Improving Properties of Cinder Blended Materials for Construction of Low Volume Roads in Mbeya Region Tanzania

Abstract

The study to improve engineering properties of cinder blended materials was conducted in Mbeya region Tanzania.The low volume roads (LVRs) comprises of 75% of the whole road network and serves about 80% of population in Tanzania. The abundant materials in Mbeya region are cinders/scoria, pumices and volcanic soils which are originated from volcanic action. The samples from four source materials which are Ituha cinder, Ituha pozzolan, Mlimanyoka clay and Mbalizi gravel were collected for laboratory tests. Characterizations of source materials were conducted and grading coefficients (GC) and shrinkage products (SP) which are the requirements for selection of materials for surface layers of LVRs were computed. The results for GC and SP for all four source materials are out of range of 16 to 34 units and 100 to 365 units respectively. The California bearing ratios (CBR) at 95%MDD (maximum dry density) for four source materials are 17.6% for Ituha cinder, 25% for Ituha pozzolan, 3.2% for Mlimanyoka clay and 5.1% for Mbalizi gravel. The results for GC, SP and CBR for all four source materials indicated that the materials are not suitable for construction of surface layers of LVRs. The four source materials were blended together to get six blended sample materials targeting GC and SP ranges. The results of CBR values at 95%MDD for the six blended samples are 28% for 10MNCl40ITPo50ITCi0MBGr, 43% for 11MNCl40ITPo39ITCi10MBGr, 56% for 12MNCl35ITPo40ITCi13MBGr, 44% for 13MNCl32ITPo35ITCi20MBG, 39% for 14MNCl42ITPo44ITCi0MBGr and 53% for 15MNCl25ITPo35ITCi25MBGr. The improvement of CBR values of the six blended sample is because of enhanced interlocking and friction properties of the mixtures and addition of clay which act as binder to the coarse grain particles. It is important to develop suitable envelopes for surfacing layer materials of LVRs since interlocking and friction resistance are enhanced by gradation characteristics of material grain particles. For easy blending process of materials, an equation have been developed which can be used to blend materials using GC and SP parameters.

Consolidation Attributes and Deformation Response of Soft Clay Reinforced with Vertical Scoria Drains under Road Embankment

“…Te Ethiopian rift valley is known for its large coverage of volcanic materials such as pumice, scoria, and cinder [27]. Melese and Hamisi Chengula and Kilango Mnkeni [28,29] reported that scoria is abundantly found in volcano-prone areas of the Ethiopian rift. From an application point of view, scoria gravel is widely used for the improvement of weak subgrade materials and as a replacement material for the production of light weight concrete.…”

Efflorescence Formation Mechanism and Control for Geopolymer Paste Specimens Made from Natural Pozzolan and Calcium Hydroxide Binders

“…Portland cement is the common material used for mortar and concrete production. Production of Portland cements requires significant amount of energy for drying of materials, calcination process, production of clinkers and grinding to fine powders [10,14,20]. The process of producing cement in the factory emits CO 2 to the atmosphere and it is estimated that 1tone of cement produces 550kg of CO 2 to the atmosphere [13,21].…”

“…Geopolymer binders has excellent properties, such as high early strength development, fire resistance, fast hardening and high resistance on aggressive environments [2,8,14]. Geopolymer binders are produced by activating materials rich in alumino-silicate by alkali metals which are mainly calcium, sodium and potassium [4,6,19,20]. Regardless of the several advantages of geopolymer binders over industrial cements, the critical challenge is the formation of efflorescence products which generally affects its durability [1,8,9,18].…”

“…The formation mechanism of efflorescence for OPC and geopolymer concrete are different. For OPC concrete, efflorescence involves the reaction of portlandite Ca (OH) 2 and carbon dioxide (CO 2 ) at the surface of the specimens [20,21]. The efflorescence in Portland cement concrete can be represented chemically as shown in equation 1 [6,23].…”

“…The efflorescence system can be represented as wP m+ •x(T) n •yR i-•zH similar to ettringite formation in cement paste, mortar and concrete [20], in which "P" stands for base elements (Na + , K + , Ca 2+ ) and "R" stands for sulfuric, chloric or carbonic. The substitution elements are represented by "T" which may be base or acid or both.…”