properties. In Germany between 1920 and 1970 industrial buildings and hydraulic structures have been built with concretes, where the content of Portland cement clinker was nearly complete substituted by latent hydraulic materials. The binders of those concretes contain large quantities of blast furnace slag and calcium sulphate and are called super-sulphated cement (SSC). Because of the high sulphate content, the compatibility of concrete structure with SSC is not given to concretes or mortars with other cements. If there is an adequate range of moisture, harmful new formations of phases will occur in the contact zone between SSC-concrete and the other concrete. In the field of rehabilitation PCC are well established. These are polymer-modified mortars or concretes with Portland cement, which are not suitable for the rehabilitation of structures of SSC-concrete. An alternative is the polymer-modification of SSC-concretes with polymers.

scholarly journals Assessment of the influence of fine aggregates on Portland cement mortar compressive strength

2021 ◽  
pp. 100182
Author(s):  
Alberto Muciño ◽  
Lauro Bucio ◽  
Eligio Orozco ◽  
Sofía Vargas ◽  
Nora A. Pérez
Keyword(s):  
Compressive Strength ◽  
Portland Cement ◽  
Cement Mortar ◽  
Fine Aggregates

Estimation of Portland cement mortar compressive strength using microcores. Influence of shape and size

2014 ◽  
Vol 55 ◽  
pp. 359-364 ◽  
Author(s):  
F.J. Alejandre ◽  
V. Flores-Alés ◽  
R. Villegas ◽  
J. García-Heras ◽  
E. Morón
Keyword(s):  
Compressive Strength ◽  
Portland Cement ◽  
Cement Mortar ◽  
Shape And Size

Experimental Study on Compatibility between Alkali-Free Liquid Concrete Accelerators and Cement

2013 ◽  
Vol 438-439 ◽  
pp. 102-107 ◽  
Author(s):  
Wen Kang Guo ◽  
Li Wang ◽  
Shu Yin Wang ◽  
Dao Yin Lan ◽  
Sheng Ping Li
Keyword(s):  
Mechanical Properties ◽  
Experimental Study ◽  
Compressive Strength ◽  
Portland Cement ◽  
Ordinary Portland Cement ◽  
Strength Ratio ◽  
Setting Times ◽  
Gypsum Content ◽  
Durability Of Concrete

This paper selected two kinds of alkali-free liquid concrete accelerators and tested their compatibility with ordinary Portland cement, Portland cement and moderate heat Portland cement by measuring the setting times, compressive strength and compressive strength ratio of samples. The results showed that the compatibility is good between alkali-free accelerators and two types of cement: ordinary Portland cement and moderate heat Portland cement. However, the compatibility of two accelerators and Portland cement are quite different, the compatibility of AFA-2 accelerator is excellent, but AFA-1 accelerator is very poor. The setting times of alkali-free accelerators is mainly influenced by the mixing materials content, gypsum content, C3A and C3S content. In order to ensure the mechanical properties and durability of concrete, the setting times of new concrete accelerator is not the shorter the better, the appropriate initial and final setting times are 1min30s~5min and 4min~ 12min respectively.

scholarly journals Predicting the drying shrinkage behavior of high strength portland cement mortar under the combined influence of fine aggregate and steel micro fiber

2017 ◽  
Vol 67 (326) ◽  
pp. 119 ◽  
Author(s):  
Zhengqi Li
Keyword(s):  
Compressive Strength ◽  
Portland Cement ◽  
Cement Mortar ◽  
Drying Shrinkage ◽  
High Strength ◽  
Fiber Content ◽  
Fine Aggregate ◽  
Aggregate Content ◽  
Normal Strength ◽  
Gardner Model

The workability, 28-day compressive strength and free drying shrinkage of a very high strength (121-142 MPa) steel micro fiber reinforced portland cement mortar were studied under a combined influence of fine aggregate content and fiber content. The test results showed that an increase in the fine aggregate content resulted in decreases in the workability, 28-day compressive strength and drying shrinkage of mortar at a fixed fiber content. An increase in the fiber content resulted in decreases in the workability and drying shrinkage of mortar, but an increase in the 28-day compressive strength of mortar at a fixed fine aggregate content. The modified Gardner model most accurately predicted the drying shrinkage development of the high strength mortars, followed by the Ross model and the ACI 209R-92 model. The Gardner model gave the least accurate prediction for it was developed based on a database of normal strength concrete.

scholarly journals Mechanical Properties of OPC - Geocement Concrete

2019 ◽  
Vol 8 (4) ◽  
pp. 3733-3736
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Portland Cement ◽  
Ordinary Portland Cement ◽  
External Heat ◽  
Partial Replacement ◽  
Strength Development ◽  
Strength Increase ◽  
Heat Curing ◽  
Compressive Strength Development

Nowadays geopolymer concretes are subjected to heat curing. A large amount of highly corrosive and the hygroscopic alkaline activators are nowadays generally utilized in producing geopolymer concretes. In this paper, hybrid Ordinary Portland Cement (OPC) and geopolymer mixes are developed. The mainly used activator id the Solid potassium carbonate at different percentage is used as 5% & 10% of the weight of geopolymeric materials and OPC was blended with geopolymeric materials in different proportions. By adding cement, improves all the geopolymer properties except workability. By Applying external heat, it plays an important role in gaining strength. Strength gained by the absence of external heat is achieved by using Portland cement as a partial replacement of geocement. The influence of OPC content on the compressive strength development is investigated, and the optimized amount of solid activator to be used in the mix is also investigated. It is observed that percentage of strength increase decreases from52.24% to 14.77% as the OPC content increased from 20% to 60%.

THE EFFECT OF ADDITION NANOPARTICLES ON SHRINKAGE PROPERTY OF ORDINARY PORTLAND CEMENT

2021 ◽  
Vol 25 (Special) ◽  
pp. 2-78-2-82
Author(s):  
Haider K. Ahmed ◽  
◽  
Mohammed A. Abdulrehman ◽  
Keyword(s):  
Compressive Strength ◽  
Carbon Black ◽  
Portland Cement ◽  
Cement Mortar ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Carbon Black Nanoparticles ◽  
Flow Table ◽  
Compressive Strength Test ◽  
Negative Effect

Two types of nanomaterial: Tio2 nanoparticles (NPs) and carbon black NPs have used in this research to study their effect on compressive strength, shrinkage and flow table tests Cement mortar. The mixing ratio was 1:2.7:0.485 (cement, sand, water/cement ratio) for compressive strength test and 1:2 (cement, sand) with the water/cement ratio was a variable value for dry shrinkage test. The two nanoparticles’ ratios are (0.25%, 0.75%, 1.25 % and 1.75%) by weight of the Portland cement. The test results show that the highest value of compressive strength was obtained when using Tio2 at 1.25% wt. of cement. But when using carbon black nanoparticles, the greatest value was obtained when adding it with a ratio of 1.75 % wt. of cement. Using two NPs when added to cement mortar has a negative effect on the shrinkage value.

Functional properties of foam concrete with ultra-small additives of carbon nanotubes

2021 ◽  
Vol 1 ◽  
pp. 49-57
Author(s):  
R. D. Sldozyan ◽  
◽  
A. G. Tkachev ◽  
Z. A. Mikhaleva ◽  
A. E. Burakov ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Compressive Strength ◽  
Portland Cement ◽  
Water Absorption ◽  
Bending Strength ◽  
Testing Machine ◽  
Control Sample ◽  
Strength Increase ◽  
Foam Concrete ◽  
High Concentrations

We studied the properties of foam concrete based on Portland cement, modified with of the ultra-low concentration carbon nanotubes addition. Carbon nanotubes (Taunit-24) with a mass percentage of 0.0004, 0.0006, 0.0008, 0.001 and 0.0012 % by weight of cement were used for the dispersed reinforcement of foam concrete based on Portland cement. To determine of the modified concrete samples strength characteristics an IP-M testing machine was used. The results of the study showed that the use of the carbon nanotubes additives in concentrations of 0.0004, 0.0006, 0.0008 % allows to gradually increase the compressive strength compared to the control sample. The compressive strength increase on 1, 12.4 and 68 %, respectively, and gradually decreases at concentrations of 0.001 and 0.0012 % from 55.5 to 45.7 %, respectively. A positive effect of the carbon nanotubes additive (0.0004, 0.0006 and 0.0008 %) is also noted when testing the bending strength by 3.7, 13.7 and 33.7%, respectively. With a further increase in the additive content (0.001 and 0.0012 %), the strength decreases to 20 and 14.8 %, respectively. When assessing water absorption, a decrease was showed with additives with concentrations of 0.0004 and 0.0006 %. However, at high concentrations of additives (0.0008, 0.001 and 0.0012 %), the highest percentage of water absorption was established.

Strength of Portland Cement with Several Composition of Bottom Ash in Different Fineness with Curing Time of 28 Days

2016 ◽  
Vol 857 ◽  
pp. 311-313
Author(s):  
Ng Hooi Jun ◽  
Mohd Mustafa Al Bakri Abdullah ◽  
Kamarudin Hussin ◽  
Soo Jin Tan ◽  
Mohd Firdaus Omar ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Compressive Strength ◽  
Portland Cement ◽  
Environmental Effects ◽  
Coal Combustion ◽  
Cement Mortar ◽  
Bottom Ash ◽  
Curing Time ◽  
Cement Replacement

Concrete is produced increasingly worldwide and accounting 10-20% emission of carbon dioxide. The potential long term opposing cost of environmental effects need to recognize. Residue of coal combustion ashes especially bottom ash will use to develop reuse application. This study focused on compressive strength of several composition of bottom ash as cement replacement in mortar. Curing of cement mortar techniques and duration also plays an important role and effects on the strength. The objective of this research is to examine the compressive strength of bottom ash in Portland cement under various compositions and fineness of bottom ash.

Sign in / Sign up

Export Citation Format

Share Document